[GreenKeys] Might be a bad weekend...

[David I. Emery]

On Sat, Dec 01, 2007 at 11:01:20PM -0800, David Ross wrote:
> 
>    Dave -
>       What sort of TU did you use to receive the 85CPS shift VFT MUX sigs
>    back then?

	Various depending on precisely when.  The one I first used was a
modification of Vic Poor's tube TTL II using commercial 85 hz tone
filters I found surplus (I think made by Northern Radio) and various 88
mhy toroid discriminator hacks.   I also played around with some surplus
TUs designed for those shifts, but the TTL and a model 28 was my
mainstay for quite a while.

	Later I did some playing with heterodyne (superhet) type designs
using ICs... and with digital processing of the tty (speed and code
conversion).


>       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.

	I have some Plantronics 1280s that are also tunable in mark and
space - I think up to 6 KHz... but I admit to not having played with HF
TTY much in MANY years... (My wife will SHOOT me if I acquire a 28 for
old times sake...)

>       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.

	I've seen those receivers, but never owned one.  I eventually
landed a broken R-1051 at a hamfest in the early 70s and fixed it and
used it a bit in the 70s for VFT, but by that time my focus was more on
satellite signals than HF...

>       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.

	I've never seen a 116...


>     (My  CV-157  has  USAEC UCLRL engraved on the front panel, and I have
>    often wondered just what the weapons boys used it for...)

	I'm sure there were lots of HF VFT circuits in support of bomb
tests in the Pacific ... and I understand that one of the earliest PAL
designs (Permissive Action Links) was based on reed relays and precise
audio tones sent in particular sequences, so the ability to track HF
pilot carriers and recover tone frequencies accurately would have been
important for that if it was ever fielded...


-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."