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[EarthNSky <erthnsky AT bellsouth.net>]

It is a dipole, and you have described it exactly.  The stereo connect 
wire is the flat ribbon wire setup you described.  I'll forward your 
post to Ron, it is really over my head...

Clansgian AT wmconnect.com wrote:
> > Ron says it is just a single wire antenna, with insulators in the 
> > attic-grounded only through the stereo itself.
>
> Grounded through the stereo itself is what you want.  The antenna connection 
> on the back of the stereo is for the FM only.  It needs a 72 ohm load to 
> operate at the max (or to operate well at all).  What you probably have in the 
> attic is a dipole antenna, a piece of wire in two pieces with the lead to the 
> stereo between the two pieces.  The dipole well resonate at one frequency (band of 
> frequencies).  Roughly divide the frequency you are listening to (in MHz) 
> into 468 and this gives you the lenght of the wire.  Divide that in two and you 
> have the point where the impedence of the antenna at that frequency is about 50 
> ohms.  So for the FM band centering around 100 MHz the antenna is only 4.6 
> feet long, two arms of 2.3 feet each.  But to get even more signal gain and 
> usually match the impedence better, you can make it any length that is an ODD 
> multiple of the fundamental frequency.  So making the 'arms' of the antenna 6.9 
> feet each works even better and 11.5 feet even better.
>
> The wire from the atenna to the stereo needs to be either a coaxial cable or 
> else that flat ribbon wire that is two wires molded into plastic some 1/2" 
> from each other.
>
> --------------------------------
>
> The antenna for the AM part of your stereo is not connected to the antenna 
> posts in the back.  It is a ferrite rod with a coil of wire around it.  You have 
> to make an internal connection to the lead wire of this ferrite rod antenna 
> in order to enhance the AM reception.  It's true that just connecting an 
> external antenna to the FM imporves the AM but that's only because you are bringing 
> a large piece of metal within the electrical field of the ferrite rod antenna. 
>  It isn't very selective or efficient.
>
> Using our above formula, if you are tuning in an AM station just above 
> 500kHz, the dipole antenna would be nearly 1000 feet long.  Not practical.  So one 
> runs a 'long wire', just a piece of wire as long as is possible and practical, 
> I've even seen insulated fences used for this.  The impedence into the AM 
> receiver will be mismatched so we put a coil and variable capacitor (based on 
> another formula) in series with the antenna between the antenna and receiver.  By 
> adjusting the capacitor, the load created by the long wire, coil, and 
> capacitor can be made to exactly match the impedence of the reciever.  Thus the 
> desired AM signal is enhnaced and fed into the reciever while all others are 
> attenuated.
>
> ------------------------------------------
>
> For the FM bands and also short wave bands, you can make an antenna array (an 
> array type antenna) with the object of giving the antenna a directional 
> 'gain'.
>
> The most potent type is the quadrilateral array or quad-antenna.  It looks 
> like a box kite.  Formulas forthcoming if anyone is that interested.  Another 
> type is the Yagi-antenna (named after its designer).  Most of those TV antennas 
> for sale that look like a boned fish are Yagi antennas.
>
> With an array antenna, when the antenna is pointed toward the desired radio 
> station (even hundreds of miles away), the radio signal is multiplied in the 
> antenna by simulaneously receiving the singal on the main element, and then the 
> other elements (called parasitic elements) reflect the signal back onto the 
> main element in phase.  It is quite very effecitive.
>
> --------------------------
>
> The time may come when we need to know things like this.   </HTML>
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--
BevanRon of EarthNSky Farm   NW Georgia USDA Zone 7
34.498N 85.076W    Bev is Earth, Ron is Sky