Author Topic: Coax fed Fan dipole  (Read 1699 times)

Offline vulture774

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Coax fed Fan dipole
« on: January 13, 2012, 08:25:38 PM »
This is My article on hamuniverse:http://www.hamuniverse.com/kb3pkbfandipole.html

I made this and have used it to make loads of contacts!!




Hope you guy's like it!

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KB3PKB
Tom D.
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Offline idelphic

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Re: Coax fed Fan dipole
« Reply #1 on: February 20, 2012, 10:44:42 AM »
Good write up, I had someone tell me about a dual dipole of 20/40m  East West was 20 and North South was 40.  As you stated, it will "auto tune" itself to the proper legs.

Quote
The di-poles.
If the two legs of your di-pole are not EXACTLY the same length, you will drive yourself crazy trying to tune it. Let me say that again: If the two legs of your di-pole are not EXACTLY the same length, you will drive yourself crazy trying to tune it.

Here is a good method to ensure that this does not happen to you.

First, cut the dipole for the "Total Length" in the chart above.

A few of my short dipoles I have used speaker wire.  While not ideal, it works very well.  This is another way to ensure that the legs are of equal length.  Cutting 20' of speaker wire will give you two legs of 20' after you split the pair.
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Offline WWalker

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Re: Coax fed Fan dipole
« Reply #2 on: December 13, 2012, 02:34:04 PM »
Just the second paragraph was worth the price of admission for me.

Seems like I have always known that Voltage always take the path of least resistance.

I did not understand why fan dipoles worked until now though.

Maybe I am just slower than the average person but I never thought of RF as just Voltage.  I don't think I have read anything (until it just now it clicked and I looked up the definition of RF) that ever clearly stated that RF (radio frequency) is simply AC voltage AT a radio frequency.

I've been a mechanic for most all my life it is all I have ever done for a living other than a year of concrete work, and of course lawn mowing as my first paying job. 
Electronics has always been the most challenging part of the job for me. 
I got into Ham radio a little over three years ago determined to learn more about electronics through the hobby.  I have found very little written info that explains a lot of the very basic information I require to understand whats going on.  Most info seems to be written for people with an electronics back ground of some kind or years and years of experience and learning already under their belt.
I just need to be able to see how it works or be hit over the head with the obvious before I "get" it.

Thanks.

Offline Carl

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Re: Coax fed Fan dipole
« Reply #3 on: February 22, 2015, 12:17:55 PM »
Good antenna and great explanation Tom , I use a 40,20,10 meter Fan dipole
with my LDG Auto Tuner to work 40-6 meters at home.
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Offline Greekman

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Re: Coax fed Fan dipole
« Reply #4 on: February 22, 2015, 05:22:18 PM »
nice tom...

Any Greek anchestry?
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Offline armymars

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Re: Coax fed Fan dipole
« Reply #5 on: March 05, 2015, 09:05:32 AM »
  This is a great one for Ohms Law. When a 40 meter radio signal is applied, the 80 meter antenna will show about 2000 ohms impedance. The 40 meter antenna will show about 50 to 73 ohm impedance depending how high it is. Lets pick 50 ohms. that means 99.125% of the current will flow in the 40 meter antenna and .975% of the current will flow in the 80 meter antenna.

Offline Greekman

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Re: Coax fed Fan dipole
« Reply #6 on: March 05, 2015, 09:24:01 AM »
then it is time to ask my long standing question...

Why is this so? Isn't the 80 meter antenna a muliplier of the 40meter one?
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Offline Carl

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Re: Coax fed Fan dipole
« Reply #7 on: March 05, 2015, 10:32:15 AM »
then it is time to ask my long standing question...

Why is this so? Isn't the 80 meter antenna a muliplier of the 40meter one?

The voltage and current phase relationship is only conducive to conduction on ODD QUARTER WAVELENGTHS which is why a 40 meter antenna can be used on 15 as it is THREE quarter wavelengths long for 15 meters.

Now understand that the RF still can work on the wire IF the impedance is matched to the radio ,as with NON RESONANT ANTENNAS.IT IS THE RADIO that will not work with too high ,or low,impedence an antenna.That's in all that theory and equations and math that I choose to ignore because I have a TUNER that fixes most problems without any worry from me and the TUNE button should be called the EASY BUTTON.
Stop complaining about life and start Celebrating it .

I've reached the age where there is little left to learn the hard way.

I am 100% in favor of TRIGGER CONTROL.

Your best piece of survival gear is your brain,
you should carry it with you every day.

Offline vulture774

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Re: Coax fed Fan dipole
« Reply #8 on: May 21, 2015, 07:07:32 PM »
nice tom...

Any Greek anchestry?

I am the 3rd generation in the U.S.   About 1/4 Greek left, other than the Middle and Last names :)  We lost the language after the 1st Gen. Sadly.
Tom D.
KB3PKB
73  73