---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Thu 07/03/03: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:58 AM - Dual bus VM-1000 (Treff, Arthur) 2. 08:43 AM - Noise in the headset troubleshooting (long) (Treff, Arthur) 3. 09:47 AM - Transponder Technical Info (splevy@l-band-systems.com) 4. 09:56 AM - Re: Noise in the headset troubleshooting (long) (Kevin Waltz) 5. 10:33 AM - Re: Noise in the headset troubleshooting (long) (Matthew Mucker) 6. 05:47 PM - Re: Transponder Technical Info (Martini Luc J.R.) 7. 08:08 PM - Re: Transponder Technical Info (splevy@l-band-systems.com) ________________________________ Message 1 _____________________________________ Time: 07:58:26 AM PST US Subject: Avionics-List: Dual bus VM-1000 From: "Treff, Arthur" --> Avionics-List message posted by: "Treff, Arthur" Bob, Thanks for your research on my behalf. It was definately above and beyond the call of duty. You should be inducted into the EAA hall of fame. Not only did you go the extra mile and contact Vision Mirco, but you generated a schematic. None of the drawings for my plane look as good as yours. Anyway, thanks again for your tireless efforts. Art Treff RV-8 Fastback in progress ________________________________ Message 2 _____________________________________ Time: 08:43:11 AM PST US Subject: Avionics-List: Noise in the headset troubleshooting (long) From: "Treff, Arthur" --> Avionics-List message posted by: "Treff, Arthur" Listers, I wanted to share with you some recent events surrounding troubleshooting 'noisy radio' problems in my 1966 Mooney, just in case this ever happens to you. The electrical system is standard "store bought" with battery on the firewall, 60A PMA'd alternator with external Zeftronics VR with on board over voltage protection. The output of the alt goest thru the firewall to the bus bar. (NFG). Gage is battery ammeter and I monitor bus voltage via a feature on the Stormscope. Regulator has 800 hours on it, and the alternator is a rebuilt with approx 50 hours. The scenario: Over time, I have noticed two abberations in my plane, I have treated them as unrelated. Here's the setup. Every once in awhile in flight, particularly at high altitudes. I notice a slight noise in the headset that sounds like frying bacon. It is intermittent. I further notice that if I turn on a high load device like a landing light (250W) the noise goes away. So, historically, I have suspected that this has something to do with the VR, but I do nothing about it, as it's intermittent. Additionally, Every once in awhile ATC tells me my KX-155 is totally unreadable. I switch to the UPS GX60 and they say it's better, but not perfect. The King is as old as they get, and it usually has to go into the shop at least every other year, so I really do nothing about it. I'm thinking that perhaps it's getting too hot, so I usually turn it off, and xmit on the GPS comm. Why that's not as clear, I usually rationalize that it's an inferior radio, or antenna, or less power than the King's 10 watts. The scenario worsens. Last month, the 'frying bacon' noise worsened. It was louder in the headset, and loading up the alternator with Pitot heat and landing light lessened the volume but did not erradicate it. I fly legs of 3-5 hours so I have alot of time to listen and wonder. Shutting off the audio panel made the sound go away. Hmmm.....perhaps the PS Engineering unit is starting to go... or perhaps I got some Corrosion X into critical places in antenna wiring during my annual last month...I also had more calls from ATC asking me to switch to another radio than the King. So, I was thinking that the KX-155 needed to go into the shop as did the audio panel, this can't be the voltage regulator. (not so fast, silly boy). Total chaos. Last week, during climb out on a routine 190 mile trip, the noise in the headset was really bad, and my ability to hear radio xmissions was diminished. ATC did not like my radios at all. I was on an IFR plan, but it was VMC so I pressed on. I tried loading up the bus, to get rid of the noise, but this no longer helped. I shut off the audio panel and all this did was make the noise softer. Finally, my eyes alighted on the voltage monitor. It read 11.2 volts! The ammeter showed a slight discharge. No alternator. I pulled the 5A alt field CB and all quieted in the headset. Ah ha! Gotcha you little bugger. A bad somethingorother in the alt circuit. I pressed the field breaker back in and the alt came back on line, voltge came back up to 13.8, the battery was drawing a charge on the ammeter and the noise quieted down, but was not gone. Now is when I really started troubleshooting. Every time I pulled the field breaker, the noise totally died away. I happen to have a spare VR with me (I'm not so organized usually) and the connector is accessible from under the panel. I shut off everything except one radio, pulled the field breaker. I reached under, found the connector and plugged in the new regulator. I reset the field breaker, in eager anticipation of a nice fat charge, quite in the earphones and a charging battery. I was convinced that the problem was the VR. What happened surpriese me: the new regulator lighted the OV light, and popped off line! OK, so a bad alternator I thought, could it be intermittently shorts in the field, diodes, what? The solution. On the ramp, I pulled the side cowling and wiggled the alt terminal connections. The field ring terminal was tight on the post, but the whole post was loose! I wiggled the other post (goes to ground) and it too was loose as well. So much for "Gen-U-Wine FAA repair stations, yellow tags saying Return to Service and PMA's parts." This was a newly overhauled alternator, with approx 50 hours on it over 3 months. I took off the ring terms, tightened down the jam nuts on the terminal posts and reinstalled the field and ground ring terminals respectively. My sceptical self did not really thing that this could be the cause of the entire episode, but my return flight was the quietest I've had in a long time, no complaints from ATC re: the King radio's quality and best of all no frying bacon at all, not a trace. The lesson, FWIW. What started out as a radio annoyance turned out to be a mechanical problem on the alternator. The radio and audio noise, as it turns out, were the best troubleshooting tools at my disposal. Better that than total alternator failure in the goo at night. In the future, I will not take changes in headset noise lightly. It could be trying to tell me something. Art Treff RV-8 Fastback interior work. ________________________________ Message 3 _____________________________________ Time: 09:47:32 AM PST US From: splevy@l-band-systems.com Subject: Avionics-List: Transponder Technical Info --> Avionics-List message posted by: splevy@l-band-systems.com Listers, I am looking for technical information on the specifics of transponder operation, including mode C and mode S. I need the hard technical specifications, including the rf requirements and the data stream and encoding protocols. All I have been able to find are the generic boy-it's-amazing-how-does-it-work descriptions. Any information or leads to published specifications would be appreciated. Thanks. Stan RV7A (tail almost done) ________________________________ Message 4 _____________________________________ Time: 09:56:09 AM PST US Subject: RE: Avionics-List: Noise in the headset troubleshooting (long) From: "Kevin Waltz" --> Avionics-List message posted by: "Kevin Waltz" Excellent work. You story might save a life someday. Aviation Safety Magazine occasionally prints articles like this to inform people of situations just like yours. If you have the desire and energy to share this story, they might be willing to reprint. Again thanks, and I will keep your story in mind. Your story brings home the fact that small problems if left untended can become big problems. Regards, Kevin Waltz -----Original Message----- From: Treff, Arthur [mailto:Arthur.Treff@Smartm.com] Subject: Avionics-List: Noise in the headset troubleshooting (long) --> Avionics-List message posted by: "Treff, Arthur" --> Listers, I wanted to share with you some recent events surrounding troubleshooting 'noisy radio' problems in my 1966 Mooney, just in case this ever happens to you. The electrical system is standard "store bought" with battery on the firewall, 60A PMA'd alternator with external Zeftronics VR with on board over voltage protection. The output of the alt goest thru the firewall to the bus bar. (NFG). Gage is battery ammeter and I monitor bus voltage via a feature on the Stormscope. Regulator has 800 hours on it, and the alternator is a rebuilt with approx 50 hours. The scenario: Over time, I have noticed two abberations in my plane, I have treated them as unrelated. Here's the setup. Every once in awhile in flight, particularly at high altitudes. I notice a slight noise in the headset that sounds like frying bacon. It is intermittent. I further notice that if I turn on a high load device like a landing light (250W) the noise goes away. So, historically, I have suspected that this has something to do with the VR, but I do nothing about it, as it's intermittent. Additionally, Every once in awhile ATC tells me my KX-155 is totally unreadable. I switch to the UPS GX60 and they say it's better, but not perfect. The King is as old as they get, and it usually has to go into the shop at least every other year, so I really do nothing about it. I'm thinking that perhaps it's getting too hot, so I usually turn it off, and xmit on the GPS comm. Why that's not as clear, I usually rationalize that it's an inferior radio, or antenna, or less power than the King's 10 watts. The scenario worsens. Last month, the 'frying bacon' noise worsened. It was louder in the headset, and loading up the alternator with Pitot heat and landing light lessened the volume but did not erradicate it. I fly legs of 3-5 hours so I have alot of time to listen and wonder. Shutting off the audio panel made the sound go away. Hmmm.....perhaps the PS Engineering unit is starting to go... or perhaps I got some Corrosion X into critical places in antenna wiring during my annual last month...I also had more calls from ATC asking me to switch to another radio than the King. So, I was thinking that the KX-155 needed to go into the shop as did the audio panel, this can't be the voltage regulator. (not so fast, silly boy). Total chaos. Last week, during climb out on a routine 190 mile trip, the noise in the headset was really bad, and my ability to hear radio xmissions was diminished. ATC did not like my radios at all. I was on an IFR plan, but it was VMC so I pressed on. I tried loading up the bus, to get rid of the noise, but this no longer helped. I shut off the audio panel and all this did was make the noise softer. Finally, my eyes alighted on the voltage monitor. It read 11.2 volts! The ammeter showed a slight discharge. No alternator. I pulled the 5A alt field CB and all quieted in the headset. Ah ha! Gotcha you little bugger. A bad somethingorother in the alt circuit. I pressed the field breaker back in and the alt came back on line, voltge came back up to 13.8, the battery was drawing a charge on the ammeter and the noise quieted down, but was not gone. Now is when I really started troubleshooting. Every time I pulled the field breaker, the noise totally died away. I happen to have! a spare VR with me (I'm not so organized usually) and the connector is accessible from under the panel. I shut off everything except one radio, pulled the field breaker. I reached under, found the connector and plugged in the new regulator. I reset the field breaker, in eager anticipation of a nice fat charge, quite in the earphones and a charging battery. I was convinced that the problem was the VR. What happened surpriese me: the new regulator lighted the OV light, and popped off line! OK, so a bad alternator I thought, could it be intermittently shorts in the field, diodes, what? The solution. On the ramp, I pulled the side cowling and wiggled the alt terminal connections. The field ring terminal was tight on the post, but the whole post was loose! I wiggled the other post (goes to ground) and it too was loose as well. So much for "Gen-U-Wine FAA repair stations, yellow tags saying Return to Service and PMA's parts." This was a newly overhauled alternator, with approx 50 hours on it over 3 months. I took off the ring terms, tightened down the jam nuts on the terminal posts and reinstalled the field and ground ring terminals respectively. My sceptical self did not really thing that this could be the cause of the entire episode, but my return flight was the quietest I've had in a long time, no complaints from ATC re: the King radio's quality and best of all no frying bacon at all, not a trace. The lesson, FWIW. What started out as a radio annoyance turned out to be a mechanical problem on the alternator. The radio and audio noise, as it turns out, were the best troubleshooting tools at my disposal. Better that than total alternator failure in the goo at night. In the future, I will not take changes in headset noise lightly. It could be trying to tell me something. Art Treff RV-8 Fastback interior work. direct advertising on the Matronics Forums. ________________________________ Message 5 _____________________________________ Time: 10:33:42 AM PST US From: "Matthew Mucker" Subject: Re: Avionics-List: Noise in the headset troubleshooting (long) --> Avionics-List message posted by: "Matthew Mucker" Excellent story? Aviation Safety? The author replaced a voltage regulator in flight. I certainly wouldn't regard this story as a model of safety. ----- Original Message ----- From: "Kevin Waltz" > Excellent work. You story might save a life someday. Aviation Safety > Magazine occasionally prints articles like this to inform people of > situations just like yours. If you have the desire and energy to share > this story, they might be willing to reprint. > > Again thanks, and I will keep your story in mind. Your story brings > home the fact that small problems if left untended can become big > problems. > > Regards, > > Kevin Waltz ________________________________ Message 6 _____________________________________ Time: 05:47:24 PM PST US From: "Martini Luc J.R." Subject: Re: Avionics-List: Transponder Technical Info --> Avionics-List message posted by: "Martini Luc J.R." Hi The answers you want can be found in the Techorders for the APX-72, which is commonly avialable on E-Bay. That will also give you some stuff on military Mode 4 as well. That is at a pulse by pulse level.... is that the kind of data you are talking about? For wiring input and outputs of transponders, and Blind Encoders, each unit varies from one manufacturer to the next. Luc ----- Original Message ----- From: Subject: Avionics-List: Transponder Technical Info > --> Avionics-List message posted by: splevy@l-band-systems.com > > Listers, > > I am looking for technical information on the specifics of transponder > operation, including mode C and mode S. > > I need the hard technical specifications, including the rf requirements and > the data stream and encoding protocols. All I have been able to find are > the generic boy-it's-amazing-how-does-it-work descriptions. > > Any information or leads to published specifications would be appreciated. > > Thanks. > > Stan > > RV7A (tail almost done) > > ________________________________ Message 7 _____________________________________ Time: 08:08:45 PM PST US From: splevy@l-band-systems.com Subject: Re: Avionics-List: Transponder Technical Info --> Avionics-List message posted by: splevy@l-band-systems.com Luc, That's the kind of information I was looking for. Thanks. Stan At 03:55 PM 7/3/2003 -0700, you wrote: >--> Avionics-List message posted by: "Martini Luc J.R." > > >Hi >The answers you want can be found in the Techorders for the APX-72, which is >commonly avialable on E-Bay. That will also give you some stuff on military >Mode 4 as well. >That is at a pulse by pulse level.... is that the kind of data you are >talking about? >For wiring input and outputs of transponders, and Blind Encoders, each unit >varies from one manufacturer to the next. > >Luc >----- Original Message ----- >From: >To: >Subject: Avionics-List: Transponder Technical Info > > > > --> Avionics-List message posted by: splevy@l-band-systems.com > > > > Listers, > > > > I am looking for technical information on the specifics of transponder > > operation, including mode C and mode S. > > > > I need the hard technical specifications, including the rf requirements >and > > the data stream and encoding protocols. All I have been able to find are > > the generic boy-it's-amazing-how-does-it-work descriptions. > > > > Any information or leads to published specifications would be appreciated. > > > > Thanks. > > > > Stan > > > > RV7A (tail almost done) > > > > > >