[Elecraft] Diversity receive versus QRM eliminators

[donovanf at starpower.net]

Hi Alan, 


The MFJ works very well as a noise eliminator only if the noise antenna 
is very close to the noise source, so that the noise is much stronger than 
the desired signals. If the noise antenna is receiving about the same 
signals as the main antenna the noise elimination function cannot work... 


73 
Frank 
W3LPL 

----- Original Message -----

From: "Alan - G4GNX" <g4gnx at g4gnx.com> 
To: "Elecraft Reflector" <elecraft at mailman.qth.net> 
Sent: Monday, June 29, 2020 5:43:24 PM 
Subject: Re: [Elecraft] Diversity receive versus QRM eliminators 

Hi Gernot. 

I use an LZ1AQ double mag loop (rotateable) to null out as much hash as 
possible. This feeds the RX Ant In input on the K3S. I also have an MFJ 
Noise eliminator which is also inline, using the LZ1AQ as the main (RX) 
antenna and I've tried a couple of antennas (including my HF vertical) 
as the 'noise' antenna and I don't find any noise suppression by phase 
elimination with the MFJ. I've yet to try a mini-whip antenna as the 
'noise' antenna. I actually wonder if the MFJ unit is faulty, as I've 
heard that other people have at least noticed a small difference when 
using it. Once/if I get the MFJ untit to work, I may then buy one of the 
more expensive noise eliminators. 

73, 

Alan. G4GNX 


------ Original Message ------ 
From: gt-i at gmx.net 
To: "Elecraft Reflector" <elecraft at mailman.qth.net> 
Sent: 29/06/2020 18:18:30 
Subject: [Elecraft] Diversity receive versus QRM eliminators 

>Hello all, 
>In a recent rush to eliminate urban noise I bought an QRM eliminator. 
>The working principle is to null out signals by shifting the phases of 
>two antennas (one main/tx and one rx). I can see the effect sometimes, 
>but it is not the holy grail for all types of QRM. I still don't get rid 
>of the PSU/LED/plasmaish noise here, sometimes the S/N is a bit better 
>but maybe thats my inner impression to justify buying this thing. 
>Now, I do wonder how this differs from diversity receive, effectively 
>versus local QRM. 
>Note I have a 10m vertical as the 2nd ant, while the main ant is horizontal. 
>Any thoughts or hints ? 
>tnx 73 Gernot DF5RF 
> 

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