Radio question

mark treidel

Senior Member
Joined
Nov 7, 2005
Messages
1,471
Location
Beautiful Mile High Denver, Colorado
Aircraft
AR-1
Total Flight Time
3000 +
for all you electronics gurus....What causes an echo when transmitting? Sounds sorta' like a feedback loop in a hollow chamber. I recently changed out the radio (same make/model).
Never had the issue until the new one was put in. Nothing else changed.
Does adjustable microphone gain have anything to do with it (possibly set too high). I use the MGL V6 unit with built in intercom (although that was not in use).
Thanks for any imput...
 
Mark, the MGL radio uses a digital modulation scheme, which could introduce a slight delay in your outgoing audio, just a few milliseconds. Normally, if there's some pickup of the RF on your wiring which feeds transmitted signal back into the input, it would just sound like distortion. In this situation, the delay would make it sound like an echo.

It may also be that it's simply a case of two sidetone functions being on at the same time, one with delay, the other without. If you have an external intercom which provides sidetone (the ability to monitor your own mic through the earpieces while transmitting), try disabling sidetone on the MGL radio. It's detailed in the menu instructions.
 
Mike Gain and/or Headset Volume could also do it.
If the Microphone can hear the Headphones you will get an echo/delayed feedback.

If you are not using a Headset.
Do not use Sidetone with a Hand Microphone and Cockpit Speaker configuration. Echo almost guaranteed!
 
Mark - Would you lets us know how you end up fixing? Always interested in learning how to fix these isssue. Thanks!
 
I am using the Flycom helmets w/the MGL V6. Originally, the V6 was shipped to me with 'updated' software' but had NO dual volume control as indicated in its manual. I sent it back to the factory
and they updated (actually reverted) to a previous version of firmware. After reinstalling the radio, the first time I called the tower, they could not make out my transmission and reported a loud 'echo/squeal'. I turned down the mic output (gain) but the issue still persisted. After speaking with Matt @ MGL, they are sending me another 'reprogrammed' unit to try. Radio shop also suggested
a secondary ground strap from the outer box of the radio to the back of the panel which I did not do yet. They said a dual ground (one through the harness & one on the body) would not hurt anything.
Also made sure there was a positive proper connection twix the BNC connection on the antenna cable at both ends.
It sound as if it is a RF issue coupled with setting proper gain of the mic. I tried lowering the gain on the mic, worked somewhat but lost the sidetone altogether. Sidetone is set to ON via default. I will try it w/o sidetone but I don' t want to lose that. It's a valuable feature and I don't want compromise.
I'm no radio engineer...I'm just a 'plug & play' kinda man but when you pay good $$ for a unit like this, you expect it to do just that! I will keep you guys posted as to the outcome of reinstalling
the replacement unit & see if there is a difference. Chasing these fleeting bugs is a real lesson in futility. More to come.....
 
Don't think it just happens to you Mark,I recently bought a flightline 760A radio the wiring diagram in the manuel was for the 760.big difference it took me a lot of frustration to discover that error.
 
mark treidel;n1123030 said:
I am using the Flycom helmets w/the MGL V6. Originally, the V6 was shipped to me with 'updated' software' but had NO dual volume control as indicated in its manual. I sent it back to the factory
and they updated (actually reverted) to a previous version of firmware. After reinstalling the radio, the first time I called the tower, they could not make out my transmission and reported a loud 'echo/squeal'. I turned down the mic output (gain) but the issue still persisted. After speaking with Matt @ MGL, they are sending me another 'reprogrammed' unit to try. Radio shop also suggested
a secondary ground strap from the outer box of the radio to the back of the panel which I did not do yet. They said a dual ground (one through the harness & one on the body) would not hurt anything.
Also made sure there was a positive proper connection twix the BNC connection on the antenna cable at both ends.
It sound as if it is a RF issue coupled with setting proper gain of the mic. I tried lowering the gain on the mic, worked somewhat but lost the sidetone altogether. Sidetone is set to ON via default. I will try it w/o sidetone but I don' t want to lose that. It's a valuable feature and I don't want compromise.
I'm no radio engineer...I'm just a 'plug & play' kinda man but when you pay good $$ for a unit like this, you expect it to do just that! I will keep you guys posted as to the outcome of reinstalling
the replacement unit & see if there is a difference. Chasing these fleeting bugs is a real lesson in futility. More to come.....

Do NOT do the ground strap on the box. It does absolutely nothing.
Keep the volume on the Flycom helmet to be around 50 to 60 percent. No more. Keep the Mic gain in V6 menu to be 3.0 or 4.5 and use the intercom volume and radio volume (separate) to adjust what you hear. Intercom volume only effects intercom and sidetone.
If you do not have separate intercom volume and have just one volume that also works. In that case, set Mic gain to be 6.0 to 7.5 and raise the Flycom helmet volume to 75%
 
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Abid,
The issue is not in reception. That is fine.
The problem is in transmission. A higher setting of the mic gain as you suggest resulted in inaudible reception by the tower.
They reported a loud squeal/hollow echo at a mic gain setting of +1.5. After turning it down to -3.0, it subsided a bit but was
still prevalent though 'readable'. At that point, I all but lost sidetone. The problem started when the radio was 'reprogrammed' by MGL. It worked fine in both reception/transmitting before the software change. I had them do that because it came w/o the dual volume control initially. They are sending me a different unit and I will report when it is installed/tested within the next week.
 
Mark what is the dual volume control you are referring to,is it pilot/copilot,or radio/ intercom.just curious!


best regards,
 
Eddie,
The MGL V6 has both an aviation radio & (up to) 4 headset intercom built into the same compact unit.
The initial software had an issue with volume so the factory made it dual volume control...
Now, the pilot can control 'tower' volume and intercom volume separately with the same volume button.
Pressing the button once changes it from radio volume to intercom volume and back again. One can also control mic gain as well. This basically
eliminated the need to use in line volume control headsets although my Flycom helmets have an adjustable volume control.
Google MGL V6.
 
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I see. I'll talk to Matt. Looks like they screwed up something updating the firmware or sent you a different radio with a hardware issue
 
Perhaps your microphone cable is picking up RF from the antenna; this would be rectified and show up as audio superimposed on your speech but with a time delay.

Make sure the shielding braid on the mic cable is properly grounded at both the plug and socket where it goes into the radio.

Try repositioning the antenna to reduce the exposure to the mic cable.
*****************
If the antenna is a ¼ wave whip, it needs some sort of ground plane; in most cases, the airframe serves as a satisfactory ground plane. In any case, the shielding braid of the antenna cable must be adequately grounded to the ground plane at the antenna.

If not, the antenna cable will radiate RF energy along its length and this could be a source of feedback.
 
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Thanks Chuck, everything you suggest above was already addressed or n/a.
Today I installed my newly reprogrammed radio from MGL and still had some squeal issues but quickly eliminated them by going negative on the mic gain adjustment.
Tower says crystal clear now but had to really crank up the intercom volume almost to maximum just to hear the passenger clearly. Volume adjustments and vox are now
set to acceptable levels and I have full dual volume control.
Apparently, the radio that was replaced was actually bad....so, now I'm happy and can fly unfettered.
Thanks everybody, for all the input.
 
mark treidel;n1123210 said:
Thanks Chuck, everything you suggest above was already addressed or n/a.
Today I installed my newly reprogrammed radio from MGL and still had some squeal issues but quickly eliminated them by going negative on the mic gain adjustment.
Tower says crystal clear now but had to really crank up the intercom volume almost to maximum just to hear the passenger clearly. Volume adjustments and vox are now
set to acceptable levels and I have full dual volume control.
Apparently, the radio that was replaced was actually bad....so, now I'm happy and can fly unfettered.
Thanks everybody, for all the input.

Mark:
The VOX setting with Flycom helmets should be OFF. Do not use VOX, VOGAD LOW, VOGAD MEDIUM .... they should all be set to off with Flycom. They are for GA headsets that have different impedance and circuitry. Flycom has proprietary circuits, it does not work well with VOX and VOX hardly provides any advantage with it.

Flycom Standard Helmets into MGL V6 Radio

First menu

VOX – it is essential that this is in the OFF position
P1 – setting + 0.0 dB (may have to change a little)
PAX1 – setting + 0.0 dB (may have to change a little)
Mic Filter Bandpass – must be in the OFF position


Secondary Menu (Set-Up)

TX Mic – HOT
TX Lock – OFF
P.scan – OFF
Ptt – SEPARATE
Flip Flop – FS
Mic Levels – 1
Aux – OFF
Aout – 1C+RX
Sidetone – ALL
CHS - 25khz

Set helmet volume knob to about 60 to 70%. Radio volume to about 14 to 18. Set intercom volume as needed.
 
Thanks Abid,
I've been using the settings you have (Greg gave them to me) but they changed since he is not using Flycom. Also, I just installed the radio MGL sent me (again) and flew on Sat.....turns out that
the radio they sent me as new was the same serial number I used the 2nd time and sent back because it died on me twice in flight. Guess they simply reprogrammed it for dual volume and
sent it out to me again w/o fixing the (dying) issue because it died on me again after about 1/2 hr in the air. Rather frightening because I was approaching a heavily filled traffic pattern and couldn't hear
the tower or other a/c. I ended up having to reboot the radio in flight and it came back on but only long enough to land. It stopped again while taxing. I'm not sure what I will do now. They have put me in jeopardy twice now and not
fixed the issues I originally had. I'm livid!! Although Matt has been gracious, sending me a new radio w/o having to send mine in first, it still has not been resolved. I now have to tear out the panel
yet another time to re-replace the radio that I was going to send back with the echo/squeal and play around with the settings some more. Perhaps that will help but I'm not too optimistic.
....To Be Continued....
 
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mark treidel;n1123275 said:
Thanks Abid,
I've been using the settings you have (Greg gave them to me) but they changed since he is not using Flycom. Also, I just installed the radio MGL sent me (again) and flew on Sat.....turns out that
the radio they sent me as new was the same serial number I used the 2nd time and sent back because it died on me twice in flight. Guess they simply reprogrammed it for dual volume and
sent it out to me again w/o fixing the (dying) issue because it died on me again after about 1/2 hr in the air. Rather frightening because I was approaching a heavily filled traffic pattern and couldn't hear
the tower or other a/c. I ended up having to reboot the radio in flight and it came back on but only long enough to land. It stopped again while taxing. I'm not sure what I will do now. They have put me in jeopardy twice now and not
fixed the issues I originally had. I'm livid!! Although Matt has been gracious, sending me a new radio w/o having to send mine in first, it still has not been resolved. I now have to tear out the panel
yet another time to re-replace the radio that I was going to send back with the echo/squeal and play around with the settings some more. Perhaps that will help but I'm not too optimistic.
....To Be Continued....

That's retarded. I am sorry. Let me deal with Matt on this and get you a new radio. I have e-mailed him and texted him. Let me get with him on Monday
 
Mark,

Check with Flycom since my new helmet is in for repair for bad mic. Maybe transmit issue is related to Flycom mic? Send them your serial number too?

Thanks,

Dave
 
Thanks Dave, but I tested w/both helmets and mic's are fine. The radio software is the issue. Spoke MGL today & a new, properly updated unit is in the mail....I'll post again when it is installed and tested in flight later this week.
 
OK,
today I installed the replacement radio and played with the suggested settings. Took her for a flight & tower reports '5 by 5' on transmitting reception.
The only thing left to do is take a passenger up to test the intercom in the air; but on the ground, it seems to be working now. The problem actually
was a defective radio which MGL graciously replaced w/o question. Kudos to Matt at MGL. & thanks to Abid for the suggested settings.
I will follow up about the intercom once I take a up a "JAFO" (for all you old guys who remember the show).
 
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