Re: [K2] Is TX frequency susceptible to RF on chassis?

Posted by Alexander Ponomarenko-5 on Oct 16, 2007; 8:12am
URL: http://elecraft.85.s1.nabble.com/K2-Is-TX-frequency-susceptible-to-RF-on-chassis-tp454716p454721.html

Hi David!

For fine tune C22 you can use the simplest method with PC and specrpogram.
There is the original UA6HJQ's method:
-connect K2's AF-out to PC mic-input, and phones to PC phone out;
-turn On K2 and PC, and wait for 50-60 minutes (for temperature stability);
-check the connection "TP1=>Control Board";
-run the Spectrogram, and set for it: Scale -60db, FFT 8192, Band 640 -  
1329Hz
  and set marker to 1000Hz;
-set LSB-mode, and tune VFO at 10001,00kHz (WWV), if ANT is connected
you have to hear WWV-signals in headphones,
-if we see the WWV-signal peaked on 1000Hz (our marker on Spectrogram),
it's the ideal point for C22.
-if not, turn VFO for peaking the WWV-signal at 1000Hz-marker.
-f.e. if we have 10001,20kHz we'll have to subtract 20 (in later steps),
  if we have 10000,80 we'll have to add 20 (in later steps)
- MENU => CAL => CAL FCTR (don't touch VFO-knob!)
- we can see 14914,70 (for example)
- now if we had 10001,20 we must to subtract: 14914,70-20=14914,50
  (if we had 10000,80 => 14914,70+20=14914,90)
-now slowly turn C22 for 14914,50 readings (or 14914,90)
-recall CAL PLL for TP1 on 40m band
-recall CAL FIL for TP2 on each filter/mode.
Now you can recheck your K2 on WWV at 10001,00 kHz, as a rule the error  
makes
few Hz.
Same pictures you can see if follow here (in russian):
http://www.hamradio.cmw.ru/elecraft/calibrated.htm

73! Alex
K2#5287

On Mon, 15 Oct 2007 15:44:31 +0300, Don Wilhelm <[hidden email]>  
wrote:

> David,
>
> The same principles work fine for any known frequency, it is just that  
> the subtraction of the BFO frequency from the VFO frequency is not as  
> straightforward.
>
> An AM station broadcasting standard and constant tones (such as WWV) is  
> easiest because one can observe the demodulated audio tones with  
> Spectrogram assuring accurate tuning.  If you have a good ear, you may  
> be able to tune to a station broadcasting music to within 5 or 10 Hz.
>
> If you do use an AM broadcast station without standard tones as your  
> standard, I would suggest that you tune it by ear in LSB or USB first,  
> then switch to CW while observing the audio with Spectrogram - the  
> carrier should appear 'straight and tall' at the frequency you have set  
> in the K2 for the sidetone pitch - thus assuring accurate tuning of the  
> station.  Then go back to SSB mode to set C22 while doing the  
> subtraction between the VFO and BFO frequencies.  A note to help - any  
> adjustment of C22 will move the VFO frequency reading about 5 times  
> faster than the BFO reading, so do the adjustment with the counter probe  
> plugged into TP1 and then check the result in TP2.  A few trials should  
> yield an accurate setting.
>
> 73,
> Don W3FPR
>
>
> David Woolley wrote:
>> Don Wilhelm wrote:
>>
>>
>>> refer to the K2 Dial Calibration article on my website  
>>> http://w3fpr.qrpradio.com for techniques to accurately set the 4 MHz  
>>> reference oscillator and the following steps to achieve good dial  
>>> calibration.
>>
>> Unfortunately, the sun doesn't seem to favour picking up WWV.  The  
>> original calibration was against the MHz birdies on an FRG7, which was,  
>> I think, calibrated against WWV in the past.  However I just tried on  
>> some 41m broadcast stations, and it looks like the calibration might be  
>> 30 to 40 Hz high on that band, which probably equates to 50 to 70 Hz,  
>> in the same sense, on 10m, so I may try a calibration against those  
>> broadcast stations.  (Does anyone know a relatively accurate broadcast  
>> station, receivable in a noisy location in the UK, and near the high  
>> end of the VFO range?)
>>>
>>
>>
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