I have a relatively new hi fi stereo reciever. I also have regular (properly grounded) TV Antenna (because I'm too cheap to afford cable). The reciever has a hookup for an FM Antenna into which I run my regular TV antenna and it works great for FM radio.
Now, I'd like to pick up AM stations. For some reason there is a different hookup on the reciever for AM stations. Also, there is an outgoing ground hookup on the back of the reciever which is supposed to be just for AM Antenna ground.
I'm curious as to why there are separate antenna hookups for FM and AM, but mostly I just want to know if I can safely and effectively use my regular TV antenna for both FM and AM, ignoring the AM ground because I know the antenna is already properly grounded.
Antennas have to be designed for the kind of radio frequencies and modulation that are quite different for am and fm. It just so happens that tv and fm signals need very similar antennas, so you can hook up your fm to the tv lead in. You can buy a small desk or sill mounted AM loop antenna that hooks up to the am antenna connections on the back of your receiver. Often stereos have no internal am antenna, as most folks use them for fm, due to better sound, low noise, and stereo reception. Sometimes I have found a separate ground does indeed help reduce interference typical of am reception.
For AM, all you really need is a long piece of wire. The proper length will get the best reception, but a piece of bell wire about 50 feet long will do the trick. Run it out you window to a pole or something and hook to radio. Yes, a ground will greatly help. A metal water pipe will work too. Wrap wire around pipe and clamp it with a hose clamp. Hook wire to radio ground. However, to eliminate all that wire, you can buy premade coils at Radio Shack.
There is a ham radio newsgroup. Not sure of name, but look for "ham". Those guys are always experts at antennas and that stuff.
I dont have cable tv either. I dont watch it enough to justify the cost. The antenna gets me the news and a few other things. That is all I really need.
PS. The sound on your tv is actually FM. Thats why the same antenna works. I used to live where there was a channel 6 tv. I could get the sound from channel 6 on the lowest end of the FM band. I used to listen to the tv programs in my car on the radio. (That's back in the old days when having a tv in the car was not even considered). Now they got dvd in cars (not my old beater).
the ideal receive antenna will be 1/2 the wavelength of the radio signal, so:
AM .5 -1.6 MHz = 150 meters FM 88-108 MHz = 1.5 meters TV VHF 54-316 MHz = 2.3 - .5 meters
an antenna works best if it is "di-pole", two halves, each side half the length above, the antenna wires(2) connect to the middle. a meter is about 3 1/3 feet.
your TV antenna is good for FM because FM is sandwiched between TV channels 2 and 13. a tv antenna is really a series of antennas, an array of short, medium, and long "rods" to cover the very wide range needed.
AM would require an antenna 250 FEET on each side, which is not real practical. Most folks using an "outside" AM antenna will settle on a wire 50-100 feet long to the "antenna" connector, and as a substitute for the other "half" will connect a good ground connection to the "ground" connector. The ground used to be a water pipe, but since it's now plastic, an 8 ft "ground" rod is driven into the soil near where the "antenna" wire enters the house. At this point it's a great idea to install a "lightning arrestor". Lightning has a real affinity for "long wire" antennas, but it's something you really don't want in your house!
AM and FM energies are not compatible on the same wire or cable, that's why there are to sets of connectors.
Radio Shack has the wire, insulators, arrestor, and ground rod to do this (or did a year or two back). You will find there are AM radio stations on EVERY frequency on your dial, in fact SEVERAL. Day, eve, night, late night, and early morning you will hear different stations at the same spot on the dial. For some folks, "logging" these stations is a hobby. have fun, (it's good you don't have "short wave" on your receiver ;-) google "short wave listener"
-larry / dallas
Mak Wils> I have a relatively new hi fi stereo reciever. I also have regular
Check the packing box again. Any new sstereo reciever should have come with an AM loop antenna. (My Onkyo did). Check the manufacurers website and see if they sell one. Crutchfield sells one
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Antennas need to be designed for the frequencies being recieved. FM signals are between TV Channels 6 and 7 (88 to 108mHz) and a TV antenna works good for them. AM signals are way lower in frequency (.54 to 1.7 mHz) and need a different antenna. Long wire antennas work good for AM signals but almost nobody has the room for a hundred foot piece of wire. So they make loop antennas for AM signals (about cigar box size).
TO truly get the best reception of FM signals you need to turn the TV antenna sidewaks.(TV signals are horizantally polarized, FM signals are vertically polarized) but for 99% of the cases a plain old TV antenna, mounted normally will work.
Thanks for the overflow of intelligent replies. I've read then saved all this good info. I now realize my reciever DID come with an AM antenna, but I mistook it for a cheapy FM antenna (which I didn't need) and trashed it. Just using a 5 foot piece of wire made a big difference. In fact, going from the TV/FM antenna to the 5 foot wire was a noticable improvement, so I guess you guys know what you're talking about. I'd still like to do better so I'll keep looking around and experimenting. The Crutchfield link offered seems a little expensive, but the only other one I've found so far is Radio Shack, and it really doesn't look like it's made for AM despite the description:
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Anyway, thanks again. I'll keep working on it. All replies were helpful and appreciated.
$10.49, but they don't have the arrestor, i guess the $1 "twinlead" arrestor is a thing of the past. check the discount stores that have do it yourself tv stuff for an arrestor. ground the base, and hook the antenna to both terminals.
you can make an arrestor, use an old fashion NON-RESISTOR spark plug, ground the body and connect the antenna to the stud. .016 gap works well.
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