> About 30 years ago, I worked for an MATV contractor who
had lots of
> installations in high rise buildings on Chicago's Lake
Shore Drive, in the
> shadow of VHF and UHF transmitters on Hancock and Sears,
and with
> transmitting antennas having very little directivity in
the vertical plane (1
> and 2-bay on 2-6, 3 bays on 7, 4 on 9 and 11). VERY well
shielded cable was
> absolutely necessary for these installations -- anything
less simply would
> not work!
We had dozens of large headends that used the worse possible
thing, straight through 11 and 13 with strong local stations
and no conversion. There was FAR more egress into tuners of
TV's and infinitely more problems caused by flawed shield
connections in connectors than anything cable shield number
related.
A real test would be to put numbers that mean something in
the real world on this, rather than talking about systems
where other problems may be confused with shield thickness
problems.
I always see people crowing about the imagined virtues of
quad shield.
http://www.uniprisesolutions.com/docs/Uniprise_Electrical_Characteristics.pdf
shows there is barely any measurable difference between quad
shield and just a single foil with loose braid overlay. As a
matter of fact, before anyone gets all awestruck by the 50dB
change from 95% copper to foil you have to keep in mind that
50 dB over meaningless is still just meaningless.
Now there are cases where a system right on top of a very
very strong field (say a 100 kW on-channel TV station that
is just miles away and line of sight) might benefit from a
change from single woven braid to a foil shield, but it's a
HUGE exaggeration to extrapolate that situation to claiming
a rural CATV drop cable would have a noticeable change from
single foil to multi foil.
Such a claim is just plain silly. It makes no sense in
experience, it makes no sense looking at the numbers.
73 Tom
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|