[Elecraft] K3/K3S receiver and high-precision frequency determination?

[Dave Cole]

Hi,

That was me...  I used to use my Icom 756 Pro, to watch the Doppler on 
changes in the ionosphere, and on Meteors.  The K3 uses steps to correct 
frequency, while the Icom did not.  Analog vs. Digital corrections.

Accuracy is not an issue, it is the steps...  They destroy the 
continuity of the tracking...  I should have some captures if you are 
interested.  Email me off list and I'll send a set.

The issue for me, I am looking for changes in frequency, on the order of 
sub-1 hz., not looking to get an exact reading on the frequency, just 
changes in frequency across minutes, not days or hours.

I don't need to be dead on for frequency, but I do need to have a 
straight line that is affected by Doppler, and path changes.  I can't 
get that with my K3 without those annoying steps.

Keep in mind we are talking worst case 6 or 10 Hz., and the steps appear 
to be far, far, smaller than that...

So...  I have given this aspect of the hobby up.  I did just get the 
TXCO installed along with a lot of extras on my K3, and the steps are 
longer, but still there...  I will get some older rig that is analog in 
nature and return to that aspect of the hobby then...

I was able to watch echos from aircraft between Eugene, and Portland 
Oregon, (about 100 miles apart), using the KGW TV, (Ch. 2), aural 
carrier as a source.  I got the coolest traces of Doppler shifts caused 
by the aircraft movement.  Meteors were far more interesting...  Anyway, 
it is not an issue of Frequency accuracy, bit one of how the rig makes 
adjustments.  I would love to just turn off the steps, and accept the 
drift over longer times.  Oh well...  Hope that helps...  It is NOT the 
K3 having an issue with measuring frequency...

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 4/24/20 10:11 AM, Frank O'Donnell wrote:
> Sometime (probably last year) I remember seeing a discussion of why the 
> K3/K3S receiver isn't suitable to do high-precision frequency 
> measurement tests at the level of hundredths of a Hertz. As I vaguely 
> recall, the receiver is designed so that its frequency actually varies a 
> bit intentionally, and I remember someone posting a plot demonstrating 
> this. However, I'm striking out on finding any of those posts. Can 
> anyone either help with them, or point to any other 
> discussion/explanation on this?
> 
> Thanks much,
> 
> Frank K6FOD
> 
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