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what is the proper length for the FM dipole antenna?
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Wavelength of FM is ABOUT 10 feet at 98mhz. (middle of band in US)
The 58" length ref'd here is 'half wave' and will give good results.
Cut a length of 300 ohm Twin Lead to about that length. At each END, strip back 1/2" and twist together. In the CENTER of ONE run of the twin on that piece, cut it. Take another piece of twin lead, for your down lead and strip back 1/2" at each end of both wires. Attach to your 'cut out' piece by attaching 1 leg of the downlead to each side at the 'cut out'. You now have one LONG loop of wire, terminated at your radio. Use a BALUN (300ohm to 75ohm transformer) if the radio uses an F connector for the antenna. That connector should be labeled 75ohms.
Too much is never enough
They work best stretched tight on a piece of thin wood.
Taped on a broomstick so you can rotate it.
The difference between a $2 antenna stretched tight and positioned vs. left loose is surprising.
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That was the "go to" antenna for this budding audiophile (this was as I was just entering my teenage years).
Nice to see that it is still relatively cheap (I paid $2.99 for it back years ago) in the grand scheme of things. Maybe we better buy up the remains before RS closes the Shack...
Cheers,
Dman
Analog Junkie
$2 at Parts Express.
And I didn't have Parts Express in 1988 as a resource!
Dman
Analog Junkie
After exhaustive research the jury is out.....58 " seems to be the wiener.
Thanks to everyone for input,the antenna really means a lot for reception and quality of Sonics...
58 is a compromise for the whole band. Make it longer if you want it to work best on the low end (88-92) or make it smaller for the upper end of the dial. See link.
E
T
and this is in inches
http://www.radiobrandy.com/dipole1.html
I haven't noticed any particular length works the best. Mine are usually about 6' long with the last 3' being split or separated (just speaker wire) Placement seems to have a lot more effect on good reception. Just try different lengths and placements. I heard years ago that FM waves were 29" in amplitude (not sure if that is true)
IIRC ideal is 1/4 wavelength of the station you desire.
First hit on a google search.
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