Help with calcs for the safety rules QO-100

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AdrianH
Posts: 81
Joined: Thu Jul 18, 2019 2:46 pm

Re: Help with calcs for the safety rules QO-100

Post by AdrianH » Fri Jun 04, 2021 2:47 pm

I am just putting a few thoughts on down on here using the article in CQ-TV263 on required power levels. I know it is a bit out of date with respect to the MER of the beacon, but think it matters little.
If I had a 1.2m dish then the reference was 8dB MER with a 1 m dish it was 7 dB MER
So with the same 1m dish for TX and RX, The power level at the feed to give an MER of 7 dB, at 250KS with a 0.35 roll off that was said to be 43 Watts with an efficiency of 50%.

I have a 1.05 m dish,and believe from a few on line calculators to have close to 0.4 dB gain on the 1 m

So I tested my own signal at as close to 7.4 dB MER as I could make it when there was no other stations on board, ( apart from beacon ) also I tested on the slot near to the beacon as that seems to be the quietest with respect to noise and I needed 42 Watts at the PA output.

I have set 0.5 dB cable/connector loss so think at my feed point I have 37.4 Watts, I think I get an efficiency of around 0.575 or 57.5 % although, I am not sure if I am making up for the 0.4dB enough?

But it may be a better figure then just guessing I have 70% efficient antenna?

Adrian

p.s. I am eagerly awaiting any guidance to be given from the Microwave soc and others as well as the final submission of the calcs etc from the RSGB on the 7th June? But it is fun to try and work things out, it keeps the grey cells active.

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