[Elecraft] Sync AM and checking VFO accuracy using WWV

[Brendon Whateley]

Depending on why you want the accuracy, I think you could improve things by
building a phase comparator to "listen" to the radio output frequency
against a local reference. That would allow you to get much closer than
using your ears as a phase detector. That should get you accuracy of a few
% of 1Hz at your frequency you are measuring.

If you are really serious about accuracy, you can build a frequency
reference based on the WWV transmissions that will get you to within 1 part
per billion at 1MHz without too much trouble.

There was a QEX article recently, which you can find on the web at
http://www.arrl.org/files/file/QEX_Next_Issue/2015/Nov-Dec_2015/Magliacane.pdf
.

I'm sure that spending money on a GPS reference would be quicker, but less
fun than building a project.

If you go down that road, you'll be well on your way to winning frequency
measuring contests!

- Brendon
KK6AYI

On Sun, Dec 18, 2016 at 5:07 AM, Don Wilhelm <donwilh at embarqmail.com> wrote:

> Brian,
>
> The higher the WWV frequency, the possible percentage of error goes down.
> One or two Hz is a smaller fraction of 20MHz than at 5MHz.
>
> In the K3, you are calibrating the reference (out of the synthesizer)
> rather than calibrating the actual VFO frequency.  The actual VFO frequency
> is derived from and phase locked to that reference.
>
> 73,
> Don W3FPR
>
>
> On 12/18/2016 12:17 AM, Brian Denley wrote:
>
>> Fred, Don:
>> I ask because I am curious.  On any older receiver, calibration at 20 MHz
>> would not guarantee cal below that ( or at any other frequency ).  One
>> could be 5 hz high at 30 MHz but 10 hz low at 7 MHz.  Why is the K3
>> different?
>>
>> Brian Denley
>> KB1VBF
>> Sent from my iPad
>>
>> On Dec 17, 2016, at 3:43 PM, Fred Jensen <k6dgw at foothill.net> wrote:
>>>
>>> I guess it depends on how accurate you want your K3 frequency display to
>>> be.  I think AM-S will warp the frequency a tiny bit to sync the carrier so
>>> that may not be the best mode.  I'd also go as high as you can on WWV.
>>>
>>> Wayne suggested a method that is somewhere on the E-site which I used--
>>>
>>> Use the highest WWV frequency that you can hear well.  USB or LSB, WIDTH
>>> to 500-800 Hz, SHIFT so can hear the carrier beat note [it will be very
>>> low].  CONFIG-->REF CAL, wait for a tone-less minute and adjust REF CAL for
>>> exact zero beat.  You'll be counting the pulsations in the background noise
>>> as you come up on zero beat.
>>>
>>> I got mine to about 10 seconds per pulsation on 20 MHz back when there
>>> were sunspots.  That's an accuracy of 0.1 Hz and everything below 20 MHz
>>> will be at least that good.
>>>
>>> 73,
>>>
>>> Fred K6DGW
>>> - Sparks NV DM09dn
>>>
>>> - Northern California Contest Club
>>> - CU in the Cal QSO Party 7-8 Oct 2017
>>> - www.cqp.org
>>>
>>> On 12/16/2016 5:12 PM, Michael via Elecraft wrote:
>>>> If I set my K3's VFO to WWV at 5.000000 MHz with AM-S on....and I adjust
>>>> "REF CAL" to a number where
>>>> my VFO's frequency readout is exact or near this number +/- maybe a
>>>> Hertz
>>>> or two. Is this an accurate way to calibrate my K3?
>>>>
>>>> It seems to be very accurate as far as I can tell.
>>>>
>>>> Has anyone used this method?
>>>>
>>>> Michael
>>>> N2ZDB
>>>>
>>>
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>>
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