My airplane setup is pretty close to what you are describing. I have a Dynon D6 and use its encoder output to provide altitude to a used Collins Transponder I purchased on the ebay avionics list for $400. It hasn't change from 1200 since the day I installed it but it does work fine. The Collins 850 was the only "old" transponder type I could find to fit behind my panel as it is only 8.5" deep.
Rob Schmitt N1852Z www.robert7721.com -----Original Message----- From: Mike T via KRnet <krnet at list.krnet.org> To: brian.kraut <brian.kraut at eamanufacturing.com>; KRnet <krnet at list.krnet.org> Sent: Wed, Jun 4, 2014 12:08 am Subject: Re: KR> How do you test a transponder? I'm planning on getting a Dynon D6 EFIS, which is currently $1600. This replaces all the primary instruments and several others as well, and its altimeter is encoding. I'm waiting on that because the price will only go down (unless Dynon introduces a new model -- then it will REALLY go down). So at the moment, I don't have an encoder, an antenna, or anything else. But the transponder was a Terra 250 D, which I've lusted after for a long time. I was flying a few weeks ago with a guy who just put one in his Kitfox and loves it. However, it's not so rare that I can't wait awhile, especially if Mode S is really going to be required. I wish someone would introduce a cheap transponder for sport pilot planes and others who only fly VFR. It would be fine with me if it only broadcast at 1200. Mike Taglieri On Tue, Jun 3, 2014 at 11:18 PM, via KRnet <krnet at list.krnet.org> wrote: > Reminds me of something I did on my plane. As an electronics designer, > this would be too embarassing to tell this story, but hopefully it will > save someone else from doing the same thing. > > When I bought my M2 I knew that it needed a transponder test before I > could operate mode C legally. Wanting to make sure it at least worked > before I brought it to a shop to pay for a static test I thought I would > check it first. Went up a few thousand feet and called a tower to > confirm that they could read my code. Then switched on Mode C and they > had no altitude report. Tried again the next week and same thing even > though the guy I bought it from said it worked fine. > > Pulled the transponder and brought it to a friend that had the test > equipment and he confirmed it was fine so must be the encoder. No > problem, I had a spare. Put it in the plane, called a tower, turned on > Mode C, no altitude. Arrrgh. > > Bought a used one from Wentworth and tried it, no luck. Had them send > me another, still no good. > > Transponder and all wiring good so I decided that I must be overlooking > something so I built an encoder test set (fairly easy with just > resistors and LEDs to read the grey code). Hooked it up with tubing > through a T going to the encoder and an altimeter so I could read the > code and verify it was correct. Powered up and altitude read something > like 200' and would not change on all three encoders, weird. > > While pondering what could be wrong all of a sudden the altitude changed > and I verified by pulling vacuum with the syringe that it was correct. > Turns out that the old style encoders need the temperature to stabilize > for about two minutes before they start sending altitude. Not wanting > to be reporting without knowing if it worked I had been turning the > encoder on just before asking for an altitude check and the unit was not > warmed up yet. Live an learn. Anyone want to buy three tested good > encoders? > > Brian Kraut > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options > _______________________________________________ Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org please see other KRnet info at http://www.krnet.org/info.html see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options
