Re: Notching out one frequency


Just an FYI...

The Elad S2 attenuator is actually 12db, not 20 as it inidcates in SDRC. It is the S1 that had the 20db attenuator. This issue has been mentioned before but it doesn't get fixed.

Testing (Adam Farson for example) shows that the Perseus MDS is about 6 db higher (less sensitive) than the Elad S2.


From: <> on behalf of jdow <jdow@...>
Sent: Monday, March 30, 2020 2:49 AM
To: <>
Subject: Re: [SDR-Radio] Notching out one frequency
Very likely you can add attenuation beyond the Elad's 20 dB without affecting
signal to noise ratios. I think your measurements suggested you had another
external 20 dB attenuator. Note the amplitude of the 1240 kHz peak and the noise
with the ELAD attenuator enabled. Add the external 20 dB and repeat the
measurement. That should be quite informative. If the difference in readings is
20 dB or even as low as 18 dB leave it in as that is about the best you can do.


On 20200329 23:04:20, George Stein - NJ3H via Groups.Io wrote:
> Hello Joanne,
> Thank you for your analysis.  I will study it thoroughly.  I should have
> mentioned the kind of antenna I have.  It is a Wellbrook ALA1530-S2.  This
> antenna is nominally 1 meter in diameter, with an active amplifier mounter at
> the base of the antenna.  I have the antenna mounter at about 12 feet high 40
> feet from any structure.  Inside the house is an active Bias T that feed
> directly to an Elad ASA-42 amplified splitter.  In an email exchange with a
> gentleman in Washington state, with a very similar setup, he replaced the active
> bias T with a passive bias T from Wellbrook.  He mentioned that resulted in
> alleviating his issue with a 5kw station.  In an email discussion with Andrew
> Akin, Wellbrook owner, I was told that going from the active to passive bias T
> would result in a 9db reduction in signal strength.  The passive version is 60£.
> Is this a worthwhile option for me?
> I will look at disconnecting the antenna tomorrow and seeing the results as
> described in you reply.
> If I interpret your message correctly, I should be able to attenuate the
> incoming signal and not affect the week stations that I want to receive.  I do
> not transmit on HF these days (too close to neighbors).  I do monitor FT8 just
> to see what DXCC countries I can hear (158 to date).  So my goal is not to lose
> out on the weak stations (of course on FT8 a lot of them are).
> I used to use Ivory, but my wife suggested a moisturizing soap, so I got the
> 99.44% reference. HI HI
> Thank you again, Joanne.
> Regards,
> George

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