Base Station Antenna Proximity

[RollinDoughnut]

Will a 5/8 wave 11 meter antenna have any negative impact on a GMRS "J-Pole" (from KB9VBR Antennas) mounted 3 feet away at the same height (on a house roof)?  I am primarily concerned about GMRS performance and rarely transmit on 11 meters.
Thank you,

Dennis Goethe

[RollinDoughnut]

Based on your response, the fact that there is a remote potential to damage the GMRS receiver should someone transmit on 11 meters, I decided to take down the 11 meter antenna and will relocate it onto another building, at least 30 feet away.  I put the GMRS antenna in it's place and that was the easiest thing to do on this near 40 degree, sunny day.

Thank you for your reply,

Dennis Goethe

[mbrun]

Will a 5/8 wave 11 meter antenna have any negative impact on a GMRS "J-Pole" (from KB9VBR Antennas) mounted 3 feet away at the same height (on a house roof)? I am primarily concerned about GMRS performance and rarely transmit on 11 meters.

Thank you,

Dennis Goethe

Hello Dennis.

 

The answer depends on what types of impact you are concerned about. Potential things that come to my mind include the following:

 

- Impact on GMRS radiation pattern based on the adjacency of the 11 meter antenna.

- Impact on 11 meter radiation pattern based on the adjacency of the GMRS antenna.

- Impact on one receiver when the other is transmitting.

 

* The 11 meter antenna is far enough away from the GMRS antenna that the GMRS antenna’s pattern will barely be affected.

* The GMRS antenna is close enough to the 11 meter antenna that it may alter the 11 meters performance, depending upon where the antenna (and the mast below it) is located relative to the top of the 11 meter antenna. 2.75 meters (1/4 wave) is the minimum recommend horizontal distance that should exist between this antenna and another other metal monopole to keep effects minimal.

* While transmitting on either radio, it is probable that you will experience serious desense on the opposing radio. If the operating power of the 11 meter antenna is high, you could conceivably damage the GMRS receiver, although I do not have any specific power numbers for your.

 

When antennas must be mounted at the same elevation, is best to put as much horizontal separation as possible between them. When in close proximity, it is usually best to give them vertical separation and make them as close to collinear as you can so that the two antennas operate in the pattern null of the other.

 

Experimentation is what will give you the absolute answers you seek.

 

Hope this helps.

 

 

Michael

WRHS965

KE8PLM

 

Edited for spelling.