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Re: [TowerTalk] My take on small power differences

To: towertalk@contesting.com
Subject: Re: [TowerTalk] My take on small power differences
From: "Lux, Jim" <jim@luxfamily.com>
Date: Wed, 18 May 2022 17:45:49 -0700
List-post: <mailto:towertalk@contesting.com>
On 5/18/22 5:31 PM, Brian Beezley wrote:
I've been told I should post a link to this writeup I did several years ago:

http://ham-radio.com/k6sti/pileup.htm

As noted in the analysis limitations section, I'm not sure how much it really adds. But I do think a probabilistic approach is needed to tease out the effect of small power differences.

I've thought of recording pileups to try to obtain some realistic signal power distributions. But it's tricky to do that well. I was afraid I didn't know enough to avoid biased data so I've never done it.


How did you choose log-normal as the "interference power" distribution?

I've just been looking at some modeling codes, and for an individual interferer, their power will likely be Rayleigh distributed (multipath fading in the ionosphere). I'm not sure what the "sum of Rayleigh" would look like (although I'll know shortly because I'm building a model).

( I note that the literature says "/Sums of Rayleigh/random variables occur extensively in wireless communications. A closed-form expression does not exist for the/sum distribution/." - so a Monte Carlo is where it's at.)

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