[Antennas] Simple dipole

Sat Apr 1 17:59:20 EST 2006

Exactly the opposite.
The 300 Ohm twin lead and the 450 Ohm ladder line are common impedances for 
which 6:1 and 9:1 baluns are available "off the shelf". The natural 
impedance of a folded dipole is ~ 300 Ohms, so making it of 300 Ohm 
impedance cable and feeding it with 300 Ohm balanced cable or 50 Ohm 
unbalanced cable through a 6:1 balun is the common method for which 
components are readily purchaseable, or for which there are textbook 
articles describing their construction.
As was pointed out by someone else, the telephone compnay rural "C" wire 
and/or drop cables have unknown characteristic impedances. If known, they 
will NOT be of the "common/natural" values mentioned above and will require 
twinlead feedline or baluns of "uncommon" ratios to be contructed.
On the other hand, we are amateurs. Make both the antenna and the feedline 
out of telco drop wire, feed the balanced input of a tuner, and it WILL work 
very well. And that is what counts. But, you need to look at the whole 
picture and understand what you are doing.
Good luck to all in their projects.
Milt, N5IA
----- Original Message ----- 
From: "Robert Lay (W9DMK)" <w9dmk at crosslink.net>
To: "Milt, N5IA" <n5ia at zia-connection.com>; "Bill Barr" <n4uaj at mac.com>; 
<antennas at mailman.qth.net>
Sent: Saturday, April 01, 2006 2:04 PM
Subject: Re: [Antennas] Simple dipole
> Dear Milt,
>> The spacing of the conductors is incorrect for proper impedances to make 
>> a folded dipole that would match with common matching techniques and 
>> feedlines. Not impossible, but certainly not a project for someone who 
>> is not adept at constructing odd ratio baluns, etc.
>> Sounds like you are suggesting that everyone who uses ladder line (in 
> either
> the 300 ohm or 450 ohm variety) is mis-using it (because it doesn't match
> the impedance of the antenna).
>> Would you like to explain that?
>> 73 de W9DMK - Bob Lay, Dahlgren, VA
> http://zaffora.f2o.org/W9DMK/W9dmk.html
> w9dmk at crosslink.net
>>>> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.385 / Virus Database: 268.3.4/299 - Release Date: 3/31/2006
>>