I have a problem with a number of vhf transceivers that interfer with
each other. There are 8 closely related frequencies involved and the
problem only exist when 4 or more of the frqencies are in use at one
time. Circulators and filters are not practical solutions. I am hoping
that spacing the antennas further apart will help but I would like to
know how far apart should that be before I decide to try some other
method of relief. The radio now radiate approximately 5 watts, AM
modulated in the VHF aeronautical band 118 to 137 Mhz. Antennas are
arranged in a rectangular array 4 antennas long and 2 wide with 8ft
spacing between adjacent antennas. The transcievers have neither tuned
front ends or outputs and adding filters is not an option.

I have observed that the same type of intermod distortion exist at a
transmitter only site but this does not appear to be a problem because
the receivers are not co located with the transmitters. The rx site is
about a mile away. Also I have obseved that a rx equiped with the
same tpe of antenna placed abot 100 ft from the transciever sites
antenna array does not pickup the intermod. This leads me to belive
that the distortion is a result of signals mixing in the transmitters
and not in the receivers.

How far apart should the antennas be? I ask this only assuming this
will cure the problem.

Jimmie

In article .com,
"JIMMIE" wrote:

I have a problem with a number of vhf transceivers that interfer with
each other. There are 8 closely related frequencies involved and the
problem only exist when 4 or more of the frqencies are in use at one
time. Circulators and filters are not practical solutions. I am hoping
that spacing the antennas further apart will help but I would like to
know how far apart should that be before I decide to try some other
method of relief. The radio now radiate approximately 5 watts, AM
modulated in the VHF aeronautical band 118 to 137 Mhz. Antennas are
arranged in a rectangular array 4 antennas long and 2 wide with 8ft
spacing between adjacent antennas. The transcievers have neither tuned
front ends or outputs and adding filters is not an option.

I have observed that the same type of intermod distortion exist at a
transmitter only site but this does not appear to be a problem because
the receivers are not co located with the transmitters. The rx site is
about a mile away. Also I have obseved that a rx equiped with the
same tpe of antenna placed abot 100 ft from the transciever sites
antenna array does not pickup the intermod. This leads me to belive
that the distortion is a result of signals mixing in the transmitters
and not in the receivers.

How far apart should the antennas be? I ask this only assuming this
will cure the problem.

Jimmie


Since this is in the Aircraft Band, and is a Ground Station, you would
be significantly better off to seperate the antennas Vertically, rather
than Horozontally, or both. Vertical seperation will give you much
better isolation per unit of distance.

On Mar 7, 12:49 pm, You wrote:
In article .com,





"JIMMIE" wrote:
I have a problem with a number of vhf transceivers that interfer with
each other. There are 8 closely related frequencies involved and the
problem only exist when 4 or more of the frqencies are in use at one
time. Circulators and filters are not practical solutions. I am hoping
that spacing the antennas further apart will help but I would like to
know how far apart should that be before I decide to try some other
method of relief. The radio now radiate approximately 5 watts, AM
modulated in the VHF aeronautical band 118 to 137 Mhz. Antennas are
arranged in a rectangular array 4 antennas long and 2 wide with 8ft
spacing between adjacent antennas. The transcievers have neither tuned
front ends or outputs and adding filters is not an option.

I have observed that the same type of intermod distortion exist at a
transmitter only site but this does not appear to be a problem because
the receivers are not co located with the transmitters. The rx site is
about a mile away. Also I have obseved that a rx equiped with the
same tpe of antenna placed abot 100 ft from the transciever sites
antenna array does not pickup the intermod. This leads me to belive
that the distortion is a result of signals mixing in the transmitters
and not in the receivers.

How far apart should the antennas be? I ask this only assuming this
will cure the problem.

Jimmie

Since this is in the Aircraft Band, and is a Ground Station, you would
be significantly better off to seperate the antennas Vertically, rather
than Horozontally, or both. Vertical seperation will give you much
better isolation per unit of distance.- Hide quoted text -

- Show quoted text -

I see where you are coming from, two antennas mounted in each others
vertical null. This is doable. As a matter of fact they make dual
antennas specifically designed for this purpose. This will allow me to
mount the antennas with double the horizontal spacing I have now.

JIMMIE wrote:
[snip]
Circulators and filters are not practical solutions.
[snip]

I'm curious: please tell me why this isn't a practical solution.

TIA.

William

--
A little learning is a dang'rous thing;
Drink deep, or taste not the Pierian spring;
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.
-- Alexander Pope, Essay on Criticism

"William Warren" ""w_warren_noise\"@comcast(William Warren).net" wrote in
message ...
JIMMIE wrote:
[snip]
Circulators and filters are not practical solutions.
[snip]

I'm curious: please tell me why this isn't a practical solution.

TIA.

William

--
A little learning is a dang'rous thing;
Drink deep, or taste not the Pierian spring;
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.
-- Alexander Pope, Essay on Criticism

"William Warren" ""w_warren_noise\"@comcast(William Warren).net" wrote in
message ...
JIMMIE wrote:
[snip]
Circulators and filters are not practical solutions.
[snip]

I'm curious: please tell me why this isn't a practical solution.

TIA.

William


Multichannel transceivers. A filter that was broad enough for full operation
of the transceiver wouldnt help and I dont think circulators work with
transceivers very well.You could TX but not RX.