From: WA9GQT@aol.com
Date: Sun, 27 May 2001 09:12:30 EDT
Subject: [Elecraft] K0OB CW Mod
Message-ID: <9f.15f20b65.2842573f@aol.com>
Hi All!
Just wanted to let you know that I performed the K0OB
cw mod on my K2 after installing the 2nd X Fil Mod. I am very pleased with
both of these modifications.
I noticed definite improvement with the cw mod; no more
sonar type sound. I have never used spectrogram; strictly tune filters
by ear or by the book(cw). After doing the cw mod, I set all filters for
cw & cwn per manual. Like I said I could definitely tell a difference.
I have used the K2 on cw during CQ WW WPX contest and seems to perform
quite well.
By the way; I used 0.01 uf capacitors from Radio Shack-RS
272-1065 & followed Kevin's procedure to the
"T". Thanks again Kevin.
73,
Rod WA9GQT K2 #1900From: "N7SG K7FD" <k7fd@hotmail.com>
Date: Mon, 28 May 2001 12:29:13 -0700
Subject: [Elecraft] Bye bye Blow-by?
Message-ID: <F1016y4I5JvgjvSRjCf000077af@hotmail.com>
OK, I just finished up Ko0B's K2 filter mod and I'll give it a thumbs
up, if
only that it sounds better to my ears. I haven't looked at it with
Spectrogram, and I'll leave that to the computer guru's to decipher.
Wish
I'd done the mod before the WPX...not many strong signals on the band
today
to 'field' test it with...
73 John K7FD
From: Ken Wagner <kewagner@ids.net>
Date: Wed, 30 May 2001 07:39:46 -0400
Subject: [Elecraft] Ko0B Filter Mod (My Last Posting)
Message-Id: <4.3.2.7.2.20010530072942.00ac4b70@pop3.ids.net>
K2ers:
After swapping a couple of emails with John, KI6WX, and reading his
"tutorial" on Spectrogram(Thanks, John, I needed that!), I decided
that I
needed to do some more work on the before/after measurements that I
reported the other day. Actually... only the AFTER measurements got
redone
(I'm not gonna undo the mod). The results still show a marked improvement
but not nearly as dramatic as previously indicated.
The web page has been updated...
http://users.ids.net/~kewagner/917/
This is far as I'm gonna take this. It's been fun, but I gotta
find
something else to play with... xyl suggested the lawn mower<g>.
73, Ken K3IU
K2 #920
From: John <jschneider@zianet.com>
Date: Thu, 24 May 2001 17:53:25 -0400
Subject: [Elecraft] KO0B K2 filter mod, thanks.
Message-Id: <200105242153.f4OLrPY26412@listserver.qth.net>
More or less finished up K2 #2012 yesterday, still need to run it thru
Spectrogram. During alignment and test part II, I noticed some filter
blow
by on 7mhz, kind of like my old pre Sherwood filtered Drake R4C's.
I didn't
really like it, but what to heck, there weren't many receivers better
than
an R4C, even without the Sherwoods. I learned to live with the blow
by on
the R4C until I could afford the Sherwood filters.I figured if the
K2 was as
good on receive as advertised, a little blow by could be tolerated.
(it is
slight). Enter the KO0B mod. I wondered if a couple of caps and some
wire
could make a difference. After reading some posts on the reflector,
indicating the mod provided improvement, I contacted Fred, KT5X, exchanged
emails with him on the subject. Upon describing his results, he convinced
me
to do the mod while doing construction part III.
When I finished with part III yesterday and fired the K2 up, no more
filter
blow by, none that I could hear with my old ears. Is the mod worth
doing,
yes! Have you ever bought Sherwood filters? A couple .01 caps and wire
are a
lot cheaper. Thanks a ton Fred, for inspiration, and KO0B for a great
simple
mod. The radio sounds good.
So connected #2012 to a 20M antenna, rolled the power up to 5 watts
and
worked 4Z4DX, first call. Not bad from southern NM.
John, K7UP
K1#637 K2#2012
From: "Santa Fe" <kt5x@cnsp.com>
Date: Sun, 20 May 2001 18:32:45 -0600
Subject: [Elecraft] KO0B filter mod
Message-ID: <005001c0e18e$43b4c560$1f2f86cc@fmaas>
Regarding the discrepancy, I used .01 (103) not .001 (102).
My results have been gratifying. Before the mod, an S-7 signal
trailed off
FB as the filters narrowed, but an S-9 signal leaked by. In fact,
at .5 khz
away from center, regardless of filter width, that signal could be
heard
albeit weakly.
Now, with each filter narrowing, the distance away from center that
an S0+
signal can be heard is less, quite a bit less.
Spectrogram clearly shows slopes that stay steeper, and stay steep right
to
near the noise floor.
TNX KO0B
72,
# 700
From: "Bob Tellefsen" <n6wg@earthlink.net>
Date: Fri, 18 May 2001 09:23:58 -0700
Subject: [Elecraft] KO0B cw filter mod
Message-ID: <MABBJOEABOILMKCJCLFCMEFACHAA.n6wg@earthlink.net>
On Sunday Larry WA2DGD asked if anyone had tried the KO0B filter mod.
I
hadn't heard of it,
so I followed the URL he gave,
http://www.rt66.com/~hypoxic/K2stuff/ultreject.html
and got the details.
In a nutshell, I tried it and it works.
You can get the details from the web page. It is easy to do and
didn't take
very long.
For results, my first check was subjective. Before the mod, when
I would
tune past a signal I could hear it for quite a ways past its frequency.
The
pitch would be rising and growing fainter, but it hung in for quite
a while.
Now, when I tune past a signal, I can hear the pitch rise a little
bit, then
it sort of winks out.
After the mod, I took the following measurements to see what was happening.
I used the filter peak at 580 Hz with the narrowest setting, 00 bandwidth,
for the 0 reference.
At 10 db down, bandwidth is 170 Hz.
At 20 db down, bandwidth is 210 Hz.
At 30 db down, bandwidth is 270 Hz.
At 40 db down, bandwidth is 320 Hz.
At 50 db down, bandwidth is 390 Hz.
At 60 db down, bandwidth is 500 Hz.
In addition, the passband curve is more symmetrical than it had been
before
the mod.
After doing the mod, I checked it out with Spectrogram, and could see
the
improvement in the shape of the response and in the noise in the stop
band
outside the passband.
Try it, I think you will like it.
73, Bob N6WG
K2 s/n 12
From: Ken Wagner <kewagner@ids.net>
Date: Sat, 19 May 2001 09:08:21 -0400
Subject: [Elecraft] KO0B cw filter mod
Message-Id: <4.3.2.7.2.20010519085047.00ab7f00@pop3.ids.net>
K2ers:
I have to admit that I was a bit of a skeptic 'cuz my K2 sounded just
fine
to me. However, when I read the report from N6WG, I decided to try
it.
Besides, I have as much or more fun tinkering with stuff as I do operating.
It's easy to do if you take reasonable care. It took about 45 minutes
from
start to finish to do the mods.
I do believe that there is an improvement. The quality of the audio
was
pretty much the same (I had not experienced the "underwater" sound
mentioned... all of my sea time was spent on the water, not under it)
but
the cut off characteristic of the tightened up filter was noticeably
improved. Using spectogram, I roughly measured the response (using
noise
generator source) and got the same results as N6WG reported (within
reasonable tolerance).
I tried it.... I like it.
73,
Ken Wagner
K3IU K2 #920