Need Info on General Radio Frequency Meter-Monitor Type 535-A

[AJ1G]

The subject item, Serial No. 22, followed me home from Near-Fest Saturday.  I assumed that it might be a hetrodyne type frequency meter, like a BC-221/LM and a little digging via Google confirmed that it is indeed just that.  Although it looks like, and is built like, a typical piece of early GenRad lab grade test equipment, it was developed specifically for amateur radio use!  It consists of a single type 24A tube Colpitts variable oscillator/detector, that  operates over the range of 1700 to 2000 kc, "with useable harmonics through 56 mc...capable of  up to 1 part per 1500 accuracy".  So, it gives coverage over the ham bands from 160 meters and up.  Just the thing to keep from getting a pink slip when working  all the DX on the low end of 40 meters!

Very simple design, with  large vernier dial calibrated 0-300 in single digit increments over 180 degrees, with a little magnifying lens to aid in reading the dial.  A power switch, 1/4' headphone jack, and a terminal to attach a pick up wire to.  That's it.  No gain control or regen control.  There's a frame on the side of the case, which apparently held the dial calibration chart, which unfortunately is missing on mine.

Power is apparently supplied externally, as there is a terminal strip  for filament and plate voltage inside the case, and a hole in the back to lead external power in through.  Looking for a manual for it so I can try to get it going....I know it would need 2.5 V for the 24A but not certain what plate voltage might be, probably in the neighborhood of 90 volts?  

I assume the "monitor" function refers to the ability to monitor a CW transmitter note in the detector output.  If I can get it going, I'll make up a new cal chart using my HP  counter.  

Anyone out there have a manual, or could point me to one?  I may try calling  Gen Rad up in Cambridge, IET Labs, the company that now owns them, maintains a big on-line archive of old catalogs, which is where I found out what I know so far.  Wonder  how many hams actually bought one, probably not many!  Looks like early 30s manufacture, sold for $42.50, a lot of money when money was really tight!  

[Pete, WA2CWA]

From the book A History of General Radio Company 1915-1965:
"The June-July, 1933, issue of the General Radio Experimenter was remarkable. In that one issue were described three new products, each, in its own way, a forerunner of major significance in the industry.
The most important was the Variac® adjustable autotransformer...
A second instrument was the Type 535-A Electron Oscillograph."

It seems that General Radio must have reused model numbers.

[AJ1G]

I saw that also Pete...confused me right out of the gate in Google searching.  I found the freq meter info in one of their sales brochures directed at ham applications. Wonder if the history document is in error wrt the scope ID.

I have a Tek 535 lab monster scope here that was a give away from Al W1UX. It came from the URI EE labs, I probably used it there as an undergrad.

[AJ1G]

http://www.ietlabs.com/pdf/GR_Catalog/Bulletin%20936%20Jan%201935.pdf

Link to a 1935 Gen Rad sales bulletin that illustrates the 535A frequency meter...it's on page 25.  One of the things I noted in the bulletin is that  each item has a "Code Word" assigned to it.  What's up with that?  The 535's is "MERRY".  It looks  happy enough...wonder what the code words were used for, and how were they assigned, some of them are pretty funny.

[W7TFO]

Code words were very popular with all kinds of companies back in the first half of the 20th century, to be used when using a telegram for ordering or info in order to save lots of word charge $$, rather then a full description.

73DG