[TowerTalk] Folded dipole

[Tom Horton]

Back in the day (1950s) I used folded dipoles. The beauty of a simple folded dipole was that you could use 300 ohm TV twinlead to make and feed the antenna. No need for an antenna tuner. The matching was handled by the transmitter Pi-network. Oh, the simple days Hi.
You could throw up just about anything and get it to match the transmitter
Virtually no one used coax for TV reception then, so twinlead was available everywhere, even the hardware section of the grocery stores.
Oh yeah... we had to log every contact and we had to do it by hand...Some things are really better today, huh?
73
 Tom K5IID


Tom Horton K5IID 
Hillsboro, TX 




--- On Tue, 8/25/09, Andy <ai.egrps at gmail.com> wrote:


From: Andy <ai.egrps at gmail.com>
Subject: Re: [TowerTalk] Folded dipole
To: "Towertalk" <towertalk at contesting.com>
Date: Tuesday, August 25, 2009, 11:39 AM


> Looking to put up another 40 meter antenna.  Need a NVIS antenna for
> close-in work.
>
> Is there any reason to put up a folded dipole instead of a tuned-feeder
> dipole?

NVIS implies low, and dipoles mounted that low can have quite a low
feedpoint impedance.  Using a folded dipole can help counteract that.

People have used a low mounted folded dipole fed by coax, using the
folded dipole's ~4:1 impedance transformation to bring the feedpoint
*up* to around 50 ohms.  The feedpoint of such low (~6-10 feet)
mounted dipoles can be down around 10 ohms or so.

If you can handle 10-20 ohms (which would be quite a mismatch if fed
with ladderline), then there may be no need to use the folded dipole.

I am not talking about B&W (and similar) "folded dipoles", which I
prefer to call T2FD's to distinguish them from ordinary folded
dipoles.  They are very different animals.

Andy


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