[TowerTalk] Low Loss Coax

[John & Margaret Weatherley]

IF you decide to use a 90 degree UHF adaptor be VERY careful in your choice.
Make sure you choose a brand name item such as Amphenol etc.
A few years ago I needed some for a commercial project and happened to find
some at a hamfest. One of those seudo commercial swap tables was selling new
coax fittings made in the far east at a "good" price. I bought half a dozen.
I installed one in a 155 Mhz system and could not get any significant power
out at the antenna end.
I measured over 20 dbs of loss through the elbow at that frequency. I
sectioned one with a hacksaw and was astounded to find that in order to
facilitate construction the means of getting around the corner was by using
a piece of spiral spring, They had in fact installed what amounted to a
small RF choke in series with the signal path. While this would have had
less effect at HF it rendered the system totally inoperative at VHF.

I discussed the experience with the Development engineers at Amphenol and
they had heard of the problem but had never seen one, so I shipped a couple
plus the sectioned item to them and they promised to put it in their
connector museum, in the Chamber of Horrors section!
Most of us hams are tight wads as this experience proves and this is what
can happen by trying to do everything "on the cheap".
Caveat Emptor
John AB4ET


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