Topband: CAT5 cable as feeder for reversable Beverage

[Bill Wichers]

You are likely correct. I have not reviewed the spec in some time, but
it most likely is an average value over the LAN-used spectral range
(likely in the high-kHz region up to maybe 100MHz or so). It is the only
standardized measurement for crosstalk on cat-x cable types that I'm
aware of though.

Regarding the indoor-rated cable being used outdoors, there is flooded
outdoor-rated cable available and it's not much different in cost from
the usual riser-rated indoor cables. The outdoor-rated cable usually has
a black PE jacket and a floodant inside. I recently came across a new
"dry" (non-flooded) outdoor cable that has a non-halogen jacket (read
that as "expensive but safe in a fire") and a foil shield. It has an
outer jacket, a shield with drain, an inner jacket, and then the usual 4
cat5E pairs. I think the cost was in the general area of about 25
cents/foot though which likely precludes it's use for "cheap" feedlines
though :-)

If you need a "cheap" cable to use outdoors, the use of BLACK
RISER-RATED (CMR) cable would be OK as it tends to hold up reasonably
well although the jacket will eventually form cracks. DO NOT use
plenum-rated (CMP) cable as it has a very short lifetime when used
outdoors, IME.

Personally, I try to just match everything to 75 ohms so that I can use
RG6 cable. RG6 is cheap and available and easy to get in a true
outdoor-rated cable.

  -Bill


> On 4/14/2011 10:33 AM, Bill Wichers wrote:
> > There is a test used when installing this cable commercially called
> > "PowerSum NEXT". If you look that up you should be able to get an
idea
> > of the coupling between pairs.
> 
> These are most likely to be single-number values that average the
> crosstalk over a broad frequency range, but the actual performance
will
> vary as a function of frequency, and with the quality of the cable. I
> haven't done measurements, but I would expect cross-talk to be lower
> (better) at 2 MHz than at higher frequencies.  Published loss data for
> CAT5/6 shows   numbers good enough for use with RX antennas.
> 
> That said, the primary consideration is probably what Herb noted about
> how well (poorly) indoor-rated cable is likely to stand up to outdoor
> conditions.  Although I love CAT5/6/7 for lots of uses, I wouldn't use
> it for outdoor runs to antennas.
> 
> The best choice for Beverages and other RX antennas is low-cost coax
> like RG58s or RG59s, with construction that makes them rated for the
> outdoor conditions where you live.
> 
> 73, Jim K9YC
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