[amsat-bb] Re: AMSAT-BB Digest, Vol 7, Issue 65

Wed Feb 8 13:23:30 PST 2012


I had the same experience with my ARR.  Fortunately no harm done.  I ended
up lifting the choke connection internally.  Apparently ARR has never heard
of steering diodes.  

My other issue was that the "waterproof" case filled up with water.  You can
imagine my face, and vocabulary, when I opened it on the work table.  Easily
fixed with RTV.  Another reason I personally prefer the SSB units.


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Burns Fisher
Sent: Wednesday, February 08, 2012 2:33 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: AMSAT-BB Digest, Vol 7, Issue 65

Here are a couple things that were less than obvious to me about the ARR
70CM switched preamp.

If you are going to power it with phantom power (i.e. up the feed line) you
need to add a -C to the part number so they will add in the required choke
from the feed line to the power input.  But note that once you do this, you
can't just use either phantom or external power.  In my case, I got the
choke ("I might need it someday") but used the external power. Oops...a
nice short.  It turns out that unless your transceiver has a high-pass
filter (or just a cap!) you are probably going to be shorting out back
through the feed line.  When you do that, you may blow the choke and have
to remove it anyway, depending on how much current got through it. (I'm not
sure why they did not put a diode in, but hey...)

The other thing is that I was going to get one of their phantom power
injectors also.  The problem there is that they only work with
receive-only.   So unless you can find one elsewhere, phantom power may be
useful mainly if you transceiver supplies it (sigh, mine does not).

And finally, another inobvious thing:  The power connector has a third pin
which, if you ground it, switches to transmit mode.  So if you hook this up
to the transciever, that's a way of getting around the "minimum power to
switch" spec.  (I think minimum power to switch is maybe 5W; my transceiver
goes down to 5W, but with a 75' feed line, it's not gong to be 5W by the
time it gets to the pre amp.

The SSB preamp (or at least the 2M one that I have) comes with the choke,
diode, etc and has a lower minimum switching power.  It is more expensive,

I hope this helps!

Burns, W2BFJ

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