[GreenKeys] 10cps shift

[Roy Morgan]

On Dec 1, 2009, at 11:48 AM, Nick England wrote:
>  ...
> When/where was 10cps shift used? - seems awful narrow for 1950's
> technology to me.
> I'm guessing it may have been used for VLF -

Nick and others.

Yesterday I read most of the Transmitter Visits site for WLW in  
Cincinnatti.
hawkins.pair.com/wlw.shtml
(Cruise the rest of the site for some real heavy metal.)

They are still on the air at 700 kc, by the way.   WLW did also  
transmit the narrow shift signals you'll learn.  WLW was (still is?)  
one of the 50 kw clear channel stations. WLW did also transmit the  
narrow shift signals you'll learn.

>  if you're transmitting
> into a high-Q antenna at 18kc there ain't much wiggle room.

Yes, indeed.

I was fortunate to visit the VLF station at NSS Annapolis before it  
was dismantled.  On that trip we learned that the narrow shift FSK  
keying put the carrier alternately on either side of the center of the  
tuned system.  It was some 10 percent down the slope (memory of the  
details are faint.)  But the antenna current was monitored at the  
console and would vary depending on how far down the slope the tuning  
had shifted the center of the very narrow sweet spot.  The operator  
could vary one of the inductors in the system by remote control to  
match the two currents.  That system operated at 20.4 kc I believe, at  
an output power of about eight tenths of a megawatt.   The shift may  
have been on the order of 10 to 15 CPS.  The antenna was one mile  
long, about 800 to 1200 feet up, and was tuned with a massive inductor  
made of five inch diameter litz wire.  Cutler Maine still operates  
with similar parameters, as far as I know.

Roy

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073
Home: 607-898-3607
Cell: 301-928-7794