Re: Noon question now noob question
The fuse is there to protect the power supply in case your radio develops a short! ?8-)
_._
On Sat, Apr 11, 2020 at 3:03 PM Don - KM4UDX < dontAy155@...> wrote: Ahem -- You can take Bill Cromwell's guidance to the bank.?
I used a 3amp fuse, and discarded the diode.? The way I figure it, every single power source in my house (and my zip code) has center pin positive (+) and the sleeve or shank or outside is negative (-).? So I have no fear of reversing the power.?
But I do have well founded fear of screwing things up, so the fuse is essential protection from fat fingering, lapse in judgement, intemperate decision making, lack of impulse control, or nature's choice of the moment to humiliate you (me).? If there is a wire or screwdriver or plug that can go where it shouldn't, then the cosmic forces of nature will ensure it goes there. It's like my daily dose of humiliation.?
So fuse up and get on the air.
By the way, when you get there, your uBITX is a perfect radio to send digital (sound card-based) modes. The native 10W will do wonders to get your around the world when conditions are good.
Don
km4udx
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Re: Noon question now noob question
Ahem -- You can take Bill Cromwell's guidance to the bank.?
I used a 3amp fuse, and discarded the diode.? The way I figure it, every single power source in my house (and my zip code) has center pin positive (+) and the sleeve or shank or outside is negative (-).? So I have no fear of reversing the power.?
But I do have well founded fear of screwing things up, so the fuse is essential protection from fat fingering, lapse in judgement, intemperate decision making, lack of impulse control, or nature's choice of the moment to humiliate you (me).? If there is a wire or screwdriver or plug that can go where it shouldn't, then the cosmic forces of nature will ensure it goes there. It's like my daily dose of humiliation.?
So fuse up and get on the air.
By the way, when you get there, your uBITX is a perfect radio to send digital (sound card-based) modes. The native 10W will do wonders to get your around the world when conditions are good.
Don
km4udx
|
Re: Noon question now noob question
I will second Bill's assertion.? A fuse does not prevent the magic smoke from leaving your radio, though it's blowing "might" mitigate further damage if you're lucky.
A fuse keeps your house or car from suffering the same fate as whatever went wrong in your radio.? Period.? FWIW, I use a 4 amp in my field build and a 6 amp in the mobile [with 20 volts on the finals].
Ted
K3RTA
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Rechecked and it will not work reliably.? Will need to look at it some more.? As stated, I just did a quick? sketch.
Sorry,
73
Evan
AC9TU
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Rob,
I was following the examples in the attached.
Not sure if that will work moving both of the diodes to a single resistor to Vcc, however it is just slightly different from the 2 resistors with positive voltage switching.? Again, not sure if it will work, I would breadboard and try first.
73
Evan
AC9TU
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Hey Evan, thanks for the quick response.? I follow the logic of the NAND gate, and also the forward biasing.? What I'm confused about is the reversing biasing, i.e. turning off a given input.? My thought is that when a given input is supposed to be off, the corresponding diode needs to be reverse biased, but I don't see that happening.? Or are you assuming that the forward voltage drop across the diode will be sufficient to block that input?
Thanks again!
-Rob KC4UPR
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Re: Circuit for second PTT that will mute Mic but allow line-in...
ROB,
The gates are NAN gates.? A NAN Gate logic is
A? ?B? ? out
========
0? ? 0? ? ?1
1? ? 0? ? ?1
0? ? 1? ? ?1
1? ? 1? ? ?0
For the input, we take the PTT of the Mic direct and invert the Computer.??
When the logic gate is High the diode is off
When the logic gate is Low the diode is on
The only time the computer diode should be forward biased is when Mic PTT is open (logic 1) and the Computer PTT is low (which is inverted to High or a logic 1).? When the gate output is LOW it would turn on the diode to be forward biased.
As stated in the text of the message, if the logic family selected cannot drive the diode, then a transistor or MOSFET needs to be used, and the inverted output needs to be inverted again.? I guess an alternative would be to use a PNP transistor but did not look into that in detail.? I did go back and look at TTL specs, and a standard 7400 quad 2 input nan gate IC should work.
I may have the thinking messed up, but that was what I came up in the spur of the moment.
73
Evan
AC9TU
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Evan (looking at yours specifically in this reply),
Can you help me understand what is happening in the "both PTT open" state?
Specifically, I'm trying understand the status of the "Mic In" and "Computer In" diodes in this condition.? If the "Computer PTT" switch is open, then the output of the logic circuit is HI (+5V), which is present at the cathode of the "Computer In" diode.? Meanwhile, Vcc (+5V) is applied at the anode.? It's not clear to me what the bias state of the diode is here.? Now, if the "Computer PTT" switch is closed, then I think the "Computer In" Diode is biased to essentially 1/2 Vcc, so I think I understand that path.
In general, I think I understand how either input is passed (forward bias of +2.5V, I think), but I don't understand how either path gets blocked (i.e. I don't see any reverse bias being applied across the input diodes).??
What am I missing?
Thanks!
-Rob KC4UPR
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Hi Rob,
Check the switching and circuits in your mic. I don't know what is inside ALL mics, especially not the el cheapos. My mics have always had a separate pole on the switch for the mic audio. If the mic switch is not pressed then mic audio does not get to radio. If you have to modify anything it might be easiest/best to modify that switch even if you have to buy a new switch.
73,
Bill KU8H
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On 4/11/20 1:49 AM, Rob French (KC4UPR) wrote: Hello!
So I want to have a separate line-in for my uBITX, separate from the Mic input.? I also want to have a separate PTT.? The intent is to have the regular mic/PTT plugged into the front of the radio, and then also have the computer hooked up in the back.
Requirements/Constraints/Desirements:
- Always keep the computer plugged in.
- Always keep the mic plugged in.
- If the mic PTT is pressed, don't transmit computer audio.
- If the computer PTT is asserted, don't transmit mic audio.
- Don't require a mechanical switch between the inputs (I have a fairly compact case and don't have room for more switches).
- Don't require a relay*. (* This is not a hard requirement, but I'd rather not use a relay if I can help it.)
- Don't require use of any Arduino pins (I'm using parallel display, don't have anything available.).
I was looking at schematics for some old Ten-Tec Omni V rigs, and saw the diodes in the transmit audio line, where a pair of diodes was alternately forward/reversed biased to route the audio either to the speech processor, or not, and I thought, maybe I could use a similar diode arrangement to enable just the audio from the mic or the line-in... except that they switch the bias voltage to the diodes via a front panel switch, so still a problem to solve.
So my thought is, in the "default" configuration, only the Mic audio would be routed to the uBITX.? But, IF the rear panel PTT was activated, then only the Line-in audio (for as long as the rear panel PTT is activated).? Any thoughts on a circuit--preferably simple :-)--to achieve this?
Thanks!
-Rob KC4UPR
--
bark less - wag more
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Hey, all.
I have two 6-pin (RJ14) ports on the front of my portable setup, one for a microphone and one for JS8, etc. It's really simple and requires no extra parts.
The data transmit audio (and the rx data audio) lead to a $6 sound card dongle. The computer burps and beeps out of it's own speakers, not out the dongle; when the dongle makes noise that the radio might transmit, it's because my digital modes (FT8, JS*, etc) are doing what I told them to do. If I'm not doing anything that utilizes "USB Sound Card 2", that input remains silent.
The microphone audio can be clipped by judicious wiring of the mike element. Take the negative lead of the eletric mic element and join it with the PPT line and allow the push switch to ground them both together when using SSB. That, or if your microphone chassis of choice has a double-pole switch, use one path for audio cut-in and the other for PTT functions. The rest of the time, the mic line makes no sound.
At least, the parts count is low.
Ted
K3RTA
Justice will not come (to Athens) until those who are not injured are as indignant as those who are injured.
Thucydides
On Saturday, April 11, 2020, 09:12:24 AM EDT, John (vk2eta) <vk2eta@...> wrote:
Hello Rob,
I have the same situation and was looking at a simple solution too. Here are my thoughts based on your idea.
Have a look at this page for examples:?http://www.k7tty.com/development/electronicprojects/Diode Switching Circuits.htm
Instead of using +/- voltages for switching I would use a voltage divider, say 1/2 of Vcc (say 47k and 47k) off the 5v from a regulator on the common output side and use the ptt signal from each ptt source for switching through a 22 to 47k biasing resistor to ground on the input side. On the input side I would connect each diode to the +5v via a 100k to 220k resistor.
That way with all PTT off you get reverse bias of +5 - 1/2 of +5 = 2.5v of reverse bias, and with ptt on you get +5 - 22/122 * 5v/2 = 1.6v of forward bias (if using 100k and 22k resistors on the input side).
Since you are dealing with max audio signals of around 100mv the biasing should keep you cleanly in the on or off region.
The output impedance of the electret is a few k ohms so small enough compared to the biasing circuit values.
For the logical OR of the ptt inputs I would use a pair of schottky diodes (e.g. Bat46) since the ptt input on the nano is an analog input (A3 pin) and the threshold for ptt on can be changed in software.
I would take care of stray RF which would cause issues with these circuits (screened cables, good ground, decoupling capacitors and ferrite sleeves if required).
Hope that helps,
73, John (VK2ETA)
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Re: Circuit for second PTT that will mute Mic but allow line-in...
Hello Rob,
I have the same situation and was looking at a simple solution too. Here are my thoughts based on your idea.
Have a look at this page for examples:?http://www.k7tty.com/development/electronicprojects/Diode Switching Circuits.htm
Instead of using +/- voltages for switching I would use a voltage divider, say 1/2 of Vcc (say 47k and 47k) off the 5v from a regulator on the common output side and use the ptt signal from each ptt source for switching through a 22 to 47k biasing resistor to ground on the input side. On the input side I would connect each diode to the +5v via a 100k to 220k resistor.
That way with all PTT off you get reverse bias of +5 - 1/2 of +5 = 2.5v of reverse bias, and with ptt on you get +5 - 22/122 * 5v/2 = 1.6v of forward bias (if using 100k and 22k resistors on the input side).
Since you are dealing with max audio signals of around 100mv the biasing should keep you cleanly in the on or off region.
The output impedance of the electret is a few k ohms so small enough compared to the biasing circuit values.
For the logical OR of the ptt inputs I would use a pair of schottky diodes (e.g. Bat46) since the ptt input on the nano is an analog input (A3 pin) and the threshold for ptt on can be changed in software.
I would take care of stray RF which would cause issues with these circuits (screened cables, good ground, decoupling capacitors and ferrite sleeves if required).
Hope that helps,
73, John (VK2ETA)
|
Re: Circuit for second PTT that will mute Mic but allow line-in...
Interesting idea.? After some quick sketching, I think it could be done with 3 capacitors, 3 resistors, 4 diodes, and a Nan gate (Not And).? I have not worked out the details, but here is a rough diagram in the attached PDF.
I do not have a selection for the diodes.? You do want diodes with low forward voltage drop and high reverse resistance (Schottky?).? ?The resistors are to provide enough forward current to ensure that the AC signal will not be clipped.? I would check your diode selection and adjust accordingly.?
If the Nan gate cannot handle the current, then use the third gate as an inverter driving a transistor or MOSFET to switch the computer audio diode.
A potential reference :
Please verify before building, as this was early morning musing, and I am not confident that I have thought through all of the requirements.
73
Evan
AC9TU
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Re: Circuit for second PTT that will mute Mic but allow line-in...
I have successfully used a dpdt arrangement. The center goes to the radio and the switched inds going to the mic/soundcard speaker and the other to the speaker/sound cardmic.
One uBITX used a regular pushbutton dtdp switchsalvaged from something and the other a relay controlled by a spst switch.
Neither used any electronics
--
73
Dave
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FS: V4.3 in case, W/fan, CEC Firmware, USB cord, (Mostly) working.....
Well this week I got this in the mail, and it had stuff skittering about inside the (banggood?) case when I unboxed it. (Always a bad sign!). First thing: off with the cover. Bits rattling around are 3 odd balls of solder, and a blade off the fan. (Shrouded, not sure how it would get broken in shipment, but who knows.) Any way, here is what I know. It's off frequency about 1.75 Kc or so on 40M, it will go into TX with supplied (included in this sale)? hand mic, but NO power output. NO power output in CW with a key, but it does go into TX. Receive seems to work fine, although a bit off Freq, as noted. Fan is variable with a pot on rear of case, and it works great, but now unbalanced, so vibrates the rig.... I will send the broken blade, maybe simple super-glue fix? Hooked USB to my old Linux laptop last night, and I could get FLDIGI to recognize the rig, and see signals on waterfall with cord from phones jack on rig to PC mic input. From non-smoking homes. This thing is ALMOST really nice. More good news is, I bet someone can fix it pretty easily. Bad news- it won't be me. Not interested, nor capable. It was advertised as in good working order, which is why I bought it. Looking to recover some of my $$. Will ship DOUBLE BOXED this time, to lower 48 only for $120. I take PayPal only.... would like this out of my life.
Contact me via an "I'll take it" here, or via QRZ listed email.?
Greg, KC8HXO
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Circuit for second PTT that will mute Mic but allow line-in...
Hello!
So I want to have a separate line-in for my uBITX, separate from the Mic input.? I also want to have a separate PTT.? The intent is to have the regular mic/PTT plugged into the front of the radio, and then also have the computer hooked up in the back.??
Requirements/Constraints/Desirements:
- Always keep the computer plugged in.
- Always keep the mic plugged in.
- If the mic PTT is pressed, don't transmit computer audio.
- If the computer PTT is asserted, don't transmit mic audio.
- Don't require a mechanical switch between the inputs (I have a fairly compact case and don't have room for more switches).
- Don't require a relay*. (* This is not a hard requirement, but I'd rather not use a relay if I can help it.)
- Don't require use of any Arduino pins (I'm using parallel display, don't have anything available.).
I was looking at schematics for some old Ten-Tec Omni V rigs, and saw the diodes in the transmit audio line, where a pair of diodes was alternately forward/reversed biased to route the audio either to the speech processor, or not, and I thought, maybe I could use a similar diode arrangement to enable just the audio from the mic or the line-in... except that they switch the bias voltage to the diodes via a front panel switch, so still a problem to solve.
So my thought is, in the "default" configuration, only the Mic audio would be routed to the uBITX.? But, IF the rear panel PTT was activated, then only the Line-in audio (for as long as the rear panel PTT is activated).? Any thoughts on a circuit--preferably simple :-)--to achieve this?
Thanks!
-Rob KC4UPR
|
Richard
Audio is scarce with a v4 using a speaker, much better with headphones. Any external amplified speaker you can find should help. For cw an audio filter with narrow bandwidth is a big help. If you can build a cw audio filter, check out various qrp merchants and clubs. Not available last I knew, but I use a necaf with my v4.
73 curt
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Re: Noon question now noob question
Ahem,
Fuses were not developed because of one mistake that one person made 125 years ago! Get and install the fuse as close to the power source as is practicable. The kits do not come with a fuse nor a fuse holder. They are not expensive. Just do it.
73,
Bill KU8H
Retired Firefighter
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On 4/10/20 7:00 PM, Evan Hand wrote: Different Hams have different views.? One of the RF Engineers on this board does not use fuses for anything other than keeping a fire from happening.
I would recommend a fuse more than 3 amps and less than the wire size can carry that you are using to power the rig. I use 3 amps, and it has saved me a couple of times that my fat fingers sauced a short that could have taken out some other components.? You diffidently want a fuse IF you are putting in the reverse voltage protection diode across the supply lines as the HF Signals assembly instructions suggest.
73
Evan
AC9TU
--
bark less - wag more
|
Different Hams have different views.? One of the RF Engineers on this board does not use fuses for anything other than keeping a fire from happening.??
I would recommend a fuse more than 3 amps and less than the wire size can carry that you are using to power the rig. I use 3 amps, and it has saved me a couple of times that my fat fingers sauced a short that could have taken out some other components.? You diffidently want a fuse IF you are putting in the reverse voltage protection diode across the supply lines as the HF Signals assembly instructions suggest.?
73
Evan
AC9TU
|
Thank you for your reply.? BTW, the subject line should have read noob instead of noon, autocorrect has become my worst enema.
I am okay not using the volume for power.? From what I understand I will connect the silver side of the diode with the red and brown wire on the + and black side of the diode with the black wire on the -.? I dont have a fuse in my kit, should I have???
Thanks for the help.
73 de Don KG5CMS.
On Fri, Apr 10, 2020, 4:23 PM Evan Hand < elhandjr@...> wrote: The polarity will be correct, but where are you switching the power?? Do you plan to use the switch on the volume control supplied with the v4 and v5 kits?? Also, are you planning to do the reverse voltage protection diode?? Fuse?
From what I can see of the board, it looks like a v4.
73
Evan
AC9TU
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The polarity will be correct, but where are you switching the power?? Do you plan to use the switch on the volume control supplied with the v4 and v5 kits?? Also, are you planning to do the reverse voltage protection diode?? Fuse?
From what I can see of the board, it looks like a v4.
73
Evan
AC9TU
|
Ted
_Dave_ AD0B