[Elecraft] Determining zero-beat

[Guy Olinger K2AV]

I guess you can tell I never use CWT   :>)

Thanks for the tip.  73, Guy.

On Fri, Dec 3, 2010 at 8:48 AM, Bill VanAlstyne W5WVO
<w5wvo at cybermesa.net> wrote:
> Just one caveat on this procedure (thanks Guy!) -- make sure you have CWT
> turned OFF; otherwise, SPOT will not do what you want it to. (It will
> attempt to retune the VFO.)
>
> Bill W5WVO
>
>
> -----Original Message----- From: Guy Olinger K2AV
> Sent: Friday, December 03, 2010 13:38
> To: n4zr at contesting.com
> Cc: Elecraft List
> Subject: Re: [Elecraft] Determining zero-beat
>
> Set mode to CW.  Set width to 200 Hz.  Do a HOLD on MON. Set level to
> 20-25. Tap MON to turn off beat.  Tune to 10.000.000.  Tap SPOT.
> Should hear a beat, albeit a slow one.  Advance or retard AF gain to
> get the obvious beat. In CONFIG: go to REF CAL.  This will have turned
> off SPOT.  Tap it again. Adjust VFO A to get slowest beat.
>
> With some patience and careful listening this is usually clearly a
> specific setting, in my case 49.379.737.  You will find that the beat
> frequency wavers around due to changing propagation path length so you
> have to listen for a while.  Having accounted for the variation in
> propagation it is quite clear in my case, albeit subtle, that 738 is
> too high, and 736 is too low.  It is also more clearly heard at some
> times of day on a given frequency than others.  There are also times
> where there is a fast QSB on the signal that can be confusing and you
> may just have to wait until the signal steadies.  When you have it
> spot on, there will be periods of several seconds or more where the
> beat does not vary, something which does not happen nearly as much up
> or down one Hz on the REF CAL frequency.
>
> After this adjustment it is clear that my K3 is within +/- 0.5 Hz at
> 10.000000 MHz with no drift, probably within +/- 0.2 Hz though I won't
> claim that.  I have the KTCXO3-1 option in mine.  It may be that a K3
> without it may be a bit more cranky, I would imagine so, but I'm not
> pulling it out to see  :>)
>
> 0.5 Hz at 10 will be less than 2.5 Hz at 50, though I don't know the
> formula.  It's not a straight multiply because of the conversion
> scheme.  With this adjustment in the menu, the chief contribution of
> the KTCXO3-1 is no drift, not an absolute accuracy.
>
> My K3 is way more accurate than they spec, and accurate enough to show
> up the propagational variations in the WWV frequencies. I would think
> that if you have left it on for a while, and calibrate it before an
> "exercise", you can count on it for spot on.
>
> 73, Guy.
>
> On Fri, Dec 3, 2010 at 6:09 AM, Pete Smith <n4zr at contesting.com> wrote:
>>
>> I want to use my K3 to calibrate the QS1R receiver used here as part of
>> the Reverse Beacon Network.  For technical reasons, it's desirable to
>> calibrate the QS1R at as high a frequency as possible, so I wanted to do
>> so in the 6-meter band.  I thought that if I knew how accurate the K3's
>> frequency display was at 10 MHz WWV, I'd know whether I needed to
>> compensate for any systematic error when comparing the two up on 6M.
>>
>> Here's where the problem comes in.  AM mode isn't usable for finding
>> zero-beat, of course.  On CW, it appears that the zero-beat frequency is
>> displayed as 10 MHz minus the "pitch" frequency (which can only be
>> adjusted down to 300 Hz).  I'd like to know the frequency accuracy of
>> the K3 within 20-30 Hz if possible for this exercise.
>>
>> How to proceed?
>>
>> --
>> 73, Pete N4ZR
>>
>> The World Contest Station Database, updated daily at
>> www.conteststations.com
>> The Reverse Beacon Network at http://reversebeacon.net, blog at
>> reversebeacon.blogspot.com,
>> spots at telnet.reversebeacon.net, port 7000
>>
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