Advice on using a two-tone oscillator to set up a Hendricks bitx20a
Dear All,
I am still messing with final alignment of my bitx20a. Having read advice, and given I quite like building things, I have just built a simple "tone tone oscillator" kit to help set up the bitx20a. The kit has an "optional" resistor to let me reduce output levels. Without it, the maximum p-p voltage is about 450mv, but I can reduce that lots with a pot on board. They then say I should fit a resistor they supply, it says it will drop maximum output to about 30mv p-p. I have had some troubles getting a mike that will drive the bitx20a properly... What maximum p-p I am best setting on my test oscillator to drive into bitx20a mike socket?
Thanks, Dave Price - now MW0PRI (was 2W0DVP). p.s. kit from Walford electronics in uk and generates a mix of about 1590hz and 725hz (or one or other).
|
Re: BitX20 Additional PCB
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Howard I usually do my reports like you. HI Hi Ron
--- In BITX20@..., "g3upz" <howardwj@> wrote:
I think you're right. It probably is an S meter board.
I've never looked at the S meter on a rig. when I give a report it's always as I hear it. I find the S meter varies with AGC gain etc. Nothing like the human ear!! And this old codgers ear is not so good these days. XXX
The schematic for the board is in the files section under "Modifications". Also a nice AGC circuit (which is incorporated into the smd BITX v.4). john AD5YE
|
Re: BitX20 Additional PCB
Howard I usually do my reports like you. HI Hi Ron
toggle quoted message
Show quoted text
--- In BITX20@..., "g3upz" <howardwj@...> wrote:
I think you're right. It probably is an S meter board.
I've never looked at the S meter on a rig. when I give a report it's always as I hear it. I find the S meter varies with AGC gain etc. Nothing like the human ear!! And this old codgers ear is not so good these days. XXX
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Hi Howard I received that board also,S meter board!! I didn't use it. I used my own larger board and followed the diagram that is with instruction package. Ron
--- In BITX20@..., "g3upz" <howardwj@> wrote:
When I ordered the PCB for BitX 20 I received in addition a small PCB measuring 42 x 21 mm (1.68 x 0.85 inch) as well as the supurb BitX and PA boards. I don't know what this board is for. Help please. Thanks. Howard. G3UPZ.
|
Re: BitX20 Additional PCB
I think you're right. It probably is an S meter board.
I've never looked at the S meter on a rig. when I give a report it's always as I hear it. I find the S meter varies with AGC gain etc. Nothing like the human ear!! And this old codgers ear is not so good these days. XXX
toggle quoted message
Show quoted text
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Hi Howard I received that board also,S meter board!! I didn't use it. I used my own larger board and followed the diagram that is with instruction package. Ron
--- In BITX20@..., "g3upz" <howardwj@> wrote:
When I ordered the PCB for BitX 20 I received in addition a small PCB measuring 42 x 21 mm (1.68 x 0.85 inch) as well as the supurb BitX and PA boards. I don't know what this board is for. Help please. Thanks. Howard. G3UPZ.
|
Re: BitX20 Additional PCB
I think you're right. It probably is an S meter board.
I've never looked at the S meter on a rig. when I give a report it's always as I hear it. I find the S meter varies with AGC gain etc. Nothing like the human ear!! And this old codgers ear is not so good these days. XXX
toggle quoted message
Show quoted text
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Hi Howard I received that board also,S meter board!! I didn't use it. I used my own larger board and followed the diagram that is with instruction package. Ron
--- In BITX20@..., "g3upz" <howardwj@> wrote:
When I ordered the PCB for BitX 20 I received in addition a small PCB measuring 42 x 21 mm (1.68 x 0.85 inch) as well as the supurb BitX and PA boards. I don't know what this board is for. Help please. Thanks. Howard. G3UPZ.
|
Re: BitX20 Additional PCB
Hi Howard I received that board also,S meter board!! I didn't use it. I used my own larger board and followed the diagram that is with instruction package. Ron
toggle quoted message
Show quoted text
--- In BITX20@..., "g3upz" <howardwj@...> wrote:
When I ordered the PCB for BitX 20 I received in addition a small PCB measuring 42 x 21 mm (1.68 x 0.85 inch) as well as the supurb BitX and PA boards. I don't know what this board is for. Help please. Thanks. Howard. G3UPZ.
|
When I ordered the PCB for BitX 20 I received in addition a small PCB measuring 42 x 21 mm (1.68 x 0.85 inch) as well as the supurb BitX and PA boards. I don't know what this board is for. Help please. Thanks. Howard. G3UPZ.
|
Re: Recorded Scope levels Xmit Bitx20a
800mv's at Q20-R83 pretty much says everything before that is working fine. I've had a couple of 20a's that didn't put out and after redoing the pa bias's worked fine.
Leonard
toggle quoted message
Show quoted text
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Hi Leonard Yes had about 800mv Q20 and retuned and it started working again full output!!! Thanks Ron PS. audio xmt great also
--- In BITX20@..., "Leonard" <dredger@> wrote:
At the junction of Q20-R83 you ought to have at least 800mv's pk-pk with 50mv's audio into the mike jack. If you have that, the problem will be in the PA. You shouldn't have to turn R83 up more than about 3/4th to get 12 watts out. If you have the 800mv's, I'd go back and redo the pa bais adjustments.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Leonard what happened rig was working fine and then R83 pot wouldn't adj high enough. I did check all the transistor voltages.The last scope picture of Q20 I will check,but any idea what level out of Q3 and Q18 and Q19. I haven't looked at what is the purpose of Q3.Maybe you can tell me without me searching. Thanks Ron
--- In BITX20@..., "Leonard" <dredger@> wrote:
The waveforms should get you to a stage that isn't working. Or it lets you say the stage is good if you have the waveforms. A good physical inspection and transistor voltage checks should get you the rest of the way. Between the hard copy version and the transnitter troubleshooting video, you even get a fair circuit operation description. The pair go very well together as the video uses the hard copy and gives some extra info.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Thanks Leonard I remember watching the Videos but I didn't remember seeing the pictures of the xmit waveforms.I borrowed a scope and im looking at my Bitx20a. Thanks for the direct link. Ron
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: Recorded Scope levels Xmit Bitx20a
Hi Leonard Yes had about 800mv Q20 and retuned and it started working again full output!!! Thanks Ron PS. audio xmt great also
toggle quoted message
Show quoted text
--- In BITX20@..., "Leonard" <dredger@...> wrote:
At the junction of Q20-R83 you ought to have at least 800mv's pk-pk with 50mv's audio into the mike jack. If you have that, the problem will be in the PA. You shouldn't have to turn R83 up more than about 3/4th to get 12 watts out. If you have the 800mv's, I'd go back and redo the pa bais adjustments.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Leonard what happened rig was working fine and then R83 pot wouldn't adj high enough. I did check all the transistor voltages.The last scope picture of Q20 I will check,but any idea what level out of Q3 and Q18 and Q19. I haven't looked at what is the purpose of Q3.Maybe you can tell me without me searching. Thanks Ron
--- In BITX20@..., "Leonard" <dredger@> wrote:
The waveforms should get you to a stage that isn't working. Or it lets you say the stage is good if you have the waveforms. A good physical inspection and transistor voltage checks should get you the rest of the way. Between the hard copy version and the transnitter troubleshooting video, you even get a fair circuit operation description. The pair go very well together as the video uses the hard copy and gives some extra info.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Thanks Leonard I remember watching the Videos but I didn't remember seeing the pictures of the xmit waveforms.I borrowed a scope and im looking at my Bitx20a. Thanks for the direct link. Ron
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: Recorded Scope levels Xmit Bitx20a
At the junction of Q20-R83 you ought to have at least 800mv's pk-pk with 50mv's audio into the mike jack. If you have that, the problem will be in the PA. You shouldn't have to turn R83 up more than about 3/4th to get 12 watts out. If you have the 800mv's, I'd go back and redo the pa bais adjustments.
Leonard
toggle quoted message
Show quoted text
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Leonard what happened rig was working fine and then R83 pot wouldn't adj high enough. I did check all the transistor voltages.The last scope picture of Q20 I will check,but any idea what level out of Q3 and Q18 and Q19. I haven't looked at what is the purpose of Q3.Maybe you can tell me without me searching. Thanks Ron
--- In BITX20@..., "Leonard" <dredger@> wrote:
The waveforms should get you to a stage that isn't working. Or it lets you say the stage is good if you have the waveforms. A good physical inspection and transistor voltage checks should get you the rest of the way. Between the hard copy version and the transnitter troubleshooting video, you even get a fair circuit operation description. The pair go very well together as the video uses the hard copy and gives some extra info.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Thanks Leonard I remember watching the Videos but I didn't remember seeing the pictures of the xmit waveforms.I borrowed a scope and im looking at my Bitx20a. Thanks for the direct link. Ron
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: Recorded Scope levels Xmit Bitx20a
Leonard what happened rig was working fine and then R83 pot wouldn't adj high enough. I did check all the transistor voltages.The last scope picture of Q20 I will check,but any idea what level out of Q3 and Q18 and Q19. I haven't looked at what is the purpose of Q3.Maybe you can tell me without me searching. Thanks Ron
toggle quoted message
Show quoted text
--- In BITX20@..., "Leonard" <dredger@...> wrote:
The waveforms should get you to a stage that isn't working. Or it lets you say the stage is good if you have the waveforms. A good physical inspection and transistor voltage checks should get you the rest of the way. Between the hard copy version and the transnitter troubleshooting video, you even get a fair circuit operation description. The pair go very well together as the video uses the hard copy and gives some extra info.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Thanks Leonard I remember watching the Videos but I didn't remember seeing the pictures of the xmit waveforms.I borrowed a scope and im looking at my Bitx20a. Thanks for the direct link. Ron
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: Recorded Scope levels Xmit Bitx20a
The waveforms should get you to a stage that isn't working. Or it lets you say the stage is good if you have the waveforms. A good physical inspection and transistor voltage checks should get you the rest of the way. Between the hard copy version and the transnitter troubleshooting video, you even get a fair circuit operation description. The pair go very well together as the video uses the hard copy and gives some extra info.
Leonard
toggle quoted message
Show quoted text
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Thanks Leonard I remember watching the Videos but I didn't remember seeing the pictures of the xmit waveforms.I borrowed a scope and im looking at my Bitx20a. Thanks for the direct link. Ron
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: Recorded Scope levels Xmit Bitx20a
Thanks Leonard I remember watching the Videos but I didn't remember seeing the pictures of the xmit waveforms.I borrowed a scope and im looking at my Bitx20a. Thanks for the direct link. Ron
toggle quoted message
Show quoted text
--- In BITX20@..., "Leonard" <dredger@...> wrote:
Surely you've seen these Ron. Specifically but the transmitting video goes through a lot of the webpage process.
I don't have waveforms for the linear. It's hard to take them.
Leonard
--- In BITX20@..., "ronbaechle" <ronbaechle@> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: Recorded Scope levels Xmit Bitx20a
Surely you've seen these Ron. Specifically but the transmitting video goes through a lot of the webpage process.
I don't have waveforms for the linear. It's hard to take them.
Leonard
toggle quoted message
Show quoted text
--- In BITX20@..., "ronbaechle" <ronbaechle@...> wrote:
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Recorded Scope levels Xmit Bitx20a
Does anyone have recorded scope levels of xmit sections on the Hendricks Bitx 20a or know of a file? Thanks Ron
|
Re: S-meter hookup Bitx 20 B3
On the diagram I received with my Bitx ver 3 it shows the S meter
ckt across the vol control pot.In other words one side of pot to ground. Ron
toggle quoted message
Show quoted text
--- In BITX20@..., "itsbeen29years" <maund.n@...> wrote:
I am working on completing the Bitx20 version 3. Can someone advise on where to connect the S Meter? If I connect on the Audio output at the speaker terminal it will deviate along with the volume control. I tried connecting to the top of the potentiometer feeding the audio amplifier but it didn't swing the meter.
|
S-meter hookup Bitx 20 B3
I am working on completing the Bitx20 version 3. Can someone advise on where to connect the S Meter? If I connect on the Audio output at the speaker terminal it will deviate along with the volume control. I tried connecting to the top of the potentiometer feeding the audio amplifier but it didn't swing the meter.
|
Re: irf510 push pull amplifier
Arnab
If it's 180 degrees out of phase then it should not oscillate because to
oscillate you have to have the feedback in phase.
It seems that you may have a feedback loop when you connect the changeover
relay etc.
This could be due to an earth loop, something unscreened, etc.
Try screening the BITX and driver from the PA and the PA itself.
Another thing you can try is to use a double pole relay to short the input
to the exciter.
I do not have a circuit before me so I am just giving you hints where to
look and what generally is required for stability.
I have to go out now so I will try to find some time to have a look at te
circuits.
Can you post the circuit of the BITX and the PA and perhaps a few photos so
that we can see what may be happening.
Thanks and regards,
Lawrence.
|
Re: irf510 push pull amplifier
hi lawrence, 听听听听听听听听听 it is working perfectly without the switching circuit or the feedback loop. with the output connected directly the 50ohm dummy load i am getting 24v peak to peak rf across dummy load in my oscilloscope. (12volt supply). but whenever i complete the rxtx relay switching circuit and connect the antenna wire to the base of the q14 (after band pass filter transistor) it starts oscillating terribly. and also linear input open or short shows no sign of oscillation. 听 听 听 听 听 somewhere i have seen someone mentioned about the phase matter for oscillation . as i have used one 2n2218 stage, one bd139 based push pull stage and one irf based push pull stage. the output signal must be in 180degree different with the input signal of q14. please highlight on this matter. 听 听 听 听听 i may have to insert a unity gain transistor stage between q14 and 2n2218 stage. arnab/vu2bpw ________________________________ From: Lawrence Galea <9h1avlaw@...> To: BITX20@... Sent: Saturday, 8 June 2013 8:50 PM Subject: Re: [BITX20] Re: irf510 push pull amplifier Did you try a small resistor such as 22 or 47脵 in series with the drive right at the gates of the FET's? Regards Lawrence On Sat, Jun 8, 2013 at 5:10 PM, arnab bhaumik <arnab_bhaumik2000@...>wrote: **
please go through the file section of the group. in the folder BITX pcbs i
uploaded the schematic(print.ps) and the upper layer of the pcb(top2.ps)
please comment on these. the circuit works fine . only oscillate when
rceiver antenna cable to the main board (after band pass filter)
arnab/bu2bpw
________________________________
From: arnab bhaumik <arnab_bhaumik2000@...>
To: "BITX20@..." <BITX20@...>
Sent: Saturday, 8 June 2013 5:42 PM
Subject: Re: [BITX20] Re: irf510 push pull amplifier
hi john,
听 听 听 thank you for your reply. yesterday i tried a lot with the new push
pull amplifier. after lots of experimenting, it seems that actually the
push pull linear is working fine. connecting the relay is also fine. but
whenever i connect the receiver antenna cable to the main board (after band
pass filter) it starts oscillation.
听 听 after searching the net i came to know that in the single irf qrp
linear there is a phase matching so there no oscillation (180degree for
2n2218 and 180 degree for 2n2222), but here there is three stage
听 amplification. the feedback is just 180 degree out of phase perfect for
unstability.
听 听 听 today i will try to add another transistor stage into the power chain
and see what happens.
there is already a ceramic cap in the primary of the output transformer. .
thanks again
will update and post the circuit
ps - attaching the circuit i followed in push pull. but in the input there
is 2n2218 stage
________________________________
From: "iam74@..." <iam74@...>
To: BITX20@...
Sent: Saturday, 8 June 2013 8:26 AM
Subject: [BITX20] Re: irf510 push pull amplifier
--- In BITX20@..., arnab bhaumik <arnab_bhaumik2000@...>
wrote:
hi,
听 听 previously i build a irf510 based push pull amplifier with the self
made pcb design. i tested it with the bitx20 (old) board.
听 听 听 听 it has a 2n2218 based first amp stage, then bd139 push-pull stage
and finally irf510 push pull stage. after irf stage . there is a low pass
filter.
working in 12v power supply and giving clean 24v peak to peak rf voltage at the dummy load.
听 but the problem comes with when i connect it with a relay for rxtx switching. everytime i connect the relay before or after the low pass
filter the amplifier goes into noise mode ie in oscilloscope i see only 40v
p-p rf oscillation. i think it is for impedence mismatch. the final rf
transformer is primary 2turn & secondary 3 turn load 50ohm. after lots of
trying could not improve anything.
听 听 guys please help...
later on i will publish the pcb artwork for bitx 12 volt qrp operation
(mobile??)
arnab/vu2bpw
Try placing a ceramic cap across the primary of the output
transformer...somewhere around 200-1000 pf.
Try increasing the finals voltage to 24v. Usually the IRF510 is more
stable at higher voltages.
Try placing a ceramic or sm cap between the drain of each IRF510 to
ground...about 200 pf. Or sometimes back to the source.
Try a small resistor, about 10 ohms, on the source of each IRF510, placed
very close to the device.
Your problem is almost certainly HF or VHF oscillation in the finals.
john
AD5YE
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
听
------------------------------------ Yahoo! Groups Links [Non-text portions of this message have been removed]
|
Re: irf510 push pull amplifier
Did you try a small resistor such as 22 or 47� in series with the drive right at the gates of the FET's? Regards Lawrence On Sat, Jun 8, 2013 at 5:10 PM, arnab bhaumik <arnab_bhaumik2000@...>wrote: **
please go through the file section of the group. in the folder BITX pcbs i
uploaded the schematic(print.ps) and the upper layer of the pcb(top2.ps)
please comment on these. the circuit works fine . only oscillate when
rceiver antenna cable to the main board (after band pass filter)
arnab/bu2bpw
________________________________
From: arnab bhaumik <arnab_bhaumik2000@...>
To: "BITX20@..." <BITX20@...>
Sent: Saturday, 8 June 2013 5:42 PM
Subject: Re: [BITX20] Re: irf510 push pull amplifier
hi john,
thank you for your reply. yesterday i tried a lot with the new push
pull amplifier. after lots of experimenting, it seems that actually the
push pull linear is working fine. connecting the relay is also fine. but
whenever i connect the receiver antenna cable to the main board (after band
pass filter) it starts oscillation.
after searching the net i came to know that in the single irf qrp
linear there is a phase matching so there no oscillation (180degree for
2n2218 and 180 degree for 2n2222), but here there is three stage
amplification. the feedback is just 180 degree out of phase perfect for
unstability.
today i will try to add another transistor stage into the power chain
and see what happens.
there is already a ceramic cap in the primary of the output transformer. .
thanks again
will update and post the circuit
ps - attaching the circuit i followed in push pull. but in the input there
is 2n2218 stage
________________________________
From: "iam74@..." <iam74@...>
To: BITX20@...
Sent: Saturday, 8 June 2013 8:26 AM
Subject: [BITX20] Re: irf510 push pull amplifier
--- In BITX20@..., arnab bhaumik <arnab_bhaumik2000@...>
wrote:
hi,
previously i build a irf510 based push pull amplifier with the self
made pcb design. i tested it with the bitx20 (old) board.
it has a 2n2218 based first amp stage, then bd139 push-pull stage
and finally irf510 push pull stage. after irf stage . there is a low pass
filter.
working in 12v power supply and giving clean 24v peak to peak rf voltage at the dummy load.
but the problem comes with when i connect it with a relay for rxtx switching. everytime i connect the relay before or after the low pass
filter the amplifier goes into noise mode ie in oscilloscope i see only 40v
p-p rf oscillation. i think it is for impedence mismatch. the final rf
transformer is primary 2turn & secondary 3 turn load 50ohm. after lots of
trying could not improve anything.
guys please help...
later on i will publish the pcb artwork for bitx 12 volt qrp operation
(mobile??)
arnab/vu2bpw
Try placing a ceramic cap across the primary of the output
transformer...somewhere around 200-1000 pf.
Try increasing the finals voltage to 24v. Usually the IRF510 is more
stable at higher voltages.
Try placing a ceramic or sm cap between the drain of each IRF510 to
ground...about 200 pf. Or sometimes back to the source.
Try a small resistor, about 10 ohms, on the source of each IRF510, placed
very close to the device.
Your problem is almost certainly HF or VHF oscillation in the finals.
john
AD5YE
[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]
|
Leonard