Pages: [1]   Go Down

Author Topic: Two MLA-30's with MFJ-Noise cancelling signal enhancer  (Read 225 times)

KK4GMU

  • Member
  • Posts: 366
Two MLA-30's with MFJ-Noise cancelling signal enhancer
« on: December 22, 2021, 12:05:15 PM »

Has anyone tried pairing a couple of MLA-30 powered loop antennae with the MFJ-1026?

In additional to the potential to null out some noise (if the right "type"), I understand that it can also combine signals from two antennae by inverting the phase.

Is there anything to this?  Among those who tried anything similar, what have been your experiences for SWL?
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

G4AON

  • Member
  • Posts: 2178
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #1 on: December 22, 2021, 02:24:36 PM »

I have an MFJ-1026, it was bought to null out local QRM. They are tedious to adjust as the phasing is critical.

Some interference can be significantly reduced, and is particularly effective against “point sources” of noise such as a plasma TV. It will not work against all interference, particularly widespread hash radiated along power and telephone lines.

The “noise” antenna can be a length of hookup wire along a fence, it only needs to receive the interference well.

An active loop antenna can be located away from house wiring and turned to minimise interference. A single loop on its own is probably all you need.

73 Dave
Logged

KK4GMU

  • Member
  • Posts: 366
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #2 on: December 22, 2021, 02:57:17 PM »

I was more wondering about the "signal enhancing" aspect of the potential benefit of the 1026.  I wonder if two similar antennas, whatever they may be, could be set up to enhance the signal.  Or alternatively, two similar directional antenna set up in two different orientations to allow the 1026 to adjust the strength of either antenna to enhance the signal from different directions as opposed to the single direction of a single directional antenna.

In other words, have folks used the 1026 for uses other than noise reduction?
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

W1VT

  • Member
  • Posts: 6071
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #3 on: December 22, 2021, 08:07:55 PM »

I used an MFJ 1025 to combine my North and NorthEast Flag antennas to work MU5A in Guernsey on 160CW.
I intentionally have two arrays of four antennas offset by 45 degrees for the purpose of combining two antennas in phase.

After a winter of low band use, I moved my flag antennas around during the summer to minimize local noise pickup.
The power company fixed the noisy power pole a few months ago.  They moved the power transformer to a brand new pole.

Zak W1VT
« Last Edit: December 22, 2021, 08:12:59 PM by W1VT »
Logged

KX2T

  • Member
  • Posts: 1545
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #4 on: December 23, 2021, 05:44:45 AM »

I have used the MFJ 1025 for about 6 years now but it really came to light when we moved to the new QTH in SW Florida. First off I did mod the noise antenna input since I have never had enough property to place the noise antenna far enough away from my transmit antenna so there is a relay on the input of that port so when I am transmitting that input goes to ground, no worries about blowing that little wheat bulb. I have tried different type of noise antenna's and this is were you should throw there manual away cause a vertical is the best overall noise antenna to us so far, tried a 30ft vertical but at this time am using a 40ft vertical wire inside a spiderpole, this has worked best especially on the lower bands. I can take an S9 noise level created usually from a nearby 70Kv lines lightning arrestor gone mustang and take it down to S1 or 2, now when there are several of these arrestors that have gone south that noise is compounded and you may not get that overall best performance but it is still better than nothing.

Is there some attenuation on the received signal, yes but it far outweighs not being able to copy the signal at all buried in the noise plus after you null the noise you still have residual signals that the vertical does pick up that at times give you the effect of both your horizontal antenna and the vertical antenna so there seems to be some diversity reception going on. The vertical noise antenna also works well enough on 20m and above to lower the noise floor to copy weak signals being covered but hi levels of static. On 20m and above the line noise from power lines get more aggressive and the amount of level you can back it off on is not as great, maybe a shorter noise antenna would work best but the improvement on the lower bands is outstanding, the differences on the spectrum display is amazing, night and day.

I would assume that the box could be used on phasing two RX only antennas as well but here again you would have to cut off the signal coming in from both antennas while you transmit on your main station antenna.
Logged

KK4GMU

  • Member
  • Posts: 366
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #5 on: December 23, 2021, 08:06:47 AM »


I would assume that the box could be used on phasing two RX only antennas as well but here again you would have to cut off the signal coming in from both antennas while you transmit on your main station antenna.

Fortunately for my limited brain power, limited resources, and limited space (HOA), I do only SWL.  No transmitting.  But I'm trying to make the most of it with what I've got.  ;D
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

KD7RDZI2

  • Member
  • Posts: 689
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #6 on: December 24, 2021, 11:25:10 AM »

Has anyone tried pairing a couple of MLA-30 powered loop antennae with the MFJ-1026?

In additional to the potential to null out some noise (if the right "type"), I understand that it can also combine signals from two antennae by inverting the phase.

Is there anything to this?  Among those who tried anything similar, what have been your experiences for SWL?

I think it is a good idea. Just put them at some distance (not too close) each other possibly parallel. I used it with a vertical and an inverted V below the vertical and it also worked well. Just practice a bit. There are cheaper solutions as well called QRM eliminator, using a similar but not exactly the same circuit. My Russian unit also worked well but I assembled it as a kit. The MFJ -1026 is by the way a neat solution. If you have a specific noise source you can cancel it even 60 db. It makes a huge difference. To get acquainted with the unit try to cancel a strong broadcast shortwave station.
Logged

KD7RDZI2

  • Member
  • Posts: 689
Re: Two MLA-30's with MFJ-Noise cancelling signal enhancer
« Reply #7 on: December 24, 2021, 11:33:39 AM »

Has anyone tried pairing a couple of MLA-30 powered loop antennae with the MFJ-1026?

In additional to the potential to null out some noise (if the right "type"), I understand that it can also combine signals from two antennae by inverting the phase.

Is there anything to this?  Among those who tried anything similar, what have been your experiences for SWL?

You can also combine but doubling the signal it only gives the signal 3db stronger. In practice it can be also more during fading as one antenna may pick more signal than the other.  But a simpler solution is adding a splitter/combiner (Minicircuits). You may try also cheap TV splitters but have much worse specs on HF.
Logged
Pages: [1]   Go Up