Antenna placement ?

[jcefd10]

I have a 2018 F-150 and am running a NX5700 for use with our, and several surrounding counties Fd/Ema/EMS systems.
I currently have a EM Wave EM-MX0152 quarter wave mounted above the 3rd brake light.
I was just curious If I were to move the antenna to the center of the roof would it be beneficial at all, or would anything difference most likely not be noticed? I just want to make sure Im getting the most out of it. Nothing wrong with it where it is that I can tell so just kind of a random, general knowledge for myself for future installs.

 

[prcguy]

It would be best if you could get the antenna at least a 1/4 wavelength from the edge of the roof which would be a good 18" at VHF and that would provide a reasonable omni pattern. The best signal would still be in the direction of the most surface area of metal. If your right up against the rear roof edge it can skew the radiation pattern and loose a little signal to the rear.

Mounting close to the edge can also affect the match where a full 1/4 or more metal around the antenna should produce the best match and when you loose some ground plane there is less capacitance between the whip and ground plane and that can raise the impedance some. In this case you can usually cut the whip a little long and it will compensate slightly and improve the match.

 

[jcefd10]

Awesome answer man, thank you!
With that being said, which method do you guys use to plug NMO holes? 😂.
I’ve been kicking around the idea of getting a vehicle cell booster so I may can use the current hole for that.

 

[jeepsandradios]

Just leave the NMO and put a cap on it. Great backup mount or otehr use in future

 

[mmckenna]

Awesome answer man, thank you!
With that being said, which method do you guys use to plug NMO holes? 😂.
I’ve been kicking around the idea of getting a vehicle cell booster so I may can use the current hole for that.

Cell booster antennas usually want some good separation between the outside antenna and the inside antenna. Putting the antenna on the back of the cab like that can result in the amplifier self oscillating, as in the signal starts looping through the amp like audio feedback. Any legit cell booster will shut itself down when it sees that happening.

Might work, might not. It is not the ideal place for that sort of setup. You could try it, but you may find that the amp shuts down and won't do anything.

 

[jcefd10]

Yeah, I don’t want that. I’ll probably just cap it and save for later. I wish I’d drilled center roof the Corey time but Noooooooo. Leave it to me

 

[mmckenna]

Yeah, I don’t want that. I’ll probably just cap it and save for later. I wish I’d drilled center roof the Corey time but Noooooooo. Leave it to me

That's a good plan.

I had a 2011 F-150 crew cab, and now a 2018 F-350 crew cab. Both had the NMO installed in the center of the roof. It really is the way to go. Nice radiation pattern, low SWR.

I did run an 800MHz antenna on the rear of the F-150. The spacing from the rear of the roof was fine for 800MHz. Ran a CB on it for a long road trip, and it worked well enough. No, not perfect, but it did work.