Antenna advice

[RealCowboy]

I'm currently using approximately 25 mobile Kenwood VHF radios in the 160 MHZ range using a mixture of Maxrad MHB 5802 and Tram 1159 antennas.
The maxrads are 20 years old and the trams are slightly newer and both were cut to be tuned to the 160 MHZ range.
I am in the process of adding a repeater which will be in the 140 MHZ range and I will also have a talkaround channel so I plan on eliminating the 160 MHZ channel.


To tune the antennas to the 140 MHZ range they have to be longer so I will need to get different whips.

Seeing as the antennas are that old my dilemma is should I just get different antennas or should I replace the whips.
If I do replace the antennas should I go with a different brand antenna.

Just thought I'd ask some more knowledgeable people and TIA.

 

[RealCowboy]

The reason I'm asking is there seems to be be a low opinion on the tram 1159 so I'm wondering if I go to a better quality mobile antenna can I expect more range.

 

[ladn]

tram 1159

In the case of Tram antennas, the issue isn't really "range", it's build quality. and (perhaps) specs. Look at similar VHF gain antennas from suppliers such are Larsen, EmWave, Laird and PCTel.

 

[mmckenna]

The reason I'm asking is there seems to be be a low opinion on the tram 1159 so I'm wondering if I go to a better quality mobile antenna can I expect more range.

Tram is popular in the hobby world due to price. They have some good products, but I personally do not believe the minor cost savings is really worth it. I've been doing this professionally for a few decades and one of the things I learned early on is that the antenna is the most important part of a radio system, and it should be the last place you cut costs.

Sounds like you are in Canada, so pricing/availability will be different than what I've got down here.
Larsen has been my go to mobile antenna for decades, and they've never let me down. I've got a lot of them on police vehicles, public works as well as my own vehicles. I've never had one let me down.
Problem is, most vendors have cranked the prices on them recently. Used to be they were affordable, but now some dealers have them priced really high. Still, a good antenna.

I've recently started using a lot of EM Wave antennas. I'm very happy with them, they are durable and well built. Prices are reasonable.

I'd take the opportunity to replace the antennas at this point, rather than just the whips. If these antennas have been out there this long, there may be some hidden issues once you start looking at them. I'd be concerned about the gaskets rotting over time. Just replacing the whip would be the cheap/easy option, but I think it would be well worth just getting them all updated at once.
Take a good look under the antennas when you replace them. Look for any signs of damage, moisture, corrosion, etc.

 

[RealCowboy]

Thank you for taking time to answer my questions.


25% of my vehicles rooftops are steel and 75 % are fiberglass.

My antennas are all mounted using a NMO mount but most of them are mounted on the side of the vehicle on mirrors or on brackets beside the hood.

Seeing as most of my cabs are fiberglass is there an advantage to mounting a NGP antenna in the middle of a fibreglass cab or will it perform just as well on a bracket beside the cab?

If an NGP antenna is mounted on a steel roof does it perform better than it would on a fiberglass roof?

 

[mmckenna]

Seeing as most of my cabs are fiberglass is there an advantage to mounting a NGP antenna in the middle of a fibreglass cab or will it perform just as well on a bracket beside the cab?

If there's zero ground plane under the antenna, then it doesn't matter where you mount them. But I'd focus on getting them on top of the vehicle so they have a clear 360º view. Down below roof line is going to result in shadowing.

If an NGP antenna is mounted on a steel roof does it perform better than it would on a fiberglass roof?

Yes.
A no ground plane antenna (usually a 1/2 wave design) will have 0dBi gain when it is not mounted directly on a ground plane.
If you mount the same 1/2 wave antenna over a suitable ground plane, the antenna will now exhibit 2.1dBi of gain since the ground plane now helps focus more of the RF energy towards the horizon.


Half wave antennas are great problem solvers for some applications, but whenever possible get them mounted over some metal. Even on your fiberglass roof vehicles, a piece of sheet metal under the antenna, foil, screen, even an "X" shape of something conductive directly under the antenna will improve performance.