[Antennas] dipole question

2002年8月18日 21:55:23 -0400

You are a class act, George - with style. Good emails. Makes me want to go
re-do my 90 ft high dipoles.
73 Bill WM4SG
___________________________________
----- Original Message -----
From: George, W5YR
To: [email protected]
Cc: rb ; [email protected]
Sent: Sunday, August 18, 2002 9:44 PM
Subject: Re: [Antennas] dipole question
Right, Chris - I blew it big time on that one. I have no idea what I must
have been thinking to have written that! I apologized and made nice in
response to a previous posting of correction, but I appreciate hearing from
you as well.
The funny part is that for the first few years I was a ham back in the mid
40's, I seldom used anything but folded dipoles made from TV twinlead!
Keep an eye on me, Chris! When you get to the point where "73" is not only
Best Wishes but your age, these things happen, so keep me honest! <:}
73/72/oo, George W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121 Kachina 505 DSP #91900556 Icom IC-765 #02437
[email protected] wrote:
>> "George, W5YR" wrote:
>> > > OK, let's go to a 140' folded dipole made with 600 ohm ladderline for
the
> > > horizontal element, and fed with 450 ohm ladderline. Will this one
load 160
> > > much easier than the simple dipole?
> >
> > First, a folded dipole does not behave any differently from a
conventional
> > wire dipole. Adding the second parallel element and connecting them
> > together at the ends just raises the driving-point impedance by a factor
of
> > four (number of conductors^2). So, you don't want to use 600 ohm line
for
> > the flattop since that would give you a 2400 ohm input Z with you trying
to
> > feed it with 450 ohm ladderline.
>> I have to disagree here George (your math is somewhat flawed above)
> A dipole is always 75ohms for argmument sake; yes it will vary +/-
> due to height above ground, etc.....BUT regardless of wire size,
> the average single wire dipole is 75ohms....a FOLDED two wire dipole
> is always then 300ohms at feed point....regardless of the Z of the wire,
> spacing, etc used in the folded dipole....I cannot see how using 600ohm
> Z line for the dipole element makes it 2400ohms at the feedpoint...
> The Ladderline's Z used for the DIPOLE element is a moot point...
> The same rules apply to it as a std dipole or folded dipole..
> Folded dipole (conventional) is usually 300ohm Z...+/- 10-20%...
>> Chris
> WB5ITT
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