[Ares-races] Your opinion requested

[Dave Colter]

I would not used either type of cable. To begin with, you should try to keep
the total transmission system loss to well under 6dB total for good system
performance, IMHO. That includes all "passive" devices like the duplexer,
filters, feed line, connectors, etc. Neither of these cables are likely to
be large enough given the distance you mention.

I'm not familiar with LMR 195 specifically, (although based on Times
Microwave's numbering system, it sounds like a very small diameter cable and
therefore way too lossy anyway,) but all of the LMR cables use an aluminum
foil and braid shield. Belden and others offer cables with a similar
construction. While it's fine for base-station use, this type of cable
should never be used for duplex signals, like repeater antenna feeds, since
the transmitted signal will generate RF noise within the cable (caused by
the two shields rubbing against each other, even with only a very slight
vibration), which is simultaneously picked up by the receiver. It will make
your receiver quite deaf - been there, done that, should have read the
instructions.

RG8X is pretty lossy for a run this long. If the antenna is 150-175' away,
I'd be willing to bet that the cable route is much longer. You should be
looking for a way to either get the repeater closer to the antenna (in the
attic or an upper floor closet) or consider using hardline. If you can get
the repeater to within 75' total cable length of the antenna, the RG8X foam
might be OK.

Based on a 200' cable run:
    RG8X foam: -7.4dB (3.7dB/100') - way too much loss
    RG8 or RG213 foam: -3.8dB (1.9dB/100') - marginal depending on other
system losses
    1/2 foam hardline: -1.6dB (.8dB/100') - very acceptable, but not cheap
    5/8" foam hardline: -1.2dB (.6dB/100') - overkill for the money

Remember, foam dielectric has lower loss than solid polyethylene dielectric
for the same RG number. 73,
Dave Colter WA1ZCN
Repeater Manager
Twin State Radio Club, W1FN

> To: ares-races@mailman.qth.net
> Reply-To: kd5czm1@iwon.com
> From: "" <kd5czm1@iwon.com>
> Cc:
> Date: Wed,  7 Jan 2004 18:24:48 -0500 (EST)
> Subject: [Ares-races] Your opinion requested
>
>
>
> Here's what I have.
>
> Brand new repeater, preprogrammed. Matching antenna.  Where? Courthouse
basement--home of the EOC.  The antenna to be mounted on the courthouse
apex, 150 to 175 feet up. Between the two are dozens upon dozens of coaxial
cables, mostly RG8 and others snaking their way through all three floors.
Few are terminated.  I proposed hosting a 'coax party' to find and terminate
some runs so as to finish the installation of the repeater station.  The
Emergency Program Manager said, 'Why bother? Here is some brand new coaxial
cable. Go ahead and use it.'  His idea is to save us the work of
identifying, tagging and terminating the cables already in place.
>
> What's the problem, you say?  He gave me two spools of cable. One is
LMR195, given to him by the same shop who sold him the repeater.  The other
spool is RG8X.  I have to agree, routing and terminating new cable would
save us time but of the two types which would you use?
>
> Your help appreciated.
>
> Joe Guerra KD5CZM ARES EC Kleberg County TX
>
>