Intefearance reducing/anti jamming antenna

Useful information regarding antennas for SDR products.
illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Intefearance reducing/anti jamming antenna

Postby illllm » Tue Jan 29, 2019 12:36 am

See this website:

http://heanvaincs.blogspot.com/2012/03/ ... tenna.html

I wonder if it works :?:

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sdrom33
Posts: 77
Joined: Sun Dec 09, 2018 4:38 pm

Re: Intefearance reducing/anti jamming antenna

Postby sdrom33 » Tue Jan 29, 2019 9:10 pm

Yes, it works like perpetual motion machines, free energy gadgets and the like. It is difficult to invent new things that really work in antennas!

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g1hbe
Posts: 456
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Intefearance reducing/anti jamming antenna

Postby g1hbe » Tue Jan 29, 2019 9:44 pm

I'd like to see an 'equivalent circuit' to that, as I can't work out what is meant to be happening. It looks like (perhaps) it's a version of the QRM eliminator idea, where a null is introduced into the radiation pattern of the radio's antenna by combining the signal from the other antenna in antiphase. It'll probably do something but it will depend greatly on each individual noise situation. I suppose you adjust it by moving the second antenna.
I use two antennas, one is a loop the other is a wire for picking up noise. The signals from both are combined in a control unit in the shack and the amplitude and phase are adjusted to null out the noise.

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Andy

DanubeBCL
Posts: 201
Joined: Sat Jul 02, 2016 12:39 pm

Re: Intefearance reducing/anti jamming antenna

Postby DanubeBCL » Wed Jan 30, 2019 8:00 am

g1hbe wrote:I use two antennas, one is a loop the other is a wire for picking up noise. The signals from both are combined in a control unit in the shack and the amplitude and phase are adjusted to null out the noise.
That's the only way to get rid of at least partly the RF noise polluting our environments today. You have to carefully adjust phase and amplitude of the auxiliary antenna to achieve a decent notch effect for the noise part. This is simply impossible with such a construction shown in that "Anti Jamming Antenna". Sorry, but such "constructions" are useless.
Even sophisticated two antenna arrays with phasing/noise cancelling circuits have their limits. You only can reduce one noise source from the neighbouring houses. But nowadays all houses around you have strong sources of noise and you cannot catch all of them with the phaser/noise cancellor.
In this context: There is still no noise cancelling feature by phasing and spectral subtraction available for the RSP duo (except for some Linux experimental software which not everybody can use). This would bring noise cancelling to the market at an affordable price.
73, Heinrich

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arcosine
Posts: 30
Joined: Wed Jan 02, 2019 6:24 pm
Location: 41.678472, -88.051762

Re: Intefearance reducing/anti jamming antenna

Postby arcosine » Wed Jan 30, 2019 1:25 pm

The scheme only works if the interference is in one direction, if you have two sources, then it can only null one. The circuit can be tuned to null two sources, but would be very trick to do. A much less complicated solution is a plane loop antenna, which will null the noise source as well, much easier to use and typically has a deeper, sharper null.

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Tony
AA9CC


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