FM broadcast receiving antenna

[k4kyv]

What would make the best outdoor receiving antenna for the low end of the FM BC band?  I resurrected my old FM tuner for the shack, and the usual short piece of wire indoor antenna doesn't pull in all the stations well enough to make them full quieting.

Which would be better, a quarter-wave ground plane, halfwave dipole or folded dipole?  I prefer something simple that would not need to be rotated, so a yagi would be my last choice, only if a simple non-directional didn't work.  Vertical polarisation seems to work ok in the car, and the GP would probably be the easiest to construct (I once made a 2m CB GP out of coat hangers and an SO-239), but IIRC, factory-made FM antennas were always horizontally polarised.  I haven't seen any kind of commercially built rooftop FM antenna for years, but back in the 60's I used an ordinary rooftop TV antenna and it worked well, but I prefer something less cumbersome.

[ka3zlr]

Hi Don,

 Good Topic, and i remember the directional FM antennas very well, considering your needs and what your looking for i would avoid a broadband antenna they are basically a compromise for FM it would have one half the gain of an FM antenna, it would be sufficient in the "Prime" reception area of an FM signal from 2 to 25 miles out, in considering "Normal" and "Fringe" reception i would consider a good base loaded vertical, a simple 2 meter base loaded 5/8 gain antenna would do the job quite nicely, trimmed for the FM band.

[KD3CN]

Hi Don,

I have one of these omni types and it works okayfine!

http://www.starkelectronic.com/acantena.htm#FMSS

Karl

[Pete, WA2CWA]

Make a simple turnstyle antenna (crossed dipoles) with stiff or coat hanger wire. Use a quarter wave matching section between the dipoles. Feed with 52 ohm coax. I built a simple turnstyle antenna for 2 meter mobile that worked great. Of course, wife wouldn't ride in the car with me if I put it on the car roof (it was held in place with magnets). Still have it around here somewhere.

[W1RKW]

Don,
I built a J-pole several years ago for FM using 1/2" copper pipe and matched the feed point with a coaxial balun/impedance transformer.  It does circles around a dipole or even a folded dipole.  It has some gain and is omni directional to boot.  I have it in my attic and works pretty good expecially down at the low end of the band for which it is tuned and where those more interesting stations that have lower power.  If you want dimensions and pictures let me know.  I can pop up into the attic and snap some photogs.

[k4kyv]

i would avoid a broadband antenna

I am aiming for the non-commercial low end of the band where the NPR and university stations are, so something designed for 90 mHz would be close to optimum.  I  may have to use something directional, since one of the university stations is 70 miles from here, and a local bible beater wipes them out on the receiver I am using.  I get the station perfectly on the Bo$e Wave Radio in the kitchen.

I wish to thank everyone for your comments and advice so far.

[WU2D]

Don,

Nice talking to you on 3700 and 3725 this week. Wish more folks would come on down!

A simple folded dipole beam will give you some directivity.

You can feed it with twin lead or a balun and 75 Ohm coax like RG-6.

Driven Element for 90 Mhz   About 62 or 63 Inches.

This site has by W4RNL has a good 3 element design   http://www.cebik.com/vhf/fm2.html

Mike WU2D

[K1ZJH]

If you could find a single band Channel 6 TV antenna it would be ideal for
the bottom end of the FM BCB.

Single band yagi TV antennas were made by Channel Master at one time.
Not sure if the Stark Electronics supply house referenced earlier could
supply them?

Pete

[Ed KB1HVS]

  Had this up for years. Works FB.

[W4EWH]

I am aiming for the non-commercial low end of the band where the NPR and university stations are, so something designed for 90 mHz would be close to optimum.  I  may have to use something directional, since one of the university stations is 70 miles from here, and a local bible beater wipes them out on the receiver I am using. 

A two or three element yagi may be the best choice if you're getting interference from a local station. It will allow you to null the "bible beater" without losing two much gain the way a "long john" yagi might. Of course, this depends on the FM Tuner you have: if it's low on gain, you might need both a high-gain antenna and a cavity filter to null the local interference.

FWIW.

73, Bill W1AC

[KA1ZGC]

Don't go through the hassle of making a turnstile until you know for a fact that all the stations you want to tune are, in fact, tranmsitting a horizontally-polarized signal. Few of them are these days.

Unlike TV, it's assumed that most FM broadcast receivers are installed in automobiles, and the receive antennae are vertical.

This is why the vast majority of FM broadcast stations' antennae are ciruclarly polarized.

Fortunately, each broadcast station must state its polarity on it's license application, so this information appears on their license.

To view an FM broadcast license, go to:

http://www.fcc.gov/mb/audio/fmq.html

You can either type in the call letters to retrieve licensing info or you can scroll down towards the bottom of the page, specify a given radius and a set of coordinates. The latter will probably be your best choice.

Once you find the station you want, you'll find several entries for it (APP, CP, LIC). You obviously want the LIC entry.

Once there, just below the tranmsitter coordinates lives the antenna info. This info is given for both horizontal and vertical planes. If there's an ERP stated for both planes, then they're circularly polarized and you can use whatever kind of antenna you want.

Chances are you won't need a horizontal omni, and a folded dipole or two will give you what you want. They have a very broad match and can be run at DC ground.

I'd be very suprised if anyone was only running horizontal FM broadcast in this day and age, though stranger things have happened.

--Thom
Killer Agony One Zipper Got Caught

[KD6VXI]

What would make the best outdoor receiving antenna for the low end of the FM BC band?  I resurrected my old FM tuner for the shack, and the usual short piece of wire indoor antenna doesn't pull in all the stations well enough to make them full quieting.

Which would be better, a quarter-wave ground plane, halfwave dipole or folded dipole?  I prefer something simple that would not need to be rotated, so a yagi would be my last choice, only if a simple non-directional didn't work.  Vertical polarisation seems to work ok in the car, and the GP would probably be the easiest to construct (I once made a 2m CB GP out of coat hangers and an SO-239), but IIRC, factory-made FM antennas were always horizontally polarised.  I haven't seen any kind of commercially built rooftop FM antenna for years, but back in the 60's I used an ordinary rooftop TV antenna and it worked well, but I prefer something less cumbersome.

This is just my two cents worth, but I have VERY good luck with a eggbeater style antenna.

Basically, two quad elements, mounted at right angles, and fed out of phase.  The trick, though, instead of making them both vertical or horizontal, I make one of each.  One of the quad elements is vert., one is horizontal.

I use it, at 6K feet, to pull stations in from SoCal in Central California.  Works FB for me.


--Shane

[W1DAN]

Don:

Try a Blonder Tongue BTY-5 series FM antenna.

73,
Dan
W1DAN

[aafradio]

I had a similar problem, Don.  I know this may sound like a bit of heresy, but a pair of crossed wire  rhombics pinned to the ceiling (or laid over the attic insulation, as I did) work very well.  We're out in the farm country of central Virginia, and it was a matter of an hour to rig them up and connect to the receiver.  A switch allows selection of the best signal/max unwanted signal reject.  The amazing thing is that in this new QTH I get six classical music stations versus one in our old digs in Washington DC!

 - Mike