In article ,
dave wrote:

Heliax is good. Double-braid shielded cable (with silver-plated
copper braid, not aluminum) seems to be almost as good.


Interesting. I always hear people bragging about LMR. Are we using the
term "Heliax" generically?

Yes... I meant "cable with a solid or near-solid outer conductor".

Is semi-flex no good too, (It's all aluminum
and brass metallically isn't it?)

I think that the key is avoidance of (1) contact of dissimilar metals
and (2) ferromagnetic materials. And, you want a cable where you can
get a really good electrical contact between the outer braid, and the
connector shell. I believe that solder beats crimp in this
application, since you end up with a connection which will reliably
remain gas-tight and won't oxidize. A good semi-flex would probably
be fine, I'd guess.

LMR-400 seems to be dodgy (for repeater use) over several of these
issues.

I do like it for simplex applications.

Did your guru make a profit on the replacement cables? How do you know a
$15 can of Cramolin wouldn't have helped just as much?

Nope... he's one of the volunteers in the repeater group. He donates
his time, we use donated materials (e.g. the heliax cable,
ex-cell-site) when possible, and any supplies the repeater needs are
bought from independent commercial suppliers (e.g. the connectors, in
this case). He was annoyed at having to go to the trouble of
replacing the existing pigtails, but *very* pleased at the result...
it turned the system from a "basket of snakes" into one in which the
three repeaters in the cabinet can all operate simultaneously and
independently without any cross-band interference that we can detect
in any way.

We're also sharing the hospital-roof site with at least one cellphone
system, one pager transmitter (for several years - gone now), and
several public-safety LMR repeaters... and so doing things carefully
is quite important!

Both sets of cables (the original LMR and the replacement hardline)
had high-quality commercial-grade connectors... no cheap nickel-plated
imports. Hence, I do think it's accurate to ascribe the difference in
performance to the cable itself.

Cramolin is nice stuff for dealing with connector-to-connector contact
issues, but it doesn't do a thing for problems internal to the cable.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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