I'd like to try building a loaded Yagi. I came across plans for a 20 meter
mini Yagi while Googling, but I want something for 15 meters. Are there any
simple, free calculators available? Also, can anyone tell me a ballpark
figure how a 15 meter shortened (by 40%) 3 element Yagi would compare to a
full sized one? How about if I added an additional element for 4 loaded
elements instead of 3?

Thanks,
harry

In message , Harry Brown
writes
I'd like to try building a loaded Yagi. I came across plans for a 20
meter mini Yagi while Googling, but I want something for 15 meters.
Are there any simple, free calculators available? Also, can anyone
tell me a ballpark figure how a 15 meter shortened (by 40%) 3 element
Yagi would compare to a full sized one? How about if I added an
additional element for 4 loaded elements instead of 3?

Thanks,
harry

MMANA has a 3 element loaded yagi as an example.

Http://hamsoft.ca/pages/mmana-gal.php and it's free

Short Yagi W1FBY & WA1LNQ

It's got a gain of about 4.7dB

I dare say 4NEC2 will model it as well.

Brian GM4DIJ
--
Brian Howie

On Fri, 20 Jan 2012 15:07:37 -0500, "Harry Brown"
wrote:

I'd like to try building a loaded Yagi.
I came across plans for a 20 meter
mini Yagi while Googling, but I want something for 15 meters. Are there any
simple, free calculators available?

Modeling programs I like and use:
http://www.yagicad.com
http://home.ict.nl/~arivoors/
http://www.eznec.com (the demo version should work).

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

"Brian Howie" wrote in message
...

MMANA has a 3 element loaded yagi as an example.

Thanks. I downloded this "MMANA-GAL basic" but couldn't find the example
loaded Yagi anywhere in any of the antenna menus. Can you tell me what the
file is called and/or should I have tried out the "pro" version? Thanks,
harry


Http://hamsoft.ca/pages/mmana-gal.php and it's free

Short Yagi W1FBY & WA1LNQ

It's got a gain of about 4.7dB

I dare say 4NEC2 will model it as well.

Brian GM4DIJ
--
Brian Howie

ARRL Antenna Book has all the answers.

Shortening the antenna will reduce the effective radiated power and will reduce the amount of gathering ability of the antenna.
Every time you reduce the size by 25% - you throw away - probably 50% of it's ability.

Antenna's are always a compromise when you get into the lower ranges.
It is easier to BUY a Mosley tribander - about $1000.00, then to try to make your own.

As the elements are shortened or lengthened, all of the variables has to be recalculated because the spacing will also change and the boom length.

http://fermi.la.asu.edu/w9cf/yagipub/index.html

http://www.ac6v.com/antsoftware.htm

In message , Harry Brown
writes

"Brian Howie" wrote in message
...

MMANA has a 3 element loaded yagi as an example.

Thanks. I downloded this "MMANA-GAL basic" but couldn't find the
example loaded Yagi anywhere in any of the antenna menus. Can you tell
me what the file is called and/or should I have tried out the "pro"
version? Thanks, harry



Yes it's the basic one, the file is in

\MMANA-GAL_Basic\ANT\HF short

and the file is called

"3el short Yagj W1FBY.maa"

Brian


--
Brian Howie

"Brian Howie" wrote in message
newsbNQuPH3DcHPFwfT@b-

Yes it's the basic one, the file is in

\MMANA-GAL_Basic\ANT\HF short

and the file is called

"3el short Yagj W1FBY.maa"

Brian

Interesting. I don't seem to have either that folder nor file. I'm using
version 3.0.0.25.

Harry

In message , Harry Brown
writes

"Brian Howie" wrote in message
newsbNQuPH3DcHPFwfT@b-

Yes it's the basic one, the file is in

\MMANA-GAL_Basic\ANT\HF short

and the file is called

"3el short Yagj W1FBY.maa"

Brian

Interesting. I don't seem to have either that folder nor file. I'm
using version 3.0.0.25.

Harry

Same here. I'll e-mail it .

Brian

--
Brian Howie

Ok, sounds good and thanks. You can send it to
(remove nospam).

Thanks,
Harry

"Brian Howie" wrote in message
...
In message , Harry Brown
writes

"Brian Howie" wrote in message
newsbNQuPH3DcHPFwfT@b-

Yes it's the basic one, the file is in

\MMANA-GAL_Basic\ANT\HF short

and the file is called

"3el short Yagj W1FBY.maa"

Brian

Interesting. I don't seem to have either that folder nor file. I'm using
version 3.0.0.25.

Harry

Same here. I'll e-mail it .

Brian

--
Brian Howie

On 1/24/2012 8:28 AM, Harry Brown wrote:
Ok, sounds good and thanks. You can send it to
(remove nospam).

Thanks,
Harry

One note.. When designing a loaded dipole or yagi, you can
consider it pretty much the same as designing a loaded vertical,
except you have two back to back.
The same rules apply as far as current distribution, etc.
The only difference is the vertical is half an antenna
fed against ground, and the yagi is two verticals back to
back, which form a complete antenna independent of ground.

So.. if you look at the various forms of loaded verticals,
you can apply the same designs to loaded yagi's.
For instance, up to a point, the farther up the vertical
the loading coil is, the better the current distribution
will be. The tradeoff point where the coil losses outweigh
the improved current distribution, which can be modeled, but
is probably around 3/4 the length of the radiator in most
cases. Maybe slightly more.. I checked this one time, but
forgot the best exact location that I came up with..
Been a long time since I did that.
If the loading coils are at the feed point, that
would have the least desirable current distribution with
a vertical, and this will apply also to the elements of a
loaded yagi.
The farther up/out the loading coil is from the feedpoint,
the more coil turns you will need to tune.
If the world was perfect, and coils had no loss, all
the way at the end would be the best place. :/
In the real world, you have to use the best compromise.
Which averages about 3/4 the way up/out from the feed
in most cases.

You could use the usual antenna modeling program to
calculate the performance, but you could also use
a vertical design program, such as vertload, and
also determine the best place for the loading coils.
You could then use the modeling program to design the
best spacing for what you want to optimize. IE: most
gain, or best f/b, etc.

Placing the coils at 1/2 out from the feedpoint is
a fairly good location as far as coil loss, vs current
distribution. But if you wanted every last drop of gain,
you could go out a bit farther. I probably wouldn't go
any farther than 3/4 out though. You can also use capacitive
loading hats on the ends of the elements. That will further
improve the current distribution, and also slightly reduce
the number of coil turns you need.