http://elecraft.85.s1.nabble.com/K3-K3S-receiver-and-high-precision-frequency-determination-tp7660104p7660119.html
Thanks for the explanation, I have always wondered why... I'm good with
close, it is not too bad. I had a friend that lived 700 feet from me,
and had a Collins S-Line, including the KW... It was horrid for being
far too wide... He switched to a K3, and for the most part things were
far better. Prior to the switch, I could not operate on the same band
changed to the new one, and as he changed to the new one. It is totally
obvious how much better the new synthesizer is than the old... See:
ARRL Asst. Director, NW Division, Technical Resources
> Dave,
>
> Thanks, that may have been the thread I was remembering.
>
> While searching old messages, I also came across a post from Ed Cole
> KL7UW from June 2018 in which he stated that, even if an external
> reference is connected, the K3 frequency "is established by the
> [internal] TCXO and the external reference merely performs a periodic
> check. ... the EXREF system does not phase-lock the TCXO. It
> periodically corrects the error but the TCXO drifts normally between
> freg corrections ... . Now if you want to know why Elecraft chose
> periodic freq correction over true phase-locking, the answer is low LO
> phase noise. Much harder to get low phase noise in a PLL than in a TCXO."
>
> 73,
>
> Frank K6FOD
>
>
> On 4/24/20 12:37 PM, Dave Cole wrote:
>> 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)
>>
>> 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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