Home FM Antenna

So what's the best plan? If I string a dipole antenna, what are the optimum leg lengths? Are the circular indoor "amplified" units any good?
Any other ideas? JR Dweller in the cellar
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Get a copy of The Radio Amateurs Handbook (ARRL), and read the chapter on antennas. It has lots of tables and charts and nomograms.

No.
If you listen to a particular station, you can make a rhomboid antenna from copper wire, aimed directly at the station's antenna tower. This can be done very cheaply, in the attic. The radio waves have no problem getting through all but a metal roof, and with antennas, higher is better.
Joe Gwinn.
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JR North wrote:

Mr. Cebik has a pretty good page on the subject.
http://www.cebik.com/vhf/fm1.html
Kevin Gallimore
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JR North wrote:

1/4 wavelength. A good way to go is to get about 12 feet of 300 ohm twin-lead and figure out the wavelength of 100MHz (remember the speed of light equals frequency times wavelength, plug in speed of light and 100MHz and get out your wavelength, pay attention to units). Then cut a piece of the twinlead to 1/4 wavelength length, strip the ends, and solder two 300 ohm resistors across each end. Then carefully find the middle, and cut just one of the twin-lead wires right in the middle, then cut it away from the body on each side of the cut until your cut is the width of the twin-lead, then strip the 2 pieces and strip the ends of another long piece of twin-lead and solder the wires so the whole thing makes a T. Strip and attach the other end of the non-quarter-wavelength piece to your 300 ohm antenna input, and stretch the top of the T out so you get good reception.
Are the circular indoor "amplified" units any good?
Better than connecting the inputs to a bowl of Jell-O maybe, not really very good antennas. But you don't need much if your desired signal is strong.

Yes. Go to Goodwill and get an old school rabbit ears with the FM antenna built into it, and just use it for the FM antenna part. Don't spend more than a buck or two in case you don't like it.
GWE
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On Sat, 11 Feb 2006 14:19:47 -0800, Grant Erwin

You're not having a good day, Grant! Total length should be 1/2 wave, not 1/4 wave, and you just short the ends -- no resistors.
Check Cebik's site cited in another post.
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Don Foreman wrote:

Maybe. At 1/2 wavelength, yes, you can short the leads. At 1/4 wavelength, I believe a standing wave should be terminated by what looks like an infinite stretch of 300 ohm twinlead - a 300 ohm resistor. Maybe I'm remembering it wrong, in any case the design cited should work for the OP.
GWE
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On Sat, 11 Feb 2006 21:04:55 -0800, Grant Erwin

I think you want/need a standing wave in the antenna portion of a folded dipole. Sections of T-line terminated in Zo don't radiate much signal, right? By reciprocity, if they wouldn't transmit they also won't receive.
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As Don sez, loose the resistors. The top of the "T" should be aprox. 1/2 wavelength. Characteristic Z of a folded dipole is aprox. 300 Ohms, same as that of twin lead. This suggests your receiver has a 300 Ohm antenna terminal on the back. Otherwise if the twin lead is fed to a 75 Ohm coaxial port on the receiver, then (theoretically) it should be matched to that port via a "balun" type of Z matching device.
Bob Swinney
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I used to make lots of FM antennas in HS - this was before everything came with antennas in the box- take 5 feet of 300 ohm twinlead - short both ends. cut one of the wires in the middle and splice into a fresh piece of twinlead. takes about 2 minutes to make - somewhat directional though
On Tue, 14 Feb 2006 09:16:00 -0600, "Robert Swinney"

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wrote:

Try something simple before you spend money. A lot of those fancy indoor antennas are bogus.
If you are reasonably close to the transmitter, make one out of twin-lead/lead-in. Put it broad side to the transmitter.
How to make an FM antenna http://www.kgnu.org/howtohear/antenna.html
I'm pretty close to the transmitters and a couple feet of wire dangling down works pretty well.
-- W§ mostly in m.s - http://members.1stconnect.com/anozira
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Folded dipole - with graphics - like I suggested.
Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder
Winston Smith wrote:

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Ok - easy - did it in school while in the dorms at TAMU.
Take a length of twin lead - 2 meters long. strip both ends and short both so it now becomes a long loop. At the center of one side only, cut. Cut back each side of the cut - and splice another length of twin lead - attaching both sides to the two wires from the center cut strip back point.
You should have a T now. The long 6' loop should be somewhat taught and held in place by rubber bands. The angle is directive - so sweep or simply point the perpendicular at the station. Then simply connect the twin lead.
If your radio has 75 ohm - then adapt the twin lead to the common transformer that changes the impedance.
It worked for me over 200 miles from radio to station tower. Tower is important. It might not be where the station is.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder
JR North wrote:

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Try this thread -
http://audiokarma.org/forums/showthread.php?tX057
I came across it awhile back when I was looking to improve my FM reception. Both of these are pretty simple to build. I think I may try the J-Pole design when the weather improves up here (Boston) and I can get out & mount it.
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I live in an area with marginal signal strength and interference from stations in another nearby city. I had the twinlead FM antenna that came with some radio tacked to the wall. You can buy one from Radio Shack for a couple bucks.
I made a MUCH better antenna by cutting a piece of thin PVC pipe the length of the antenna, about 4 ft, and taping the antenna to it with the feedline dropping down from the middle. I got some monofilament fishline and hung the pipe from the ceiling above the radio, at the balance point and then at one end hung a piece of fighline down a couple feet so I could swing the antenna around to make the best of the signal I want to hear and minimize the interferance.
The hang point is just far enough away from the wall to allow swing and the fishline is tied to the PVC an inch off-center so that one end touches the ceiling just enough so that it stays where I want it.
It's all white or transparent and is almost invisible.
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Is there just one station you are trying to receive? Or do you want a better antenna for all FM stations? And how much better of an antenna do you need? The dipole antenna will be an improvement. Going to a Yagi or Rhombic would be more work but a still better antenna that is more directional.
An amplifier at the antenna is good if you need a major increase in signal.
Dan
JR North wrote:

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I didn't catch the original post on this but if the OP is in the USA Radio Shack sells a pretty good omni antenna for FM, they also sell a 6 element directional beam for FM. I have both and they're not expensive or hard to assemble. http://www.radioshack.com/product/index.jsp?productId !03089&cp 32057&f=Taxonomy%2FRSK%2F2032057&categoryId 32057&kwCatId 32057&kw=fm+antenna&parentPage=search
I couldn't find the omni antenna on their site.
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