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Diversity receive versus QRM eliminators

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gt-i

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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Alan - G4GNX

Re: 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: [hidden email]
To: "Elecraft Reflector" <[hidden email]>
Sent: 29/06/2020 18:18:30
Subject: [Elecraft] Diversity receive versus QRM eliminators

donovanf

Re: Diversity receive versus QRM eliminators

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" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
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: [hidden email]
To: "Elecraft Reflector" <[hidden email]>
Sent: 29/06/2020 18:18:30
Subject: [Elecraft] Diversity receive versus QRM eliminators

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donovanf

Re: Diversity receive versus QRM eliminators

In reply to this post by gt-i

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: [hidden email]
To: "Elecraft Reflector" <[hidden email]>
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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Tommy

Re: Diversity receive versus QRM eliminators

In reply to this post by donovanf

I have the MFJ 1026, with the built in whip and it eliminated a local
broadcast station from my overloaded Kenwood 450S. I use a Myantenna
endfed for the Kenwood.

73 de Tom KB2SMS

On 6/29/20 1:47 PM, [hidden email] wrote:

Elecraft mailing list

Re: Diversity receive versus QRM eliminators

In reply to this post by gt-i

Using something like the MFJ-1026 works well for me, BUT the 2 receceiving antennas must be similar to work well in my experience - i.e. 2 dipoles or 2 verticals with similar gain characteristics to get the most out of the little black box.

Hank
K4HYJ

----- Original Message -----
From: [hidden email]
Date: 06/29/20 13:19
To: Elecraft Reflector ([hidden email])
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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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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hb9cvq

Re: Diversity receive versus QRM eliminators

In reply to this post by donovanf

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: [hidden email] <[hidden email]> On
Behalf Of [hidden email]
Sent: Montag, 29. Juni 2020 19:51
To: Elecraft Reflector <[hidden email]>
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: [hidden email]
To: "Elecraft Reflector" <[hidden email]>
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

______________________________________________________________
Elecraft mailing list
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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http://www.qsl.net/donate.html Message delivered to [hidden email]

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gt-i

Re: Diversity receive versus QRM eliminators

In reply to this post by donovanf

Good hint - tnx Frank.
Will try a mini whip or small loop.
73 Gernot DF5RF

Am 29.06.2020 um 19:47 schrieb [hidden email]:

> 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" <[hidden email]>
> To: "Elecraft Reflector" <[hidden email]>
> 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: [hidden email]
> To: "Elecraft Reflector" <[hidden email]>
> 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
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Martin Sole-3

Re: Diversity receive versus QRM eliminators

In reply to this post by gt-i

QRM eliminators can work surprisingy well at times and appear next to
useles at others. It's rarely the unit, rather the situation. All of
these similar units, of which the MFJ noise cancelling signal enhancer
is but one operate by combining two essentially identical signals, the
unwanted noise. With the phase of one 180 degree from the other and the
amplitude matched total cancellation should occur, and it will, almost
certainly.

The difficulties are two fold. First is that whilst phase adjustment can
be made over a reasonable range the amplitudes must be the same. That's
not so easy and the noise antenna often needs to hear a lot more of the
noise signal than you might think necessary. The second problem is that
these units can only eliminate one noise source. If you are surrounded
by plasma and switch mode devices removing one just leaves a bunch more.
The problem here, other than amplitude matching is that all of the
arriving noise signals from different sources have a different phase
relationship between your main and noise antenna. So adjusting for one
noise signal to have 180 degree relationship between main and noise
antenna will make every other signal have a different phase
relationship, the signals come from different directions and different
distances so reach the two antennas at different times, and hence
different phases. Cancelling one doesn't do much for the other. If you
have one noise source coming from one direction and you can collect
enough of it then the so-called QRM eliminators work rather well, until
something shifts and the phase changes and your tweaking again.

Of course once Wayne gets done with all the K4 trickery he will have
time to develop the K-null that will eliminate all unwanted noise from
all sources on all frequencies at all times at the push of a button.
Join the queue :-)

Martin, HS0ZED

On 30/6/63 00:18, [hidden email] wrote:

> 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
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

gt-i

Re: Diversity receive versus QRM eliminators

In reply to this post by hb9cvq

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 [hidden email]:

> 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: [hidden email] <[hidden email]> On
> Behalf Of [hidden email]
> Sent: Montag, 29. Juni 2020 19:51
> To: Elecraft Reflector <[hidden email]>
> 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: [hidden email]
> To: "Elecraft Reflector" <[hidden email]>
> 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
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email list:
> http://www.qsl.net/donate.html Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

hb9cvq

Re: Diversity receive versus QRM eliminators

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

73 Andy HB9CVQ

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of [hidden email]
Sent: Montag, 29. Juni 2020 23:37
To: [hidden email]
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 [hidden email]:

> 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: [hidden email]
> <[hidden email]> On Behalf Of [hidden email]
> Sent: Montag, 29. Juni 2020 19:51
> To: Elecraft Reflector <[hidden email]>
> 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: [hidden email]
> To: "Elecraft Reflector" <[hidden email]>
> 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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