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Antenna question
My outdoor longwire antenna works just about as well as I could imagine.
Very long wire, very high, attached to shielded 50ohm coax about 40 feet from the house to avoid all the noise, and connected through a MLB. I get amazing reception on all my radios. So now I have a second "listening post" on another floor, and have decided that I'll feed a high-impedance antenna to that spot. Some radios, mostly my older ones, don't have a low-impedance input, just the normal slotted-screw antenna wire hookup. This will give me an easy way to play with these. I might try a slinky outside, or maybe not. (Any real-world opinions on a slinky vs. long wire?) My real question is this: Can I use similar 50ohm shielded coax as my feedline, to take advantage of the shielding and get the antenna away from the house? I would of course not use the balun or even the connectors, just connect the antenna to the center conductor, and strip away enough inside the house to connect the center conductor directly to the radio. Will this work? Is it a sound design? Thanks, Jeff |
#2
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Antenna question
In article ,
"Unrevealed Source" wrote: My outdoor longwire antenna works just about as well as I could imagine. Very long wire, very high, attached to shielded 50ohm coax about 40 feet from the house to avoid all the noise, and connected through a MLB. I get amazing reception on all my radios. So now I have a second "listening post" on another floor, and have decided that I'll feed a high-impedance antenna to that spot. Some radios, mostly my older ones, don't have a low-impedance input, just the normal slotted-screw antenna wire hookup. This will give me an easy way to play with these. I might try a slinky outside, or maybe not. (Any real-world opinions on a slinky vs. long wire?) My real question is this: Can I use similar 50ohm shielded coax as my feedline, to take advantage of the shielding and get the antenna away from the house? I would of course not use the balun or even the connectors, just connect the antenna to the center conductor, and strip away enough inside the house to connect the center conductor directly to the radio. Will this work? Is it a sound design? There are three things to consider: 1. Antenna impedance. 2. Transmission line impedance. (example 50 ohm coax) 3. The receiver input impedance. 1, 2, and 3 all have to match. Lets pretend the radio input is 500 ohms (to ground and the antenna is also 500 ohms but you want to use 50 ohm coax between them for receiving. You could use an UNUN on both ends (example the MLB) on the antenna end and make a UNUN at the coax to receiver input. You would use the same ratio as the MLB only use the windings in reverse so antenna step down and at the other end step back up to the radio input. -- Telamon Ventura, California |
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