[Elecraft] Notch

[George, W5YR]

In daily and direct comparison of the K2 with the Icom PRO2, the one
situation which most often occurs in which the K2 fails altogether and
the PRO2 succeeds is the case of a weak CW signal with a carrier or
heterodyne almost on the same frequency. Such a signal renders the K2
unable to pass the signal regardless of filter bandwidth(s). The PRO2
on the other hand offers a manual DSP notch filter for CW plus almost
infinitely adjustable DSP IF filters. A combination of selecting the
right manual notch frequency, the right filter passband and location
does away with the carrier and leaves the weak CW signal completely
readable. On the K2, the carrier literally fills in between the dits
and dahs rendering the code unreadable.

I have often wondered why the optional audio filter did not include
some form of notch filtering to combat this situation. I have external
analog and DSP audio filters that I can use with the K2 to get around
this, but it would be nice to keep the station in one package.

On the positive side, apart from QRM that the K2 filter simply cannot
deal with and/or a level of QRN beyond the capabilities of the Noise
Blanker, the K2 does a creditable job of keeping up with the PRO2 on
most signals.

Bottom line: addition of i-f or audio notch filtering and i-f shift
and/or some form of passband tuning would substantially improve the K2
in my opinion.

Ron, I guess we got spoiled on the HRO-5 the same way. I got mine in
1946, though!   <:}

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489  IC-765 #2349 IC-756 PRO  #2121 IC-756 PRO2 #3235


----- Original Message -----
From: "Ron D'Eau Claire" <rondec@easystreet.com>
To: "'Elecraft Reflector'" <elecraft@mailman.qth.net>
Sent: Sunday, January 12, 2003 7:39 PM
Subject: RE: [Elecraft] Notch


> No, Tim, you didn't miss anything.
>
> For SSB, it seems like more and more rigs are going to some sort of
DSP
> that includes an automatic notch function. As a brass pounder, I
have
> little experience with those.
>
> For CW, current operating practices seem to favor using the
> narrowest-possible bandwidth which eliminates the need for a notch
> filter.
>
> I miss a notch filter, because I like using a w-i-d-e bandwidth
filter -
> as wide as QRM will allow. And sometimes I must crank down the
bandwidth
> just because of ONE loud signal nearby. It feels like I'm a horse
> wearing blinders, using a very tight filter. I'm completely unaware
of
> what's going on around me "on the band".
>
> A good notch filter can be added at the audio output. One
disadvantage
> of doing that is that the AGC MUST be turned OFF, or a loud signal
will
> cause the AGC to turn down the overall gain on the weaker signal you
are
> trying to copy. For us OTs who still tend to ignore "newfangled"
gadgets
> like AGC and control the gain ourselves, that's no problem. But it
can
> be irritating to someone used to AGC.
>
> As for "why not?", I can't answer that question. I've had a "notch
> filter" on almost every "high performance" receiver I've owned,
since
> the HRO-5 I bought in the mid 1950's. And the "notch" was handled by
the
> i-f filter where it should be to boot!  You are absolutely right.
It's
> nothing new. Gee, maybe it's gotten too old... <G>.
>
> Ron AC7AC
> K2 # 1289
>
>
> Hi folks -
>   I very seldom have ever needed to use a notch control, but the
other
> night I used one on another rig and was surprised at how well it
worked
> and useful.
>   Have I missed something or is there no notch control on the K2/100
and
> if not, why not? Looks like it was pretty standard on rigs at least
as
> far back as Drakes. Can some one clue in the clueless. Thanks.
>
> 73/Tim NZ7C
>
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