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#11
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GNS 430 reception problems
Thanks everyone for their feedback and opinion. I am now convinced what
is going on is a simple case of demonic possession. We swapped the antennas. No difference Tonight we replaced the BNC connector; no difference. We tested it with and without the KX-155 on; no difference. When running the recv sensitivity test, the KX drops out much later than the GNS. So I am left with demonic possession. I'm thinking I need a new avionics guy. Unless someone has a wild idea. thanks, KC Kevin Clarke wrote: Hi, I'm looking for folks that might have a similar experience. Recently upgraded the panel to include a GNS 430 and replace one of those old NARCO all in one VOR instruments plus an old NARCO radio. Anyway great upgrade. The GPS function works wonderfully. Filing /g is the best. The NAV function works great. Dual glide slope indicators(the other is slaved to a KX-155) really makes IFR manageable. The problem is the COM function of the GNS 430. We're only getting about 40 miles of range on the receive side of the COM. I'll call for flight following on COM1(the GNS) and never get an RX indication. When I flip over to COM2 (the KX-155) it works just fine. The KX has a range of at least 80 miles. The GNS seems uneven. We can xmit and be heard over distances but the receive side is really only useful in and about the terminal area. This is less than optimal. When we did the upgrade we kept the original antennas that were on the plane(PA28-180). Our avionics guy is baffled, maybe useless at this point. He swapped out the GNS plus ran a myriad of other tests. He says everything is checking out just fine. But that is surely not our experiences. So I turn it over to the collective wisdom of the net. Has anyone else ever experienced anything similar? Thanks. |
#12
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GNS 430 reception problems
On 7-Sep-2006, Kevin Clarke wrote: When running the recv sensitivity test, the KX drops out much later than the GNS. Was the RX sensitivity test done on the bench or in the airplane? How "much later" (in dB)? If it's more than a few dB then the GNS 430 is probably defective. There should be a published specification for receive sensitivity, which will be shown in the Garmin shop service manual if nowhere else. If what you get, with a bench test, does not meet spec then troubleshooting needs to move to internal circuitry. Probably best done by a Garmin authorized repair facility if there is such a thing. Good luck! -Elliott Drucker |
#13
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GNS 430 reception problems
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#14
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GNS 430 reception problems
No way the sensitivity difference between the two radios should be 20 dB --
that reflects an incident signal strength difference of 100-fold! If the Garmin is not defective (and the unit swap seems to confirm this) then the receive signal is being attenuated by roughly 20 dB someplace. This should be fairly easy to find using a spectrum analyzer or similar instrument, again something any avionics shop should have available. However, I must wonder why your avionics shop isn't going through these rather obvious diagnostic steps without outside help. -Elliott Drucker |
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