Doc,
I have some similar needs at my QTH. I suggest you try the following:
1. Google up "Winegard" and check out their line of mast mount pre-amps.
Look very carefully at the spec sheets, which can be downloaded from their
web site. The AP-series of pre-amps are available in a couple of
different gain and noise figure configurations, and they also publish the
overload capabilities. I have been VERY pleased with my Winegard pre-amp;
it really is resistant to overload. One more thing: it's actually made
in USA!!! (The wall wart power supply and bias-T are made in China, but
that's expected.) If you like what you see, follow the click links to
their on-line retailers. I found that Solid Signal has very good prices
on the Winegard products.
2. Next, keep in mind the following: NO such broadband device as a
VHF/UHF pre-amp is going to have brick wall filtering characteristics at
the bottom and top ends of its passband. If you are concerned about HF
overload, put a good, in-line high pass filter at the INPUT to the pre-amp
to minimize any effects from your HF operations. That is very important
if you are going to operate 6m. I have had no problem with 2m, but when I
transmit on the 222 MHz band with 30 watts, I do get some problems on a
couple of channels. I'll live with that for now, but I do plan to put a
222 suck-out trap on the input to the pre-amp one of these days to see if
it will reduce or eliminate the interference. I've had no problems at all
when using 70 cm band, any mode, at 100 watts.
3. I placed my pre-amp about half-way down the tower so as to keep it out
of the near field of my VHF and UHF antennas. That seems to work OK. The
unit is in a plastic case (rats!). I can also tell you that if your tower
takes a lightning hit, as mine did in April, the pre-amp will be toast. I
am trying a new idea to see if I can keep the replacement pre-amp from
heading to that big silicon pile in the sky: I am providing a physical
grounding and bonding link between the IN and OUT ports of the pre-amp and
tying that link to the tower itself. The idea is to not have any
lightning current pass thru the pre-amp (which is probably what killed
it), and to reduce the chances of arcing by bonding it to the tower
structure. The IN and OUT type F connectors are the ONLY means to make
this connection. If that idea doesn't work, the next try will be to
totally repackage the pre-amp into an all-metal case.
4. Besides the aforementioned high pass filter on the pre-amp input, you
may also wish to insert an in-line surge suppressor. These are available
with type F connectors at MCM Electronics, and perhaps other places. You
really have to be careful what you place on the output of the pre-amp
because DC operating power for the pre-amp is fed to it via the supplied
bias-T and into the "OUT" connector. That method saves having to run a
separate power cable to the pre-amp.
Good luck.
73, Dale, WA9ENA
kd4e <doc@kd4e.com>
Sent by: rfi-bounces@contesting.com
06/03/2009 08:27 PM
Please respond to
doc@kd4e.com
To
RFI List <rfi@contesting.com>
cc
Subject
[RFI] Mast-mount TV Pre-Amp -- Avoiding RFI & Overload?
We are out in the woods and I need a mast-mount pre-amp for
TV signals.
This one is only $26. but I worry that it is junk which will
fail early and may
distort signals and fail to exclude Ham signals below 6M as
well as 6M, 2, &
440.
http://www.summitsource.com/product_info.php?ref=7&products_id=5741
AntennaCraft 10G212 Antenna Pre Amplifier 30 dB UHF / VHF / FM
Has anyone used one of these?
Can anyone recommend a better device?
Since using a mast-mount pre-amp will eliminate the need for
a rotator
it is worth the investment of a few extra dollars.
WDYT?
--
Thanks! & 73, doc, KD4E
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