Message-ID: <3B3595AE.8E5E5261@alg.demon.co.uk>
Date: Sun, 24 Jun 2001 08:24:30 +0100
From: "Steve Rawlings" <steve@alg.demon.co.uk>
MIME-Version: 1.0
To: "LF Group" <rsgb_lf_group@blacksheep.org>
Subject: LF: Noise canceller revisited
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

Hi All,

In early June, and within a few days of each other, John G3CCH;
Ron G6RO; and Bob G8RW all mentioned to me how new sources of
local QRM on 136 kHz had suddenly appeared at their respective
QTHs.

The increasing number of LF operators experiencing QRM problems
in suburban locations prompted me to see if I could redesign my
noise canceller so that the phase-shift network could be built
using readily available RF chokes, instead of using custom coils
wound on 3C85 cores.  Well, to cut a long story short, three
weeks of effort (and virtually no operating!) has resulted in no
alternative to using the custom coils, without incurring a
significant re-design of the canceller.  

Of course, after all the trial and error attempts to get the RF
chokes to work, my original (previously, neat and tidy) noise
canceller now looks like a bird's nest.  So it will take a few
days to restore it!

Nevertheless, I now know the way I'd like to proceed when I get
time to build a new version of my dual noise canceller.  I won't
clog up the Reflector with the detail, but I have posted my
thoughts at:
http://www.alg.demon.co.uk/radio/136/noise_can.htm#ideas

I've also updated the constructional details for my QRP LF TX at:
http://www.alg.demon.co.uk/radio/136/qrptx.htm

Regards to all,
Steve GW4ALG