[SCCC] Effectiveness of MFJ-1026 Noise Filter??

Wed Apr 3 01:38:30 EDT 2019

   - Noise arriving *from the ionosphere *is randomly polarized. It arrives
   at whatever polarization the ionosphere happens to favor at the moment. It
   has the same ratio of electric to magnetic fields (also called field
   impedance) as a "good" signal

The vast majority of noise from the ionosphere is QRN. I've never
experienced RFI from TVs or switch mode supplies propagated via the
ionosphere. If that were the case everyone would experience nearly the same
amount of RFI no matter where they lived . The other way to think about
this is backwards. Why are HF beams all horizontally polorized? Because
they receive much less QRM than antennas that are vertical. There's plenty
of anecdotal evidence that this is true. So we can pretty much eliminate
RFI from the ionosphere.

The other piece of evidence is magloops or very small loops compared to
wavelength. I have a RX only loop that's very quiet compared to my lowband
transmit antennas. Mag loops work mostly on the magnetic field of a signal.
The mag field contains the same info as the voltage field as w8ji claims or
does it? If that were the case magloops wouldn't provide any benefit at all
with RFI and would be just as noisy as a much larger antenna. Of course we
know this isn't true because mag loops work in the magnetic domain. So I
have to disagree with w8ji on this one. RFI appears different than a
regular modulated signal where the mag field and voltage field do contain
the same information. Conversely it appears RFI is mostly a voltage field.

   - Sources *within a few wavelengths* of the antenna combine and produce
   a randomly polarized noise. Local noise generally has *no* particularly
   dominant field. Very local noise, in the nearfield of the antenna, can
   either be electric or magnetic field dominant.

Due to the performance of small loop antennas I also disagree on this one.
The mag field has to be much quieter then the voltage field or RFI contains
more noise in the voltage field than the mag field. If noise sources were
mag field dominant mag loops wouldn't provide any benefit.

   - Noises arriving *from groundwave sources* some distance from the
   antenna are vertically polarized. This relatively fixed polarization occurs
   because the earth "filters out" horizontal components.

This one I agree with but would need to research why this is true. It sort
of contradicts the second claim because within a few wavelengths is the
same as ground wave. How much distance is needed between a noise source and
RX antenna in order for the earth to filter it out? Would make interesting
research.

So this brings up the $64K question. How is the noise getting into the
receiver? Is it through the antenna or common mode noise on the outside of
the coax? This is how to figure that out. Take the earth ground off the rig
and run it off battery if possible. Unscrew the barrel of the antenna
connector and slightly pull the connector out so just the center pin is
connected. If the noise is gone you have RFI coming through the braid. An
antenna noise canceler will not work on this noise. The only option is a
bunch of toroids to wrap coax through. Connect your rig back to mains PSU.
Noise? Toroids on the power cable to the PSU and also again as close to rig
as possible. Continue doing this on all cables connected to the rig until
the noise is gone or greatly reduced. If it's not reduced enough stack more
toroids or loop more coax through the toroids.

If the noise is coming from the antenna then a noise canceler can be
beneficial. Before assuming it's something with you neighbors or power line
noise check your own QTH too. With the rig on a battery flip all breakers
off. If the noise goes away there's something in your home causing RFI.
Flip a breaker on and if the noise returns grab a portable shortwave radio
and do some searching. Actually do this first then start at the 64K
paragraph to help narrow things down. It's MUCH easier to eliminate RFI in
your own home.

The final thing to understand is that we're not just after improving a
signal or reducing noise. We're after obtaining the best signal to noise
ratio. Most modern rigs today have way more sensitivity than we really
need. What I do is turn the volume up about 3/4 of the way and reduce the
RX gain to almost deaf. I use the gain control to reduce amplifying noise
yet have the signal "pop" out of the noise. I use the gain control as my
volume control.

I think I should do a live stream going over all this.

HTH

73! Mark KA6WKE

Website: https://www.ka6wke.net
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Author: 4NEC2 The Definitive Guide
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On Tue, Apr 2, 2019, 20:23 Paul Kube <K6PO at outlook.com> wrote:

> Mark, re:
>
>
>
> Noise antenna is the critical piece to the puzzle. I'm surprised to hear a
> horizontal antenna works but in my situation that didn't happen…  All
> man-made noise is vertically polarized.
>
> I wonder what your take is on these statements from W8JI’s “Radio Noise”
> page https://www.w8ji.com/noise.htm:
>
>
>
>    - Noise arriving *from the ionosphere *is randomly polarized. It
>    arrives at whatever polarization the ionosphere happens to favor at the
>    moment. It has the same ratio of electric to magnetic fields (also called
>    field impedance) as a "good" signal
>
>
>    - Sources *within a few wavelengths* of the antenna combine and
>    produce a randomly polarized noise. Local noise generally has *no* particularly
>    dominant field. Very local noise, in the nearfield of the antenna, can
>    either be electric or magnetic field dominant.
>
>
>
>    - Noises arriving *from groundwave sources* some distance from the
>    antenna are vertically polarized. This relatively fixed polarization occurs
>    because the earth "filters out" horizontal components.
>
>
>
> 73, Paul K6PO
>
>
> ------------------------------
> *From:* SCCC <sccc-bounces at contesting.com> on behalf of Mark Schoonover <
> mark at ka6wke.net>
> *Sent:* Tuesday, April 2, 2019 4:48:04 PM
> *To:* Steve
> *Cc:* SCCC
> *Subject:* Re: [SCCC] Effectiveness of MFJ-1026 Noise Filter??
>
> Steve,
>
> Noise antenna is the critical piece to the puzzle. I'm surprised to hear a
> horizontal antenna works but in my situation that didn't happen. What I
> ended up having for a noise antenna was winding about 50' of wire
> hellically on an 8' crappy fishing pole. All man-made noise is vertically
> polarized.
>
> Next up is tuning the thing. What I do is set the noise antenna gain to 0
> then adjust the main antenna gain so there's about S4-5 noise level.
> Remember the dial number. Set the Antenna gain to 0. Do the same process
> with the noise antenna. If you can't reach the same signal strength as the
> main antenna you need to make your noise antenna larger. Once you have the
> same S reading on both antennas then it's time for phasing. Start with that
> knob all the way counter-clockwise then slowly sweep to fully clockwise.
> The dips can be rather narrow so go slow. If no noticeable dip or the noise
> level increases push the phase button and slowly turn counter-clockwise.
> You should find the sweet spot. What I do after that is to rock the main
> and noise antenna gain to get a deeper null.
>
> There's also a button for high and low frequencies give that a try too no
> matter what frequency you're using.
>
> Good luck! It's a process to figure out but once you know how to do this
> any new noise source can easily be removed.
>
> 73! Mark KA6WKE
>
> Website: https://www.ka6wke.net
> Live Stream: https://www.ka6wke.net/live-stream
> Facebook: https://www.facebook.com/ka6wke-live-stream
> Twitter: https://www.twitter.com/ka6wke
> EMail Announcement: ka6wke-announce+subscribe at groups.io
> Author: 4NEC2 The Definitive Guide
> EMail List:: 4nec2defguide at groups.io
>
> On Tue, Apr 2, 2019, 15:17 Steve <k0xp at k0xp.com> wrote:
>
> > Anybody actually have experience with the MFJ-1026 "Noise-Cancelling
> > Filter", specifically whether it's really effective at cancelling
> > plasma TV noise (at least, that's what I think my intermittent noise
> > is; I'm not about to go next door and ask the nayboors to turn their
> > TV off and on in this HOANazified area just to confirm 8-O )?? Is
> > there a better-such filter? Needs to go between my FT-991A at 100W
> > output and an antenna tuner.
> >
> > Thanks,
> > Steve K0XP
> >
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