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From: "Chris Trask" <christrask@earthlink.net>
To: <rsgb_lf_group@blacksheep.org>
References: <572685.58103.qm@web86501.mail.ird.yahoo.com>
Date: Wed, 16 Dec 2009 14:50:47 -0700
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Subject: Re: LF: Noise cancelling by using optic transmission of RX signals
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>
> I want to start a new subject (for me it's new)...
>
> The last weeks I still had RX problems, either with the tx antenna or with
> the short E-flied RX antenna.
>
> I found out that the noise was/is generated by my notebook which made
> RXing difficult, even in regions without any else local QRM (what could
almost
> bring me to shut down the PC and just do nice and easy CW QSOs without
anything
> else! (but most traffic is in QRSS...)).
>
> Then I have done mni tests with many many ferrite cores (that I found
> in an older emc lab in our institute), e.g. 20x FT50-77 plus 20x FT50-43
plus
> 20x FT50-61 and e few others. I placed them all in series, partly in the
near of
> the preamp and/or in the near of the RX. Sure, there was a significant
reduction
> of noise but lastly the noise remains.
>

    <<SNIP>>

    You've done fairly well in reducing the noise that is conducted through
your power supply lines, but the inband noise being induced into the antenna
and then into the receiver is not going to be quite as simple, as you seem
to have learned thus far.

    I'm going to assume, for the moment, that you are dealing with impulse
noise coming from your laptop and elsewhere.  I've had to deal with a
similar problem at HF frequencies resulting from what is very likely faulty
sodium vapour street lights near where I live, and more than just one.  That
sent me into the literature of noise reduction, and I came up with the
following for dealing effectively with reducing impulse noise prior to the
receiver:

    http://www.home.earthlink.net/~christrask/Paper020.html

Chris