In message , Rob
writes
Bob E wrote:
OK, Bob E - it appears that the ball is in your court. In the interests
of peace and harmony, and to prevent confusion, please could you please
tell us exactly (and I mean EXACTLY) which RG-6 vs RG-6Q parameters you
are concerned about?
Ian

OK, thanks for the discussions.

I have a VHF/UHF omnidirectional antenna with integral amplifier for TV
reception:

http://www.amazon.com/Antennacraft-5...mplified-HDTV-
Antenna/dp/B007Z7YOKS

Several broadcast towers surround me, from 40 to 50 miles:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d5b9405cba93e1 5

Terrain is pretty flat.

The antenna is currently connected to RG6 located indoors, up high in a
1-story cathedral-ceiling home. Signal reception is marginal, gauged by the
HDTV's (relative) Signal Strength display; dropouts occur regularly on some
channels.

I plan to mount the antenna outdoors on the peak of the roof. I was planning
to use RG6 quad-shield, but wanted to check whether it is truly a better
solution or not.

Cable run indoors now is about 50 ft. From the roof location this will
increase to 75 or 100, depending on the route I choose, hence my question.

Thanks.

When you have an antenna with integrated amplifier, the loss of the
cable normally will not be a prime concern. Of course this only holds
true when the antenna+amplifier is well designed. I don't know the
situation in the USA, but here in Europe there are only very few good
manufacturers and all the rest sell crap and snake-oil. Don't know what
category your antenna is in.

I would say that all omnidirectional TV antennas (amplified or not) tend
to be in the snake-oil category, and should not be used unless there is
not a more-sanitary alternative. The antenna itself has low gain (at
least 3dB down on a halfwave dipole - so analogue pictures could be
noisy), and offers no protection to the effects of multipath reception
(analogue picture could have lots of ghosts). That said, an
omnidirectional does have its uses - provided it works well enough for
what you want. The advent of digital TV has meant that - up to a point -
reception is much more tolerant of the impairments that often gave you
poor analogue reception.

With a bare antenna (without amplifier), loss is very important as the
signal from the antenna is attenuated and the noise at the input of
the receiver is constant, so your signal/noise ratio worsens.

However, with an amplifier near the antenna, the signal should be raised
sufficiently to be above the noise at the receiver, and the signal/noise
ratio at the input of the amplifier becomes the predominant factor.

Indeed. If you need an amplifier, it should be located at or near the
antenna. This gives you the best signal-to-noise ratio (whatever the
length of the drop cable is).

In this case, the loss from your coax should not matter too much.
The good-quality shielding is often more important.

Note that in digital TV, the occurrence of dropouts is not only determined
by signal strength, but also by signal quality. This will improve
dramatically when you put the antenna on the roof, especially when this
results in a more or less clear view of the transmitter. What you
receive now is probably a jumble of reflections.

Quite.

While digital TV is
more tolerant to that than old analog TV, it still eats from the margin
that you need for dropout-free reception.

In the UK, I don't think that many homes use installed omnidirectional
antennas. You see some on caravans and mobile homes, and on boats, but
never on houses. Those living close to the transmitter might use
'rabbit's ears' set-top antennas (or some fancy variant) - especially
now that all TV is UHF (small antenna) and 'you can get away with
murder' digital - but you don't see any proper installations.

One big difference between the UK and many other countries (and in
particular the USA) is that we have generally received all our TV
signals from one direction (initially from closely-located transmitter
masts, and latterly from a single mast). It is only in outlying 'fringe'
areas where you used to see homes with two (or more) antennas pointing
in different directions - and as the TV signals were weak, these were
always high-gain yagis.

Regarding the original question, on looking at the specs for RG-6, it
appears that Mr Heinz and his '57 varieties' is left standing. 'RG-6'
seems to be a generic number for many types of coax. Various parameters
differ - including the loss (typically 6 to 7.5dB per 100' at 1000MHz)
and - in the case of RG-6Q - the outside diameter could be 1mm more (in
which case the diameter of the dielectric is probably the same as
ordinary RG-6).

One caveat sometimes mentioned is the relative high loop resistance
(because the inner is steel, copper plated, and not all copper), and
this can cause problems if you're line powering up the drop cable. It's
unlikely to affect the working of (say) a straightforward, relatively
low current antenna preamplifier, but with a satellite LNB the voltage
drop could confuse the band-switching operation.

In the OP's situation, it's pretty obvious that the addition of another
50' RG-6 will drop the signal at the TV set by (at the most) around 3dB
- and (with luck) this will probably be more-than-be-made-up-for by
mounting the antenna outside, higher, and in-the-clear. [Depending on
the roofing material that the TV signal is presently having to pass
through to reach the antenna, the received signal could be a lot
stronger.] All the OP can really do is try it, and see what happens. If
that doesn't provide satisfactory reception, the best advice might be to
consider an antenna with inherent gain - possibly with a rotator to
enable him to get all the transmissions.
--
Ian

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