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Circular Polarity and The Water Wheel in Dale's Moonbounce Amplifier
I'll attach some pix of the feedhorn and LNA for you.
The importance of circular feeds is that as a linear wave passes through the ionosphere, it undergoes Faraday rotation. So it may arrive at the station you are talking to having been twisted 90 degrees. This is a slow progressing process and on all bands except 23cM, may cause EU for example to be locked out for hours at a time for linear stations.
With circular polarity, Faraday is a non issue. The feedhorn almost all of us use is a VE4MA that has separate TX and RX probes. The circular polarity is synthesized as the linear wave propagates down the circular waveguide and encounters sets of capacity stubs. The exact opposite occurs for waves entering the waveguide. The result is we get CW and CCW without having to use any relays (loss) and phasing lines (loss).
My LNA has a noise figure of under 0.24dB and uniquely connects to a protection relay with no cable or adapters (loss).
The position of the feedhorn and its scalar ring is tediously adjusted by measuring the difference between sun noise and cold sky. W4SC developed a very accurate and repeatable process that uses an SDR RX for this.
I use a modified C band satellite drive system known as a polar mount so I only need one motor drive to track the moon.
Anyway, hearing my own echoes off the moon was and still is the highlight of my amateur career.
The photos are the feedhorn + LNA, My first water cooled 500W tube amp, my previous 400W solid state amp (mounts right at the dish). My current design is 600W solid state and will also mount at the dish.
BTW, that little circle in the middle of the tube amp is a paddle wheel that turns as long as water is flowing. A tachometer on the wheel sounds an alarm and shuts down plate voltages should the wheel stop turning.
I'll keep you up to date on my BB RX progress- thank you again Bill.
Dale W4OP
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20
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