[Elecraft] K2: A question about band-pass filter adjustment using Spectrogram?
Don Wilhelm
w3fpr at embarqmail.com
Wed Oct 3 20:29:43 EDT 2012
dw,
You are missing one very important point - you should be using a
broadband noise source when viewing the filter passband response with
Spectrogram. The presence of any signals will confuse things and not
give you a good view of the filter passband.
If you do not have a broadband noise generator (Elecraft N-Gen or
equivalent), you can use broadband "antenna noise" Turn the preamp on
and make sure there are no signals within the received region.
Spectrogram will show you the entire filter passband.
For a more complete explanation, see my webpage article on K2 Dial
Calibration. Part 3 of that article deals with setting the K2 filters.
73,
Don W3FPR
On 10/3/2012 8:17 PM, dw wrote:
> Hi all,
> I never used Spectrogram for setting my K2 band-pass filters until a
> month ago.
> I used to set the pass-bands by using the S-meter with a fixed frequency
> signal source.
>
> I followed these steps:
> 1) Zero beat to get a maxed S-meter reading.
> 2) Dial frequency down until the S-meter drops one LED, and record the
> count.
> 3) Dial frequency up until the S-meter drops one LED, and record the
> count.
> 4) Adjust the pass-band so that the count is equal in both directions.
>
> I ran the K2 this way for about 3 years, and this month I thought I
> would try resetting the pass-bands with Spectrogram. I’m pretty sure I
> was super careful to follow the directions.
> But now I’m not sure If I should re-do them again using my old method
> because the up/down count is no longer equal.
>
> For example:
> With zero beat @ 704031mhz, I adjust RF gain for an S-meter reading of
> 7.
> When I adjust the frequency dial up to 704046 (15 counts) , the S-meter
> will drop 1 LED.
> When I adjust the frequency dial down to 704006 (25 counts), the S-meter
> will drop 1 LED.
>
> Is my assumption that the up/down count should be equal wrong?
> Perhaps the pass-band characteristics are such that best setting is not
> in the center?
> Am I missing something?
> Thanks
> N1BBR
More information about the Elecraft
mailing list