[Elecraft] Re: REF OSC Frequency

Tue Jan 1 00:41:50 EST 2008

Greg,
  You are right about the bold faced caution on Page 47 and indeed I 
waited long before doing the REF CAL, which I did using Method 2 with 
the cover closed.  However, I am still surprised by the frequency 
excursion measured on start up.  I did wait a lot longer and calibrated 
it using method 2, zero beating it with WWV.  This was at ref cal value 
of 49,379,611, which is a lot closer to the frequency noted on the sheet 
that came with the TCXO - 49,379,964.
  With the ref cal set, I have re done VCO CAL and other calibrations.  
For now all seems to be as it should be.  I have my fingers crossed.
  Thanks for your help,
Raj

Greg wrote:
> Raj,
>
> You have to read the manual when doing this....Please note this BOLD FACED
> caution on page 47.
>
> Before attempting reference calibration,
> allow the transceiver to warm up at room
> temperature for about 15 minutes (cover on).
>
> Greg
>
>
>
>
> -----Original Message-----
> From: Rajiv Dewan, N2RD [mailto:n2rd at arrl.net]
> Sent: Monday, December 31, 2007 7:38 PM
> To: Greg; k3support at elecraft.com
> Cc: Elecraft List
> Subject: REF OSC Frequency
>
>
> 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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>>>>         
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>>     
>
>   