Dipole, how to tune a dipole with a pencil

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KG7ODP
Posts: 8
Joined: Sat Jul 11, 2020 8:44 pm

Dipole, how to tune a dipole with a pencil

Post by KG7ODP »

Dipole Tuning for Lowest swr

New Dipoles first attempt in the air!

1. First write down the total length of your new antenna after using the old formula. (468/freqMhz = total length in feet) Hopefully you kept notes!

2. Find the frequency (F) of the lowest swr of your first attempt dipole.
(Check several frequency points between top and bottom end of the band.)
Record the lowest swr frequency!

3. Multiply length from step 1, (L) times frequency (F) in step 2 of lowest swr to get new constant.

Step 1 L x Step 2 F = new constant

4. Now use the new "constant" obtained from step 3 above in the formula rather than the 468 to get new length in total feet.

Existing dipole
(modify it's center design frequency)

1. Find lowest swr frequency (Old center Freq) of the existing antenna.

2. Find length (L) of existing antenna. You did write it down I hope!

3. Multiply length (L) times OLD dipole FREQUENCY (where the swr was lowest) (Old F) to get it's resulting constant number.
Existing L x Old F = new constant
Use the new constant, (not 468), in the formula again using your new design frequency.

New constant / new frequency = total length in feet

It is assumed that your dipole is used without an antenna tuner and you want the lowest swr possible on your design frequency. It must be noted that you can only use this "find the formula constant" method AFTER you have used the old formula first OR have the correct length of your existing antenna for getting close to the antenna center frequency. This is due to any number of variables in the original antenna installation due to surroundings, height above ground, bare or insulated wire, angle of antenna relative to it's center, (horizontal, inverted V, etc), diameter of conductor, insulation thickness, etc.

Hopefully if you did the math correctly, you will only have to make no more than a couple of attempts at tuning your antenna for lowest swr rather than taking up your valuable on the air time by the cut, and try over and over method! Have fun!

Math does not lie, but sometimes your antenna, it's composition and the environment plugs in a variable or 2 into to the "standard" formula.
Using the methods in the articles above should help with getting you on the air much faster!
Please send us feedback on how either one worked for you. If you have an easier method, let us know! No antenna analyzers allowed...please. Just an swr meter and your skill.

n4ujw AT hamuniverse.com

73 ~ N4UJW
Last edited by KG7ODP on Mon Aug 03, 2020 4:04 pm, edited 1 time in total.

k7mkanv7cc
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Re: Diple, how to tune a dipole with a pencil

Post by k7mkanv7cc »

And if you would like to use an online calculator for dipole length, go to my url by clicking below.

http://64.113.166.21/calculator.htm

I would suggest right clicking the link and selecting "Open Link in New Tab".
K7MKA
"Try not. Do, or do not, there is no try." - Yoda
"Help you I can. Yes, mmm." - also Yoda
http://www.k7mka.com

KG7ODP
Posts: 8
Joined: Sat Jul 11, 2020 8:44 pm

Re: Diple, how to tune a dipole with a pencil

Post by KG7ODP »

k7mkanv7cc wrote:
Mon Aug 03, 2020 3:43 am
And if you would like to use an online calculator for dipole length, go to my url by clicking below.

http://64.113.166.21/calculator.htm

I would suggest right clicking the link and selecting "Open Link in New Tab".
Good Plan I'm not very good with math
also If the antenna is to be portable you don't need to cut it. Simply fold it back on itself.

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