Recommendations for mobile GMRS antennas

[jnojr]

I bought a Larsen NMO https://www.amazon.com/dp/B00M255NL2... and a TYT TH-7900.

Will that through-hole mount automatically provide an RF ground plane? Is there something specific the installer needs to do to make sure?

I want to get a "stubby" antenna I can leave on most of the time to clear the garage door. I may want to get a longer / "better" antenna for longer trips.

 

[FFPM571]

Depends on where you mount it... You want a nice flat place preferable in the center of the roof if possible and the best short antenna is a 1/4 wave UHF that is a 6" stainless steel whip.

 

[mmckenna]

In your other post you were talking about a dual band radio and a 2 meter/70 centimeter antenna.
Is this the same radio?

If it's just GMRS, I agree, a basic 1/4 wave is hard to beat.

 

[K6GBW]

A quarter wave or a PCTel short antenna. I think some people call them “Ghost” antennas. I use one on my Subaru Crosstrek and it works amazingly well. I have it in the back between the luggage rack and the AM/FM antenna. You really don’t even see it unless you’re looking for it.

 

[jnojr]

In your other post you were talking about a dual band radio and a 2 meter/70 centimeter antenna.
Is this the same radio?

If it's just GMRS, I agree, a basic 1/4 wave is hard to beat.

Yep. I'm mostly interested in GMRS but want to be able to use VHF & UHS as well.

And I'm OK carrying a GMRS antenna and a 2M antenna.

 

[jnojr]

Another question... I intend to have the mount where the roof will be a ground plane, but it's possible that might not happen. If I run a NGP antenna on a ground plane, will that cause problems? I know a GP antenna without a ground plane won't work out well at all. I want to make sure I have something when it gets installed.

 

[K6GBW]

If you install a proper NMO mount on a metal roof, you’ll be grounded. If you want a dual band antenna thats small but still works well take a look at the Comet B-10NMO. I ran for for years on three different cars and for only being 12” tall it worked really well.

 

[mmckenna]

Another question... I intend to have the mount where the roof will be a ground plane, but it's possible that might not happen. If I run a NGP antenna on a ground plane, will that cause problems?

Will not cause a problem.

A 1/2 wave "no ground plane" antenna will have 0dB of gain without a ground plane under it. It should tune down to low SWR without any issues.
A 1/2 wave "no ground plane" -with- a proper ground plane under it should give you about 2.4dB of gain and tune up just fine.

If you are going to do a permanent mount NMO for these antennas, make sure you consider suitable ground plane size for what you are doing:
GMRS/70 Centimeters will want 6" of ground plane in all directions under the antenna.
2 meter band will want around 19" of ground plane in all directions under the antenna. That's why center of the roof is ideal.

I know a GP antenna without a ground plane won't work out well at all. I want to make sure I have something when it gets installed.

The NMO mounts have some 'teeth' that bite into the underside of the sheet metal. As long as you install it on some sort of conductive material, and tighten it down reasonably tight (knuckles should NOT turn white for this procedure), you'll be just fine. You do not need to sand/grind the metal under the mount, the teeth will bite in just fine. You absolutely do not need to sand/grind around the top of the sheet metal under the antenna.

Long term, you'll be very happy you put the effort into a permanent mount. It does help performance and looks way more professional that the compromise mounts.

 

[jnojr]

If you are going to do a permanent mount NMO for these antennas, make sure you consider suitable ground plane size for what you are doing:
GMRS/70 Centimeters will want 6" of ground plane in all directions under the antenna.
2 meter band will want around 19" of ground plane in all directions under the antenna. That's why center of the roof is ideal.

I have a Hyundai Palisade. There are two glass panels up there, so no 19" If I get UHF and have to forget about VHF, I'll be OK.

In that scenario, will 2M be useless, suck, just not be "as good", etc.?

 

[mmckenna]

In that scenario, will 2M be useless, suck, just not be "as good", etc.?

No, won't be useless, just less than ideal. Plenty of 'less than ideal' installs out there that work just fine.
California Highway Patrol running low band from the roof of their cars has no where near enough ground plane, yet they can be heard all over the country when conditions are right.

 

[nd5y]

Plenty of 'less than ideal' installs out there that work just fine.

Yes. Just look at almost any military vehicle.

 

[mmckenna]

Yes. Just look at almost any military vehicle.

Exactly. Haven't seen a road legal vehicle running a CB antenna with a perfect ground plane, either.

 

[jimg]

Will not cause a problem.

A 1/2 wave "no ground plane" antenna will have 0dB of gain without a ground plane under it. It should tune down to low SWR without any issues.
A 1/2 wave "no ground plane" -with- a proper ground plane under it should give you about 2.4dB of gain and tune up just fine.

If you are going to do a permanent mount NMO for these antennas, make sure you consider suitable ground plane size for what you are doing:
GMRS/70 Centimeters will want 6" of ground plane in all directions under the antenna.
2 meter band will want around 19" of ground plane in all directions under the antenna. That's why center of the roof is ideal.



The NMO mounts have some 'teeth' that bite into the underside of the sheet metal. As long as you install it on some sort of conductive material, and tighten it down reasonably tight (knuckles should NOT turn white for this procedure), you'll be just fine. You do not need to sand/grind the metal under the mount, the teeth will bite in just fine. You absolutely do not need to sand/grind around the top of the sheet metal under the antenna.

Long term, you'll be very happy you put the effort into a permanent mount. It does help performance and looks way more professional that the compromise mounts.

What brand SWR meter for GMRS do you recommend?

 

[jnojr]

What brand SWR meter for GMRS do you recommend?

I use a Surecom SW-102

 

[mmckenna]

What brand SWR meter for GMRS do you recommend?

There are some basic ones on Amazon that will work well enough for hobby type use without breaking the bank.
You don't need a super expensive one to get acceptable/hobby level results. Just make sure you get one that covers the 462/467MHz frequencies and will handle at least 50 watts. I wouldn't make a recommendation as I've not used any of the ones available on amazon. The one I have at home is rather expensive and not user friendly.

 

[nokones]

I picked these up used for a very good price. I've had the Telewave for some time and I bought the Bird 43 for $175 about a year and half ago. The Bird and the slugs were recalibrated earlier this year.

 

[prcguy]

I would not get a SWR meter that relies on a separate transmitter. Instead get an antenna analyzer that will give you more info and test out of band. I have many with the Comet CAA500 being very reliable and I also like this brand, which comes in many different frequency ranges:

N1201SA+ Antenna RF Vector Analyzer RF Vector Impedance Analyzer 34.375M~2700M | eBay

N1201SA+ Antenna RF Vector Analyzer High Performance RF Vector Impedance Analyzer 34.375MHz ~ 2700MHz. - Model: N1201SA+. Impedance: 0.1ohm ~ 1000ohm (The absolute value of impedance). 8.2pF capacitance test at 140MHz.

www.ebay.com

 

[nokones]

Unfortunately, the Rig-Expert Antenna Analyzer was not cheap, a matter of fact, the cost was a very pretty penny, but I do not regret getting it. It has been a very valuable tool and appears to be a quality brand.

 

[jimg]

Thanks to all for your replies!

 

[DOAUSMC0331]

On no ground plane antenna's. Can't you just run a ground strap to the chassis of a vehicle?