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1/16/2020 9:48:49 PM
Posted: 10/6/2007 10:09:30 AM EST
[Last Edit: 10/6/2007 10:10:10 AM EST by Watermaker]
3 Element Yagi

I want to build a small portable three element yagi antenna, I have found plans for one on the intraweb and I am just wondering if you can scale down the dimensions of the driven element, driectional element and reflecting element or is there a minimum length of these. I would presume the only critical length is the driven? Then the reflecting and directing are set according to the driven?
Link Posted: 10/6/2007 3:42:18 PM EST
You can try loading the elements, but I'm wondering why? An AR15 is bigger than a 3 el 2m yagi and the reflector is no longer than your arm.

Doesn't get much easier than a simple 2m beam...remember, the element (diameter) determine bandwidth.

Link Posted: 10/6/2007 3:52:52 PM EST
Normally I'd have a response but I'll reserve it after that code thread.
Link Posted: 10/6/2007 3:59:11 PM EST
all the lengths are "critical"

and "critical" is a relative term.

your reflector is typically larger than your driven element and just the opposite for your directors.

get an antenna book or look on line for calculating element length.
Link Posted: 10/6/2007 11:49:45 PM EST
height=8
Originally Posted By JaxShooter:
Normally I'd have a response but I'll reserve it after that code thread.
Link Posted: 10/7/2007 8:16:32 AM EST
Link Posted: 10/7/2007 10:18:48 AM EST
height=8
Originally Posted By JaxShooter:
huh.
Link Posted: 10/7/2007 12:45:08 PM EST
Feel free to kiss my ass now.
Link Posted: 10/7/2007 12:56:28 PM EST
If you scale down an antenna, it operates at a proportionally higher frequency range.


CJ
Link Posted: 10/7/2007 1:31:47 PM EST
height=8
Originally Posted By JaxShooter:
Feel free to kiss my ass now.
Link Posted: 10/7/2007 2:16:31 PM EST
No, really.

These smileys are great fun.
Link Posted: 10/7/2007 2:30:52 PM EST

Originally Posted By JaxShooter:
Normally I'd have a response but I'll reserve it after that code thread.



Ok, what code thread? Sounds like someone got their coax in a bunch
Link Posted: 10/7/2007 2:34:51 PM EST
No comment.
Link Posted: 10/7/2007 5:35:04 PM EST
Go look up 4nec2, which is one of the free antenna modelling programs. Note that without a modelled feedline and a ground plane and the mount and so on, you're (over)simplifying, but at least you can get some ideas of what will happen on the frequencies you're interested in.

I've only glanced at it myself - I have yet to figure out how to add anything to a model (or even modify it, really, other than hand editing the text file), but I didn't spend more than a few minutes with it, either.
Link Posted: 10/7/2007 5:38:21 PM EST
[Last Edit: 10/7/2007 5:45:11 PM EST by GlockTiger]
How's about a folding version of a 2m handheld yagi? This is on my list of projects in the near-term. Collapses down pretty nicely! Oh, and I don't think there's an easy way to change the element lengths on a homebrew beam such as this, since it's basically a dipole antenna if you ignore the director/reflector. The driven must be resonant on the op frequency and the other elements are set at pre-calculated lengths and spacing for the best directional effect.
Link Posted: 10/7/2007 8:43:42 PM EST
2 meter antennas have to be some of the easiest to make. When I first got my license, I was using nothing more than an ancient Kenwood HT hooked up to a variety of home made antennas ranging from coat hanger 1/4 wave groundplanes to 3 and 5 element beams made of 12ga solid copper wire and 2x2 lengths of wood. There is plenty of info online on how to make them, or get some of the ARRL antenna books.
I'm sure there's probably going to be a few useful links if you dig around at www.ac6v.com.

And then there are the totally insane things that I do...
Lots of bamboo and 70 feet of wire
Link Posted: 10/8/2007 1:53:34 AM EST

Originally Posted By cmjohnson:
If you scale down an antenna, it operates at a proportionally higher frequency range.


CJ


Not always...there are many options to shorten a yagi.

It's quite common to see them on HF antennas where element lengths can get quite long, but it's too simple and easy to build a full size yagi for 2m. There are many comprises with shortened yagi's.
Link Posted: 10/8/2007 3:10:21 AM EST

Originally Posted By jrollins:
And then there are the totally insane things that I do...
Lots of bamboo and 70 feet of wire
home.teleport.com/~kd7bcy/images/bug2003.jpg




Ok, you might not win the internet, but you win this thread


Now just what is that for? That's Hamsexy
Link Posted: 10/8/2007 3:47:05 AM EST

Originally Posted By GlockTiger:
How's about a folding version of a 2m handheld yagi?

I need to finish mine. I've had everything done except the SO239 connector for a couple of months. You'd think I could get off my butt long enough to solder the stupid thing on. fwiw you can get steel tape measures at Harbor Freight dirt cheap. This is about all they're good for. I bought two. The one I didn't cut up won't go back into the case. But for the price I didn't expect much.
Link Posted: 10/8/2007 3:34:14 PM EST

Originally Posted By Grog:
Now just what is that for? That's Hamsexy


It was an experiment to create a mobile NVIS antenna for 80/40m. Not as successful as I had hoped. I might try it again someday, hopefully slightly more compact
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