[600MRG] LF boat anchor receivers

[Kenneth G. Gordon]

On 24 Sep 2016 at 13:56, Rudy Severns wrote:

> To those LF/MF ops within driving distance to Eugene, OR.
> 
> I have a collection of very old LF/MF navy receivers (WWII) some of which
> actually work.  I do not need more than one sample of each but I have some
> multiples which I would be happy to give to those willing to pick them up
> (60-80 lb each!):
> 
> 1)      RBL 2
> 
> 2)      RBL6

For those who don't know, the RBL series were VLF receivers covering 15 through 600 kHz, 
designed by National which have direct-frequency readout dials and good filters. They have 
a built-in 110 VAC supply. The circuit type is TRF with 2 RF amplifiers (6SK7s), a 
regenerative detector (6SK7), 2 stages of audio amplification, (6SG7, 6K6) and an audio 
limiter (6H6). Rectifier is a 5Y3. They are very robust receivers and work well.
 
> 3)      RBA

This is possibly the last TRF designed by RCA and is considered the peak of the VLF TRF 
receiver design. It can use the same power supply as the RBB and RBC recievers. It has 3 
RF amplifiers, the third of which is operated at very low plate and screen voltages (15V) so 
that it operates as a limiter. This last stage also has an input to it from a local heterodyne 
oscillator operating 1 kHz from the operating frequency and tuned with it. The output of the 
3rd RF amp then feeds a triode plate detector. This is followed by a 1st audio amp, an audio 
limiter, and an audio output stage which is designed to feed from 1 to 20 sets of 
headphones. 
 
> 4)      HF mate to RBL
> 
> 5)      RAL 7, HF mate to RAK

I consider the RAL-7, also designed by RCA, to be the finest HF TRF receiver I have ever 
known. It covers from 300 kHz through 23 MHz. I used one for at least 12 years as my only 
station receiver. It uses the older 6 pin tubes, has 2 RF amp stages, a regen detector, 2 
stages of audio and an "audio AGC" which is basically a limiter. It is unusually stable, very 
sensitive, and very selective for a TRF. It has a very wide-ranged switchable (to frequency) 
audio filter system.

I have photos of some of these receivers on my website at:

http://www.w7ekb.com/glowbugs/BA/index.html

> 6)      BC348

My first GOOD station receiver. A very fine piece of equipment

> 7)      RAS

A National "HRO" type of receiver using plug-in coils, but with an IF of 175 kHz. An 
excellent receiver for the lower bands. Its 175 kHz IF does not produce good image 
rejection on the higher bands.

Manuals for all of the above arfe available from http://bama.edebris.com/manuals/ under 
Military.

> It's time for me to clean house and I have other stuff like large air
> capacitors, RF ammeters, etc, which could be very useful for an LF/MF
> station.  I would be happy to send these to a good home.
> 
> Contact me off the reflector.
> 
> 73, Rudy N6LF, WD2XSH/20

Thanks, Rudy. 

Ken W7EKB

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