First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?

the gain probably wouldn't be the same... but the advantage of stacked yagis
is that you can fill in the gaps in the vertical takeoff angles that a
single yagi has with the 2nd, (or 3rd, or 4th) in the stack.

"N4aeq" wrote in message
ups.com...
First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?

On 3 Dec 2006 07:54:37 -0800, "N4aeq" wrote:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?
It has been my experience that a single, long Yagi has a narrower beam
width and a narrower bandwidth.

A longer one is easier to feed than a stack but harder to keep in the
air... If the birds like sitting on one end...
John Ferrell W8CCW

"N4aeq" wrote in news:1165161277.556098.152350@
79g2000cws.googlegroups.com:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?

One advantage is that you can dual-feed them all the way from the shack
and, with proper phasing control, can actually manipulate the take-off
angle. Plus they tend to be less sharp in the azimuth plane (not so
pointy).


--
Dave Oldridge+
ICQ 1800667

John Ferrell wrote:
On 3 Dec 2006 07:54:37 -0800, "N4aeq" wrote:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?
It has been my experience that a single, long Yagi has a narrower beam
width and a narrower bandwidth.

That is absolutely correct. with the stack you have a downward vector
on the nain lobe which widens the bandwidth as well as lowering the
TOA. Ofcourse when stacking you really should use similar antennas or
you will get in trouble with bandwidth Stacking does a couple of things
for you. The top antenna protects the lower antenna against static
noise
and the use of the top stack is in use only for a short time for low
angle pragation. The stack is easer on the rotor ofcourse and needs
little landspace compared to a long boom.
Art




A longer one is easier to feed than a stack but harder to keep in the
air... If the birds like sitting on one end...
John Ferrell W8CCW

Thanks but after reading some other post i think i will put up a
stacked set of four in a H
pattern, according to what ive read if i use a folded dipole to feed
them (about 200ohm)
& use equal length feed line then i could conbine then in parallel and
come out with 50 ohms?

rt wrote:
John Ferrell wrote:
On 3 Dec 2006 07:54:37 -0800, "N4aeq" wrote:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?
It has been my experience that a single, long Yagi has a narrower beam
width and a narrower bandwidth.

That is absolutely correct. with the stack you have a downward vector
on the nain lobe which widens the bandwidth as well as lowering the
TOA. Ofcourse when stacking you really should use similar antennas or
you will get in trouble with bandwidth Stacking does a couple of things
for you. The top antenna protects the lower antenna against static
noise
and the use of the top stack is in use only for a short time for low
angle pragation. The stack is easer on the rotor ofcourse and needs
little landspace compared to a long boom.
Art




A longer one is easier to feed than a stack but harder to keep in the
air... If the birds like sitting on one end...
John Ferrell W8CCW

On 3 Dec 2006 07:54:37 -0800, "N4aeq" wrote:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?

Depends to some extent on whether you are focussed on gain in the
desired direction, or rejection of unwanted signals, or a balanced
system assessment (eg G/T).

Stacking a pair yagis in one plane narrows the beamwidth in the
orthogonal plane... so if you stack two horizontal yagis above each
other, you achieve the gain increase by reducing the vertical
beamwidth without much change to the horizontal beamwidth or pattern.
The stacking distance influences the pattern, the location of the
pattern nulls near the main lobe, the magnitude of side lobes.

Obviously there are a bunch of mechanical / physical issues depending
on the required gain, and the stacked yagis requires a more
complicated feed arrangement which has additional loss which might be
significant if you were chasing best G/T ratio.

Owen
--

N4aeq wrote:

First off if size is no problem then what would be the advantage to
two stacked yagis opposed to one long yagi, considering the gain of
each setup would be equal?


We use a 4 over 4 array for 6m that I designed for the VHF contests.
The advantage for us, in the northern midwest, is that I was able to
make a relatively high gain system, 10.5dBd free space, that had no dead
spots in the pattern, as well as a main lobe that was over 45 degrees
wide at -3dB. The F/B is intentionally only about 18dB. It's nice to
have a pattern with no deep nulls in the midwest, because the signals
can come from any direction, and there are usually no, or few, big
signals to cause problems. We can also cover a broad area, easily 90+
degrees, during openings with the main lobe without turning.

On the other hand, if I was on either coast in a high population density
area, I would want a long yagi with as much F/B and F/S as I could get.

Whenever possible, you design and build what is best for your location.

tom
K0TAR