Instrument Interference

[Station Kariba]

Good morning Lads

HELP PLEASE. We are having a problem on a Skydac GX2. This problem started in flight where the gauges were rising every time you push the PTT to transmit. This seems to have got progressively worse where the gauges are now fluctuating up and down sporadically, without pushing the PTT and causing the alarm to go off? We also have the same problem on another aircraft, which is analogue. When you push the PTT to transmit, the analogue Engine Temp Gauges also shows an increase, needle goes up.This is the only gauge that is effected on this aircraft. Can anyone give us a pointer as to where to start looking and what we maybe looking for. I suspect it maybe an earthing problem on both units? Would appreciate any help from more qaulified folk in this field. Thank you.

[ZULU1]

If you can give us a clue what aircraft it is then we can help...

[justin.schoeman]

Instrument readings going up would generally mean a ground fault (loose wire/poor connection) between the battery and the panel.

[Tailspin]

Have also had the problem when the Antennae cable was too close to the Wiring loom.
This caused feedback through the wiring and the screwey readings.

Make sure the aerial cable is away from your wiring. Could also be a problem.

[Zim Zulu]

both problems are on 1st Aquilla with skydat, and other Airborne edge with analogue! both trikes!

[ZULU1]

OK, some basic help, firstly the radio in question if its a Icom ICA3/22, 4, 5/23 series it may be fixed relatively easily. The rf transmission is as Tailspin put it is coming from the antenna coax. Yes I have measured it. Assuming that you are using the standard whip antenna on the nose. It means in layman terms that the signal is not going out of the antenna but coming back and it has to go somewhere. Normally in squeals and squeaks but it may be enough to sort those dials out. So first thing is to sort out the antenna ground, then the earth on the trike. When you have finished that, the antenna will not like like to perform if the antenna runs parallel to the profile tube. It may look super cool, but all its doing is reflecting rf off the profile tube and sending back down the cable..So a very simple tip and I advise this to everybody that doesnt wish to become a radio ham with a Vee Rabbit. Adjust the antenna base in such a way that you can lean the antenna forward about 15 degrees from Vertical. Thus ensuring that as much as possible is transmitted out. Try that first. If its an Ica 6/24 throw in the towel at this stage, buy a Vertex VXA220. Bet it works. I attach a pic with the antenna leaning forward. Its a hassle in the parking mode though...

[Station Kariba]

Thanks Guys

Will check all as recommended and give you results. By the way the Airborne has an Icom A5 and the Aquilla has a Vertex Radio, not sure of the model. Have a good one, fly nicely. Cheers.

[Station Kariba]

Morning Gentleman

Happy to report with your assistance, Top Gun,Tailspin and Zulu1. We have resolved the instrument problems. On the Aquilla we moved the Radio and away from the instrument panel, went through all the wiring and re-tightened all the connections, made sure the coax cable was away from the wiring loom, hey presto, problem solved. On the Airborne it was a bad earthing that was causing a problem on gauge, this was retified and problem solved. Thanks guys for your contributions and advise. Cheers