[Milsurplus] RAK question

[Kenneth G. Gordon]

On 25 Dec 2017 at 14:26, Joe Connor via Milsurplus wrote:

> Merry Christmas everyone!

Merry Christmas, Joe, to you and yours.
 
> My wife got me a nice RAK receiver for Christmas. I haven't messed with these 
> lower frequencies before, so I'm wondering what I can expect to hear below 600 
> khz, other than the low end of the AM BCB.

Lots, Joe. The "new" 630 meter ham band, and another at 2200 meters. NDBs (it is fun  
"dxing" those), and many other sources. You can still find a few of the Navy VLF stations, 
but they are all transmitting TTY now. Russian and other foreign stations are still there.

The RAK is, in my opinion, one of the finest VLF receivers ever made. Supremely stable, 
VERY and unusually selective, very sensitive. The "other side" of zero-beat simply didn't 
exist in my RAKs.

Which model did you get? The number after the "K" indicates both who made it, and some 
extremely minor upgrades from earlier models. For instance the only real difference 
between the "6"  and the "7" was the inclusion of a shielded antenna connector in the "7" 
from the large "push" connector of the "6". The RAK-8 was made by Motorola and its front 
panel "labels" are some sort of phenolic which was printed on.

BTW, all the by-pass capacitors in those receivers were oil-filled and as long as the receiver 
was stored upright, they are still good. I have one RAK here which was stored for many 
years upside down and all the oil-caps leaked.

There are some very few capacitors which couple between stages and some of those can 
be leaky by now. The way you can tell if one or more of those are bad is if you hear "static" 
with no antenna connected. They are easy to reach and can be replaced with modern 
micas.

Lastly, there is no good reason to use the huge ballast tube in the power supply, since your 
line voltage is not being swung up and down as your ship's turrets are being swung around. 
It is by far best to both switch it out of the circuit (there is a switch inside the power supply to 
do this), and totally remove the ballast tube. This removes some 300 watts from the load on 
the power supply and its resultant heat. 

Also, you can lightly couple a frequency counter to the output of the detector and have 
direct frequency readout.

> The power supply appears to be in good shape, so I'll be hunting the hamfests 
> next summer and searching the ham ads looking for an RAL receiver.

You might also watch for the small control box which made it easy to listen to either, or both, 
the RAK and RAL at once. I have one here, due to the kindness of Dave Stinson, which I 
intend to restore and use with my RAK/RAL setup.

> Given the 
> weight of these receivers, I'll have to find one in the northern N.J. area because 
> shipping would be prohibitive. The Navy sure liked its receivers heavy!

Yes. I used an RAL-7 for at least 12 years as my only station receiver and REALLY liked it. I 
have at least 6 of them here now (only one in operation), having received a bunch of RAKs 
and a few RALs from the estate of an old employer some time ago.

I used my RAK-7 to copy high-speed CW from the Navy VLF stations then (1960s), in order 
to get my code speed up. They transmitted almost continuious 5-letter code groups at 
around 30 wpm,. It was excellent practice. I really miss those.

Their station in Jim Creek, Washington put a signal into Missoula, Montana you could read 
with a crystal set and a wet string, 24/7/365. 

As you say, though, the receivers are really heavy to ship.

Enjoy your RAK. I am sure you will become fascinated with it.

Ken W7EKB

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