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Author Topic: Best MWDX antenna?  (Read 1968 times)

Offline alpard

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Re: Best MWDX antenna?
« Reply #75 on: May 04, 2021, 1237 UTC »
Good point on MLA30, and DIY mods.

It is just I saw the old thread about MLA30, and one of the poster showed his modded MLA30 with the extra larger element magnetically coupling to the MLA30, and also tuning the larger element with variable cap. 

He seems very pleased with the increased performance on DXing with the mods, and I was wondering about the increased performance on MLA30 DX capabilities after the mod.  As you say, I would have been doubtful to see the active antenna coupled to a larger element loop for possible overloading.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #76 on: May 06, 2021, 0140 UTC »
Received my phasing unit from Ukraine.

https://www.ebay.com/itm/284239070097

Usually I have a moderately low local noise floor anyway, so I have been using it more for peaking and nulling signals instead of local noise. IOW, another radio toy with knobs to turn. :)

It rolls off into MW, but I have found usable phasing with my antennas down to approximately 1000KHz or so, at least for strong signals. YMMV for weak signals, especially as frequency decreases.

I have been phasing my 31' vertical against my 148' LoG, and the setup can help separate some overlapping MW stations. For a test I am currently listening to music on 1110 by significantly phasing out WBT from North Carolina. It is not perfect, but it can help turn a jumble of stations into something listenable. Thing is it might not always be the specific station you want to peak or null out from the two or more present. ;)

Two matching antennas would be preferable for the type of phasing I am doing, or maybe even three with the center antenna grounded. Not sure I would want to bother deploying another 31' vertical with a ground radial field, but I might toss out another LoG sometime. Alternatively, I have an affordable active vertical collecting dust, so I could consider ordering another to deploy a pair. Decisions for another day IMO.
« Last Edit: May 06, 2021, 0202 UTC by RobRich »
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
148' "Shielded" Loop-on-Ground | 18' End-Fed Vertical | 9' + 31' Verticals

Offline RobRich

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Re: Best MWDX antenna?
« Reply #77 on: May 06, 2021, 0158 UTC »
Quick demo of the 1110AM station. You can hear WBT mixing into the music with the phasing unit off. Also added receiver attenuation to hopefully drop the now much weaker WBT towards or even into the noise floor.

https://youtu.be/SgkZhl0IrKE
« Last Edit: May 06, 2021, 0209 UTC by RobRich »
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
148' "Shielded" Loop-on-Ground | 18' End-Fed Vertical | 9' + 31' Verticals

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Re: Best MWDX antenna?
« Reply #78 on: May 06, 2021, 0306 UTC »
Thanks for sharing. It seems to give a nice null. I'm going to have to think about one of these.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #79 on: May 06, 2021, 0858 UTC »
Welcome. :)

Here is the flip-side of the above. Nulling the music on 1110 to hear Coast to Coast AM on WBT.

https://youtu.be/yK13MTGLTKU
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
148' "Shielded" Loop-on-Ground | 18' End-Fed Vertical | 9' + 31' Verticals

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Re: Best MWDX antenna?
« Reply #80 on: May 07, 2021, 0121 UTC »
That is very nice. I like it. It makes a world of difference. With all of the antennae options alpard has this would probably greatly enhance his MWDX reception. It probably doesn’t even have to be identical antennae. We still use similar technology in direction finding where there is a centre whip (omni) and a bunch of directed antennae pointing at the various compass headings. You null the directors against the whip until the signal disappears. That null represents the direction in which the signal is emanating from.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #81 on: May 07, 2021, 1053 UTC »
Yeah, matching antennas are not a requirement, especially if using phasing for local noise reduction. I was surprised my vertical and LoG was able to achieve such results given their vastly different characteristics.

Otherwise I was thinking more about using phasing to help steer an antenna array. Ideally that would be two similar antennas with the same polarization and similar impedance characteristics. Staggered parallel beverages, two verticals, etc.

Active antennas typically have wide bandwidth (low Q) and hopefully somewhat stable broadband impedances. Since I would be doing the project on the cheap, I already have one the following miniwhips on a shelf doing nothing and could order another:

https://www.ebay.com/itm/222469570201

I will think about it. In the meantime I might try phasing a couple of simple wire verticals or whatever if/when I feel like deploying them.

A three vertical array for additional enhancement might be possible as well. Probably phase the two outer verticals and ground the center vertical to the radial field. YMMV.
« Last Edit: May 07, 2021, 1056 UTC by RobRich »
Airspy HF+ Discovery | Kenwood R-600 + R-2000 | 2x RTL-SDR V3 | Si-Tex 200 | Soft66LC4 | Yaesu FRG-7
148' "Shielded" Loop-on-Ground | 18' End-Fed Vertical | 9' + 31' Verticals