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Need help with weak signal on passenger side

A

Apexeon

Member
Need help with weak audio on passenger side (Problem Solved)

I have a KX-125 nav/com and a PS intercom in my -6. Everything sounds fine on the pilot side. Radio transmission/reception and intercom are both loud and clear. However, on the passenger side the intercom transmission/reception is fine but the radio reception is about 30% as loud as on the pilot side. I can't understand why there would be reduction in the output on the radio but not on the intercom. Would appreciate any ideas on where to start.
 
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Volume issue

Start, check the headphone volume control....just sayin...

Also, need more details of your system. Isolated ground on headphone jack?

John
 
Apexeon said:
I have a KX-125 nav/com and a PS intercom in my -6. Everything sounds fine on the pilot side. Radio transmission/reception and intercom are both loud and clear. However, on the passenger side the intercom transmission/reception is fine but the radio reception is about 30% as loud as on the pilot side. I can't understand why there would be reduction in the output on the radio but not on the intercom. Would appreciate any ideas on where to start.
Click to expand...

Interested in any replies, I have the same combination of devices...and the same problem.
 
Flyingleap said:
Start, check the headphone volume control....just sayin...

Also, need more details of your system. Isolated ground on headphone jack?

John
Click to expand...
John I tested by tuning the ATIS and switching the headphone from pilot jack to passenger jack. I have also had passengers who could hear intercom fine but could hardly hear radio reception. Both the phone jacks are ground isolated from the aircraft frame.

Don
 
Volume problem?

Don,
Pin 2 of the Kx125 is your audio out with pin 6 being the comm audio lo. This might be the problem if wired wrong. Aircraft ground (AC) is pins 4,5.
Also, disconnect the headphone jack and plug in the headphone to see if the audio changes volume. These are just troubleshooting tests, but lets see.
I have a manual on the KX125, but don't know the audio panel/amp you are using.
John
 
Sam Buchanan said:
Interested in any replies, I have the same combination of devices...and the same problem.
Click to expand...

I have a *different* combination and the same problem reported by passengers (I have a GMA340), but frankly, I've never been able to replicate it through any combination of switching headphones and such while on the ground.

I suspect that's it's the combination of too many variables that sometimes results in a set of bad settings...there is headphone volume (Bose A20s or Bose Xs), comm radio volume, and intercom volume.
 
Here's one possible check!

I did find in the manual of the KX125 regarding a loss in audio and the microphone on the passengers side. So, unplug mike on passenger side
and see if audio comes back to that side. Yes, this sounds odd...
There are so many notes on this install.....

John
 
Flyingleap said:
I did find in the manual of the KX125 regarding a loss in audio and the microphone on the passengers side. So, unplug mike on passenger side
and see if audio comes back to that side. Yes, this sounds odd...
There are so many notes on this install.....

John
Click to expand...

Thanks John, I will give that a try next time I get out to the airport.

Don
 
If you swap headsets does the problem follow?
Does the problem remain with the intercom power switched off? On my PS intercom turning the LH knob fully CCW the intercom is switched off and the connection is direct between the radio output and headset.
My thinking is that the headset impedance may be different between the headsets which will affect the relative audio level if the radio's output impedance is high. Also, check both headsets are set to Mono (or Stereo if that is how it should be).
 
Doug said:
If you swap headsets does the problem follow?
Does the problem remain with the intercom power switched off? On my PS intercom turning the LH knob fully CCW the intercom is switched off and the connection is direct between the radio output and headset.
My thinking is that the headset impedance may be different between the headsets which will affect the relative audio level if the radio's output impedance is high. Also, check both headsets are set to Mono (or Stereo if that is how it should be).
Click to expand...

In my case none of those suggestions are factors. The passenger's relative volume is lower than the pilot's regardless of headset used and volume settings on the intercom or radio. That side just doesn't have as much intercom gain for some reason.

I work around it by turning radio volume up and my (pilot) headset volume down. Been this way for years, just never taken the time to figure out why. I've always assumed it is an intercom amp issue.
 
Sam Buchanan said:
In my case none of those suggestions are factors. The passenger's relative volume is lower than the pilot's regardless of headset used and volume settings on the intercom or radio. That side just doesn't have as much intercom gain for some reason.

I work around it by turning radio volume up and my (pilot) headset volume down. Been this way for years, just never taken the time to figure out why. I've always assumed it is an intercom amp issue.
Click to expand...

My intercom volume on the passenger side is fine. It is the output from the radio that is weak on the passenger side. I haven't had a chance to try some of the suggestions that have been posted. I have been working around like you have. Turning up the radio volume to about 75% and turning down my headset.
 
Sam Buchanan said:
In my case none of those suggestions are factors. The passenger's relative volume is lower than the pilot's regardless of headset used and volume settings on the intercom or radio. That side just doesn't have as much intercom gain for some reason.

I work around it by turning radio volume up and my (pilot) headset volume down. Been this way for years, just never taken the time to figure out why. I've always assumed it is an intercom amp issue.
Click to expand...

Apexeon said:
My intercom volume on the passenger side is fine. It is the output from the radio that is weak on the passenger side. I haven't had a chance to try some of the suggestions that have been posted. I have been working around like you have. Turning up the radio volume to about 75% and turning down my headset.
Click to expand...

I probably didn't state that very clearly.

Pilot-to-passenger volume is fine, the radio audio coming through the intercom is weaker on the passenger side.
 
Sam Buchanan said:
I probably didn't state that very clearly.

Pilot-to-passenger volume is fine, the radio audio coming through the intercom is weaker on the passenger side.
Click to expand...

Exactly. I'm going to print out the suggestions and go out to the airport at lunch and see if I can troubleshoot some more. I'll let you know what I find.
dt
 
Audio Low...

Just reread the notes on the KX125:

**They (King) talk about low or distorted audio but don't reference the headphone when talking about low audio. I wonder if they mean the Mic is distorted or is low in volume. Hmmm Also required is a relay for two microphones so one is hot at a time.

**They (King) also say to use the 100mw audio to drive external headphones at P501-12. This may be the answer to the low audio. It was buried in the notes section and could have been overlooked at install time. Hard to believe the same thing happened in multiple cases.

Sorry, I think there is more to this story. The design is "different" than most KX155,165,170B older stuff. I believe the KX125 was designed after Gary and Min left from engineering to start a new company...... Garmin.
John
 
Flyingleap said:
Just reread the notes on the KX125:

**They (King) talk about low or distorted audio but don't reference the headphone when talking about low audio. I wonder if they mean the Mic is distorted or is low in volume. Hmmm Also required is a relay for two microphones so one is hot at a time.

**They (King) also say to use the 100mw audio to drive external headphones at P501-12. This may be the answer to the low audio. It was buried in the notes section and could have been overlooked at install time. Hard to believe the same thing happened in multiple cases.

Sorry, I think there is more to this story. The design is "different" than most KX155,165,170B older stuff. I believe the KX125 was designed after Gary and Min left from engineering to start a new company...... Garmin.
John
Click to expand...

I think there is a relay for the mic as the PPT button controls each mic independently.

Unplugging the mic had no effect on the volume. I also discovered that the pilot side audio from the radio does not go through the intercom. My intercom is turned on and off by pushing the volume pot. When the intercom is off there is no radio output to the passenger side. How would I check to see if it is using the 100mw output? For now I can just do like Sam and work around it.
 
Kx125

Don,
That was the copilot side mike you disconnected, right? And, I like the method that Sam is using, except be careful, when you plugin a new headphone on the pilots side it could get very loud. Not much of a problem though.

It looks like the audio is the 100mw for the pilot and they did put in the relays to isolate the mics. OK, here is what The KX125 says:

"The Mic audio must be switched from P100-H, Mic audio Hi to P501-16, Mic intercom Hi and P100-8 Mic key must be open to prevent com transmission"

P100-H = output mic audio Hi
P501-16 = Mic intercom Hi
P100-8 = Mic key

I "believe" the audio PS eng is not needed with the intent of the KX125
to solve that task. Not much of a solution now as the wiring is done.

The drawing does not show any type of audio panel/amp as an example.

The intent of the main drawing is to put in the relays to isolate mics, 100mw. output to both headphones, volume from KX125, done.

My work here is done, it's not fixed.
John
 
Flyingleap said:
Don,
That was the copilot side mike you disconnected, right? And, I like the method that Sam is using, except be careful, when you plugin a new headphone on the pilots side it could get very loud. Not much of a problem though.

It looks like the audio is the 100mw for the pilot and they did put in the relays to isolate the mics. OK, here is what The KX125 says:

"The Mic audio must be switched from P100-H, Mic audio Hi to P501-16, Mic intercom Hi and P100-8 Mic key must be open to prevent com transmission"

P100-H = output mic audio Hi
P501-16 = Mic intercom Hi
P100-8 = Mic key

I "believe" the audio PS eng is not needed with the intent of the KX125
to solve that task. Not much of a solution now as the wiring is done.

The drawing does not show any type of audio panel/amp as an example.

The intent of the main drawing is to put in the relays to isolate mics, 100mw. output to both headphones, volume from KX125, done.

My work here is done, it's not fixed.
John
Click to expand...

John,

Thank you so much for attempting to help. I realize you spent a lot of time on this and I really appreciate your efforts.

I'm going to print out all the information and will do some more digging as time allows.

Thanks Again!!!
Don Thompson
 
Update: Problem solved!!! :)

After lots of troubleshooting, I decided that the problem was most likely in the PS PM501 intercom. I called PS and talked with Greg who confirmed my thoughts. The 501 is an older unit and after weighing the cost to repair vs purchasing new, I ordered a PS 500EX intercom from Spruce. It is a direct plug and play replacement and my testing on the ground indicates that the old 501 was bad. The wife and I will test it out tomorrow on a flight to N. AL. (KANB):)
 
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