[Antennas] Simple dipole

Sat Apr 1 23:24:39 EST 2006

Bob,
The comment was reference folded dipoles, not dipoles with open feed line. 
Going back to my Novice days in 1960, I have used many folded dipoles and 
always inserted the impedance transformation device at the antenna 
feedpoint. Also, I have always constructed resonant antennas. I have never 
utilized an antenna which required open wire for feeding to a tuner. Those 
have been my choices and I have my reasons for doing it that way.
The only time I have ever used a tuner (and built into transceiver type 
only) is when I use a frequency in the band where my resonant antenna is a 
bit out of its 2:1 VSWR bandwidth and the modern transceivers start folding 
back on power out without the tuner.
So, Bob, that is the difference. You say "For me, personally, I could care 
less whether I have a good match or not at the antenna end of the line" 
where as I am totally opposite. I do not use an antenna unless it does 
provide a good match at the antenna because I will work with the antenna 
design and construction until it does provide a good match to 50 Ohm coaxial 
transmission line at the antenna feedpoint.
Here follows your original comment and my simple reply comment reference the 
characteristic impedance of the telco drop wire.
----------------------------------------------------------------------------------------------------------------------
> You could use it any way that you would use any other wire - it's just
> insulated wire. You could make a simple dipole, or you could make a
> folded dipole.

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.
My dos centavos, de Milt, N5IA
------------------------------------------------------------------------------------------------------------------------
I stand by my simple statements regarding Folded Dipoles, characteristic 
impedances and "COMMON MATCHING TECHNIQUES AND FEEDLINES". Nothing else is 
intended except to be helpful to Bill, who asked the question, and to any 
others who might have the same or similar question.
I apologize if I have somehow projected otherwise. Thanks, and have a good 
evening.
Milt, N5IA
----- Original Message ----- 
From: "Robert Lay (W9DMK)" <w9dmk at crosslink.net>
To: <antennas at mailman.qth.net>
Sent: Saturday, April 01, 2006 8:36 PM
Subject: Re: [Antennas] Simple dipole
> Dear Milt,
>>>> 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.
>> You seem to be under the impression that there is a majority of antennas 
> being fed with balanced line that use a balun at the antenna end. I don't 
> remember ever seeing such. In fact, in those instances where baluns are 
> used, it is usually at the tuner end - not at the antenna end.
>> So, again, I ask, why are you presuming that everyone using balanced lines 
> are doing it incorrectly.
>> For me, personally, I could care less whether I have a good match or not 
> at the antenna end of the line. That's why I use balanced line - because 
> it is relatively unaffected by the high SWR - certainly more so than is 
> coax.
>> My rationale is that even if it IS a good match at this frequency or that 
> frequency, it is going to be severely mis-matched at MOST frequencies.
>> Agreed?
>> 73,
> Bob
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