[Elecraft] K2 L34 tuning revisited

Sat Jan 26 20:50:41 2002

I had set L34 as described in the manual and never touched it again.
Noticed when using Spectrogram to set up the passband for each of the
filters that the pasband had a slope similar to those shown in the graphics
with the alignment method and thought that it was alright.  I have seen the
MODS for evening out the USB and LSB and thought that the USB/LSB mod.
After reading Toms reply (below) I tried his method of tuning L34 for
flatness of the passband.  WOW - WOW - WOW !!! After making this simple
adjustment my display looks as good as the graphics for the USB/LSB
flattening MOD.  It even increased the gain over the passband and had
negligible affect on the CW passband.  Actually helped on the two lower CW
bandpass filters.  This technique is strongly recommended.

Rich

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Tom Hammond NOSS
Sent: Wednesday, January 23, 2002 1:33 PM
To: Rick Shindley; [email protected]
Subject: Re: [Elecraft] K2 L34 tuning revisited

Rick:

>I retuned my K2's filters the other day.  I made the filter flattening mod,
>PSK-31 mod, and used a noise source and the latest tuning advice from the
>Elecraft web site.  I got to the part where L34 had to be adjusted for
>lowest noise and maximum signal while listening to the birdie at 7 MHz.  I
>built the rig a year ago and anxiously moved through the adjustment
>procedure. L34 was tough to set, but I forgot about it and moved on.  This
>time I wanted to be very careful and deliberate.  ARRRRGGGH!!!
>
>I could not discern a point on L34 where the signal was more pronounced
>relative to the noise. I finally used Spectrogram to display the audio
>signal and found that no matter where I set the coil slug, the relative
>difference between the noise and the audio peak remained the same. (The
>manual indicates to adjust for max sig/noise.) I ended up peaking the slug
>where the audio peaked without regard to the noise level, since it made no
>difference. The slug ended up about one turn down from the top (not near
the
>bottom where my ears believed it belonged).
>
>I wonder if others see a relative change between signal and noise while
>adjusting L34 using spectrogram?

Since you have performed the SSB 2nd Xfil Mod, I think I'd urge you to use
Spectrogram and to adjust L34 for the best 'flatness' between LSB and USB
and to not worry about THAT much squeezing out the best S/N ratio. Well,
that is unless SSB operation is anything more than just a passing thought.
If you're a dedicated CW op, and will only use SSB periodically, then go
for S/N ratio... however, there's a good chance you'll never really notice
the actual difference, while you might well notice the diff between the two
sideband settings if you don't tune L34 to equalize performance there.

Tom Hammond   N0SS

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