---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Thu 08/26/04: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:07 AM - Re: Antenna placement. (LessDragProd@aol.com) 2. 05:28 AM - RADIO SCREAM (Robert Riegner) 3. 06:01 AM - Re: RADIO SCREAM (Paul McAllister) 4. 07:10 AM - Re: RADIO SCREAM (Doug McNutt) 5. 09:13 AM - Re: RADIO SCREAM (David Lloyd) 6. 10:41 AM - Re: RADIO SCREAM (John Rippengal) 7. 11:11 AM - Re: RADIO SCREAM (Robert Riegner) 8. 11:13 AM - Re: RADIO SCREAM (Robert Riegner) 9. 04:22 PM - Re: RADIO SCREAM (David Lloyd) ________________________________ Message 1 _____________________________________ Time: 05:07:36 AM PST US From: LessDragProd@aol.com Subject: Re: Avionics-List: Antenna placement. --> Avionics-List message posted by: LessDragProd@aol.com Simple. It's designed to work as part of the total aircraft airframe. I'm not the expert. Talk to Bob Archer. Bob knows antennas on aircraft from empirical data he helped obtain as an antenna designer at TRW. Or ask Lectric Bob about Bob Archer. He knows Bob Archer. Jim Ayers Less drag Products, Inc. In a message dated 08/25/2004 11:32:53 PM Pacific Daylight Time, Ron@Koyich.com writes: Wow! Big claim. A pair of balanced blades works pretty well - JUST to be argumentative, how is the Archer antenna better, Jim? Ron ________________________________ Message 2 _____________________________________ Time: 05:28:38 AM PST US From: "Robert Riegner" Subject: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "Robert Riegner" 1980 172N SKYHAWK II....2-TKM Slide-in replacements were installed a couple of years ago[Which by the way have worked flawless till now] The last 6 months or so i have been getting tremendous squealing or feedback when Ptt is pushed. Radios have been switched top for bottom with no change. headsets have been changed, different PTT's have been used. Radios were sent back to factory and nothing found.Radios receive loud and clear.Cleaned all radio contacts and antenna contacts, reinstalled everything and checked on the ground with handheld[engine not running],everything sounded fine.Started plane,taxied,took off, and radios were unusable again. Transponder light lites[sometimes] and vor needles move when PTT is pushed.Problem is only with transmittion and when PTT is pushed, static and squeal are so bad it's hard to stand on the headset. If i remember correctly, radio volume control does nothing to increase or decrease noise.It's like the Bremuda Triangle in there!!! BOB RIEGNER N60846 1980 172N SKYHAWKII RADIO SQUEAL ________________________________ Message 3 _____________________________________ Time: 06:01:24 AM PST US From: "Paul McAllister" Subject: Re: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "Paul McAllister" Hi Bob, Did you happen to change headsets recently? I had the same problem and it turned out to be RF breaking into my headsets and causing audio feedback when I transmitted. Paul ________________________________ Message 4 _____________________________________ Time: 07:10:19 AM PST US From: Doug McNutt Subject: Re: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: Doug McNutt At 08:25 -0400 8/26/04, Robert Riegner wrote: >The last 6 months or so i have been getting tremendous squealing or feedback when Ptt >is pushed. It might not be feedback. Check for variation in tone with engine speed or landing lights. A bad diode in an alternator can be confused with feedback oscillation. -- --> Halloween == Oct 31 == Dec 25 == Christmas <-- ________________________________ Message 5 _____________________________________ Time: 09:13:22 AM PST US From: "David Lloyd" Subject: Re: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "David Lloyd" Bob, Was anything done or changed in your audio panel unit? Most audio boxes do a lot of isolation of one comm. from the other when TX'ing. If this isolation fails then comm. RF energy can leak to the other comm. and cause the headset scream that you mention. If you turn one radio off, do you still get the noise in the headset when the PTT is pressed? You may have a common ground for the panel bus or other that has a loose connection or a broken wire causing a ground loop that is active during TX'ing because of the higher current going to the comm. unit. If anything in your antenna coax, connectors, antenna is not right, grounds, feeds, etc., the TX'ing comm. will radiate RF that could blast into the 2nd comm. Let us all know what you find.....? David ----- Original Message ----- From: "Robert Riegner" Subject: Avionics-List: RADIO SCREAM > --> Avionics-List message posted by: "Robert Riegner" > > 1980 172N SKYHAWK II....2-TKM Slide-in replacements were installed a couple > of years ago[Which by the way have worked flawless till now] The last 6 > months or so i have been getting tremendous squealing or feedback when Ptt > is pushed. Radios have been switched top for bottom with no change. headsets > have been changed, different PTT's have been used. Radios were sent back to > factory and nothing found.Radios receive loud and clear.Cleaned all radio > contacts and antenna contacts, reinstalled everything and checked on the > ground with handheld[engine not running],everything sounded fine.Started > plane,taxied,took off, and radios were unusable again. Transponder light > lites[sometimes] and vor needles move when PTT is pushed.Problem is only > with transmittion and when PTT is pushed, static and squeal are so bad it's > hard to stand on the headset. If i remember correctly, radio volume control > does nothing to increase or decrease noise.It's like the Bremuda Triangle in > there!!! > > BOB RIEGNER > N60846 > 1980 172N SKYHAWKII > RADIO SQUEAL > > ________________________________ Message 6 _____________________________________ Time: 10:41:04 AM PST US From: "John Rippengal" Subject: RE: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "John Rippengal" Sounds very much as though there is a lot of RF leaking into the cabin causing feedback through your audio/intercom/headset. Check the coax connection to the antenna particularly the outer sheathing for good solid non-corroded connections both ends right through to the radios. Could seem ok until the vibration of engine running causes poor connection. John --> Avionics-List message posted by: "Robert Riegner" 1980 172N SKYHAWK II....2-TKM Slide-in replacements were installed a couple of years ago[Which by the way have worked flawless till now] The last 6 months or so i have been getting tremendous squealing or feedback when Ptt is pushed. Radios have been switched top for bottom with no change. headsets have been changed, different PTT's have been used. Radios were sent back to factory and nothing found.Radios receive loud and clear.Cleaned all radio contacts and antenna contacts, reinstalled everything and checked on the ground with handheld[engine not running],everything sounded fine.Started plane,taxied,took off, and radios were unusable again. Transponder light lites[sometimes] and vor needles move when PTT is pushed.Problem is only with transmittion and when PTT is pushed, static and squeal are so bad it's hard to stand on the headset. If i remember correctly, radio volume control does nothing to increase or decrease noise.It's like the Bremuda Triangle in there!!! BOB RIEGNER N60846 1980 172N SKYHAWKII RADIO SQUEAL ________________________________ Message 7 _____________________________________ Time: 11:11:07 AM PST US From: "Robert Riegner" Subject: Re: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "Robert Riegner" Thanks for all the great ideas guys. David, The stock[cessna] audio panel was replaced by an avionics tech.[ KMA24] The radios worked fine when the replace was done. The radio still squeals when the second radio is turned off and PTT pushed. Bob >From: "David Lloyd" >Reply-To: avionics-list@matronics.com >To: >Subject: Re: Avionics-List: RADIO SCREAM >Date: Thu, 26 Aug 2004 09:10:12 -0700 > >--> Avionics-List message posted by: "David Lloyd" > >Bob, >Was anything done or changed in your audio panel unit? Most audio boxes do >a lot of isolation of one comm. from the other when TX'ing. If this >isolation fails then comm. RF energy can leak to the other comm. and cause >the headset scream that you mention. If you turn one radio off, do you >still get the noise in the headset when the PTT is pressed? > >You may have a common ground for the panel bus or other that has a loose >connection or a broken wire causing a ground loop that is active during >TX'ing because of the higher current going to the comm. unit. > >If anything in your antenna coax, connectors, antenna is not right, >grounds, >feeds, etc., the TX'ing comm. will radiate RF that could blast into the 2nd >comm. > >Let us all know what you find.....? >David > > >----- Original Message ----- >From: "Robert Riegner" >To: >Subject: Avionics-List: RADIO SCREAM > > > > --> Avionics-List message posted by: "Robert Riegner" > > > > 1980 172N SKYHAWK II....2-TKM Slide-in replacements were installed a >couple > > of years ago[Which by the way have worked flawless till now] The last 6 > > months or so i have been getting tremendous squealing or feedback when >Ptt > > is pushed. Radios have been switched top for bottom with no change. >headsets > > have been changed, different PTT's have been used. Radios were sent back >to > > factory and nothing found.Radios receive loud and clear.Cleaned all >radio > > contacts and antenna contacts, reinstalled everything and checked on the > > ground with handheld[engine not running],everything sounded fine.Started > > plane,taxied,took off, and radios were unusable again. Transponder light > > lites[sometimes] and vor needles move when PTT is pushed.Problem is only > > with transmittion and when PTT is pushed, static and squeal are so bad >it's > > hard to stand on the headset. If i remember correctly, radio volume >control > > does nothing to increase or decrease noise.It's like the Bremuda >Triangle >in > > there!!! > > > > BOB RIEGNER > > N60846 > > 1980 172N SKYHAWKII > > RADIO SQUEAL > > > > > > ________________________________ Message 8 _____________________________________ Time: 11:13:42 AM PST US From: "Robert Riegner" Subject: Re: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "Robert Riegner" HI PAUL, HAVE USED 4 DIFFERENT AND ALL ARE THE SAME. BOB >From: "Paul McAllister" >Reply-To: avionics-list@matronics.com >To: >Subject: Re: Avionics-List: RADIO SCREAM >Date: Thu, 26 Aug 2004 07:58:32 -0500 > >--> Avionics-List message posted by: "Paul McAllister" > > >Hi Bob, > >Did you happen to change headsets recently? I had the same problem and it >turned out to be RF breaking into my headsets and causing audio feedback >when I transmitted. > >Paul > > ________________________________ Message 9 _____________________________________ Time: 04:22:49 PM PST US From: "David Lloyd" Subject: Re: Avionics-List: RADIO SCREAM --> Avionics-List message posted by: "David Lloyd" Bob, Do both radios squeal the same when turned on one at a time? If they do then you can probably rule out an antenna or coax feed problem. Any chance that you have a cabin speaker over head that is active when it should only be supplying audio to the headphones. I once found feedback from the speaker going back via the mike and setting up a feedback squeal...but, that is rare. And, I think you said that they check out fine as long as the engine is not running. Then, it has to be in the charging or magneto system. Maybe a noise filter failed... Let us know.... David ----- Original Message ----- From: "Robert Riegner" Subject: Re: Avionics-List: RADIO SCREAM > --> Avionics-List message posted by: "Robert Riegner" > > Thanks for all the great ideas guys. > David, > The stock[cessna] audio panel was replaced by an avionics tech.[ > KMA24] The radios worked fine when the replace was done. The radio still > squeals when the second radio is turned off and PTT pushed. > Bob > > > >From: "David Lloyd" > >Reply-To: avionics-list@matronics.com > >To: > >Subject: Re: Avionics-List: RADIO SCREAM > >Date: Thu, 26 Aug 2004 09:10:12 -0700 > > > >--> Avionics-List message posted by: "David Lloyd" > > > >Bob, > >Was anything done or changed in your audio panel unit? Most audio boxes do > >a lot of isolation of one comm. from the other when TX'ing. If this > >isolation fails then comm. RF energy can leak to the other comm. and cause > >the headset scream that you mention. If you turn one radio off, do you > >still get the noise in the headset when the PTT is pressed? > > > >You may have a common ground for the panel bus or other that has a loose > >connection or a broken wire causing a ground loop that is active during > >TX'ing because of the higher current going to the comm. unit. > > > >If anything in your antenna coax, connectors, antenna is not right, > >grounds, > >feeds, etc., the TX'ing comm. will radiate RF that could blast into the 2nd > >comm. > > > >Let us all know what you find.....? > >David > > > > > >----- Original Message ----- > >From: "Robert Riegner" > >To: > >Subject: Avionics-List: RADIO SCREAM > > > > > > > --> Avionics-List message posted by: "Robert Riegner" > > > > > > 1980 172N SKYHAWK II....2-TKM Slide-in replacements were installed a > >couple > > > of years ago[Which by the way have worked flawless till now] The last 6 > > > months or so i have been getting tremendous squealing or feedback when > >Ptt > > > is pushed. Radios have been switched top for bottom with no change. > >headsets > > > have been changed, different PTT's have been used. Radios were sent back > >to > > > factory and nothing found.Radios receive loud and clear.Cleaned all > >radio > > > contacts and antenna contacts, reinstalled everything and checked on the > > > ground with handheld[engine not running],everything sounded fine.Started > > > plane,taxied,took off, and radios were unusable again. Transponder light > > > lites[sometimes] and vor needles move when PTT is pushed.Problem is only > > > with transmittion and when PTT is pushed, static and squeal are so bad > >it's > > > hard to stand on the headset. If i remember correctly, radio volume > >control > > > does nothing to increase or decrease noise.It's like the Bremuda > >Triangle > >in > > > there!!! > > > > > > BOB RIEGNER > > > N60846 > > > 1980 172N SKYHAWKII > > > RADIO SQUEAL > > > > > > > > > > > >