[Elecraft] REF OSC Frequency

[Rajiv Dewan, N2RD]

Great suggestion Greg.

I did not have an appropriate cable to hook into J1 on KEF3. So I 
unhooked it from KSYN3 and used the cable to J2 and some clips I had.  I 
have an HP5343A counter slaved to an HP3801Z GPA stabilized 10MHz 
reference.  Using this setup, I measured the frequency of the KREF3 
(with KTCXO option) at 30 second intervals from cold start.  Here is 
what I got:

Time min:sec -  Frequency 49.xxx.xxx MHz, only the KHz part is noted below:
0:00  - 361.250
0:30 - 361.261
1:00 - 361.306
1:30 - 365:350   big jump!!
2:00 - 377.346 another big jump!!
2:30 - 377.380
3:00 - 377.419
3:30 - 377.471
4:00 - 377.464
4:30 - 377.457
5:00 - 377.507
5:30 - 377.504
6:00 - 377.500
6:30 - 377.490

Turned off and on right away

377.405

Is this normal?

Thanks for the suggestion to check this.  I am now going to turn it on, 
wait for ten minutes, set the REF CAL and then do the VCO calibration.

PS: I am also forwarding it to the elecraft list as the frequency drift 
seems interesting.

Raj, N2RD







Greg wrote:
> Raj.  You need to do the REF CAL procedure.  If you do not have an accurate
> frequency counter for method 1, use method two using USB/LSB to zero beat
> WWV.  Set the radio to 10.000 MHz or 15.000 MHz.  Alternate between USB and
> LSB while listening.  Adjust the ref oscillator frequency  so that there's
> no change in the tones.
>
> What's probably happening is the RO is off by enough that when you use the
> narrow filters you are loosing the signal as its outside the passband.
>
> Let me know how it goes.  I'll be up for awhile longer.
>
> Greg
>
>
> -----Original Message-----
> From: Rajiv Dewan, N2RD [mailto:n2rd at arrl.net]
> Sent: Monday, December 31, 2007 6:37 PM
> To: Greg
> Subject: Re: [Elecraft] K3 #170 CW Filter oddity
>
>
> It is the default 49.380Mhz.
>
> Raj
>
> Greg wrote:
>   
>> Raj.  What freq is your reference oscillator set to?
>>
>> Greg
>>
>>
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net]On Behalf Of Rajiv Dewan, N2RD
>> Sent: Monday, December 31, 2007 4:49 PM
>> To: k3support at elecraft.com; Elecraft List
>> Subject: Re: [Elecraft] K3 #170 CW Filter oddity
>>
>>
>> Added note: the change in the DDS frequency occurs by just changing the
>> filter width or selecting the narrower filters.
>>
>> Raj
>>
>> Rajiv Dewan, N2RD wrote:
>>
>>     
>>> I have 250Hz, 400Hz and 2.8KHz roofing filters installed.  After
>>> update to the latest firm ware I am noticing that the radio goes
>>> really deaf when the 250Hz or the 400Hz filters are used.  I have set
>>> the appropriate gain of 4db and 2db, respectively for the 250Hz and
>>> 400Hz filters.  The FLX FRQ is 0.0 for all.  But the deafness is much
>>> more profound than a few dB.
>>>
>>> I noticed that the peak in my signal is not where CWT indicates
>>> perfect tune
>>> While I am tuned to a CW signal at 7.02706KHz, I turned on CONFIG:DDS
>>> FRQ and noticed that this frequency changes from 3.581367 MHz to
>>> 3.581579 MHz and the radio goes deaf.  No change in tuned frequency.
>>> I checked that the FL FREQ for these filters is 0.0.  What gives?
>>>
>>> Does any of you have the same behavior?
>>>
>>> Regards,
>>> Raj, N2RD
>>>
>>>
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>
>