Hi,

I posted here a few years back about my TV antenna:
http://tinyurl.com/a93e9

I'm now thinking of adding a pre-amp as someone suggested.

The antenna rotator receives some power through the walls and roof. Is
it possible to use this power to provide power to a pre-amp? If so,
does this apply to any particular model(s) of pre-amp?

I'm not using the rotator and would be glad to disconnect it from its
power supply if that would simplify matters.

I get good reception on NBC/ABC/CBS (all VHF) in general, but my
Dish-811 HDTV receiver only locks onto a sufficient HDTV signal from
PBS (UHF), FOX (VHF) and some of the other OTA channels about 75% of
the time, and I'd like to do better.

Thanks,

Jonathan

In article . com,
wrote:

Hi,

I posted here a few years back about my TV antenna:
http://tinyurl.com/a93e9

I'm now thinking of adding a pre-amp as someone suggested.

The antenna rotator receives some power through the walls and roof. Is
it possible to use this power to provide power to a pre-amp? If so,
does this apply to any particular model(s) of pre-amp?

I'm not using the rotator and would be glad to disconnect it from its
power supply if that would simplify matters.

The rotator looks like one of the standard sort, which is powered by a
low-voltage AC signal when it's rotating, and is unpowered when it's
not.

It might be possible to "piggyback" DC onto that arrangement to run
the preamp, but I think it'd be bothersome to try.

A more common approach is to use a mast-mounted preamp which is
designed to have its power fed up the coaxial feedline. You install a
small "DC injector" between the TV set and the feedline, and plug a
wall-wart DC adapter into the injector.

I get good reception on NBC/ABC/CBS (all VHF) in general, but my
Dish-811 HDTV receiver only locks onto a sufficient HDTV signal from
PBS (UHF), FOX (VHF) and some of the other OTA channels about 75% of
the time, and I'd like to do better.

Preamps are not without their disadvantages. They can do a pretty
good job of helping boost the signal to overcome losses in the coax
feedline and any downstream signal splitters. They don't help at all
with signal-quality problems due to external noise sources, or
multipath reflections due to trees or buildings, both of which will be
amplified just as much as the desired signal. And, if cheaply
designed (and many are!) they can be prone to strong-signal overload
from nearby transmitters.

The antenna you are using looks like a low-to-medium-gain variety,
without all that much directionality... it might not have enough
multipath rejection to keep your signals ghost-free. If it's old, it
may be suffering from enough corrosion on the elements and the
log-periodic line to be costing you some signal strength even before
the signal gets into the feedline.

Have you checked your coax feedline for quality and health? It's
quite possible that the original homeowner installed a relatively
inexpensive (and thus relatively high-loss) 75-ohm coax such as RG-59.
If the cable's been up for some years, it's possible that its
termination fittings (often simple crimp-on F connectors) have worked
loose, corroded, or allowed water to seep into the cable dielectric.

You might find it beneficial to replace your whole run of coax
feedline with a more modern type - a low-loss RG-6, rated for use with
satellite dishes, would be a good choice. Install new F connectors of
the appropriate sort, replace the 75-to-300-ohm balun on the antenna,
and waterproof all of the connections with Coax Seal or self-
amalgamating rubber tape or brush-on "liquid electrical tape" or the
like.


--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Replacing the coax makes a lot more sense, and is a good opportunity to
add some more outlets inside the house ... thanks.