[Premium-Rx] Racal RF preamp

[Carcia, Frank A. HS]

You get a choice with Racal Dynamic range or MDS.
A good antenna system doesn't need the amplifier.
Check with Gary Wingerd on the preamplifier.
He may have the real part.    fc

-----Original Message-----
From: Thomas Adams [mailto:103360.2133 at compuserve.com]
Sent: Sunday, February 16, 2003 3:36 PM
To: Premium RX
Subject: [Premium-Rx] Racal RF preamp


Greetings!

I suppose that a lot of you, like me, are looking for
the somewhat scarce A1 RF preamp module to add to
thier RA6790/GMs and RA6793s.

I took a chance in the EBAY fishing hole, and it looks like
there's a way to go to deal with this need.

I got high bid on the RF preamp for the RA1792. From the
photos in the ad, it looked a LOT like the preamp in the
6700 series rigs...  in fact, almost identical to it. So, I took
a chance.

The preamp that came in the mail is VERY close! From
the electrical standpoint, it has a few very minor changes 
which shouldn't make any difference.  Mechanically, it
is again almost a spot on match, except that the cover is
somewhat different, and not attached as securely as it is
on the 6700 series preamps. 

I've been looking for one of these to add to my RA6793,
and this should take care of that need quite nicely.

Now...   the downside.

I was a bit disoriented mechanically at first when I looked
at how much of a problem installation will be. It appeared 
at first that everything on the preamp was mounted mirror
image to the 6700 series preamps, but that turns out to
be fatigue induced dyslexia <<grin>>, and confusion caused
by getting fixated on the preamp's RF input connector 
position!

Upon reflection, it appears that the RF output cable exit will
have to be moved to the opposite end wall. Other than the
possibility that the cable MIGHT not be long enough (not
sure as yet), I forsee no great problems with the preamp
itself.

What IS a problem (at least an irritation) is that I have to
remove the back panel of the radio for drilling. Standard
back panels for RA6790/GM and RA6793 do NOT have
the required mounting holes or RF input connector hole.
The existing antenna connector hole (for the low pass
filter) is in the wrong place and will probably have to be
filled with a snap in plug...   tho the preamp case will
cover it if you're not that picky.

One good part...  my "pet" RA6790/GM has the RF preamp
rear panel already (and the preamp), so I have a good 
reference for the drilling pattern.

One last point...  the mounting screw hole bosses in the
preamp are, much to my consternation, threaded for
METRIC screws! I thought at first they took #8 SAEs, but 
that is not the case. A quick trip to the hardware store got
me four stainless steel metric screws (out of the EXPENSIVE
hardware bins...   ain't it always the way? <<smile>>).


This preamp brings up a very good question to ponder.

A lot of folks will swear up and down that the RA1792 is the
ULTIMATE receiver for DXers. If that's the case, why is the RF
preamp a standard issue item in the RA1792, but it's an
OPTIONAL item in the RA6700 series rigs? 

Did Racal originally design it to cure a doggy front end in
the RA1792? 


73's,


Tom, W9LBB

Owner & Operator of the 
Mahon Loomis Memorial Monitoring Station &
Irish Setter Retirement Home

Sun Prairie, Wisconsin


 

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