[Elecraft] RE: REF OSC Frequency

[Greg]

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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>
>