[Milsurplus] RAK AND RAL RAB landed at SMECC anyone got a

[Kenneth G. Gordon]

On 21 Jul 2016 at 19:56, Robert Goff wrote:

> As others have said the RAK and RAL are excellent receivers.  Last
> time I checked the manuals were still available on BAMA.
> 
> I've had a lot better luck with a homebrew regulated supply on both of
> my RALs than with the big black RCA power supply.

Which weighs 65 lbs and draws 300 watts when the ballast tube is in operation. Gee!!!

> Lowering B+ from 180
> to 135 volts seemed to really tame the regenerative detector and
> eliminate microphonics.

I never, ever had any problem with microphonics. Sounds to me like you had a bad 6D6 or 
something ahead of the detector or behind it.

>  I believe I also changed the grid leak
> capacitor from the original 500pf to 100pf or so - more in line with
> most other regen circuits you'll find in the old magazines.

Reducing the grid coupling capacitor really improves selectivity at the detector stage. And 
increasing the grid leak resistor to a high value also increases selectivity. In one case, using 
something like 20 PFD and 20 megohms made a huge difference in selectivity. In fact, that 
may be too much for the RAL. I have never tried that with the RAL. Only with homebrew 
regennies.

> As an AM operator, the big drawback to the RAL (versus the RBB, or any
> other superhet) is the lack of AVC.

Well, the RAL/RAK does have what the manual CALLS an AVC, but all that really is is an 
audio limiter. It uses a 41 or 42. I forget which.

> With one 300W station within a
> mile in our roundtable riding the regeneration and sensitivity
> controls is a must - better be on your toes, too.

Ha ha! Yes, you can say that again. ;-)

> On CW, however, the
> audio filters are extremely effective.  Also, the RAL just seems
> quieter than your average superhet.

To me, the RAL had a sort of "transparency" to signals. I love the sound of it on CW. Signals 
just sound "cleaner" through it than through most superhets I've used: even good ones.

> It's still my go-to when the
> local noise gets bad.

Yes.

> I've logged a few NDBs with my RAK, but I believe the longwave
> broadcast is just about gone.  I recently read the Voice of Russia had
> cut back to just one station in the Transcaucasus.  The megawatt-level
> station on Sakhalin Island (now closed) had been in operation since
> the late twenties.  I'd really love to see some pictures of that gear!

Boy, you and me too. :-(

Ken W7EKB