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.
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