Topics

Microphone audio leaking into speaker

Jay - WS4JM
 

I installed an SSM2167 pre-amp processor on my V3 uBitx. I am getting microphone audio into the speaker. It only appears from about 1/2 to 7/8 of the volume pot range. Verified with my scope. It does not go out over the air, verified by QSOs. Reducing the mic gain reduces the leakage, but does not eliminate it (also as seen on the scope). More of an annoyance than anything, but it would be nice to get rid of it, because it is in the "sweet spot" for listening.

Any ideas?

Thanks,
WS4JM
Jay

Joe Puma
 

I have a V3 and use the same mic amp and I have the same problem.  I too would like to get rid of the problem. When I crank the mic pot up it feedbacks with audio bleeding through. Its pretty depressing lol. 

Joe
Kd2nfc 





On Jun 3, 2019, at 8:37 PM, Jay - WS4JM <ws4jm@...> wrote:

I installed an SSM2167 pre-amp processor on my V3 uBitx. I am getting microphone audio into the speaker. It only appears from about 1/2 to 7/8 of the volume pot range. Verified with my scope. It does not go out over the air, verified by QSOs. Reducing the mic gain reduces the leakage, but does not eliminate it (also as seen on the scope). More of an annoyance than anything, but it would be nice to get rid of it, because it is in the "sweet spot" for listening.

Any ideas?

Thanks,
WS4JM
Jay

 

Hook up the SSM2167 board to TX 12V line. This way it will be off while receiving.

Raj

At 04-06-19, you wrote:
I installed an SSM2167 pre-amp processor on my V3 uBitx. I am getting microphone audio into the speaker. It only appears from about 1/2 to 7/8 of the volume pot range. Verified with my scope. It does not go out over the air, verified by QSOs. Reducing the mic gain reduces the leakage, but does not eliminate it (also as seen on the scope). More of an annoyance than anything, but it would be nice to get rid of it, because it is in the "sweet spot" for listening.

Any ideas?

Thanks,
WS4JM
Jay

Olivier Grand
 

Hello !
And Hook up the LM386 to RX 12V line. This way it will be off while transmitting.
Olivier.

Garanti sans virus. www.avast.com


Le mar. 4 juin 2019 à 06:32, Raj vu2zap <rajendrakumargg@...> a écrit :
Hook up the SSM2167 board to TX 12V line. This way it will be off while receiving.

Raj

At 04-06-19, you wrote:
>I installed an SSM2167 pre-amp processor on my V3 uBitx. I am getting microphone audio into the speaker. It only appears from about 1/2 to 7/8 of the volume pot range. Verified with my scope. It does not go out over the air, verified by QSOs. Reducing the mic gain reduces the leakage, but does not eliminate it (also as seen on the scope). More of an annoyance than anything, but it would be nice to get rid of it, because it is in the "sweet spot" for listening.
>
>Any ideas?
>
>Thanks,
>WS4JM
>Jay




John (vk2eta)
 

Or use the disable pin as per that post:
https://groups.io/g/BITX20/message/45897

73, John

Jay - WS4JM
 

First of all thank you all for your suggestions!

A little more information to clarify my issue. The microphone I am using has switched audio. The leakage occurs during transmission, similar to a monitor function, but the audio is distorted. I can reduce the gain to the point where this doesn't happen, but then the transmitted audio is inadequate.

I am planning on adding the N6DT pop fix. It switches the audio on and off during rx/tx maybe this will solve the problem. I'll post when this is complete. Any other ideas are welcome!


Thanks again to all who posted,
73 de WS4JM
Jay

Adrian Chadd
 

I'm sure someone else mentioned but - that could just be RF leaking
back into the amplifier output path or speaker.

If you hook it up to a dummy load do you get the same effect? That'll
help identify if it's RF from the whole antenna system making it back
or something in the rig.

Normally one solves this with a combo of shielded cabling for
low-level signals, short cabling for everything, inductors on power
rails and bypass capacitors to ground. Eg, if it's coming into the
audio amplifier via the 12v line you could try a 100uH inductor in
series with the 12v line to see if it helps. And/or a 0.1uF cap to
ground on the amplifier side of the power input. You could also try a
bypass cap on the audio input into the amplifier if you think it's
coming in there.

It could also be where you route your speaker wires. Is your speaker
hooked up with shielded cable? Maybe try a 100nF cap across your
speaker terminal to see if that bypasses RF. Eg, there's a fun issue
with the Kenwood TS-440 where if you route your speaker cable
(shielded!) a certain way across the IF board it picks up SSB signals
from said IF board. So you have to route the cable around those parts.
:-P

HTH,


-adrian

On Tue, 4 Jun 2019 at 07:51, Jay - WS4JM <ws4jm@...> wrote:

First of all thank you all for your suggestions!

A little more information to clarify my issue. The microphone I am using has switched audio. The leakage occurs during transmission, similar to a monitor function, but the audio is distorted. I can reduce the gain to the point where this doesn't happen, but then the transmitted audio is inadequate.

I am planning on adding the N6DT pop fix. It switches the audio on and off during rx/tx maybe this will solve the problem. I'll post when this is complete. Any other ideas are welcome!


Thanks again to all who posted,
73 de WS4JM
Jay

Evan Hand
 

I had a similar issue with 2 of my v4 ubitx.  Traced the problem to RF on the coax shield that I resolved with snap on ferrite chokes on the coax to the antenna.  The antenna is an off center fed dipole (OCFD) that is know to have RF issues without the isolating baluns or ferrite chokes.  I have not tried removing the ferrite chokes for the v5 ubitx, as it is working as is.  Should also note that both of the v4 radios had an added audio amp that could have been part of the feedback issue.  Signal reports prior to the choke addition where distorted audio on transmission as well.  Corrected after the chokes were installed.  That would suggest the the chokes are needed for the v5 as well.

Bought an assortment on Amazon: https://smile.amazon.com/s?k=snap+on+ferrite&crid=QJ38J9GEVF4G&sprefix=snap+on+ferrite%2Caps%2C156&ref=nb_sb_ss_i_2_15

The chokes solved the issue for me.  
73
Evan
AC9TU

Jay - WS4JM
 

I have found a work around, I had previously added a relay to key an external amplifier. I used one of the original relays that I replaced with the Axicom relay. I put the audio line on the unused half of the relay's NC contact and switched out the audio. Success!

Next step is to add a bypass switch to restore the CW side tone.

Thanks to all who offered suggestions

WS4JM
Jay