[Elecraft] K1 band pass filter alignment

[Alexey Kats]

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.
>>
>>
>



-- 
Alexey Kats (neko)