(Fractenna) wrote in message ...

There is no problem. Dipoles and other antennas always show multiple
resonances. Just take an SWR analyzer and sweep a wide frequency range.
You'll find resonances all over the place.

Bill W6WRT



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




Dipoles are essentially harmonic devices, so they experience harmonic
resonances.

If you find resonances that are not harmonic on a dipole, then there are
loading objects that are producing them.

What exactly is your dipole? What is in proximity to it? How do you know that
the coax is choked properly?


Garden variety dipole.

But you have hit on one of the factors, i believe, which
is that initially, i was only about 4 feet off the ground.
Supposedly, dipoles need to be significantly over a 1/4 wavelength
above the ground. The second time, i had it at 6.5 feet or so.

I didn't need a choke with this one.

I'm using an MFJ-259.

What do you think was the other factor?


Slick

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

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

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
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
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
Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm
Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Irv Finkleman wrote:
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.

Awwwwhhhhhh Irv, everyone has a senior moment now and then.
--
73, Cecil, W5DXP

Cecil Moore wrote:

Irv Finkleman wrote:
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.

Awwwwhhhhhh Irv, everyone has a senior moment now and then.
--
73, Cecil, W5DXP

The devil made me do it. Aside from senior moments I also have
second childhood flashbacks!

Irv
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
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
Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm
Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Cecil, W5DXP wrote:
"Awwwwhhhhhh Irv, everyone has a senior moment now and then."

That`s my experience.

Arnold B. Bailey in "TV and Other Receiving Antennas" is more thorough
than most. Bailey writes on page 291:
"We have already seen that such conditions (efficient operation) can
exist for many resonant lengths of the rod. The rod if divided into two
sections and connected to a load at its center, will exhibit resonance
when the total length of the rod is any multiple of one half-wave.
----only two resonant lengths will give a simple directivity pattern ---
if the rod operates at its fourth resonant frequency, no signal is
picked up from directions broadside to the antenna in contrast to
operation at its third, second, or first resonance. Only at first
resonance is the directivity pattern as indicated by Figs. 6-20 and
6-21.

At all other resonances above the first, the pattern is going through a
progressive change which will later be more explicitly shown in a
quantitative manner."

On page 348, Bailey gives radiation resistances and drivepoint
resistances for dipole resonances 1 through 10, and shows their current
distribution patterns.

Best regards, Richard Harrison, KB5WZI

Irv Finkleman wrote in message ...


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.



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


What if the resonant frequencies are 88.1 and about 92.0 MHz?

Not exactly harmonically related, are they! Think about it.

I think you need to change your diapers, Irv.



Slick