[GreenKeys] Big Bird Dovetrons - More

[Jack]

ZCZC

Greenkeyers,

The Big Bird units have a modification which allows
them to copy RTTY tones from 300-3000 HZ. 
Most Dovetrons, including other Tempest models,
can copy from 1000-3000 HZ. There are two small
PC boards inside that are used to extend the
range of the VFO's (for the heterodyne circuits). It would be very
interesting to find out what these units were used
for (or, rather, were supposed to be used for, since 
a lot of them seem to be brand new). The switch that
reverses the AFSK tones is probably the 
strangest option. 

The keyboard transmit option is called "KOS", not
"KOX" as previosuly reported. Some ham circuits
were developed in the "old days" that were called 
KOX ( the same idea as KOS).

I got tied up with a "honey do..." project
today, so I'll get to the keyer schematic
tomorrow and hopefully get the unit running
to check some other curiosities.

By the way, some of the gang have recently acquired a
few Electrocom 402DL RTTY TU's that have real CRT scopes
but are otherwise the same vintage as the Dovetrons.
These units have two thumbwheel switches for selecting
the received mark and space tones. The units were
modified for the Canadian government and the loop
supplies were jumpered out, only outputting the
MIL188 signal. There is no autostart or AFSK. There
is a tone oscillator that outputs 1500 HZ when the
unit is receiving. Seems our government(s) had
unusual requirements which called for modifications
which "dumbed down" the units.

73,
Jack WA2HWJ