On Jul 5, 11:04 pm, Cecil Moore wrote:
Michael wrote:
According to the ARRL handbook the highest gain is achieve with a
5/8ths wave spacing between the upper and lower elements. The
handbook gives the following figures for estimated gain.

3/8 wave spacing = 4.4 dbd
1/2 wave spacing = 5.9 dbd
5/8 wave spacing = 6.7 dbd
3/4 wave spacing = 6.6 dbd

It seems to works on 14 MHz (stacked dipoles at 14 MHz), but on 10
meters the single 10 meter dipole blows it away.

Quoting the ARRL Antenna Book: "It should be designed
for the higher of the two frequencies using 3/4 lamda
spacing between parallel elements. It will then operate
on the lower frequency ... with 3/8 lamda spacing.

If you have 5/8 lamda spacing on 20m, you will have
5/4 lamda spacing on 10m with poor performance.
--
73, Cecil http://www.w5dxp.com

Not only that, but will depend if feeding end fire, or broadside.
It's only as a broadside array that max gain is at 5/8 wl
spacing.
And he is feeding his as an end fire array. The elements would
need to be end to end IE: collinear, array to be fed as a broadside
array.
As an end fire, the spacing must be quite a bit closer. If I remember
right, max gain with an end fire array is appx 1/8 wl spacing.
But from my own experimenting around with them, it's not
ultra critical as far as getting them to work.
In my case, I was feeding each element with a separate
feed line, and changing lengths to steer the array.
It was quite crude, but worked pretty well.
In my case, I tried to compromise on the spacing so I
could feed it both end fire, and broadside. I think I used
about 1/4 wl.
I also used about the same scheme on 10m, using two
5/8 wl ground planes. I forgot the exact spacing I used.
It was more dictated by available mast/.vent pipe locations
more than trying to get an exact length.
But it was a compromise spacing, and I fed it both ways
depending on the pattern I wanted.

On Jul 6, 12:59 am, wrote:

But it was a compromise spacing, and I fed it both ways
depending on the pattern I wanted.

Just thinking about another thing.. I think feeding in phase
would give a bi directional pattern, but if he wanted an
omni directional pattern, I think he'd have to have the elements
90 degrees out of phase. But I fergot...
He could fire up eznec demo or whatever and he can
quickly get a pretty good idea what to expect in theory
with any particular spacing and phasing.
He could crudely steer the pattern if he used various
length feeders to each element.
Some also use the "L/C" phasing boxes to steer the
pattern. Again fairly crude compared to some methods,
but it will work. Just don't expect perfect textbook patterns.
You have to take what you get...
The ARRL antenna book has better methods if want
cleaner patterns.

wrote:
On Jul 6, 12:59 am, wrote:

But it was a compromise spacing, and I fed it both ways
depending on the pattern I wanted.

Just thinking about another thing.. I think feeding in phase
would give a bi directional pattern, but if he wanted an
omni directional pattern, I think he'd have to have the elements
90 degrees out of phase. But I fergot...
He could fire up eznec demo or whatever and he can
quickly get a pretty good idea what to expect in theory
with any particular spacing and phasing.
He could crudely steer the pattern if he used various
length feeders to each element.
Some also use the "L/C" phasing boxes to steer the
pattern. Again fairly crude compared to some methods,
but it will work. Just don't expect perfect textbook patterns.
You have to take what you get...
The ARRL antenna book has better methods if want
cleaner patterns.

Or, if you don't wish the built-in limitations of Eznec (the demo
version), try MMANA GAL. Will feed the same data to the nec engine(s.)

Regards,
JS

John Smith wrote:

Or, if you don't wish the built-in limitations of Eznec (the demo
version), try MMANA GAL. Will feed the same data to the nec engine(s.)

Regards,
JS


Forgot, should have given a URL to go with that:

http://mmhamsoft.amateur-radio.ca/mmana/index.htm

Regards,
JS

On Jul 6, 1:16 am, wrote:

Ya know what, I guess he is running as a broadside
array after all.. I was thinking he had the elements
horizontal, but after rereading the first post, he does
have them stacked.
And if they were in phase, that should be a broadside
array.
Sooo... I finally decided to check it in the program using
two 1/2 wave elements for 10m, with the lower element
at 1/2 wave up, "16 ft", and the upper one at appx 5/8 wave
higher. "37 ft"
Using the single lower element alone, I got 2.08 dbi.
Using both in phase, I got 6.8 dbi.. So, it should work
as planned.. Not sure what the problem would be though,
unless you have coupling problems with other metal in
the area, etc..