[Elecraft] Checking VFO accuracy using WWV

[Emory Schley]

Hi Guys;
 
I really don't mean to show my ignorance, but all this talk about calibration and power out is good up to a point, but if your signal is off the mark by a couple Hertz, does it really make any REAL WORLD difference? Even when running PSK31 surely you can be off the "beam" a Hertz or two or three, maybe more– and you'll still have rock solld communications.
 
One fellow seemed unhappy with a rig putting out "only" 80 watts instead of the full 100, but there is no way the ham on the other end of the QSO is going to detect the "deficit". It pretty much boils down to "Can he hear me" and "Can I hear him"? If the answer is yes to both questions, then all the rest is just fodder for textbooks and endless discussion/arguing.
 
I know engineers and wannabe engineers want absolute accuracy. I'm no fan of sloppiness myself, BUT if you actually consider what you're dealing with along with the vagaries of propagation, then "close enough" should be good enough for anyone. If the tool (the radio/antenna system, in this case) is good enough to get the job done, then isn't that "good enough," period?
 
I really don't wish to start any in-fighting here, and I freely admit I'm not technologically competent enough to sustain my opinions in any absolute way in a technical discussion, but really, instead of wasting so much time slicing hairs, wouldn't you really rather be on the air instead, having fun? I would. :-)
 
Merry Christmas/Happy Hannukah/Have a Good Day (Take your pick),
 
Emory Schley
N4LP
 
 

Sent: Sunday, December 18, 2016 at 12:18 PM
From: "Brian Denley" <b.denley at comcast.net>
To: brian <alsopb at comcast.net>
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Checking VFO accuracy using WWV
Thanks to all for the explanations.

Brian Denley
KB1VBF
Sent from my iPad

> On Dec 18, 2016, at 8:46 AM, brian <alsopb at comcast.net> wrote:
>
> Expectations may be too high.....
>
> All these WWV methods assume there is no Doppler shift present on the WWV signal. Other things to consider: TCXO drift, synthesizer limitations and new synthesizer quirks.
>
> During disturbed times, Doppler could be 1 Hz or more.
> Unfortunately, the Doppler shift present depends upon just about everything-- location, time of day, atmospheric reflecting layer heights, path, the list goes on.
>
> Keep in mind the new synthesizers add an additional quarter Hz (+/-) uncertainty. The syncing of the SI570 to the master oscillator produces sawtooth jumps of that magnitude, sometimes more vs time.
> There are also band to band variations introduced by limitation in finding exact synthesizer divide ratios. Old synthesizers showed many Hz deviations from band to band and as one tuned up the band. These variations are much smaller with the new synthesizers.
>
> Then there is drift. If you are not using XREF, you will experience maybe 10 Hz or more warm up drifts. The high stability oscillator takes about four hours to reach its most stable point. The standard oscillator reaches that point a few hours earlier.
>
> The old engineer cautioned: "Never believe the last digit displayed in any device". In this case, don't expect to be within 1 Hz on all bands, all frequencies at all times-- no matter what calibration method you use. Look at the K3 specs. Nowhere will you find an expectation of such accuracy.
>
> 73 de Brian/K3KO
>
>> On 12/18/2016 12:40 PM, K9ZTV wrote:
>> The R.L. Drake Company referred to the zeroing or beating indicators as "canary chirps," the goal being to slow the "chirping" until there was a steady tone indicating you were then dead-on. I still find that the most descriptive way to tell someone how to identify the pulsing when doing the Reference Calibration against WWV in a K3 (at the highest frequency you can copy them). The trick is to get the right balance in volume between WWV's main carrier tone and the K3's sidetone so you can hear the "chirps."
>>
>> Kent, K9ZTV
>>
>>
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