[Elecraft] More Control Board R1 experiments

[John McClain]

I have replaced R1 with a 47K and am very pleased with the results.  I
haven't done any experimenting with other values yet but I will as
soon as I dig down deep enough in my spare parts drawer to find a pot
that I can play with.

John
K7SVV
K2 #2569, SST 20, Rock Mite 20

----- Original Message -----
From: "Rod N0RC" <rod@n0rc.us>
To: "Elecraft-list" <elecraft@mailman.qth.net>
Sent: Thursday, September 26, 2002 6:36 AM
Subject: [Elecraft] More Control Board R1 experiments


> Folks,
>
> I now have R1 set to ~41k ohm, and the overall radio performance is
much
> better.
>
> Recall I posted about changing R1 to 33K, and that I thought the
radio
> sounded "harsh" on 40m. That post yielded a good discussion with Ron
> AC7AC
> and posts by others. After mulling things over I still wasn't
satisfied,
> so back to the bench....
>
> Still I wished for test equipment to make a better evaluation of
> different R1 values. No chance of getting any, but it occurred to me
WWV
> might
> make a good "test signal". It is only 10-15 miles away, and the
10MHz
> freq.
> produces a SOLID/STEADY S9 signal at my QTH (on my 746pro).
>
> I checked WWV with the K2 and my 33k R1. WOW S9 +20, preamp-off, way
too
> much. I reasoned that close in strong signals on the amateur bands
would
> degraded K2 RX performance. But where to set R1? I checked the
> sensitivity S-meter specs in ARRL report.  K2 @14 MHz: preamp off,
115
> uV to yield S9. 746pro S9 signal at 14.2 MHz: preamp off, 82 uV. So
> theory-wise if the 746 is reading S9, the K2 should read a little
less.
> Again I set about trying different R1 values, and finally settled on
> ~41k ohms. (not a std value, 220k in parallel with the original
51k).
> This value causes the K2's "S9" bar to just flicker. Still a little
high
> maybe, but I'll take a little extra gain & resulting noise to
compensate
> for my poor antenna system.
>
> I've been using my K2 for a few days and find this latest change to
be
> quite useable. The "harsh" sound on 40 is gone. I also notice that
often
> I now have the pre-amp switched off. Before I would always have the
> pre-amp on.
>
> So that's the story here, submitted for peer review. And if the
> methodology is worthy, perhaps it can be useful to others.
>
> 73, Rod N0RC
>
>
>
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