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Title: CUSHCRAFT MA160V Post by: flintstone mop on October 22, 2007, 08:26:11 PM Hello fellow Ham ops
I have assembled the MA160V by Cushcraft. It's one of those short miracle antennas. Only this dessign is top loaded with a capacity hat. The length of the radiating element is 28 feet tall. The problem is with the ground radial system. I have a total of 22 radials and an Earth ground connection and I am seeing on the MFJ 259 2.5:1 SWR with an R sub S reading of 23 ohms and an X sub S of 8. Someone please explain the R sub S and the X sub S. I'm wild ass guessing Series Resistance???? And X sub S is some sort of reactance. The manual is not very clear OK I started experimenting as Cushcraft recommends: I removed the Earth ground and 9 of the radials and have the perfect match of 1.5:1 SWR and R sub S of 40 and X sub S of 6. I woulkd hate to think that another lossy tuning network has to be designed into this thing to give me the match I'm looking for. Cushcraft says that a "robust" radial system would make the antenna perform more effeciently. I'm guessing that it would start having the characteristics of a real vertical, which is around 30 ohms, if memory is serving me. Cushcraft says that a matching transformer or a unuun(?) (A fixed ratio) would help match the transmitter to the antenna. I'm hoping someone out here has some ideas how to make this a nice working system. I wouldn't mind experimenting with a fixed transformer for matching rather than an adjustable L network. THanks Fred Title: Re: CUSHCRAFT MA160V Post by: WA1GFZ on October 22, 2007, 09:39:24 PM http://en.wikipedia.org/wiki/Susceptance AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
makes mw want to drag out the old GR bridge and fondle it...hmmm where are my GR adapters |