[Milsurplus] Question ( RBS; submarine )

[Kenneth G. Gordon]

On 24 Aug 2016 at 7:38, Bill KA8VIT wrote:

> It is my understanding that U.S. subs in WW2 used the RAL/RAKs because
> they are TRF radios and not superhets which emit a local oscillator
> signal onto the antenna which can be DFed when the receivers are in
> use. 

Well, that is definitely, but only, true when receving an AM or MCW signal, since the 
regenerative detector is in the non-oscillating condition for those modes.

However, during WWII, all submarine comms were carried out via CW. In order for the 
RAK/RAL to receive CW, the regenerative detector must be in the oscillating condition in 
order for the operator to hear the CW signal.

In fact, during the time that the regenie was being used by experimenters in the early days 
of the broadcast industry, there was so much interference to other receivers from those 
detectors that they were roundly hated. They were called "bloopers" and had no RF amp 
between the detector and the antenna.

The RAK/RAL (and other receivers somewhat like those) included at least one RF amp 
stage in order to "decouple" the detector from the antenna. In the case of the RAK/RAL 
there are two RF amp stages, the main purpose of which is isolation, not amplification.

FYI, I used an RAL-7 as my main station receiver for at least 12 years, so I am quite familiar 
with the way it operates. I have at least one operational one now. I really like them.

All of the above is yet another reason I am in agreement with Meir concerning DFing 
receiver radiation: it didn't happen.

One more thing: the RBO is a Scott receiver. It is a superhet and has an LO. The Scott 
receivers of that time period were specifically designed to minimize the radiation from the 
LO. Scott's model designations began with SLR for Super Low Radiation. 

For instance, the Scott designation for the Navy model RCH was SLR-F. Some RCHs still 
had the SLR-F model name on their nomenclature plates. The RBO also had an SLR 
designation. It may have been SLR-B, but I cannot remember now.

The Navy specificed no more than 400 micro-micro-watts of LO radiation reaching the 
antenna. All Scott receivers of the period easily met that specification. National had to add a 
second RF amp stage to one of their "full-dial" receivers in order to meet it. That RF amp 
stage was added to a special "porch" on the back of the receiver. I cannot remember the 
model though.

Ken W7EKB

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