So-called "UHF" connectors...

[John Ragle]

     Even at 144 MHz, UHF connectors are probably acceptable, with the
"bump" being < 1 cm in length compared to 200 cm. I think more at issue
is the environmental quality of the dielectric. The "old military" ones,
with what we used to call "mud" as the dielectric material are really
not very forgiving of anything outdoors on the long term. They shrink,
crack, hold water, etc. On the other hand, the PTFE ("teflon")
dielectric versions will hold up under quite vile conditions,
particularly if properly "booted." Personally, I like the Type N
connectors, and even prefer them over the BNC and other variations. They
go together much more easily (one might even say "rationally") than the
UHF male cable ends, and anyone who has ever taken a UHF cable-end male
apart has seen what a mess the sweat-soldering can make of the
inside....but I do think that the issue with standard "mud" type UHFs is
with the durability of the dielectric, not with the impedance bump, at
HF and even low VHF frequencies.

John Ragle -- W1ZI
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[W8JI]

> inside....but I do think that the issue with standard "mud" type UHFs is
> with the durability of the dielectric, not with the impedance bump, at
> HF and even low VHF frequencies.

That's an accurate statement John. The largest bump I've even measured with
a SO239 PL259 pair was about  1.05:1 at 147 MHz.

The highest SWR with two in tandem, with optimum spacing between bumps to
enhance SWR error, was around 1.1 :1.

Like Motorola and other have done in the past, I think nothing of a few UHF
connectors on 2 meters. Barrel connectors can be a problem at VHF, because
they can have a long mismatch area, but not properly installed UHF pairs or
good short barrels.

That goodness length matters, because look at the horrible mismatches in
wiring inside our radios and tuners.

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[k6dgw]

Tom W8JI wrote:
>> inside....but I do think that the issue with standard "mud" type UHFs is
>> with the durability of the dielectric, not with the impedance bump, at
>> HF and even low VHF frequencies.

A long time ago, the USAF told me that N-connectors, when screwed down
tightly [with fingers, not tools] were essentially weather-proof.  I
don't think that included immersion.  Once saw a PL-259 in northern AK
that was split open ... I guess water got into it and it froze [happens
around the Arctic Circle :-)]

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2010 Cal QSO Party 2-3 Oct 2010
- www.cqp.org
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