[600MRG] RAKs and such - ballast tube.

[Kenneth G. Gordon]

On 4 Nov 2014 at 11:17, Bill Cromwell wrote:

> I haven't played with superregens. I wonder if the signal is stronger or 
> more pronounced than a plain regen.

Supers only really work decently at frequencies above about 30 MHz since 
the "quench" frequency must be some fraction of the operating frequency. 
The signal is quite a bit stronger than a simple regen, but using one at HF is 
very difficult.

> I have read of some hams using superregens to copy local repeaters 
> accidentally jamming some local hams - within a few city blocks of the 
> superregen. My impression of superregens has always been one of it being 
> a particularly 'dirty' radio.

Yes, they most certainly are: even with an RF amp stage ahead of the 
detector. The RF amp doesn't evey really have to exhibit any gain, but even 
then, the receiver radiates a very strong signal.
 
> In private email somebody offered a reference to a WWII german submarine 
> being discovered when a destroyer noticed a signal from the submarine's 
> superregen radar detector.

Well, there is far more to that story than simply that issue. I believe the unit 
was called a "Metox", although I am not certain about this. 

The Germans captured one of "our guys" and when interrogating him, asked 
him how the Allies were able to detect their submarines so easily. He lied like 
a real trooper and told them that they had homed in on the Metox...which 
was a downright lie. The truth of the matter was that the Allies at that time 
had some radar that was operating WAAAAY above the frequencies the 
Germans were aware of.

His little lie was taken for gosple truth, and the Germans ordered their 
submarine captains to turn off the Metox detectors. This, of course, resulted 
in more sinkings by the Allies.

> The reference came with a starting point on 
> the trail and I'll chase that one to it's conclusion. Information like 
> that is likely to have come from logs and action reports.

Agreed.

> Those reports 
> and logs can still be found in archives. Even logs and reports from 
> vessels that did not survive the war are still available up to a point 
> before the vessel was lost. In some instances the log were removed by 
> the survivors when they abandoned the ship. I would like to see "first 
> contact with the enemy vessel came from detection of it's radio receiver" 
> (from 30 miles away?). No logs are available from the Titanic I suppose. 
> Maybe a few reports that were filed before she left on her maiden 
> voyage. The captain and senior officers did not leave Titanic with logs.

In point of fact, after WWII the Germans were asked if they had ever used 
radiation from receivers to home in on Allied shipping, and they categorically 
denied that that method was ever used. As I understand it, they actually 
thought the entire idea was funny. They insisted that they had far more 
certain methods than that.

Even so, the U.S. Navy took the matter very seriously and tests all receivers 
for LO output, mandating that any receiver accepted by the Navy had to 
exhibit a very, very low LO output.

The Scott company sold many, many receivers which were specifically 
designed for "Super Low Radiation", the SLR series.

I have two SLR-Hs here, both of which are nomenclatured RCH.

National was forced to add a second RF amplifier to at least one of their 
receivers, the RAO, via a "back porch" to achieve the specified low radiation.

Ken W7EKB