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1. 06:01 AM - Re: Garmin SL-30 poor VOR reception (D L Josephson)
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| Subject: | Re: Garmin SL-30 poor VOR reception |
Matt wrote:
>
> Are you using "RG-58A" or "RG-58C/U"? "RG-58A" is really lossy. ""RG-58C/U"
is
> better, but still not that great. I would strongly recommend RG-142 or RV-400
> for that application. I have RG-142 installed in my RV-8 connected to an SL-30
> and to a CI-158C antenna mounted in the top of my vertical stab and I get
> outstanding
I wonder what the source of that information is. Commercial RG-58A, mil
spec RG-58 (MIL-DTL-17 M17/28-RG058) such as Belden 9203, RG-142 and
RG400/LMR400 are all rated between 3.3 and 4.9 dB per 100 ft at 100 MHz
-- around 1 dB for a practical airplane installation.
>
> Pull the RG-58 out, get some RG-142 and some high-quality BNC connectors (the
crimp-on
> kind NOT the screw-on kind) and then see how things work. You may still
> have a problem with the NAV receiver on the SL-30, but upgrading your cable
> will go a long way in improving your reception in any case.
Original RG-58 cable was just fine for decades with receivers far worse
than the Garmin. In my experience, connectors are the problem nine times
out of ten. Commercial grade crimp connectors from a manufacturer that
also supplies military grade connectors (Amp, Amphenol, Kings) crimped
with the manufacturer-specified tool checked for the correct crimp
dimensions by someone experienced with this process is the key. Original
military soldered connectors are also OK but only if the installer is
experienced enough to get the dimensions right without melting the
dielectric.
Quick test, after you've confirmed that the cable has continuity end to
end and isn't shorted: grab the cable in one hand and the body of the
connector in the other. Using moderate force, can you rotate the
connector body with respect to the cable? If so, cut it off and try
again, it is not terminated correctly. This isn't the cause of all
problems but is usually diagnostic of whether it was crimped right in
the first place.
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