[amsat-bb] Re: New Preamp

[Gary Memory]

Indeed....a preamp can be a good thing.  I own one myself.  But, in my
current location, a preamp is causing too much compression and I end up with
lots of unwanted noise and other products that make it worse.  It is true
that I get a good amplification of the received signal, but the total,
overall result is worse.  Sigh.....the term location, location, location is
so true.  I overlook the city of Frankfurt, Germany and there is simply too
much high power RF that gets sucked into my amp, along with the signals I do
want.

I have a WACCOM cavity filter for both VHF and UHF that I'd like to use at
the mast head, but they are too big to get up there (and they are not
weather proof).  Oh, and they are only a couple dozen KHz wide, which makes
tuning to a different frequency a bummer.

My moral, if it works, by all means do it.  But from my experience,
attenuation is just as valuable as amplification.  It all depends on your
individual situation.  Maximum gain doesn't always mean maximum useable
signal.  Maximum total system noise figure can be a bit daunting to achieve.
I sometimes need to keep reminding myself that this is only a hobby and I am
getting way too serious!!

Gary, N7BRJ/DA1BRJ


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Jim Jerzycke
Sent: Tuesday, September 18, 2007 6:26 AM
To: Bob Stewart; Amsat-BB
Subject: [amsat-bb] Re: New Preamp

 
Welcome to the wonderful world of mast-mounted
preamps! 90% of the people who get involved with
satellites (INCLUDING myself) think they don't *need*
a preamp. After doing all you can (better antenna,
lower loss feedline, etc) to get your receive setup
maxed out, you finally decide to "just try one; I can
always sell it on eBay", and are usually amazed at the
improvement it gives you.
The _first_ thing I suggest to newcomers is to buy a
good preamp. Sadly, most are like I was, and stumble
around for weeks or months worrying about other things
before finally buying one.
Congrats, and enjoy your preamp!
73, Jim  KQ6EA


--- Bob Stewart <bob at evoria.net> wrote:

> My new 70cm preamp came in today!  I got the ARR
> mast-mount
> version.  I wasn't sure I'd hear any improvement,
> but it's very
> noticeable.  I was able to hear QSOs on SO-50 down
> to about
> 15 degrees tonight, whereas before, 20 was really
> stretching.
> I am using a turnstile in the attic with reflector
> elements at about
> 9.25" below the radiators.  I can see that I'm
> eventually going to
> have to build more robust versions of my turnstiles
> and put them
> on top of the roof.
> 
> My power supply is a bit odd, so maybe someone will
> get a kick
> out of it.  I have an Atlas 210X left over from
> years ago, and
> the PSU will power either of my bricks.  The 210X
> slides into the
> PSU which an SO-239 on the back of it.  In order to
> get the power
> up to the preamp, I added a fused switchbox and sent
> the power 
> through that SO-239.  This allowed me to just screw
> on a Radio 
> Shack 50 ft length of RG-58 without having to cobble
> up a 
> connector on the rig end.
> 
> Bob - AE6RV
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