[time-nuts] VLF Phase-tracking receivers.

Kenneth G. Gordon kgordon2006 at frontier.com
Sun Aug 10 21:27:10 UTC 2014


On 10 Aug 2014 at 15:24, Martin VE3OAT wrote:

> As I recall (it was a long time ago), it was called Minimum Shift 
> Keying

You're correct: I just looked it up.

> and used the minimum frequency shift (FSK) that would permit 
> reliable detection of a bit (mark or space) at the given information 
> rate.  Something like 25 Hz shift at 50 baud keying.  But it was 
> necessary to control the instantaneous phase of the signal very 
> carefully.

Yes again. Back in the 1970s, I was working with a fellow who was doing 
VLF propagation research. We were notified that the U.S. Navy had shifted 
to MSK and some method of stable phase transmission. The Navy told us 
they were installing special equipment to make that happen. As I remember 
it, they called it something like "coherent phase transmission", but I could be 
wrong.

There is a note in the manual I found for the 599-CS to that effect, in MY 
handwriting and signed with my initials.

>  As a result the spectrum of an MSK signal is quite 
> distinct from that of an ordinary FSK signal.  As I recall.

Well, you have an excellent memory. :-)

Ken W7EKB



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