Hey All,
I want to try an antenna that would be for temporary use in areas of possible power line noise.
I envision running 2 insulated multi stranded wires ( AWG size TBA , aluminum vs copper composition TBA ) ,
air spaced at 1" to "simulate " foam twin lead in the ball park 300 to 450 ohm range .
Conductors are shorted at the elevated end.
I am shooting to build a supposed folded vertical "quarter" wave/ "low noise " design for 1 Mhz. It's a bit unclear to me what length is "ideal" and what length actually represents a TRUE quarter wave when it is folded .
FWIW, At 1 Mhz a quarter wave MONOpole would be 234 ft ( for now I am disregarding any "Earth" side considerations such as 45 degree drooping radials, buried "spoke" radials, etc). 234 feet is WAAAAY TOOOOO TALL !
But I AM thinking about a possibly alleged "desired" electrical length of 117 ft.
117 ft is also a "practical " length to actually be able to work with. I am not sure whether (2X) 117 ft would still only "represent" an 1/8 monopole in reference to the wire run's total vertical height -OR- whether it acts as a "true" folded 1/4 wave, having one leg running up to full height and one leg running back down to "lawn level" (117 ft "plus" 117 ft).
BTW, I am sure that there is no way I can hang it "fully" vertical. I'd be LUCKY to get it up 40 or 60 ft. So there would probably be more than HALF of the antenna's total length arcing over and running fairly low horizontal to the lawn (like a kite string). I can probably get a tie off on a low tree branch at 6 ft or so , then down to radio. Implications ?
I also wonder if giving this "twin lead " a few twists is advantageous. I have seen this done when twin lead is actually used to FEED a "real" antenna ( ie a horizontal dipole ).
For the receiver, I'd make up a 175 or 220 uH (wound with #28) ferrite bar with maybe 4 or 5 "taps" mostly bunched up at the cold end- hopefully one of which winds up at a ball park 300 ohms or greater (otherwise put, guesswork).
A properly spec'd ceramic var cap would be across full coil,so the project would end up being a twin lead tuned ferrite auto transformer air /magnetically coupled to the receiver's internal ferrite.
I know that design specs and "rules" are much less important on receive antennas as opposed to transmit antennas.Also the "characteristic response" is going to vary as one moves up or down in frequency away from the "design reference" of 1 Mhz. There is one school of thought that says "Just try it and see how it works". The problem is that I don't have NEARLY as much to time play radio as I would like, so I'd like to get a bit of back round , input and "predictions" before I forge ahead.
Also, it can be a bit of learning experience and if nothing else, a theoretical exercise on how antennas work.
ANY help GREATLY appreciated,
de N1NQC