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  • Radio question

    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
    __________________

    Risk lurks in the edges of marginality.. ..There are penalties to be paid for pushing the envelope..
    The speed in which a woman says "nothing" when asked "What's wrong?" is inversely proportional to the severity of the storm that's coming.
    No tyrant, foreign or domestic, should be permitted to die a natural death.

  • #2
    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.
    Paul W. Plack
    Private ASEL, SP Gyroplane
    Secretary, URA & PRA2
    Editor, Western Rotorcraft

    Comment


    • #3
      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!

      Comment


      • #4
        Mark - Would you lets us know how you end up fixing? Always interested in learning how to fix these isssue. Thanks!

        Comment


        • #5
          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.....
          Mark
          __________________

          Risk lurks in the edges of marginality.. ..There are penalties to be paid for pushing the envelope..
          The speed in which a woman says "nothing" when asked "What's wrong?" is inversely proportional to the severity of the storm that's coming.
          No tyrant, foreign or domestic, should be permitted to die a natural death.

          Comment


          • #6
            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.

            Best Regards,
            Eddie Sigman,Polvadera,nm
            (575) 835-4921

            Comment


            • #7
              Originally posted by mark treidel View Post
              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%
              Last edited by fara; 08-09-2017, 08:03 PM.

              Comment


              • #8
                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
                __________________

                Risk lurks in the edges of marginality.. ..There are penalties to be paid for pushing the envelope..
                The speed in which a woman says "nothing" when asked "What's wrong?" is inversely proportional to the severity of the storm that's coming.
                No tyrant, foreign or domestic, should be permitted to die a natural death.

                Comment


                • #9
                  Mark what is the dual volume control you are referring to,is it pilot/copilot,or radio/ intercom.just curious!


                  best regards,
                  Best Regards,
                  Eddie Sigman,Polvadera,nm
                  (575) 835-4921

                  Comment


                  • #10
                    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.
                    Last edited by mark treidel; 08-10-2017, 01:29 PM.
                    Mark
                    __________________

                    Risk lurks in the edges of marginality.. ..There are penalties to be paid for pushing the envelope..
                    The speed in which a woman says "nothing" when asked "What's wrong?" is inversely proportional to the severity of the storm that's coming.
                    No tyrant, foreign or domestic, should be permitted to die a natural death.

                    Comment


                    • #11
                      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

                      Comment


                      • #12
                        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 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.
                        Last edited by C. Beaty; 08-11-2017, 05:38 AM.

                        Comment


                        • #13
                          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
                          __________________

                          Risk lurks in the edges of marginality.. ..There are penalties to be paid for pushing the envelope..
                          The speed in which a woman says "nothing" when asked "What's wrong?" is inversely proportional to the severity of the storm that's coming.
                          No tyrant, foreign or domestic, should be permitted to die a natural death.

                          Comment


                          • #14
                            Originally posted by mark treidel View Post
                            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.

                            Comment


                            • #15
                              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....
                              Last edited by mark treidel; 08-13-2017, 04:46 AM.
                              Mark
                              __________________

                              Risk lurks in the edges of marginality.. ..There are penalties to be paid for pushing the envelope..
                              The speed in which a woman says "nothing" when asked "What's wrong?" is inversely proportional to the severity of the storm that's coming.
                              No tyrant, foreign or domestic, should be permitted to die a natural death.

                              Comment

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