[GreenKeys] FSK Keyer Information Request

[Roy Morgan]

At 11:46 AM 10/13/2004, jhhaynes at earthlink.net wrote:
...
>Then there was the classical circuit used by the military and commercial
>operators.  They ran a 200 KHz oscillator, frequency modulated by a
>reactance tube.  ...  it's another box, quite a big one
>in vacuum tube days,

Yup.  Both the Northern Radio Corporation and the TMC FSK exciters are 19 
inch rack mount units about 10-3/4 inch high.  I have one of each here and 
intend to set them up in my TTY station.

>and the VFO frequency has to be 200 KHz away from
>the intended operating frequency.

Indeed.  The instructions for the TMC gear explain that.  It gets more or 
less complicated when the output of the FSK exciter is multiplied up to the 
transmit frequency.  NRC does it one way, TMC does it anther way.

>   And the 200KHz oscillator has its
>own drift - they usually put it in an oven.

Or two concentric ones.  When I fired up one NRC unit, it let some smoke 
out. The former residents (presumably mice) had peed upon the flat heater 
element.  I assume that electrical conductivity caused the thing to burn in 
a small area.  It's not yet repaired, but I expect success after washing 
and re-connecting the heater wires by crimping them.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --