I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only be
transmitting with one at a time but one could be receiving and the other
transmitting, the 70cm will be for ATV receive only for now.

--
Chris W
KE5GIX

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give the gifts they want
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Chris W wrote in news:IT3tf.45644$ih5.19066@dukeread11:

I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only be
transmitting with one at a time but one could be receiving and the other
transmitting, the 70cm will be for ATV receive only for now.

A good rule of thumb is to separate them by at least a half-wave at the
lowest frequency. In this case that means about a meter (39") apart.


--
Dave Oldridge+
ICQ 1800667

On Mon, 02 Jan 2006 14:33:18 GMT, Dave Oldridge wrote:
Chris W wrote in news:IT3tf.45644$ih5.19066@dukeread11:

I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only be
transmitting with one at a time but one could be receiving and the other
transmitting, the 70cm will be for ATV receive only for now.

A good rule of thumb is to separate them by at least a half-wave at the
lowest frequency. In this case that means about a meter (39") apart.

Not when they are orthogonally polarized. They can be 0.000 wavelengths
apart. I.e., in the OP's case, the 2M elements can be _mounted_ on the
70cm's boom.

I have a 6-el, close-spaced 2m vertical mounted on the forward boom of
my CC A3S. (Not that I give a crap much about 2M vert. propagation...)

HNY es 73
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
Pueblo, Colorado | @ | Jonesy | OS/2 __
38.24N 104.55W | config.com | DM78rf | SK

Allodoxaphobia wrote in
:

On Mon, 02 Jan 2006 14:33:18 GMT, Dave Oldridge wrote:
Chris W wrote in
news:IT3tf.45644$ih5.19066@dukeread11:

I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only
be transmitting with one at a time but one could be receiving and
the other transmitting, the 70cm will be for ATV receive only for
now.

A good rule of thumb is to separate them by at least a half-wave at
the lowest frequency. In this case that means about a meter (39")
apart.

Not when they are orthogonally polarized. They can be 0.000
wavelengths apart. I.e., in the OP's case, the 2M elements can be
_mounted_ on the 70cm's boom.

You're right. I didn't catch the polarization thing. In fact, building
them on the same boom would be quite workable.

--
Dave Oldridge+
ICQ 1800667

Dave Oldridge wrote:

Allodoxaphobia wrote in
:



On Mon, 02 Jan 2006 14:33:18 GMT, Dave Oldridge wrote:


Chris W wrote in
news:IT3tf.45644$ih5.19066@dukeread11:



I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only
be transmitting with one at a time but one could be receiving and
the other transmitting, the 70cm will be for ATV receive only for
now.


A good rule of thumb is to separate them by at least a half-wave at
the lowest frequency. In this case that means about a meter (39")
apart.


Not when they are orthogonally polarized. They can be 0.000
wavelengths apart. I.e., in the OP's case, the 2M elements can be
_mounted_ on the 70cm's boom.



You're right. I didn't catch the polarization thing. In fact, building
them on the same boom would be quite workable.



What if they are 2 different antennas and you can't put them on the same
boom, how close can I put them?

--
Chris W
KE5GIX

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
http://thewishzone.com

On Tue, 03 Jan 2006 13:01:32 -0600, Chris W wrote:
Dave Oldridge wrote:
Allodoxaphobia wrote:
On Mon, 02 Jan 2006 14:33:18 GMT, Dave Oldridge wrote:
Chris W wrote:

I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only
be transmitting with one at a time but one could be receiving and
the other transmitting, the 70cm will be for ATV receive only for
now.

A good rule of thumb is to separate them by at least a half-wave at
the lowest frequency. In this case that means about a meter (39")
apart.

Not when they are orthogonally polarized. They can be 0.000
wavelengths apart. I.e., in the OP's case, the 2M elements can be
_mounted_ on the 70cm's boom.

You're right. I didn't catch the polarization thing. In fact, building
them on the same boom would be quite workable.

What if they are 2 different antennas and you can't put them on the same
boom, how close can I put them?

OK, if we're still talking about one vertically polarized and one
horizontally polarized, I'd slap'em together so that the vertical
elements are at least 1/4 wavelength from the horizontal's boom.

Or, you could do what some fellers seem to do: Spend all your time in
rraa, anguishing and arguing about antenna installation choices. After
all, which propagates best: The antenna on the floor of the garage, or the
one up in the air? HI!HI!

JONESY'S AXIOM:
You never put an antenna up just once.

Good Luck and Happy New Year!
73
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
Pueblo, Colorado | @ | Jonesy | OS/2 __
38.24N 104.55W | config.com | DM78rf | SK

"Dave Oldridge" wrote in message
...
Chris W wrote in news:IT3tf.45644$ih5.19066@dukeread11:

I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized, end
mounted 6 foot boom. How far apart do they need to be? I will only be
transmitting with one at a time but one could be receiving and the other
transmitting, the 70cm will be for ATV receive only for now.

A good rule of thumb is to separate them by at least a half-wave at the
lowest frequency. In this case that means about a meter (39") apart.


Sofar all the answers are assuming the question is will one antenna affect
the other antenna. One other thing to look at is will the transmitter
'kill' the receiver of the other rig ?

"Ralph Mowery" wrote in
nk.net:


"Dave Oldridge" wrote in message
...
Chris W wrote in
news:IT3tf.45644$ih5.19066@dukeread11:

I want to put a short 2 meter yagi and a long 70cm yagi on the same
vertical mast. The 70cm will be a horizontally polarized, center
mounted 17' boom and the 2 meter will be a vertically polarized,
end mounted 6 foot boom. How far apart do they need to be? I will
only be transmitting with one at a time but one could be receiving
and the other transmitting, the 70cm will be for ATV receive only
for now.

A good rule of thumb is to separate them by at least a half-wave at
the lowest frequency. In this case that means about a meter (39")
apart.


Sofar all the answers are assuming the question is will one antenna
affect the other antenna. One other thing to look at is will the
transmitter 'kill' the receiver of the other rig ?

Indeed, though not too likely since the frequencies are a fair bit apart.


--
Dave Oldridge+
ICQ 1800667