Hi all,
I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two.
I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi.
This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
|
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information.
Arv K7HKL _._
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Show quoted text
On 09/13/2011 09:44 AM, Mark wrote: Hi all,
I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two.
I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi.
This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
|
Any time Arv,
Let me know how it works for you...
73s,
Mark - N7EKU
toggle quoted message
Show quoted text
--- On Tue, 9/13/11, Arv Evans <arvid.evans@...> wrote: From: Arv Evans <arvid.evans@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... Date: Tuesday, September 13, 2011, 7:48 PM ? Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote: Hi all, I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem. I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-) I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two. I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi. This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded). Cheers and have a great day everyone! Mark - N7EKU [Non-text portions of this message have been removed]
|
Mark, Arv,
Would reversing the diode and picking up the PTT ground work? That way the audio amp would be muted before the transmitter was turn on. This might eliminate the pop all together.
Frank - W4NHJ
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Show quoted text
On 9/13/11 6:29 PM, Mark wrote: Any time Arv,
Let me know how it works for you...
73s,
Mark - N7EKU
--- On Tue, 9/13/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Tuesday, September 13, 2011, 7:48 PM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all, I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem. I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-) I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two. I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi. This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded). Cheers and have a great day everyone! Mark - N7EKU [Non-text portions of this message have been removed]
|
Hi Frank,
Good idea, I think it should work -- the ptt jack is close so the connection should be easy.? I think I did test for muting using the diode either way with Vcc and Ground and both worked fine.? I also tried different diodes (silicon, germanium, schottky) to see if the different drops changed anything, but I couldn't tell a difference by ear anyway.
Maybe Arv can compare the two methods since he has a board on the bench!
Mark - N7EKU
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Show quoted text
--- On Tue, 9/13/11, Frank <w4nhj@...> wrote: From: Frank <w4nhj@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... Date: Tuesday, September 13, 2011, 11:23 PM ? Mark, Arv, Would reversing the diode and picking up the PTT ground work? That way the audio amp would be muted before the transmitter was turn on. This might eliminate the pop all together. Frank - W4NHJ On 9/13/11 6:29 PM, Mark wrote: Any time Arv, Let me know how it works for you... 73s, Mark - N7EKU --- On Tue, 9/13/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Tuesday, September 13, 2011, 7:48 PM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
|
Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl
toggle quoted message
Show quoted text
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...> wrote: From: Arv Evans <arvid.evans@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... Date: Wednesday, 14 September, 2011, 1:18 AM ? Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote: Hi all,
I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two.
I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi.
This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
|
Hi Kishore,
You're very welcome!? I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for.
NOTICE!!! ?? I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position.? I think it has something to do with large inductive energy in the relay coil.? I do have a protection diode in there, but I'm afraid I may have partially fried my lm386.? So, I wouldn't recommend using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s,
Mark - N7EKU
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Show quoted text
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...> wrote: From: kishore vagisetty <kishorev001@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... Date: Wednesday, September 14, 2011, 3:39 AM ? Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@...> wrote: From: Arv Evans <arvid.evans@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... Date: Wednesday, 14 September, 2011, 1:18 AM ? Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote: Hi all, I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem. I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-) I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two. I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi. This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded). Cheers and have a great day everyone! Mark - N7EKU [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
|
Frank & Mark
After a bit of playing I find that it eliminates part of the change-over noise, but not all. Possibly some sort of RC network is required to delay un-muting when going from Tx to Rx.
Part of the click is apparently related to the LM386 output lead going to ground when the power is removed for Tx mode and then coming back up to 1/2 Vcc when power is re-applied for receive mode activation.
Now that Mark came up with mute for the LM386, maybe we should try leaving it powered up but muted during transmit mode?
This whole thing with muting the LM386 has some interesting options to consider. What about instead of using pin-7 we were to use a MOSFET to switch the two inputs together when transmitting so that input would be common-mode, and then letting the alternative input pin revert to ground when receiving? Normal audio is input on pin-3 with pin-2 connected to ground. Pin-2 could be grounded through a resistor and then use a MOSFET switch to connect pin-2 and pin-3 together when transmitting. This might avoid the DC offset transition when changing from transmit to receive. Also might be able to use a MOSFET (2N7000...?) to short the LM386 input pin (pin-3) to ground during transmit.
I may have to build up another ugly-constructed BITXxxA because thoughts now are running toward adding MOSFET switches in series with C77 and C8 to totally separate send and receive audio from the BFO mixer. This might eliminate the charge and discharge cycling of C77 and C8 as their respective circuits are powered up and down when switching between receive and transmit. Disconnecting the mic amp output during receive and disconnecting the receive audio input during transmit could allow those two circuits to remain powered up instead of switching them up and down and causing the current surge through C8 and C77. This could also provide a way to add sidetone if adding a keyed oscillator for CW.
Arv _._
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On 09/13/2011 05:23 PM, Frank wrote: Mark, Arv,
Would reversing the diode and picking up the PTT ground work? That way the audio amp would be muted before the transmitter was turn on. This might eliminate the pop all together.
Frank - W4NHJ
On 9/13/11 6:29 PM, Mark wrote:
Any time Arv,
Let me know how it works for you...
73s,
Mark - N7EKU
--- On Tue, 9/13/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Tuesday, September 13, 2011, 7:48 PM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all, I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem. I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-) I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two. I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi. This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded). Cheers and have a great day everyone! Mark - N7EKU [Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
Mark, & others... You could probably use a small transistor to switch Pin-7 and avoid possibility of damaging the LM-386 during the experimentation process. I routinely use a socket for the LM-386, mostly because I like to tinker with things and have fried a few AF amp IC's. If you do have to replace a soldered-in-place LM386, the easy way is to cut all the legs off and then remove them from the PCB one at a time. Arv _._ On 09/13/2011 10:29 PM, Mark wrote: Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for.
NOTICE!!! I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position. I think it has something to do with large inductive energy in the relay coil. I do have a protection diode in there, but I'm afraid I may have partially fried my lm386. So, I wouldn't recommend using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all, I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem. I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-) I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two. I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi. This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded). Cheers and have a great day everyone! Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
Excellent advice Arv :-)?
Turns out my amp chip was OK.? For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit.? That wasn't happening before so I'm not sure what's up.? I had the chip in a socket already and switched it out but no change.? Not a big deal just wierd.? Maybe my mic wiring is running with different routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
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Show quoted text
--- On Wed, 9/14/11, Arv Evans <arvid.evans@...> wrote: From: Arv Evans <arvid.evans@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... Date: Wednesday, September 14, 2011, 5:08 AM ? Mark, & others... You could probably use a small transistor to switch Pin-7 and avoid possibility of damaging the LM-386 during the experimentation process. I routinely use a socket for the LM-386, mostly because I like to tinker with things and have fried a few AF amp IC's. If you do have to replace a soldered-in-place LM386, the easy way is to cut all the legs off and then remove them from the PCB one at a time. Arv _._ On 09/13/2011 10:29 PM, Mark wrote: Hi Kishore, You're very welcome! I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for. NOTICE!!! I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position. I think it has something to do with large inductive energy in the relay coil. I do have a protection diode in there, but I'm afraid I may have partially fried my lm386. So, I wouldn't recommend using the muting circuit in this position! The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it. Cheers and 73s, Mark - N7EKU --- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>> wrote: From: kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 3:39 AM Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, 14 September, 2011, 1:18 AM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
|
Mark
Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on raised the board high enough for all wiring to be run under the board instead of across the top. This made it much easier to do measurements and to troubleshoot. And, it looks better with most of the wiring hidden under the board.
It might be interesting to try a large capacitor from pin-7 to ground on the LM386? Thinking is that this might slow down how fast this amplifier recovers from power- down during transmit and thus mask part of the changeover feedback period. Idea is that this could possibly act as a timed mute function. We could add enough components to do an actual time delay before allowing the LM386 to activate but that seems contrary to the minimalist concept of BITX design.
Arv _._
toggle quoted message
Show quoted text
On 09/14/2011 01:06 AM, Mark wrote: Excellent advice Arv :-)
Turns out my amp chip was OK. For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit. That wasn't happening before so I'm not sure what's up. I had the chip in a socket already and switched it out but no change. Not a big deal just wierd. Maybe my mic wiring is running with different routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
--- On Wed, 9/14/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 5:08 AM
Mark, & others...
You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.
Arv
_._
On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore, You're very welcome! I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for. NOTICE!!! I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position. I think it has something to do with large inductive energy in the relay coil. I do have a protection diode in there, but I'm afraid I may have partially fried my lm386. So, I wouldn't recommend using the muting circuit in this position! The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s, Mark - N7EKU --- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> wrote: From: kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
Hello, maybe another idea: I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop.? It gave me no satisfaction, because the pop remained somehow. My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais. When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s.? Now the pop has gone completely. cheers and 73 Marcel - PE1LNX ________________________________ From: Arv Evans <arvid.evans@...> To: BITX20@... Sent: Wednesday, September 14, 2011 6:37 PM Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... ? Mark Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on raised the board high enough for all wiring to be run under the board instead of across the top. This made it much easier to do measurements and to troubleshoot. And, it looks better with most of the wiring hidden under the board. It might be interesting to try a large capacitor from pin-7 to ground on the LM386? Thinking is that this might slow down how fast this amplifier recovers from power- down during transmit and thus mask part of the changeover feedback period. Idea is that this could possibly act as a timed mute function. We could add enough components to do an actual time delay before allowing the LM386 to activate but that seems contrary to the minimalist concept of BITX design. Arv _._ On 09/14/2011 01:06 AM, Mark wrote: Excellent advice Arv :-)
Turns out my amp chip was OK. For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit. That wasn't happening before so I'm not sure what's up. I had the chip in a socket already and switched it out but no change. Not a big deal just wierd. Maybe my mic wiring is running with different routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
--- On Wed, 9/14/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 5:08 AM
Mark, & others...
You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.
Arv
_._
On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore, You're very welcome! I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for. NOTICE!!! I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position. I think it has something to do with large inductive energy in the relay coil. I do have a protection diode in there, but I'm afraid I may have partially fried my lm386. So, I wouldn't recommend using the muting circuit in this position! The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s, Mark - N7EKU --- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> wrote: From: kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
Nice solution Marcel!? Builders have some nice options now :-)
Mark - N7EKU
toggle quoted message
Show quoted text
--- On Thu, 9/15/11, Marcel Jacobs <pe1lnx@...> wrote: From: Marcel Jacobs <pe1lnx@...> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: "BITX20@..." <BITX20@...> Date: Thursday, September 15, 2011, 8:04 PM ? Hello, maybe another idea: I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop.? It gave me no satisfaction, because the pop remained somehow. My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais. When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s.? Now the pop has gone completely. cheers and 73 Marcel - PE1LNX ________________________________ From: Arv Evans <arvid.evans@...> To: BITX20@... Sent: Wednesday, September 14, 2011 6:37 PM Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... ? Mark Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on raised the board high enough for all wiring to be run under the board instead of across the top. This made it much easier to do measurements and to troubleshoot. And, it looks better with most of the wiring hidden under the board. It might be interesting to try a large capacitor from pin-7 to ground on the LM386? Thinking is that this might slow down how fast this amplifier recovers from power- down during transmit and thus mask part of the changeover feedback period. Idea is that this could possibly act as a timed mute function. We could add enough components to do an actual time delay before allowing the LM386 to activate but that seems contrary to the minimalist concept of BITX design. Arv _._ On 09/14/2011 01:06 AM, Mark wrote: Excellent advice Arv :-) Turns out my amp chip was OK. For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit. That wasn't happening before so I'm not sure what's up. I had the chip in a socket already and switched it out but no change. Not a big deal just wierd. Maybe my mic wiring is running with different routing now since I had the set apart. Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set. Cheers and lots of interesting ideas you have now Arv! Mark - N7EKU --- On Wed, 9/14/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 5:08 AM Mark, & others... You could probably use a small transistor to switch Pin-7 and avoid possibility of damaging the LM-386 during the experimentation process. I routinely use a socket for the LM-386, mostly because I like to tinker with things and have fried a few AF amp IC's. If you do have to replace a soldered-in-place LM386, the easy way is to cut all the legs off and then remove them from the PCB one at a time. Arv _._ On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.
Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in> <mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in> <mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
|
Marcel - PE1LNX That is a good positive solution to the problem. As far as I have been able to determine, the source of the clicks and pops, and the 20 ms of carrier that gets sent when starting to transmit, is a combination of the power bypass capacitors for each stage holding some amount of voltage after the power feed has been switched off, and the audio-to-mixer coupling caps charging & discharging causing temporary unbalance of the BFO mixer. Arv K7HKL _._ On 09/15/2011 02:04 PM, Marcel Jacobs wrote: Hello, maybe another idea:
I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop. It gave me no satisfaction, because the pop remained somehow. My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais. When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s. Now the pop has gone completely.
cheers and 73
Marcel - PE1LNX
________________________________ From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> To: BITX20@... <mailto:BITX20%40yahoogroups.com> Sent: Wednesday, September 14, 2011 6:37 PM Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
Mark
Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on raised the board high enough for all wiring to be run under the board instead of across the top. This made it much easier to do measurements and to troubleshoot. And, it looks better with most of the wiring hidden under the board.
It might be interesting to try a large capacitor from pin-7 to ground on the LM386? Thinking is that this might slow down how fast this amplifier recovers from power- down during transmit and thus mask part of the changeover feedback period. Idea is that this could possibly act as a timed mute function. We could add enough components to do an actual time delay before allowing the LM386 to activate but that seems contrary to the minimalist concept of BITX design.
Arv _._
On 09/14/2011 01:06 AM, Mark wrote:
Excellent advice Arv :-)
Turns out my amp chip was OK. For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit. That wasn't happening before so I'm not sure what's up. I had the chip in a socket already and switched it out but no change. Not a big deal just wierd. Maybe my mic wiring is running with different routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
--- On Wed, 9/14/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM
Mark, & others...
You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.
Arv
_._
On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore, You're very welcome! I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for. NOTICE!!! I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position. I think it has something to do with large inductive energy in the relay coil. I do have a protection diode in there, but I'm afraid I may have partially fried my lm386. So, I wouldn't recommend using the muting circuit in this position! The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s, Mark - N7EKU --- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> wrote: From: kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to
pin 7.
So I simply installed a 1N4148 diode between the transmit supply
line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon
closing
of the ptt switch. There is still a small pop occuring after
this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty
easy
to do on the backside as the 4-pin readymate connector header is
just
next to pin 7 on the lm386 and a diode reaches very easily
between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed
between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less
unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of
the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
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I used a reed relay in series with the LM386 output driven by the TX voltage bus... Reeds are known for their low power and fast switching time...also very low ohmic resistance I do hear a tiny, almost a light click when switching to transmit...NOTHING like the POP I heard before. Arv and I had a discussion on an early thread on the same subject... A transistor would work but much more complex K4DSB Dean To: BITX20@... From: pe1lnx@... Date: Thu, 15 Sep 2011 13:04:41 -0700 Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... Hello, maybe another idea: I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop. It gave me no satisfaction, because the pop remained somehow. My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais. When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s. Now the pop has gone completely. cheers and 73 Marcel - PE1LNX ________________________________ From: Arv Evans <arvid.evans@...> To: BITX20@... Sent: Wednesday, September 14, 2011 6:37 PM Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... Mark Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on raised the board high enough for all wiring to be run under the board instead of across the top. This made it much easier to do measurements and to troubleshoot. And, it looks better with most of the wiring hidden under the board. It might be interesting to try a large capacitor from pin-7 to ground on the LM386? Thinking is that this might slow down how fast this amplifier recovers from power- down during transmit and thus mask part of the changeover feedback period. Idea is that this could possibly act as a timed mute function. We could add enough components to do an actual time delay before allowing the LM386 to activate but that seems contrary to the minimalist concept of BITX design. Arv _._ On 09/14/2011 01:06 AM, Mark wrote: Excellent advice Arv :-)
Turns out my amp chip was OK. For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit. That wasn't happening before so I'm not sure what's up. I had the chip in a socket already and switched it out but no change. Not a big deal just wierd. Maybe my mic wiring is running with different routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
--- On Wed, 9/14/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> Date: Wednesday, September 14, 2011, 5:08 AM
Mark, & others...
You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.
Arv
_._
On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore, You're very welcome! I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for. NOTICE!!! I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position. I think it has something to do with large inductive energy in the relay coil. I do have a protection diode in there, but I'm afraid I may have partially fried my lm386. So, I wouldn't recommend using the muting circuit in this position! The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s, Mark - N7EKU --- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> wrote: From: kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote: From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem... To: BITX20@... <mailto:BITX20%40yahoogroups.com> <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench. Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
|
Hi Dean,
I saw you earlier mod and some of the others with relays and transistors. I just thought the diode mod might be usefull for those without a lot of parts - just a throw away quality doide works fine for the mod - one part and cheap and works fairly well :-)
Mark - N7EKU
toggle quoted message
Show quoted text
--- On Fri, 9/16/11, Dean Blake <dsblake1@...> wrote: From: Dean Blake <dsblake1@...> Subject: RE: [BITX20] A simple mod for the ptt pop squeal problem... To: bitx20@... Date: Friday, September 16, 2011, 11:45 AM
I used a reed relay in series with the LM386 output driven by the TX voltage bus...
Reeds are known for their low power and fast switching time...also very low ohmic resistance
I do hear a tiny, almost a light click when switching to transmit...NOTHING like the POP I heard before. Arv and I had a discussion on an early thread on the same subject... A transistor would work but much more complex
K4DSB Dean
To: BITX20@... From: pe1lnx@... Date: Thu, 15 Sep 2011 13:04:41 -0700 Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
?
Hello, maybe another idea:
I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop. It gave me no satisfaction, because the pop remained somehow. My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais. When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s. Now the pop has gone completely.
cheers and 73
Marcel - PE1LNX
________________________________ From: Arv Evans <arvid.evans@...> To: BITX20@... Sent: Wednesday, September 14, 2011 6:37 PM Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
? Mark
Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on raised the board high enough for all wiring to be run under the board instead of across the top. This made it much easier to do measurements and to troubleshoot. And, it looks better with most of the wiring hidden under the board.
It might be interesting to try a large capacitor from pin-7 to ground on the LM386? Thinking is that this might slow down how fast this amplifier recovers from power- down during transmit and thus mask part of the changeover feedback period. Idea is that this could possibly act as a timed mute function. We could add enough components to do an actual time delay before allowing the LM386 to activate but that seems contrary to the minimalist concept of BITX design.
Arv _._
On 09/14/2011 01:06 AM, Mark wrote:
Excellent advice Arv :-)
Turns out my amp chip was OK. For some reason now however (after
trying the other diode position) I have a little leakage or noise from
the mic circuit coming over the speaker at the beginning of transmit.
That wasn't happening before so I'm not sure what's up. I had the
chip in a socket already and switched it out but no change. Not a big
deal just wierd. Maybe my mic wiring is running with different
routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either,
but now it's pretty tolerable and is just a bit louder than the relay
clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM
Mark, & others...
You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.
Arv
_._
On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore, You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for. NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position! The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.
Cheers and 73s, Mark - N7EKU --- On Wed, 9/14/11, kishore vagisetty <kishorev001@... <mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM Dear Mark N7EKU, thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference. 73 v kishore vu2-002swl --- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM Mark N7EKU Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information. Arv K7HKL _._ On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of
changing the gain on the
lm386, and found a simple solution for the
popping problem.
I found in some reading that pin 7 can be
used for muting the
amplifier. Muting will occur if either 0V or
Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between
the transmit supply line
and pin 7 of the lm386 so that it conducts
Vcc to the pin upon closing
of the ptt switch. There is still a small
pop occuring after this mod,
but it is reduced in magnitude by a great
amount. I feel this is a
nice mod and in keeping with the KISS theme
of the BITX line :-)
I will put some photos up of my pcb after
the mod, but it pretty easy
to do on the backside as the 4-pin readymate
connector header is just
next to pin 7 on the lm386 and a diode
reaches very easily between the
two.
I also read that it is recommended, when
using increased gain on the
lm386 (like we are), to have a 1-10uF
capacitor installed between pin
7 and ground in order to reduce power supply
noise problems (see the
second graph on the datasheet). This in
itself helped a little bit
with the pop problem (I tried this mod
first) in that the pop sound
changed from a "squeal" to a "crunch" which
was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside
as a small radial lead
electrolytic or tantalum cap can be laid
down along the pins of the IC
and leads soldered between pins 7 and 2
(which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
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??? ???????? ?????? ??? ?
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------------------------------------
Yahoo! Groups Links
? ? BITX20-fullfeatured@...
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Reading Marcel`s report on PTT Noise Fix . I tried the relay fix but may be I got the wiring wrong Did Marcel? switch both + and - leads of the speaker to? ground or just the + lead? to speaker to a 8 Ohm resistor to speaker ground or to board ground ?
I have had no luck with switching + line to speaker to speaker ground through an 8 Ohm resistor . Still a very loud pop. Bryan vk7kwb
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