My Temporary Listening Post
Here's a temporary lash-up that I have off to the side of my Ham shack operating position.
Whether your into surveillance, intercept, or just plain monitoring, this combination is hard to beat.
KIWA MAP Unit which taps the
receivers' IF and allows various
demodulation functions, filters, and
My Type-5 Ptreselector which feeds
the Watkins-Johnson receiver.
My Type-3 Preselector feeding the
A restored Watkins-Johnson
WJ-8718A that covers VLF, LF, MF,
and HF bands
A slightly modified RACAL RA6790/GM
with similar coverage as the W-J.
Go here to see the detail development of some
of the preselector, preconditioning, and other
There's a lot to be said about all this stuff. I have played (and worked) with much more expensive
equipment. What comes to mind are the excellent Tentec RX-340 and Watkins-Johnson HF-1000
(WJ-8711). Those are all great, and easy to come by, if you have a multi-4-digit wallet. But if you want to
build an LP that meets most all the requirements, and can scrape together less than a kilo-buck for each
piece of gear, then the above LP is something to consider. The preselectors are really not needed unless
you are super serious about catching the real weak transmissions, or if you do a lot of weak signal digital
data work. Both the above receivers were good enough for many intelligence agencies around the world
in the 1980s and 1990s. many are still in use. That reminds me of the Godfather of G2 radios; the great
Collins R-390A. Some day I'll make some room and get another one. I really miss that 85-pound monster! If
that creature is out of the question, but you really want to own a Collins, there's always the great 51S-1 ...
less tubes, less weight and some compromise in performance, but what a nice receiver.
Of course, radios will only recover whatever signal voltage appears across the antenna port. So it's
important to have a clean, noise-free feed from a good antenna - or a few antennas. I'm using 160 and 80
horizontal meter wire antennas, along with an 80 meter sloper, and at times, various loops. It seems to me
that if you can put up a 60 to 90 foot end-fed, or inverted "L", that is clear of household and
neighborhood noise, and feed it to the shack with good coax, and 9:1 balun, then you've pretty much
done a good job for these radios' appetites.
A Note About Grounds:
The following is based on my experience with professional communications installations, and what I've learned at Commercial,
Military, Embassy, and Government sites - what they do and what they don't do. Some of this does not reflect what less permanent
installations, or stations beyond the purview of the law practice. An example might be found at less permanent military, embassy,
and TSCM* installations. I will expand on that in the future and try to illustrate those techniques. That's another discussion having
mostly to do with different mode communications or for different reasons and not necessarily weak signal intercept or long-term
surveillance. Opinions will vary immensely, and so will what happens in the real world. What I am offering here is some very
cursory practice that is mandated by operation and law for permanent commercial installations. Different conditions exist for other
circumstances and situations, such as the Military Field Installations, Embassy Comms, and some Government TSCMs mentioned
Here's the basic rule: "If you want to start a fight, start a discussion on antennas...or grounds."
It's not just a good receiver that is required for the absolute best performance. Signal to noise ratio is the name of the game. You
would, ideally, love to have an antenna system that is quieter that the radio's noise floor. That's going to be near impossible. But
grounding techniques will help ... a lot. Remember, your radio can only work with whatever signal voltages appear across its
antenna terminals - nothing more. The radio is as healthy as the diet you feed it! If you feed unwanted noise to the antenna port, then
the radio is going to hear it ... and so are you! Proper grounding technique may be the difference between a super quiet station and
an unusable one. I have seen many cases where coax feed lines actually adds noise to an antenna system. Common mode RFI
voltages from your home can travel up the outer surface of the coax shield and become a part of the differential received signal
that travels back down the center conductor. For end-fed antennas, the feed point should always be transformer isolated. I routinely
use a 9:1 or 10:1 balun (actually unun) with ground connections right at the feed point and a good quiet shack ground system that is
bonded to the household system. Remember, the antenna port sleeve on your radio is probably at chassis ground potential. From
that electrical point is the 3-wire AC power ground (green wire in the US) which probably is a conduit to unlimited household noise,
and the coax braid, which you want to remain RFI clean. If these two conductors are at different potentials and/or see various levels
of RFI, then the radio probably will too - the radio's chassis will NOT be at a noise free ground potential. The potential differences
between the house and RF grounds must be zero. A power line cord's ground is a very high impedance at RF frequencies and is not
the place to try and bond all grounds. The best way is by insuring that your power distribution system and RF feed system are all
electrically bonded ... for electrical, lightning, and noise safety. If in doubt, contact a specialist or learn about whole house bonding
on the Internet.
Another consideration might be a isolator transformer at the building entry point. But that's another, and involved discussion. Take
some time and surf the Internet for many of these topics - try to lean away from hobbyist opinions and more toward what
professionals have to say.
Of course, you may be lucky, and whatever grounding you have already done, or not done, and whatever combination of house and
signal grounds that exists has resulted in a dead quiet signal chain, then you may be good to go. Just remember to play safely.
Have fun and good signals.
I've recently added the brother of a receiver I used years ago. The radio that captured my affection was
an ITT Mackay Marine 3040A. I found the 3030A version of the radio through eBay where my (new) friend,
Randy McIntosh (bigapple59) had one up for auction. I'm not associated with Randy, and have never met
him, but through our e-mails and the transaction, I'd say he's a pretty cool guy. The auction went super
smooth, communications between us was great, the radio was packed professionally, and delivery was
fast. So now I once again have an ITT Mackay, at a very reasonable price. Thanks Randy.
These radios have a very low noise floor, are super stable, fantastic dynamic range, and very good
recovered audio ... with an external speaker. This is not a radio for scanning. Heck, not even for band
surfing. It uses individual decade switches to set the frequency, not unlike its namesake, but unrelated
McKay/Dymek company. In the Signal Corps, we would have called this a "Monitor," or more appropriately
a "Surveillance" receiver. It's certainly not an "Intercept" radio in the operational sense. This unit is in
the same league as the Racal and W-J pictured here. The filters are sharp, build quality is superb, and, as
the marine market dictates, it incorporates durable components.
This radio will join the other two, in a rack with a multi-coupler, a Kiwa MAP unit, and one of my
preconditioner/preselectors. I feel as though I've gone back in time and am sitting at a Listening Post in
the Army Signal Corps -- and it feels good. The ITT-Mackay is the top unit below.
|Type 5 Preselector
Type 3 Preselector
ITT Mackay 3030A
ITT Mackay Marine