Make sure the antenna base is firmly screwed to the ground plane, making a solid contact via the underside surface, or (if the GP is stuck to the underside of the ceiling like some bodges I have seen on a certain TB20) at least via all four screws.
At last ! The internal DR400 photos
Thanks for the images, I hadn’t considered that type of antenna. Food for thought.
Good wishes
Paul.
Hi
the interior antennas, behind the seats, I dont like
I dont like the antennas behind my kidneys
:)
When using the SWR meter it is very important what is around the cables
or near the antenna
an antenna looking down, near the ground has a different SWR than in flight
If you touch the cable with your hand, you can modify the SWR
if you move the controls, it is possible that you modify the SWR
………….
If you’re affecting the SWR in a significant way by touching the feedline (if it’s coax), there’s something wrong with the installation and the coax shield is radiating.
Quote……… “the interior antennas, behind the seats, I dont like
I dont like the antennas behind my kidneys”
The antenna is only marginally nearer the back seats than the top external antenna, but the internal antenna has two skins of a fuel tank between it and the rear seat passengers, the top antenna does not.
Hope I can resurrect this thread and will be thankful for advice …..
My new radios worked fine for a while but now I have the squelch turned up to 100% and they are still very noisy ………… I have found the culprit today ……. the turn and slip is producing huge amounts of RF noise a hand held next to the aircraft is swamped if on a weak channel.
My question is does this mean some internal RF filter is no good and the instrument needs overhaul ?
What it does tell me is that my radios are fine I have done all the SWR tests and resistance to ground plane tests and all are good.
Do I need to get a new turn and slip ?
Any advice appreciated.
Thanks
Paul.
Start from the grounding of the Com antenna.If no good or intermitent,you get noise and low performance.Line RF filters work as a medicine for bad or unsolved situations.
Presumably the turn and slip is electric rather than vacuum?
You could always try some ferrite beads on the wires to the turn and slip indicator to see if that helped?
