[Lowfer] Medfer freq measurement

[Ed Phillips]

Bob Roehrig wrote:
> 
> On Mon, 6 May 2002, Mick Reed wrote:
> 
> > I have heard some people mention frequency drift due to propagation changes.
> > How accurate will my reception of 2.5MHz be?  I want to measure with an
> > accuracy of 1Hz or better.
> 
> 1 Hz at what frequency?  Best you can obtain form WWV on HF is 1 part in
> 10^7. You need a good steady sig from them (minimal fading) and ideally
> watch on the S-meter for the beat as it will be difficult to hear audibly.
> 
>                     73        Bob Roehrig        K9EUI
>                     Aurora University Telecom/IS dept.

	I'd pick a higher frequency (5 or 10 MHz) unless you get a good signal
with not much fading.  When the multipath fading is severe you often get
180 degree phase reversals at the nulls; it's easy to see these if you
use the bfo to generate an audio frequency note and then make a lissajou
pattern on your scope, using an audio oscillator on the X axis.  For
really good precision, but taking a lot longer to make a measurement,
you should probably try WWVB on 60 kHz.  The advantage of the HF signals
is that you can make a measurement in a couple of seconds if you're only
going for 1 Hz accuracy.

Ed