I have two beams I want to install on the same mast. They are, Cushcraft
MA5B and an 9 element crossed Tonna.

What is the optimal distance that these antennas should be spaced?

What is the minimum distance apart can they be mounted before they have a
negative effect on each other?

Does it matter what beam is mounted on the top?

Does it make any difference how close the beams are mounted to the rotator?

This is the first time that I have put any beams up, so I thought I better
get some good advice first.

Thanks

Barrett wrote:
I have two beams I want to install on the same mast. They are, Cushcraft
MA5B and an 9 element crossed Tonna.

What is the optimal distance that these antennas should be spaced?

What is the minimum distance apart can they be mounted before they have a
negative effect on each other?

Does it matter what beam is mounted on the top?

Does it make any difference how close the beams are mounted to the rotator?

This is the first time that I have put any beams up, so I thought I better
get some good advice first.

This page will show you how to think about it:
http://www.ifwtech.co.uk/g3sek/stacking/stacking2.htm

You'll see that most of your questions have no definite answers. Very
close stacking will cause some degradation in performance - especially
for the 2m antenna [1] - but how much degradation depends on the
specific antennas, and can only be determined by modelling.

The "optimum" stacking distance will also depend on your priorities
between HF and VHF, and on how much degradation in performance you are
willing to accept.

There are also mechanical considerations. It might be better to mount
the HF minibeam at the very top of the stub mast [2], to put it a larger
number of wavelengths above ground; but that will create a lot more
bending force than mounting the HF antenna below the VHF one. Again,
this is very much your decision.

With winter coming on, I'd suggest that you go for strength over
performance, and mount the HF antenna very low on the stub mast. The 2m
yagi could then be about 1 metre above it. This may not be completely
"optimum", but it stands a better chance of still being there next
spring.




[1] Whichever way up you install the two beams, the mast will affect the
performance of the vertically polarized part of the 2m crossed yagi,
because it's in the same plane as the vertical elements. Even if you
mount the crossed yagi at the top of a fibreglass mast, the coax
feedlines will have much the same effect. However, if you are only using
vertical polarization for semi-local working with good signal/noise
margins, you may decide to accept the reduced performance. Most people
do, or aren't even aware of it.

[2] Since you are posting from the UK to an international newsgroup,
we'd better be aware of a US/UK language difference. In the USA, the
"mast" usually means only the tube above the rotator, and people may be
assuming that of course you'll have a lattice tower :-) In the UK, the
word "mast" is often applied to the whole structure (even to a lattice
tower) and we usually call the rotating part a "stub mast".



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Barrett" wrote in message
.uk...
I have two beams I want to install on the same mast. They are, Cushcraft
MA5B and an 9 element crossed Tonna.

What is the optimal distance that these antennas should be spaced?

What is the minimum distance apart can they be mounted before they have a
negative effect on each other?

Does it matter what beam is mounted on the top?

Does it make any difference how close the beams are mounted to the
rotator?

This is the first time that I have put any beams up, so I thought I better
get some good advice first.

Thanks


I have a tubular tower, with no way to have a thrust bearing. So, I have the
Hygain TH3 tribander resting right on top of the rotor flange. 6 m beam is 7
feet up from there, and 2 m beam is half way in between. I care more about
6 than I do about 2 meters. I did run an EZNEC simulation of my 6 m beam
with/without an HF beam 7 feet below it; there was no change in performance.

Tam/WB2TT

"Barrett" wrote in message
.uk...
I have two beams I want to install on the same mast. They are, Cushcraft
MA5B and an 9 element crossed Tonna.

What is the optimal distance that these antennas should be spaced?

What is the minimum distance apart can they be mounted before they have a
negative effect on each other?

Does it matter what beam is mounted on the top?

Does it make any difference how close the beams are mounted to the
rotator?

This is the first time that I have put any beams up, so I thought I better
get some good advice first.

Thanks


I don't think there is any real optimal distance within what most can put
us. I tried to look at what was needed vers what I could put up about a
year ago. I did see the url Ian listed. My requirements was to have about
15 feet of mast out the top of the tower that is 57 feet out of the ground..
At the top went a M2 432 beam, about 4 feet below that went a M2 2 meter
beam both beams were on a 15 foot boom, and close to 5 feet under that went
a 5 element 6 meter beam on a 18 foot boom. Just over the top of the tower
was a 3 element triband for 20,15,and 10 meters. All antennas are
horizontal. I am sure this is nowhere near optimal but just the best for
what I had to work with.

On Sat, 27 Oct 2007 19:44:30 -0400, Tam/WB2TT wrote:
"Barrett" wrote:
I have two beams I want to install on the same mast. They are, Cushcraft
MA5B and an 9 element crossed Tonna.

What is the optimal distance that these antennas should be spaced?

What is the minimum distance apart can they be mounted before they have a
negative effect on each other?

Does it matter what beam is mounted on the top?

Does it make any difference how close the beams are mounted to the
rotator?

This is the first time that I have put any beams up, so I thought I better
get some good advice first.

I have a tubular tower, with no way to have a thrust bearing. So, I have the
Hygain TH3 tribander resting right on top of the rotor flange. 6 m beam is 7
feet up from there, and 2 m beam is half way in between. I care more about
6 than I do about 2 meters. I did run an EZNEC simulation of my 6 m beam
with/without an HF beam 7 feet below it; there was no change in performance.

Almost an identical lash-up here, Tam. The CC A3S is at the bottom of
the mast, the CC 215WB is halfway up the mast, and the CC A50S is at the
top. The mast is about 6-7 feet high:

http://jonz.net/W3DHJ/images/W3DHJ_Tower.jpeg

The OP needs to ask whether or not the antennas radiate best when dis-
assembled in the gargae, or up in the air and connected to coax? HI!HI!

73
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: http://jonz.net/ng.htm

I have one last question.

I an using a home made tilt over mast made up of aluminium scaffold tube (
2" OD heavy duty) and the same tube for the stub mast. I have two heavy duty
brackets made up that clamp onto the scaffold tube to hold the rotator and
support bearing in place.

What would be a good average distance to have between the brackets that hold
the rotator and bearing?

Thanks



"Ralph Mowery" wrote in message
...

"Barrett" wrote in message
.uk...
I have two beams I want to install on the same mast. They are, Cushcraft
MA5B and an 9 element crossed Tonna.

What is the optimal distance that these antennas should be spaced?

What is the minimum distance apart can they be mounted before they have a
negative effect on each other?

Does it matter what beam is mounted on the top?

Does it make any difference how close the beams are mounted to the
rotator?

This is the first time that I have put any beams up, so I thought I
better get some good advice first.

Thanks


I don't think there is any real optimal distance within what most can put
us. I tried to look at what was needed vers what I could put up about a
year ago. I did see the url Ian listed. My requirements was to have
about 15 feet of mast out the top of the tower that is 57 feet out of the
ground.. At the top went a M2 432 beam, about 4 feet below that went a M2
2 meter beam both beams were on a 15 foot boom, and close to 5 feet under
that went a 5 element 6 meter beam on a 18 foot boom. Just over the top
of the tower was a 3 element triband for 20,15,and 10 meters. All
antennas are horizontal. I am sure this is nowhere near optimal but just
the best for what I had to work with.

Ralph, was the 21 foot tube you used steel or alloy?


"Ralph Mowery" wrote in message
...

"Barrett" wrote in message
o.uk...
I have one last question.

I an using a home made tilt over mast made up of aluminium scaffold tube
( 2" OD heavy duty) and the same tube for the stub mast. I have two heavy
duty brackets made up that clamp onto the scaffold tube to hold the
rotator and support bearing in place.

What would be a good average distance to have between the brackets that
hold the rotator and bearing?

Thanks

I don't have any idea. I just put my rotator mounting plate where it fit
the bracing in the tower. That put about 5 or 6 feet of a 21 foot piece
of 2 inch OD ( 1 1/2 trade size of galvinised pipe. I just based that on
where the plate fit and having enough pipe in the tower were I can pull
the rotator out if it needs repair.

"Barrett" wrote in message
o.uk...
I have one last question.

I an using a home made tilt over mast made up of aluminium scaffold tube
( 2" OD heavy duty) and the same tube for the stub mast. I have two heavy
duty brackets made up that clamp onto the scaffold tube to hold the
rotator and support bearing in place.

What would be a good average distance to have between the brackets that
hold the rotator and bearing?

Thanks

I don't have any idea. I just put my rotator mounting plate where it fit
the bracing in the tower. That put about 5 or 6 feet of a 21 foot piece of
2 inch OD ( 1 1/2 trade size of galvinised pipe. I just based that on
where the plate fit and having enough pipe in the tower were I can pull the
rotator out if it needs repair.

"Barrett" wrote in message
.uk...
Ralph, was the 21 foot tube you used steel or alloy?


I don't know what kind of pipe it is. I went to a place that sells metal
and told them I wanted some galvinised pipe. One piece 1 1/2 inch trade
size about 20 feet long and also to support the tower I got 3 pieces that
are about 3 or 4 inches in diameter and 9 feet long. Those were for the guy
wires. I put around 4 feet of the pipes in the ground and filled them with
cement. Hopefully that will keep them from bending over. The tower is
guyed around 30 feet and again near the top. It is also in a yard of
cement. More or less to Rhon's specs for a 25G tower. I bought the tower
sections used. Think it was the least expensive part of the whole thing..

Here are a few pix of the tower.

http://home.earthlink.net/~ku4pt/images/

Ralph Mowery wrote:

Barrett wrote:
Ralph, was the 21 foot tube you used steel or alloy?


I don't know what kind of pipe it is. I went to a place that sells metal
and told them I wanted some galvinised pipe. One piece 1 1/2 inch trade
size about 20 feet long and also to support the tower I got 3 pieces that
are about 3 or 4 inches in diameter and 9 feet long. Those were for the
guy
wires. I put around 4 feet of the pipes in the ground and filled them
with
cement. Hopefully that will keep them from bending over. The tower is
guyed around 30 feet and again near the top. It is also in a yard of
cement. More or less to Rhon's specs for a 25G tower. I bought the
tower
sections used. Think it was the least expensive part of the whole thing..

Here are a few pix of the tower.

http://home.earthlink.net/~ku4pt/images/


Pipe is supplied in various "schedule" sizes, starting at 10. Common iron
plumbing pipe is malleable (low carbon steel) and usually Schedule 40. So,
what are the actual dimensions? Try he
http://www.engineersedge.com/pipe_schedules.htm. So, commonly available
1-1/2" (1.90" OD) Schedule 40 would have a 0.145" wall thickness.
Bryan WA7PRC