Humming noise through speaker

[n2teb]

Hi all - I have a remoterig setup using an Icom 706 MKIIG.  On the control side, I have a small speaker plugged into the 706 faceplate in the Phones jack.  If I have the volume all the way down on the Icom, I hear a humming noise through the speaker.  I've tried to use headphones instead and I hear the humming through there as well.

Any suggestions?  Is there a setting or something that may help resolve this?

Thanks!

[Jan (Microbit)]

Do you have USB connected? If so there is an issue which can cause "humming".

[dj4mz]

Hi,

do you also hear the humming when you plug the speaker in the jack of the RRC? Thats what I do, so I can use Speaker and Headphone in parallel.

In case that the FW makes any differences: I'm still on a very old FW release.

vy 73,
Simon, DJ4MZ

[n2teb]

Thanks for the replies.  I do not have any USB connections to the remoterig.  I tried connecting the speaker to the SP port on the remoterig box and got the same humming noise.  I believe I have the latest firmware (2.42). 

Any other thoughts?  The humming isn't overbearing, but can definitely be heard.

Thanks!

[pd0swl]

Hi Dave,

Try reducing the codec gain, in the radio settings menu on the control-head RRC.
This may be at the expense of some audio volume so find the best compromise.
Mine is on 240.

73
Paul
PD0PSB

[pd0swl]

Codec *out* gain, that is...

73
Paul
PD0PSB

[n2teb]

Hi Paul - I lowered the codec out gain and that solved the problem!!  After several values, I ended up with 220 to pretty much eliminate the humming noise.  I still have more than adequate output volume (even though the manual says to keep it at 255).

Thank you!!

[pd0swl]

Hi Dave,

Good to hear.

Noise can be introduced anywhere in the chain, I suspect groundloop at the tranceiver end can be a cause. (also have the 706 in use)

What you basically do is reducing the final codec/DA output the the audio amplifier, lowering the final audio noisefloor.

Another solution would be to change the audio "strapping" wire with a small resistor.

The audio amp of the RRC itself is very silent.

73
Paul
PD0PSB

[sm2o]

Hi

I agree with pd0psb I think you have a ground problem at the transceiver end, There should not be any hum if everything is done correct, Try using the same powers supply for both RRC and Radio if you do not today.

73 de mike

[n2teb]

Hi Paul/Mike,

I do currently power the Icom 706 and Remoterig from the same power supply.  I'm guessing that a ground wire was not hooked up to the back of the radio to ground (I didn't hook up the radio at the remote site myself).  Could that be causing the problem? 

Thanks, Dave

[pd0swl]

Hi Dave,

It might be also a groundloop. Hooking different gear together with several ground schemes often causes groundloops, these are more difficult to avoid.

I wasn't able to "silence" my 706 setup completely, so I opted for the Codec gain reduction.

73
Paul
PD0PSB