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Re: Topband: Circularly Polarized Receive Antenna

To: Brian Beezley <k6sti@att.net>, topband@contesting.com
Subject: Re: Topband: Circularly Polarized Receive Antenna
From: Rick Kunath via Topband <topband@contesting.com>
Reply-to: Rick Kunath <k9ao@yahoo.com>
Date: Wed, 13 Aug 2025 16:16:25 -0400
List-post: <mailto:topband@contesting.com>
This is a very interesting idea Brian.

Have you thought about taking the idea to the next level and using 2 antennas with one vertically polarized and one horizontally polarized and feeding these via a dual-channel SDR to Linrad?

I have done this for CW and on mediumwave for years (using small flag antennas and LoG loops feeding an SDRplay RSPduo) now and Linrad is an amazing piece of software, I would say the most advanced SDR software there is and it's been that way for a while.

Linrad can use it's automatic adaptive polarization function to optimize a generated polarization based on the input from the 2 antennas. It'll generate linear, elliptical or circular, of wither handedness (LH or RH) and any polarization in between and you can see all of that going on with a phase scope that is built in. It also has the capability to lock the adaptive setting and there are a few handy presets, one that allows you to invert the optimization. When you do that it eliminates the dominant signal and leaves the DX underneath it. It al;so has full manual phasing adjustment ability, three saveable presets that work like radio buttons to recall 3 phase and amplitude sets of settings.

Additionally it has synchronous and even better coherent detection capability to allow for even more tools to dig deep into the noise or work with reducing its effects. It has a wider coherent mode to create a 3d soundscape in your headphones that helps with noise, a CW mode that spreads the signals across a soundscape too, an X+Y mode to let your head handle the logic of your ears, and a normal narrow CW mode and a weak signal CW mode that also has AFC to keep the signal in an extremely narrow filter.

It has a dumb noise blanker that works well and is usable on automatic or manual modes. And a smart noise blanker that works even better and operates in a subtraction mode. You can use both at the same time.

Adjustable filter bandwidths and shape, a second narrower carrier filter for those modes that use one, insertable adjustable notches, and either a manual or an automatic notch mode that will kill any continuous carrier. It's got an adjustable delay function on the audio that I find useful sometimes in SSB to help dig deeper.

It will operate on either the time domain or the frequency domain, this is selectable.

And lots more.

I thought it might be worth mentioning this because it would be the perfect thing to feed your antenna array into.

Rick Kunath, K9AO\

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