[Elecraft] Diversity receive versus QRM eliminators

Mon Jun 29 20:23:09 EDT 2020

Gernot,
Why ? Generally you need to make sure you are not overloading/destroying  RXin K3.

73 Andy HB9CVQ

-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of gt-i at gmx.net
Sent: Montag, 29. Juni 2020 23:37
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Diversity receive versus QRM eliminators

Andy,
mni tnx - good ideas! Will rewire my QRM box to the K3 RXIn out to avoid the extra PTT-relay clicks imposed by the QRM-box. It is the Wimo-QRM Eliminator. Not as Hi -end as the NCC-1 but a start.
Just looked-up the DXE  - now the NCC-2 is out and it now also has the same extra PTT switching as my cheap box! Why is this required, as I just learned the K3 can handle this smoothly?

tnx 73 Gernot DF5RF

Am 29.06.2020 um 22:51 schrieb hb9cvq at hispeed.ch:
> Hi All,
>
> I use in my K3S the RX in and RX out (RCA plugs) on the backside for 
> inserting the denoised signal  from my DXE NCC-1 Phasing Box output plug.
> This box has two channels, were one can do e.g. up to -180deg phase 
> reversal. CH A and B signals are finally send to an internal power 
> combiner and to K3S RX in.
>
> My have 2 selectable TX/RX antennas, 2x36m tuned doublet 160 to 6m @ 
> 24m center and a Steppir DB18E @ 18m.
> RX signal come out safely from K3S RX (out) going to CH A NCC-1.
> My QRM local noise pick-up ant is a 1m diameter ALA 1530 electronic mag.
> loop (predominantly picking up local noise, no DX , horizontally 
> mounted in the attics, about -60dB decoupled from TX antennas) This 
> signal goes into CH B of NCC-1 By carefully equalizing/adjusting the 
> amplitudes CH1 /CH2 NCC-1 I then try do "Anti Phase". This will mostly 
> reduce the local noise on the used main antenna.
>
> The limitation is you can only effectively  focus (phase) on one 
> single local QRM source. The unit NCC-1 is good up to around 17m Band. 
> It is hard to get more than 20dB S/N (about 2.5 S-Units) improvement.
>
> In some local noise cases, not being a point source (Line source : PLC 
> , VDSL etc. ) I am more successful using a LISN ( EMC , Line/Mains 50 
> Ohm stabilization, decoupling network, 230V, 50 Hz) to safely replace 
> the signal from the mag. loop.
> This procedure picks up the conducted noise on the mains in the 
> house/flat more in an integral way. This does not act as a "point source"
>
> Experiments with predominantly E-field ( small/short dipole antennas) 
> for local noise pick up are ongoing.
>
> 73  Andy
> HB9CVQ, DK2VQ, AK4IG
> https://www.qrz.com/db/HB9CVQ
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> <elecraft-bounces at mailman.qth.net> On Behalf Of donovanf at starpower.net
> Sent: Montag, 29. Juni 2020 19:51
> To: Elecraft Reflector <elecraft at mailman.qth.net>
> Subject: Re: [Elecraft] Diversity receive versus QRM eliminators
>
> Diversity is not helpful as a QRM eliminator.
>
>
> Antennas with steerable nulls can be helpful, small loop antennas have 
> very deep nulls but also require a high gain, low noise figure preamp 
> and very careful attention to common mode rejection during 
> installation
>
>
> 73
> Frank
> W3LPL
>
> ----- Original Message -----
>
> From: gt-i at gmx.net
> To: "Elecraft Reflector" <elecraft at mailman.qth.net>
> Sent: Monday, June 29, 2020 5:18:30 PM
> 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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