[Elecraft] K1 band pass filter alignment

[Don Wilhelm]

If we were in a period of higher sunspot activity, we would not have 
this problem.  If there were good signals on the 17/15 meter bands, we 
could use those to adjust the K1-4 to the correct band. Unfortunately, 
we are in a time when solar activity does not produce a lot of signals 
on the 17/15 meter bands, so the use of a known frequency signal source 
is almost mandatory.  Yes, there are 'workarounds', but those should be 
used wtth a degree of awareness for the consequences.

73,
Don W3FPR

Alexey Kats wrote:
> Don,
>
> You are absolutely right - the biggest trouble I had with my K1-4 was
> on 17m band. With 20m I used XG2, but for 17m I ended up tuning it
> after transmitter was fully built - I first tuned it roughly on low
> power transmit with dummy load and watt meter, then using noise
> generator on receive (with attenuator on), then again with watt meter
> on transmit. And as a result I had to re-tune 20m again.
>
> On Wed, May 26, 2010 at 6:04 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
>   
>> Alexey,
>>
>> Using the noise source or "dead band noise" with the K1-4 is problematic for
>> the 15/17 meter and 20 meter bands.
>> The real world situation is that it is possible to tune the 15/17 meter
>> Pre-Mixer bandpass trimmers to the region of 29 MHz rather than 23 MHz.  The
>> usual result is that 20 meters cannot be tuned properly (and the frequency
>> that 15/17 meters is tuned to is incorrect).
>>
>> The way to avoid that situation is to use a known signal source when tuning
>> 15/17 meters.
>>
>> The manual states that the initial position for the Trimmer capacitors is to
>> be with the slots parallel with the long side of the board.  The final
>> adjustment ot the trimmers will be no further than 20 degrees away from that
>> position.  If the 'peak' occurs further away from that range, it is at the
>> wrong point.
>>
>> Using a signal source of a known frequency will avoid this problem, but
>> using a wideband noise source can certainly produce this false response.
>>
>> Note that this condition does not occur as readily with the 2 band board.
>>
>> 73,
>> Don W3FPR
>>
>> Alexey Kats wrote:
>>     
>>> Greg,
>>>
>>> You can use XG2 kit from Elecraft as a signal source for K1 on 80m,
>>> 40m and 20m bands (it'll also give you a chance to adjust S-meter as
>>> well). 80m might be a little problematic if you selected 80kHz tuning
>>> range because it is close to the upper end of the band, but you should
>>> still be able to use it unless your VFO is misaligned.
>>>
>>> Or you could use N-gen kit too, but  be careful with it - it's easy to
>>> adjust all filters on receive so it will look like you reached the
>>> peak, while in reality your IF will not align properly with center
>>> frequency of crystal filters. This is because it produces relatively
>>> strong noise signal. If that happens (the giveaway is that you can
>>> hear noise generator, but nothing from the antenna) - move all
>>> adjustments for the problematic band to their neutral positions and
>>> start over.
>>>
>>> But the easiest method is to use another QRP rig or a signal generator
>>> as a signal source.
>>>
>>>
>>>       
>
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