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Old August 6th 07, 04:50 PM posted to rec.radio.amateur.antenna
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Default Questions about mast mounted pre-amps.


"Rob Brown" wrote in message
oups.com...
On Aug 6, 7:11 am, Bob Bob wrote:
Hi Rob

Thats a pretty wide open question... I don't have any model etc
recommendations for you, but since nobody has replied to your question...

Suggest you read up (web) and understand the implications of preamps,
then with understanding about gain, noise figure, IMD and power handling
go and compare various manufacturers models. Relying on empirical "it
worked well for me" from fellow amateurs is always fraught with danger!

Keep in mind that for some designs, best NF corresponds with really bad
performance in an adjacent strong signal environment. Fiddling with gate
bias current is a way to tune this to the best compromise.

You may also wish to review your choice of antennas. Higher gain and
steering may be something you'll need (eg for using the higher orbit
sats) and the wider pattern from the Lindenblad's may introduce more
terrestrial noise than you want. My next experiment for sat work will be
a quadrature fed interlaced 2/70 quad.. Cebik has some info on that..

If you are RX only you may even wish to build.

Cheers Bob VK2YQA

Rob Brown wrote:
I'm looking
for opinions on a good pre-amp, company and models. I know I need a
unit with a low noise floor, sub 1 Db.


Bob,
Thanks for the info. I won't be able to install a tower or any other
large expense project at my QTH for the near future. The XYL isn't
too keen on our hobby and so the best I will be able to do is the pair
of Lindenblad antennas. I'm going with the Lindenblad antennas after
reading the section L.B. Cebik has on his extensive web site. Antenna
is omni-directional, has gain from 3 to 50 degrees, and I can build it
with simple hand tools. I'll start looking for more information about
the pre-amps on-line. I had looked at the AMSAT site, but they didn't
mention too many manufacturers for the pre-amps.
Thanks,
Rob Brown
KB8WWS


Hi Rob

Have you considered joining AMSAT? There is a wealth of information on
HAM satellites within that organization. I consider Bob's advice about
preamps to be excellent. AMSAT Journal, Volume 28 Number 4, July/August
2005 has a good article on preamps for HAM satellite reception.
Cebik's text on Lindenblads implies that it needs to be located only a few
feet above ground in order to realize the "omni-hemispheric" pattern, so
line loss isnt likely to be reason enough to use a preamp with it anyway.

Jerry




 
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