Isolating vertical endfed antennas from their support structures

[loosecannon]

thanks doc!

so now we need to figure out the best material for insulating the antenna from the mast.

im thinking something that you could sleeve into your mast, and either clamp or bolt it in place.

it should be very UV resistant, and should be able to be tooled.

if its a plastic we are considering; we have static electricity issues to deal with.

is 1 foot above the metal mast enough?
does this matter?
hmmm...

LC

 

[1342]

i find that rubber radiator hose works very well for my midland base and it fits under those ubolts perfectly!

 

[freecell]

loosecannon wrote:

"....1:1 match and is also resonant, meaning zero reactance."

VSWR is NO indicator of resonance, a 1:1 VSWR and X=0 rarely if ever occur at the same frequency.

furthermore, fan type and multiple dipoles function NOT as a result of anything having to do with any path of least resistance or impedance (stupid) but they are able to function because an antenna is nothing more than an L/C circuit.

when two or more of them (antennas, LC circuits) are coupled to a single feedline the "selection" of the radiator for the band in use is dependent on the L/C circuit that is able to "absorb" the power generated by the transmitter as it is the combination of both inductance and capacitance which determines the frequency of the energy to be "absorbed" and exactly which of the dipoles presented will be radiating the energy fed to it. the dipole which most closely resembles the proper values of both L and C for any given frequency at which transmitter power is generated is the "loaded" element in that instance.

 

[W5LZ]

"....1:1 match and is also resonant, meaning zero reactance."

VSWR is NO indicator of resonance, a 1:1 VSWR and X=0 rarely if ever occur at the same frequency.

Hmm, read it again, he didn't say VSWR was an indicator of resonance.
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furthermore, fan type and multiple dipoles function NOT as a result of anything having to do with any path of least resistance or impedance (stupid) but they are able to function because an antenna is nothing more than an L/C circuit.

Ever heard of something called an analogy? And yes, antennas are an 'LC' circuit... in a particular form.
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"when two or more of them (antennas, LC circuits) are coupled to a single feedline the "selection" of the radiator for the band in use is dependent on the L/C circuit that is able to "absorb" the power generated by the transmitter..."

Dang! From the 'power's point of view, that appears like the path of least resistance, doesn't it?
----

"as it is the combination of both inductance and capacitance which determines the frequency of the energy to be "absorbed" and exactly which of the dipoles presented will be radiating the energy fed to it. the dipole which most closely resembles the proper values of both L and C for any given frequency is the "loaded" element in that instance."

That's certainly one way of looking at it. If you had said the "load" instead of 'loaded', which tends to mean something else when speaking of antennas, I would agree with that statement. Terrible thing to be that 'picky', ain't it?
- 'Doc


...and just cuz I'm curious, who is Mr. 'freecell' today??

 

[freecell]

"From the 'power's point of view, that appears like the path of least resistance, doesn't it?"

your exact words:
"Basically because RF seeks the path of least RESISTANCE/IMPEDANCE, right?"

Wrong. your analogy sucks. next time, label it as such. the statement is misleading, analogy or not. there is no "path" offering any resistance and anything rising to the level of "resistance" is not encountered until the feedpoint is reached due to the frequency rejection capabilities of all dipoles not having values of L and C corresponding to the frequency of the power being generated at the source.


"Hmm, read it again, he didn't say VSWR was an indicator of resonance".

1:1 match and is also resonant

it's implied by the connector "and" as a condition occurring
simultaneously with a 1:1 VSWR, yeah, he said it.


If you had said the "load" instead of 'loaded'....

i said what i meant and i meant what i said. an antenna or L/C circuit is said to be "loaded" when it is able to absorb power at the frequency for which it is tuned, or for which both values of L and C are present.

 

[HiDef]

Why not just say matched source and load impedance?

 

[W5LZ]

...Pst
'and' doesn't mean 'or', it commonly means 'in addition to'. Which does imply two conditions, 1:1 (V)SWR, -'and'- resonance. (Substitute "matched source and load impedance" for 1:1 (V)SWR if you feel like it. Or don't. Same difference.)

You are right, when dealing with AC it's 'more correct' to say impedance than resistance, and if you will notice that "/"... I gave you the option of calling it whichever one you felt most comfortable with (not to mention that there is always some 'R' in an 'LC' circuit, but that really is getting 'picky', ain't it? Sort of like those 'mills' that banks pay attention to when figuring interest, but most people don't bother with?).
- 'Doc

How about the last question I asked? Wanna answer that one??

 

[loosecannon]

freecell,

read my supposition again as one whole statement, instead of just concentrating on a few words of it.

i would think it would be pretty obvious what i meant. especially to someone of your intelligence.

nowhere in that statement did i intend to assert that a 1:1 VSWR match is any indication of resonance.

i am interested to hear your take on it, but first you have to understand what im asking about.


doc's use of analogy and terminology did not confuse me in the least.

he told me what happens, you told me how it happens.

wouldnt you agree that all of the other elements of said fan dipole "resisted" the signal while one set of elements "accepted" it?

im sure there are many synonyms that could have been used.
again, i would think that you are smart enough to see what he meant.

anyway, i thank you both for trying to increase my knowledge.
it is appreciated.
LC

 

[freecell]

"i think i see what you mean with regards to ANY antenna having only ONE design frequency."

a single antenna length can be resonant at more than one frequency.

example: a quarter wave @ 9Mhz. is 3/4 wavelength @ 27Mhz., a quarter wave @ 27Mhz. is 3/4 wavelength @ 81Mhz., a quarter wave @ the upper end of the 2M. band is 3/4 wavelength @ 440Mhz..

"the one point where it has a 1:1 match AND is also resonant, meaning zero reactance."

the frequency at which an L/C circuit is resonant has nothing whatsoever to do with impedance or matching between the line and the feedpoint. an L/C circuit is resonant at a given frequency or frequencies regardless of the VSWR.

your supposition is flawed & incorrect.

 

[W5LZ]

... sigh. More 'smoke-n-mirrors'. Why am I not surprised.
- 'Doc