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:
"I`ll give you the harmonics, but a double-dip at for example, 88.1 and
93.7 MHz would indicate a BIG problem!"

Does the dipper dip on one of these frequencies in te absence of an
antenna?

Is the receiver connected to the antenna, and can you move one of the
dips with the receiver tuning?

Does augmenting the antenna cable move one or both dips?

Does relocating the antenna change the dips?

There seem to be two coupled resonant circuits.

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote in message ...
Dr. Slick wrote:
"I`ll give you the harmonics, but a double-dip at for example, 88.1 and
93.7 MHz would indicate a BIG problem!"

Does the dipper dip on one of these frequencies in te absence of an
antenna?


???? The MFJ-259 is obviously infinity to one when you
have an open....



Is the receiver connected to the antenna, and can you move one of the
dips with the receiver tuning?


not using a receiver.


Does augmenting the antenna cable move one or both dips?


Didn't try this. Didn't have to change this
to fix the problem.


Does relocating the antenna change the dips?


Again, one of the two things i did to fix this
problem was to increase the height above the ground
from 3.5 feet to about 6.5 feet.

Can you guess what the other factor was?

Hint: no inductive choke was needed, and the radial
lengths remained the same.


Slick

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

On 11 Nov 2004 12:20:02 -0800, (Dr. Slick) wrote:
Hint: no inductive choke was needed, and the radial
lengths remained the same.

What do you grow in your garden?

Richard Clark wrote in message . ..


What do you grow in your garden?


http://www.marijuanaaddiction.info/i...d%20plants.jpg


S.

(Dr. Slick) wrote in message . com...

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!

So are you measuring _just_ the dipole, or the dipole through a
feedline? Do you have any idea at all how many coupled resonators you
are measuring? See, e.g., King, Mimno and Wing, to educate yourself
about antenna systems seen as a set of coupled resonators. Disabuse
yourself of the notion that you actually understand what your
measurements mean at this point.

(Tom Bruhns) wrote in message om...
(Dr. Slick) wrote in message . com...

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!

So are you measuring _just_ the dipole, or the dipole through a
feedline?

Through about 20 feet of RG-58.


Do you have any idea at all how many coupled resonators you
are measuring? See, e.g., King, Mimno and Wing, to educate yourself
about antenna systems seen as a set of coupled resonators. Disabuse
yourself of the notion that you actually understand what your
measurements mean at this point.

I understand it quite well... two non-harmonically
related resonances in a very narrow band (88-108 Mhz) is
a bad sign if you didn't design you antenna for broadband.


S.