On Wed, 9 Mar 2005 20:14:22 -0500, "James"
wrote (with possible editing):
I live about 8 miles from 4 local tv stations, and 25 miles from a much
desired UHF station. Luckily, they are all in the same general direction.
I plan to buy a medium size vhf/uhf antenna. My coax run will be 50 feet.
Although I don't really need "gain" for the vhf stations, I do need it for
the uhf station. "Some" extra gain will be ok for the vhf stations.
Whatever the setup, I want to use the lowest-loss RG6 that I can buy.
Here are my questions:
1. Where (online or else) can I find the very best, lowest loss RG6 coax ?
2. Assuming that I need a pre-amp, if I only have a 50 ft run of low-loss
coax, will my system work well if I mount the preamp at the tv end of the
50 ft coax, as compared to putting it at the antenna? I realize the
advantage of mounting at the antenna, yet I would like the convenience of
having the pre-amp inside. I am considering an adjustable pre-amp, and that
would be more usuable if I had it at the tv instead of at the antenna.
3. Will a brick chimney (with no steel liner or inserts) about 20 feet from
the antenna, but in-line with the desired stations, attenuate the signals
??
4. Are the Radio Shack pre-amps decent ??
------------------------------
My thoughts: Perhaps I will get a pre-amp that will produce about 20 db
of gain. I will mount it inside. The 50 ft of coax will have a loss of
perhaps 5 db, so I have a net of 15 db gain at the tv. This will be more
than enough for the vhf stations that are pretty close, but I am not sure
about the uhf station 25 miles away. It would seem to be good enough for
that as well.
What do you think ?? Thanks for any advice !!
--james--
I owned a firm which installed antennas and satellite dishes for 15
years.
First, I would install a UHF only yagi antenna pointed directly at the
station you wish to receive. I'm certain you don't have or have
access to a field strength meter, so just use a good grade of RG 6/u
coax and try hooking it up directly to your television. Rotate the
antenna for the best signal.
If the picture is still too snowy, then you need a preamp. The best
preamps these days are Blonder Tongue and they are commercial.
(residential preamps tend to be 300 ohm [flat wire] only and have too
high a signal to noise ratio to be decent). Do NOT install a preamp
at your set - that combination, as others have said, amplifies noise
with signal and won't help much, if at all. If you need to distribute
signal, a line amplifier is cheaper and better.
If you want some lightning protection, you might do this:
1. Run as direct a ground as possible with preferably copper strip to
one or more ground rods spaced 10' apart. Ground rods should be 8
foot 5/8" copper coated steel. If possible, the grounding conductor
should be welded to the rod or rods.
2. Before entering the house, coil the coax into three turns in a 12"
diameter circle. (The purpose is to create a path of greater
resistance to lightning while not affecting the rf signal).
3. Entering the house you should use a gas plug arrestor (Polyphaser
is one brand). This will set you back around $45 but they react in
microseconds and are just about the only effective lightning arrestor.
W_tom knows more about this than I do, but these are uniformly used in
all commercial installations for both cable tv, wireless internet,
cellular telephone, etc. Naturally, the arrestors need to be
connected to the ground system.
If you can't do this, just make certain you ground the antenna with
the heaviest wire you can find.
Good luck,
--
Larry
Email to rapp at lmr dot com
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