[Elecraft] Re: Updated Version of Elecraft Keying Mod

Wed Apr 7 10:48:01 2004

The leading edges were the killer in the K2. That's basically what
Wayne fixed.

1) Clicks CANNOT be heard ON-channel with a CW bandwidth. The FILTER
limits the signal bandwidth to reasonable levels (e.g. +/- 250 Hz.),
which is what the mod is  doing.

2) Clicks MIGHT be heard ON-channel with a SSB bandwidth, the signal
tuned to center of the bandwidth, *IF* the hearer had training to know
exactly what sound to listen for. Over the air tests with a VERY
clicky FT1000MP shows that very few can hear clicks ON-channel at ANY
receiver setting.

3) clicks down 33 db at +/- 250 Hz are excessive. Cleaner signals
achieve 45 down and some are even 50+ db down. It is very difficult
for most people to hear a specific synchronous artifact of a sound
down 30 db from the main energy.

3) To hear clicks OFF-channel:

a) turn the AGC *OFF*
b) turn OFF any dsp or audio processing settings (KDSP, KAF, EDSP in
an MP, etc)
c) leave the audio gain at your normal setting.
d) set the RX to the CW mode.
e) set your RX to listen USB. (Scrolling the RX frequency higher
causes the heard signals to scroll from high toward low frequency
audio.)
f) make sure that any bandwidth centering (IF shift, etc) is in the
center position, or OFF, whichever applies. (K2 does not have this
feature.)
g) Set the RX bandwidth to the minimum bandwidth not less than 250 Hz.
h) Set the RX to the maximum attenuator setting, ATT on a K2, 18 db on
an MP. If there is a separate preamp setting, turn it off
i) Tune the signal to be tested to the center of the filter. For many
TRX this is the same as the TX sidetone, or a "spot" tone.
j) Use the *RF GAIN* to get a normal audio level. If the signal is not
strong enough to do this, it is too weak to measure clicks.
k) tune the RX *LOWER* by an amount equal to 250 Hz plus 1/2 the
bandwidth in g) step. Make sure to get the arithmetic right.
l) turn off the attenuator.
m) now listen for clicks.
n) if the main CW tone is still overwhelming, your filter may not be
the bandwidth you think it is. Use spectrogram to determine what it
REALLY is, and redo the exercise.

73, Guy.

----- Original Message ----- 
From: "Ken Wagner" <[email protected]>
To: "Wayne Burdick" <[email protected]>; "John, KI6WX"
<[email protected]>
Cc: <[email protected]>
Sent: Wednesday, April 07, 2004 7:29 AM
Subject: Re: [Elecraft] Re: Updated Version of Elecraft Keying Mod

> G'morning all:
>
> I installed the Elecraft Keying Mod in #3756 with the 180K resistor.
> Shortly after that I finished assembly of #4181 with the 270K
resistor
> provided with the K2.
>
> Looking at the keying envelope on a not-too-good o'scope, I can
clearly see
> the difference in the leading edge shape between the two K2s. Any
trailing
> edge differences were not so noticable. However, limited and
unscientific
> on-the-air testing produces no discernable difference. Both
reportedly
> produce clean and crisp CW notes and no clicks detected.
>
> 73,
> Ken Wagner K3IU
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> At 12:09 PM 3/31/2004, Wayne Burdick wrote:
> >John,
> >
> >Thanks for testing this possible change to the keying mod, which
looks quite
> >promising. As you noted, we haven't tested it yet, but it looks
like the
> >risk of
> >going to 180 k is minimal, and I encourage others making the mod to
see which
> >value they like better. If the evidence shows that 180 k is a
better overall
> >choice, we'll consider revising the mod kit.
>
>
>
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