[MAMS] EWxx Eliptical Waveguide

[Lloyd Ellsworth]

I have received several notes and questions about eliptical waveguide. So, here is a bunch of comments. 
 
Eliptical Waveguide. I know Andrews makes it. The commercial industry modern way of moving around microwave power. Their coding on it is EWxx  xx being the size. I have played around with EW159, EW90 and EW42. 5, 10 and 24 GHz respectively. For some time, it was available on the surplus market fairly cheap. Until the recent rises of prices of scrap copper and brass. What I have seen in the used market. Meaning taken down from a commercial installation. Prices run, that is start, around $1 per foot. Then connectors. They are the real expensive bits. Don't be surprized to see $50 plus, used. Then, sorry, it is available in the rolls they take down. Not the larry the cable guy you need just 25 feet, so only buy 25 feet. So, if they have a 300 ft roll, then you have left overs. If it comes with kinks in it. You have to buy the entire thing. Kinks and all. No discounts for the kinks. Thing is, they know the scrap metal prices, and will not go below them.
 Last time I bought some, it was a 275 foot roll, with kinks. $275. Connectors, at the time, were $30 each. Scrap metal price. Oh, that is the connector, which goes from eliptical to waveguide, then a transition to Microwave N connector. 2 seperate sections. Sorry, you only need a basic connection, and their connector has air fitings and all the other stuff you don't need. No discount. 
 
Eliptical Waveguide, is hollow copper tube. Eliptical in shape. Hollow tube. For commercial purposes, it is often pressurized. Dry Nitrogen gas. So, the fittings, have to be gas tight, massive, and have a gas line connection. The transition from rectangular waveguide to Microwave N, also has to be gas tight. Most ham set ups with it I have seen, are not pressurized. 
 
Commercial goals, standards, and Amateur, are very different. Where the commercial list has a long list of considerations. The ham list is usually 1)$price 2)getting max power through it. Minimum loss. 3)transition 4)SWR match 5)not too complex. 
 
As a result, since we don't worry about the commercial list much, Larger size EW can be used for higher frequencies than the specifications. EG 10 GHz down 5GHz EW. Works fine. Yes, about all it does, is mode. Changes polarity. There are many ways to fix this, if it is a problem for you. Most of us, it is not a problem. So, as a result, one EW159 run, can be used for 5 and 10 GHz. Just a simple set of relays does the job. 
 
When Don ran his run, needed transitions. Dealers, too expensive. So, he decided to make his own. Can be done, but this is not a trivial task. He ran many experiments, until he got a winning solution. Take the end of the EW, and shape it to a formm, that could support a probe, and thus make a transition. This was accomplished with a series of wood maple forms, that with work, changed the ribbed shape, and formed useful surfaces. Build up a transition to a Microwave N connector. PS They are good to 18 GHz. Takes about 8 hours, to make one. Like I mentioned. Not a trivial project. But, it can be done.
 
Results. I recall a good run of EW159, had about a 5dB measured loss in 100 feet of it at 10 GHz. EW90, EW42 I was not all that impressed with. The EW42, was the only thing I have ever found to move 42 GHz 100 feet or so. You still need to mount a preamp at the antenna feed. To get around the rotor. 5 or 10 GHz, a lenngth of Andrews Super Flex FHSJ works. It is good to 11 GHz. 42 GHz, etc, a chunk of flexible waveguide is in order. Important thing here, as always, measure it. If you did  not measure it, you really don't know. If you read the spec, and said close enough, refuse to measure it, expect you will be in for some rude surprizes. Prices on the FSHJ is usually not bad. $1 per foot. $25 per connector. N Microwave. Price on the flexible waveguide. Last time I bought a 4 ft run of flexible WR42, it ran me about $40. Then figure it is only going to ben around the rotor so many times. Then need to be replaced. 
 
73, Lloyd NE8I/r
EN73 etc