Are ARES/RACES group has been given a motorhome that was used as the County's mobile Command Post. This motorhome was a stock motorhome that they converted to a mobile command post. They have about 8 antenna's VHF/UHF. Some gain, other 1/4 waves. Motorola 3/4 mounts are used. The antenna's are mounted to a metal channel that runs the entire lenght of the vehicle. RF power out for each radio is 60 watts or less.
Should the antenna's be mounted a 1/4 wave lenght apart to avoid intermod?
We want to re-due this correctly, and wisely seeking the good advice from this board. I don't want to do this twice.
Jim Duram, K8COP
Muskegon County, MI.
Mounting multible Antennas on a motorhome.
Moderator: Queue Moderator
Yes, the farther the better, take advantag of that big ground plane.
You may still get desense and intermod, so your operators need to be aware of when others are transmitting, and if they notice it, they can have the other transmitter stand by....
Train them to use LOW power as much as possible.
If you have 2 radios for the same band, put them at oposite ends.
Or put the lower priority one down on the cowel, set at low power.
Keep any lowband as far as you can from any metal in the pattern.
You may still get desense and intermod, so your operators need to be aware of when others are transmitting, and if they notice it, they can have the other transmitter stand by....
Train them to use LOW power as much as possible.
If you have 2 radios for the same band, put them at oposite ends.
Or put the lower priority one down on the cowel, set at low power.
Keep any lowband as far as you can from any metal in the pattern.
Jim, the channel you describe would not be a good ground plane. I am thinking the "channel" is just a narrow piece.
Even with a good all metal roof there is going to be interaction with some antennas and their location(s). I allow the cables from all the mounts to be able to reach all the radios so the antenna position can be changed arround easally. Also use a good well shielded coax cable, not the cheep stuff, there will be cross coupling between the cables where they are bundeled together.
Even with a good all metal roof there is going to be interaction with some antennas and their location(s). I allow the cables from all the mounts to be able to reach all the radios so the antenna position can be changed arround easally. Also use a good well shielded coax cable, not the cheep stuff, there will be cross coupling between the cables where they are bundeled together.