[Milsurplus] Question ( RBS; submarine )

[Bill Cromwell]

Hi,

I have a RAK-7 here and I tried using it with an LM to make tuning 
charts. The LM (and every receiver I have) could not hear the RAK's 
detector with oscillation cranked up! Inches away. Antenna wire probing 
an opening in the  RAK's cabinet. Nothing. Nada. Zip point s**t. The 
RAK, however could easily hear all the oscillators that are in it's 
tuning range.

73,

Bill  KU8H

On 08/24/2016 02:14 PM, Kenneth G. Gordon wrote:
> 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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