[time-nuts] Doppler and FMT

[Dan Rae]

On 9/19/2013 6:48 AM, quartz55 wrote:
> I was playing with SpecLab and my TS-2000 just to see how accurately I could measure frequencies in the HF region.  I notice when I set the rx on cw and listen to the 750 Hz output of WWV at 15 or 20 MHz with SL, I get like 2 and sometimes more tracks about 2 Hz apart constantly shifting around. I assume this is Doppler going in and out?  If that's so, how can anyone reasonably expect to measure any ionospheric HF signal in the mHz range?
>
>
Dave, it's not that easy.  I did the ARRL FMTs a few years back when 
they were transmitting from the other side of the States and thought I 
was doing well to get within 0.1 Hz.  The phase shifts on 7 and 14 MHz I 
was seeing due to Doppler were up to 360 degrees, and quite rapid.

Mind you I was using non computer techniques [1], so averaging by 
eyeball was possible.

Also if you are using WWV / WWVH, here at least, you often get both 
signals at similar strength, so you might well be seeing two different 
offsets.

Dan

ac6ao

[1]  looking at the 100 kHz IF output of the receiver on a scope, both 
scope trigger and Rx reference driven by homebrew GPS unit.