[GreenKeys] Northern type 105 model 4A

[Robert Nickels]

Turned up on eBay at a reasonable price: 
https://www.ebay.com/itm/224368853373  (less power supply)

This interesting 35 pound unit is more than just an FSK converter, it's 
a complete FSK exciter that came from the factory set to cover up to 3 
crystal-controlled frequencies between 2.5 and 6.7 MHz.   According to 
the manual, the output shift was adjustable from 0 to 1000 Hz, and the 
keying signal input was 0 volts for a space (lower frequency) and from 
15 to 150 volts for a mark (higher frequency).    The output power is 3 
watts from a 2E26 PA tube.    It was designed to replace the VFO output 
to adapt existing AM transmitters for FSK operation.

Full documentation can be found on JP's excellent site: 
http://www.tmchistory.org/NorthernRadio/northern_index.htm

The one on eBay includes a model 163 adapter unit which I didn't find a 
description for, but I'll bet someone on GK knows.   I hope someone buys 
and puts this fascinating piece on the air!

73, Bob W9RAN