[Milsurplus] RBZ vs RBZ Special?

[jvendely at cfl.rr.com]

I have an unused RBZ Special set that I picked up years ago.  The manual packed with this set is the Navy pub covering the standard RBZ receiver. The original frequency range on the front cover is simply inked out, and "5-13Mc" applied with a rubber stamp just below it.  The frontispiece of the manual is treated the same way, and I don't see any other obvious changes in the text.  

Someone once told me that any RBZ could be retuned to the 5-13 Mc range without modification and that this, plus a replacement dial drum (or perhaps its numeral tape) was the sole difference between models. I've never verified this, though.  

Be careful handling that dial!  I passed a radiac set over my RBZ and RBZ Special and was shocked to discover how "hot" they are, due to the thick radium paint on the dial numerals. The paint has no obvious protective coating, and could easily flake or dust off on your fingers.  These two tiny sets were among the most radioactive I've measured, enough to make me think twice about operating them for long periods.  A friend of mine used to listen to HF broadcasts on his RBZ in bed till late at night, clipping to the the bedsprings as an antenna.  He occasionally fell asleep with the thing.  Needless to say, he doesn't do that any more.  The horror, the horror...

73,

John K9WT 


---- WA5CAB at cs.com wrote: 
> I don't have any modification details but some years before he died, Tony 
> Grogan told me that the modifications were made by OSS/MI5 and the modified 
> sets were dropped to POW's near the end of the War.  He thought that the dial 
> was re-marked in "reddish", which I took to be either red or orange.  
> Manual supposed to be TM 11-895, which I have never seen.
> 
> In a message dated 09/16/2013 15:37:50 PM Central Daylight Time, 
> gtsrmike at yahoo.com writes: 
> > I did think it sounded a bit strange when I first read it. If one could 
> > manage to find 7mc of adjustment in a trimmer then those must be some 
> > exceptionally touchy trimmer caps.
> > 
> > - Mike
> > 
> > 
> > --------------------------------------------
> > On Mon, 9/16/13, Al Klase <ark at ar88.net> wrote:
> > 
> > Subject: Re: [Milsurplus] RBZ vs RBZ Special?
> > To: "Mike T" <gtsrmike at yahoo.com>
> > Date: Monday, September 16, 2013, 3:29 PM
> > 
> > Mike,
> > 
> > That's a big step up in frequency.  I would have never
> > expected the trimmers to take care of it.  I think
> > you'd have to rewind the coils, rather than just pruning
> > them, as they need to be spread along a particular portion
> > of the form to tune properly.
> > 
> > Take care with the radium pain to the dial.  Like maybe
> > immobilize it with clear nail polish.  Mine's pretty
> > hot.
> > 
> > Al
> > 
> > On 9/16/2013 2:11 PM, Mike T wrote:
> > >I've been trying to research what the circuit
> > differences are between the RBZ and RBZ Special. The
> > difference on paper is that the RBZ covers from 2.0mc to
> > 5.8mc whereas the Special covers from 5mc to 13mc. From the
> > limited information I've been able to find it seems like the
> > conversion was a field conversion that involved little more
> > than realigning the receiver and changing the dial face for
> > a new one. I spent some time today attempting to do just
> > that on my RBZ and found that the RF and OSC trimmers would
> > only give about +/- 300khz of adjustment. I'm not sure where
> > they found an extra 7mc or so. Does anyone have any
> > information or ideas?
> > >
> > >- Mike
> > 
> 
> Robert & Susan Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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