Newbie Antenna Question...

[Scott Hammel]

I've added 2 new pieces of equipment to my chase vehicle this year, first being a Yaesu FT7800 ham radio (just passed my Technician exam last weekend!) and the second being a Cyfre wireless cell phone amplifier. Both came with mag mount roof antenna's and was curious about mounting locations on the roof of my Jeep. I know this sounds stupid, but does it matter if they are located next to each other on my roof? Basically, if they are too close to each other is there some sort of interference with one another? Thanks in advance, this stuff is new to me

PS - A huge thanks to Maximum Signal! You guys were amazing to business with!

 

[Tim Stoecklein]

Space them a couple feet away from each other and you should be just fine

 

[J West]

As a rule, antennas on a vehicle should be spaced no closer than a 1/4 wavelength from each other, as determined by the lowest operating frequency of the installation. In your case, 144 MHz is the lowest operating frequency so the two antennas should be spaced no less than ~19 inches apart, as ~19 inches is a 1/4 wavelength at 144 MHz. Also remember that all antennas need at least a 1/4 wavelength-sized ground plane to work efficiently, so make sure the ham antenna has ~19 inches of metal around it on all sides (i.e. middle of roof). The location of the cell antenna is less critical as it only needs a ground plane in the radius of a couple inches.

Do not place them right next to each other, and more spacing is always a good thing if you can do it...so if you have more room than ~19 inches, feel free to do that. Permanent mounts are always better than mag mounts or glass mounts (the worst), but if installed and used correctly the mag mounts can produce acceptable results.

In your particular installation, interference should not be an issue. However, in installations where multiple transceivers and/or scanners are mounted in the same vehicle, antenna spacing becomes critical. It is not good for the receiver of other radios/scanners etc to get 50 (or more) watts of RF electrical energy dumped into them because the antennas are all lumped together in a small area.

I will take a picture of my current vehicle's antenna arrangement for reference later this afternoon and edit my post with it, so you can see it.

 

[Scott Hammel]

As a rule, antennas on a vehicle should be spaced no closer than a 1/4 wavelength from each other, as determined by the lowest operating frequency of the installation. In your case, 144 MHz is the lowest operating frequency so the two antennas should be spaced no less than ~19 inches apart, as ~19 inches is a 1/4 wavelength at 144 MHz. Also remember that all antennas need at least a 1/4 wavelength-sized ground plane to work efficiently, so make sure the ham antenna has ~19 inches of metal around it on all sides (i.e. middle of roof). The location of the cell antenna is less critical as it only needs a ground plane in the radius of a couple inches.

Do not place them right next to each other, and more spacing is always a good thing if you can do it...so if you have more room than ~19 inches, feel free to do that. Permanent mounts are always better than mag mounts or glass mounts (the worst), but if installed and used correctly the mag mounts can produce acceptable results.

In your particular installation, interference should not be an issue. However, in installations where multiple transceivers and/or scanners are mounted in the same vehicle, antenna spacing becomes critical. It is not good for the receiver of other radios/scanners etc to get 50 (or more) watts of RF electrical energy dumped into them because the antennas are all lumped together in a small area.

I will take a picture of my current vehicle's antenna arrangement for reference later this afternoon and edit my post with it, so you can see it.

Thank you so much, I'd love to see your setup and thanks for the great detailed responses. I'm quite excited to actually get cell phone reception this year for my data connection. That burned us many times last year...

 

[Benjamin Rock]

I have a station wagon. I put all the antennas in a row on the roof, mohawk style.. All sit at or below 1.2 swr and do not cause any interference between them. They sit about 14 or so inches apart from each other. There is a Wilson 1000 at the front(CB), a MFJ 1728(2m), and basic Radio Shack scanner antenna. Then on the gate itself is a Diamond 7900 Super Gainer/NMO mount(multi band HAM). Works great if you have the room..

 

[Jesse Risley]

I have had issues with both my 110 watt commercial ham rig and my Kenwood TM-D700A (on high power) interfering with the Verizon data signal. If I transmit on two-meters, it knocks out my Verizon signal IF I am connected to the external cell antenna. I have tried this with several cell antennas at various distances and it never fails.

I would recommend that you keep the antennas as far apart as possible without compromising your performance. If you find that you're having a problem, try operating the radio on medium or low power and you should be fine, assuming you have at least several feet of separation between the two antennas.