Posted by
Elecraft mailing list on
Apr 11, 2019; 11:46pm
URL: http://elecraft.85.s1.nabble.com/K2-filter-alignment-problem-tp7650809p7650818.html
Don...
Bingo! The F4 filter setting was too narrow, as you advised. Also, the
BFO was somewhere off from where it belonged. Once I got those two item
adjusted everything worked as per specs. I was impressed that the BFO
values that you quoted were more or less right on. Seems like you have
some experience with the K2 :-). Thanks much for your time and
attention, as always. Have a good day.
...robert
On 4/11/2019 14:00, Don Wilhelm wrote:
> Richard,
>
> Try widening the FL4 filter out to 0.2 instead of 0.1. With the more
> narrow setting there is often more attenuation with little actual
> reduction in width.
>
> When aligning the BFOs, pay attention to the DAC values (and/or
> frequencies). The ones for CW must be less than the filter center and
> those for CWrev must be greater than the filter center. Normally the CW
> FL4 will have a BFO frequency near 4913.12 and for CWrev a frequency
> near 4914.3 kHz.
>
> Make certain when aligning the filters with Spectrogram you use a source
> of wideband noise. If you are using 'antenna noise', be certain there
> are no signals nearby.
>
> 73,
> Don W3FPR
>
> On 4/10/2019 9:28 PM, Robert G Strickland via Elecraft wrote:
>> I have aligned my K2 crystal filters with Spectogram many times, but
>> this time I've run into a problem that I can't figure out.
>>
>> Using Don's [and the manual's] instructions, I can align F1,F2,F3 in
>> decreasing bandwidths. All works as per expectations. On F4, the
>> alignment goes "ok," [as per Spectogram] but when I use it with
>> on-the-air signals, the signal "disappears" and shows up about 900 cps
>> lower and in "reverse" orientation [BFO on opposite side]. When the
>> signal disappears, I can change filters [F1/F2/F3] and it's right
>> there where it should be with the bandwidth getting narrower as
>> expected. But, switching to F4, it's gone. I have tried changing the
>> BFO frequency throughout its whole range when in F4, thinking that
>> I've aligned it on the "wrong" side. No luck. I'm stumped. Any and all
>> suggestions welcomed.
>
--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
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