Richard Clark wrote in message . ..
On 10 Nov 2004 11:42:21 -0800, (Dr. Slick) wrote:

I didn't need a choke with this one = the other factor


Incorrect. I simply didn't need it for this dipole.

Anyone else?


S.

Dr. Slick wrote:
A properly tuned and positioned dipole will
be resonant at only one frequency. Double-dips
are a bad sign, and the return loss suffers.

If something is wrong with a dip on 40m and a dip on 15m,
someone should warn all the hams who are using their 40m
dipoles on 15m. :-)
--
73, Cecil, W5DXP

Cecil Moore wrote:

Dr. Slick wrote:
A properly tuned and positioned dipole will
be resonant at only one frequency. Double-dips
are a bad sign, and the return loss suffers.

If something is wrong with a dip on 40m and a dip on 15m,
someone should warn all the hams who are using their 40m
dipoles on 15m. :-)

Forgot to add that dipoles are resonant near all odd
half-wavelengths, i.e. 0.5WL, 1.5WL, 2.5WL, 3.5WL, ...
They are also antiresonant (purely resistive) on all
integral wavelengths, 1.0, 2.0, 3.0, ...

Using a Smith Chart, if one plots the feedpoint impedances
of a dipole VS frequency and connects the dots, that locus
of points will describe a (very rough) spiral. (Traversing
once around that rough spiral from resonance to resonance
is one full wavelength, not 1/2 wavelength.)
--
73, Cecil, W5DXP

Cecil Moore wrote:

Cecil Moore wrote:

Dr. Slick wrote:
A properly tuned and positioned dipole will
be resonant at only one frequency. Double-dips
are a bad sign, and the return loss suffers.

If something is wrong with a dip on 40m and a dip on 15m,
someone should warn all the hams who are using their 40m
dipoles on 15m. :-)

Forgot to add that dipoles are resonant near all odd
half-wavelengths, i.e. 0.5WL, 1.5WL, 2.5WL, 3.5WL, ...
They are also antiresonant (purely resistive) on all
integral wavelengths, 1.0, 2.0, 3.0, ...

Using a Smith Chart, if one plots the feedpoint impedances
of a dipole VS frequency and connects the dots, that locus
of points will describe a (very rough) spiral. (Traversing
once around that rough spiral from resonance to resonance
is one full wavelength, not 1/2 wavelength.)
--
73, Cecil, W5DXP

Explaining an antenna concept so simple to Dr. Slick after
the statement that he made seems to me akin to reading Shakespeare
to a cow.

Irv VE6BP
--
--------------------------------------
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Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/index.html
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--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Cecil Moore wrote in message ...
Cecil Moore wrote:

Dr. Slick wrote:
A properly tuned and positioned dipole will
be resonant at only one frequency. Double-dips
are a bad sign, and the return loss suffers.

If something is wrong with a dip on 40m and a dip on 15m,
someone should warn all the hams who are using their 40m
dipoles on 15m. :-)

Forgot to add that dipoles are resonant near all odd
half-wavelengths, i.e. 0.5WL, 1.5WL, 2.5WL, 3.5WL, ...
They are also antiresonant (purely resistive) on all
integral wavelengths, 1.0, 2.0, 3.0, ...

Using a Smith Chart, if one plots the feedpoint impedances
of a dipole VS frequency and connects the dots, that locus
of points will describe a (very rough) spiral. (Traversing
once around that rough spiral from resonance to resonance
is one full wavelength, not 1/2 wavelength.)


Granted, i'll give you the harmonics, but a double-dip
at for example, 88.1 and 93.7 MHz would indicate a BIG
problem!




Slick

Dr. Slick wrote:
"(1)A properly tuned and positioned dipole will
be resonant at only one frequency.
(2)Double-dips are a bad sign, and the return loss suffers."

(1) - Nope, just not true.
(2) - Not true either. (see #1)

With the two 'dips' not being harmonically related, it
appears that there is some 'other' reason, the feed line
for one, or something near the antenna (a person for instance?).
'Doc

'Doc wrote:
Dr. Slick wrote:
"(1)A properly tuned and positioned dipole will
be resonant at only one frequency.
(2)Double-dips are a bad sign, and the return loss suffers."

(1) - Nope, just not true.
(2) - Not true either. (see #1)

With the two 'dips' not being harmonically related, it
appears that there is some 'other' reason, the feed line
for one, or something near the antenna (a person for instance?).
'Doc

He said something about radials. Radials not attached to the
antenna are like parasitic elements. Two shorter radials will
resonate at a higher frequency than two longer radials.
--
73, Cecil, W5DXP

'Doc wrote in message . com...
Dr. Slick wrote:
"(1)A properly tuned and positioned dipole will
be resonant at only one frequency.
(2)Double-dips are a bad sign, and the return loss suffers."

(1) - Nope, just not true.
(2) - Not true either. (see #1)


What i meant to say was, a properly tuned
simple dipole will be resonant at only one
frequency and it's harmonics.

My double dips were not harmonically related.


With the two 'dips' not being harmonically related, it
appears that there is some 'other' reason, the feed line
for one, or something near the antenna (a person for instance?).
'Doc


raising the height of the dipole above the ground
from 3.5 to 6.5 feet was one of the things i did to
fix this problem.

The other one no one has guessed yet...


S.

"Dr. Slick" wrote in message
om...
'Doc wrote in message
. com...
Dr. Slick wrote:
"(1)A properly tuned and positioned dipole will
be resonant at only one frequency.
(2)Double-dips are a bad sign, and the return loss suffers."

(1) - Nope, just not true.
(2) - Not true either. (see #1)


What i meant to say was, a properly tuned
simple dipole will be resonant at only one
frequency and it's harmonics.

My double dips were not harmonically related.


With the two 'dips' not being harmonically related, it
appears that there is some 'other' reason, the feed line
for one, or something near the antenna (a person for instance?).
'Doc


raising the height of the dipole above the ground
from 3.5 to 6.5 feet was one of the things i did to
fix this problem.

The other one no one has guessed yet...


S.
This sounds like 20 questions. You are not telling us what you have. One
would not expect somebody to measure an antenna at a height of 3 feet. A
dipole would have an impedance of around 75 Ohms, which would give an SWR
into 50 Ohms of around 1.5:1 Are you using 50 Ohm coax and a 50 Ohm meter?
Is there a gamma match, or such, to adjust? Is it a dipole or a folded
dipole? Is there a balun? Did you buy the antenna or build it (I suspect the
intent would be different)? Since you are using an SWR meter, are you
putting enough power into it to get out of the nonlinear range?

Tam/WB2TT

"Dr. Slick" wrote in message
om...
Hi,

I recently tuned up a VHF dipole, and i got
a double-dip, double resonance for the swr, and
also the minimum swr was around 1.3:1

I did some modifications, and the double
resonance was was gone, plus the swr was down
to less than 1.1:1

I'm certain that one of two things (or a
combo of both) did the trick, but i wanted to
see if any of you seasoned antenna boys could
guess what the problem was.

Thanks for your input!


Slick
What happened to the total bandwidth after you tuned it?

Tam/WB2TT