[GreenKeys] Might be a bad weekend...

[David Ross]

   Dave -
      What sort of TU did you use to receive the 85CPS shift VFT MUX sigs
   back then?
      Some  of the Tempest Dovetrons which George Hutchison & Glen Galati
   sold came from TSC-60(V)7 radio shelters and the Dovetrons were set up
   to  monitor 16 channel VFT MUX signals.  The common 16 channel VFT MUX
   format has the bottom tone pair at 425CPS +/- 42.5CPS and the top tone
   pair at 2975CPS +/- 42.5CPS, and those Dovetrons will receive over the
   entire 380 - 3020 CPS range.
      Yep  the  CV-157  was  used for receiving this VFT MUX traffic, the
   mechanical  AFC  function works very well.  Surprisingly, the CV-157's
   AFC  works  better  than  the  AFC  in  my  651F-1  receiver -  better
   stability  &  squelch  on  fading sigs and also faster slew rate.  Yes
   believe  it  or not, the CV-157's mechanical AFC will slew faster than
   the   651F-1's   electronic   AFC.   The  651F-1  receiver  was  built
   specifically  to  receive  this  VFT MUX traffic, it has provisions to
   receive  four  sidebands,  has  an AFC function, and has very wide and
   flat IF filters with consistent group delays.
      The  CV-116  dual-diversity  TTY  receive  converter  uses the same
   motorized AFC setup that the CV-157 has, in fact the CV-116 has a pair
   of  the  little  motorized  air-variable  caps.  But that is where the
   similarity ends, the CV-116 is otherwise pretty remedial as far as TTY
   converters go.
    (My  CV-157  has  USAEC UCLRL engraved on the front panel, and I have
   often wondered just what the weapons boys used it for...)
   73
   Dave Ross    N7EPI
   David I. Emery wrote:

        For years when I was VERY little (about 6-8) I thought these
signals WERE airplanes trying to talk over the engine noise (the voice
circuits on the other sideband would be faintly audible...) and in
subsequent years I found quite a few other young hams who really did
believe they had something to do with airplanes or were some kind of
jamming.

        I used a R-390A and 51J3 for my signal explorations, but by the
mid to late 60s the military had the R-1051 for use with these signals
which had under 3 Hz frequency stability and accuracy... and well before
that various other exotic full rack synthesized HF receivers were in use
with VFT signals both at land stations and on larger ships.  A R-390A
was really pushing things to hold stable within the 10-15 Hz it took to
demodulate these signals with acceptable distortion.    The R-390As 
actually used with VFT signals had an outboard tracking demod (a CV-157
if I remember right) that tracked the partially suppressed carrier with
a mechanical servo (I kid you not)....