Robert Pesak wrote: >>Every time I key the mike strange things happen on my panel. The trim LED lights go all the way to the down to the bottom of the scale, the ammeter shows about + 20 amps, and it caused my clock to go hay wire.<<
N56ML would light up three of the trim LEDs...the one the trim was set to, and the one above and below it, whenever I keyed the mic, with the center one really bright. Eventually it killed off three of the LEDs in the range where N56ML always flew, due to overvoltage, I'm guessing, so after that, it was trim "by feel", which is really how you do it anyway. I blamed it on the unshielded multi-wire cable that I used to wire up the trim, because that's what came with the trim servo kit, and I couldn't find any shielded cable with that many conductors. That and I put a terminal strip from that cable to the trim servo right at the horizontal stab main spar, which I later realized was right between the two legs of the radio antenna and only inches away. Not a big surprise that keying the mic excited the trim circuit! An issue that I now have in N891JF is a conflict between the ELT remote and the APRS transmit antenna. Space is very limited back there in the fuselage, and since the deck is not removable, the space I can actually REACH is even less. So the ELT is mounted about 8" from the APRS transmit antenna. No big deal, right, since I theoretically won't care if there's interference if I crash, and it's not like I'm concerned about the "quality" of the signal the ELT emits, right? What I didn't think of when I installed it is the remote display for the ELT. As soon as I turned on the APRS circuit, the wonderful ELT turned on and started broadcasting...and it wasn't within five minutes after the hour either! Fortunately I was in a steel hangar with only one small window, and it didn't take me long to notice the red "your ELT is transmitting" LED and beeper under the panel. More experimentation proved that the APRS was feeding EMI into the little RJ11 (telephone) line that connects the remote to the ELT, and that wire runs directly under the APRS transmitter, with not much way to dodge it. So needless to say, I don't have the remote hooked up at the moment, even after rerouting the wire to the other side of the fuselage. Reading the ELT manual revealed the sentence that says something like "ensure the remote indicator wiring is routed well away from RF antennas". Something else to watch out for. You'd be surprised what you can get away with regarding antennas, but sometimes the spacing makes a real difference. I'll be smarter on my next plane. One more tidbit for anybody planning to install an iFLY 720 into their panel...get the external antenna. Mine is mounted to the surface of the aluminum panel and appeared to work OK at first, but that's only because the plane had plenty of time to acquire a signal. Within minutes of takeoff, it was simply not able to keep up with the movement and would lose GPS lock, which rendered it essentially useless. I recently bought the remote antenna and now it acquires quickly and maintains lock. I flew N891JF back from Omaha with a suction cup mount on the canopy, and that worked fine, but apparently the internal antenna is located such that putting it in contact with a flat aluminum plate obscures it from a view of the sky that's sufficient to work correctly. As for Jeff Scott's ten antennas, I have antenna envy...I only have eight that I can think of, unless you count the remote ELT display wire and the trim servo wires...then we're even! And yes, they are all internal. I can tell you one thing for sure...the next plane will have 11 antennas...for something. Having flown with a loaner Stratus ADS-B unit, some kind of ADS-B is in my future for sure, but it only requires Bluetooth...no "external" antenna. Regarding being slowly being cooked by microwaves while flying, I can think of a lot worse ways to go. Other than memory loss, skin cancer, failing eyesight, shaking hands, aches and pains, gray hair, and just plain stupidity, I've seen no evidence of microwave damage yet...... -- Mark Langford ML at N56ML.com http://www.n56ml.com
