Ground tested - Serviceable. Curses.

[Centaurus]

Sorry to throw this in on a light aircraft problem when this forum is aimed at big aircraft. But...A BE76 Duchess I fly has very poor range on both its King type VOR receivers. It will only pick up the VOR within 25 miles at 6000 ft on one set, and the other nav set only gives 5 miles. Both audios are incredibly noisy with lots of hash sounds and the ATIS is unreadable due hash.

This is Melbourne VOR in Australia, flat terrain and ground station and other VOR's nearby are definately serviceable.
Despite this, the technicians have checked the aircraft with their PFM gizmo on the ground, and they say both sets are 100% serviceable. Are there any experts among you that can advise possible causes of poor VOR performance in the aircraft while airborne.

[34DD]

Just a thought - plugs and sockets have been known to make less good contact under in flight vibration conditions

[mustafagander]

Sounds like antenna.
If you can, put 1 of the suspect boxes in another a/c or fit a know good box and see what happens.
If unable, I'd check every last bit of the antenna system for bad conx/broken wires etc.
Good luck!

[Amateur Turbines]

I've been told lots of tinfoil can do wonders for antennas.

[BEagle]

Try turning the strobe lights off (if you've got them fitted). Listen to the receiver audio at the same time - if that doesn't make any difference, suspect you've got an antenna fault. But also have the aircraft's electrical system checked for correct supply voltage to the avionic busbars (sorry, not familiar with the Beech, but low DC caused mayhem on an aircraft I once flew).

[Pengineer]

Poor reception and excessive noise are classic symptoms of Antenna or VSWR problems.
In this case you say both systems are affected. How many aerials does your machine have? if its two seperate systems with seperate aerials and feeders its unlikely that they both have exactly the same defect so isolate the common component, the control panel for instance, check that its correctly fitted and connected and if possible swap that with a known good one.
If the aerial is common a VSWR check will tell you if its good or not, and a time domain reflectometer can be used to isolate any problems with the feeder cable.
To help troubleshooting,
When did the defect arise? did it just appear or was it a gradual thing?
Could both systems have been disturbed on a recent hangar visit?

[Centaurus]

Pengineer and others. Thanks for advice - I will pass this on to the owner. I suspect that the faults have been there for some months before I flew the aircraft, and that previous pilots have ignored the problem. It happens.