NigelCharles writes:
> I see from his [Bob Nuckolls] reply to
> you he now recommends RG-400 which doesn't appear to be available yet in
> the UK catalogues. I would have thought that you should get satisfactory
> results from RG-58 or RG-223 otherwise they wouldn't have been recommended
> in the first place.
I'm not sure we need much info more here, but FWIW, both Narco and King
supply RG-400 for their xponders, and they say it's good up to 9 foot length.
Beyond that, they specify something else entirely. RG-400 is less lossy
than RG-58, but at 9-feet only a little. Also, the loss is greater at
xponder frequencies, less so for VHF (where RG-58 A or C /U is fine).
As a practical matter, transponders are more critical for IFR than for VFR,
and they have more power (and sensitivity) than what ATC needs. There is
more variance in power output among brands, proper installation, and
out-of-alignment over time, so that the performance difference between RG-58
and 400 alone is small in comparison.
Regards,
Fred Fillinger, A063
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