Transponder antenna installations

I hate to break it to you, but a Becker 4401-175 installed using RG-58
as an antenna line violates Becker’s instructions. They state in
paragraph 5C that only RG-223 is to be used with the 4401-175. RG-58
can only be used with a 4401-250. Don’t overlook that you also must
comply with paragraph 6E, where you must check the power at the
antenna end of the cable. I’d bet that a 4401-175 using RG-58 will not
meet Becker’s power spec of 18.5 dBW.

As far as the non-mention of LM240 in the Becker manual, I’d bet
you’re allowed as an A&P to attach data showing that LM240 exceeds the
performance of RG-223. This data, combined with the mandatory power
test proving that the 4401-175 installed using LM240 exceeds the
Becker requirement of 18.5 dBW at the antenna end of the cable, would
make you golden.

Unfortunately, you have to buy male BNC and male TNC crimp connectors
when you buy the LM240. They’re a buck more expensive than RG-58
connectors. But your crimper will definitely work.

Your log book entry would simply say that the Becker 4401-175 was
installed in accordance with the manufacturer’s instructions, except
for the use of an antenna cable that exceeds the manufacturer’s cable
specifications which results in greater power being delivered to the
antenna. I guess you could attribute the idea of using a better cable
to RAS, if you liked – humor shouldn’t a violation of the A&P code, is
it?

-John

On Feb 7, 9:18 am, JJ Sinclair wrote:
The Becker 4401-175 manual does say that RG-223/U is preferred over
RGU-58, but it doesn't mention LM-240? As a mechanic I am bound to
follow the appropriate tech data. Does LM-240 use the same BNC
fittings I have in stock? Can I use my crimper? What would my log book
entry say? Installed Becker 4401-175 transponder in accordance with
opinions found on ras?
:) JJ