Hi. I have sl-30 in wooden experimental plane. Because of wood construction I have a bit interferences when transmiting. I have tuned antena with ground etc but anyway 8W is too much. I’m looking for service manual how to adjust (decrease) output power to 6W. Maybe someone can help?
Where is the interference seen?
Normally this sort of issue is addressed by using a high quality RF cable that doesn’t leak – RG400. Most avionics shops don’t use it; on my last job they refused and I had to free issue them with 50m of it.
Reducing power from 8W to 6W will make no difference to interference issues.
@Peter, I definitely concur with you in general, but is there any compelling reason to use RG-400 and not, say, LMR-200-FR? The latter seems to be even better in all respects except being less flexible because of a solid inner conductor. Do we really need a soft cable for a permanent installation?
P.S. Oops, just realised there is also LMR-200-UF, which is flexible and better than RG-400, though not as good as the stiffer LMR-200.
And by the way, what would produce a more reliable crimp – a solid inner conductor or a braided one?
You need to replace it soon anyway, it’s not 8.33 ;-)
I do not see that option but i didn’t go into all the detail…
@ultranomad I had not seen that type before. I am not surprised it exists. There is a huge range of speciality cables out there. I found some on this project. Also RG400 is very old, and unpopular on big jets because you can easily have hundreds of kg of it there.
I would still like to know what kind of interference Przemek is getting. VHF interference issues are widespread and often manifest themselves in poor GPS reception on certain frequencies – more details here. They are IME nearly always due to bad cabling although obviously a wooden plane isn’t going to make it easier.
One more possible cause is the antenna design: an antenna intended for a metal aicraft may need some kind of counterpoise when installed on a wooden fuselage.
The antenna will definitely need “something” in the bottom – I guess a ground plane is the usual way because you get less radiation into the cockpit than with a dipole.
Re the Q about crimping, I don’t know which is better. Here is an old thread on crimping but it doesn’t cover that. Crimping relies on creating a gas-tight joint and I would think you get a better opportunity to create that with a stranded wire.
Hi. I have new RG-400, high quality connectors, metal ground plane under antena and low SWR.
Also no ground loops in installation (is new).
Problem is that when I trasmit my intercom loops and/or fuel flow computer reset.
This is small, wooden aircraft and it’s just too close and too strong, that’s why I’m looking way to decrease to 6W with I’m sure decrease level of interferences.