Recommendations for mobile antennas?

[WRXR374]

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.

[WRYZ926]

You are looking at 38 inch or longer antennas to cover 2m, 70cm, and GMRS. Most of the stubby antennas won't work that well for all three bands.

I can vouch for the Comet 2x4SR-NMO being a good antenna. The highest SWR I have across 2m, 70cm, and GMRS is 1.8. I run that antenna on my SxS with a TYT TH-8600 dual band radio. I have also used the same antenna with my Wouxun KG-XS20 G radio with great results.

I am running a Comet SBB1 NMO mount on my Ford Escape due to height restrictions. It does well for 2m and 70cm and is passible on GMRS with a SWR of 2.0.

[Lscott]

18 hours ago, dosw said:

The full length monster of a mobile antenna, the Comet CA-2X4SR-NMO covers 2m, 70cm, MURS, and GMRS. It even has reasonable SWR in Marine VHF and 1.25m. But it's 40 inches long. However, it can be folded down when you need to get into a garage, as it has a folding hinge.

It's a good antenna. Yes it's on the large side. I did an SWR scan with it on a tri-magnet mount on a sheet metal ground plane for testing. The SWR was reasonable over most of the Ham VHF/UHF range. On VHF MURS it was really good. On UHF GMRS it was under 2:1 on the repeater end and around 1.5:1 to 1.6:1 on the 462 end. Most radios are fine with SWR's of 2:1 or less so it should be OK. Using a different mount type might improve the SWR.

https://forums.mygmrs.com/gallery/image/268-ca-2x4sr/?context=new

I would recommend getting the optional spring bottom section.

https://cometantenna.com/wp-content/uploads/2013/09/CA-SPR-instructions-x-1.pdf

That way if the antenna wacks something it won't rip up the roof using a through hole NMO mount or damage the antenna.

For an emergency backup antenna you can also get a cheap 1/4 wave. Those are about 6 to 7 inches tall. Good for urban application getting into local repeaters and not having to worry about low clearances such as drive through windows and garages.

https://www.amazon.com/Antenna-410-490Mhz-Motorola-Kenwood-Blackbox/dp/B00L9D2N6Q

You can also make your own using some parts found at local Ham flea markets.

https://forums.mygmrs.com/gallery/image/338-cheap-14-wave-gmrs-antenna/?context=new

 

[LeeBo]

Another vote for the Comet CA-2X4SR antenna.  Really good 2m, 70cm and GMRS tx/rx.

[WRUE951]

36 minutes ago, WRXR374 said:

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.

yes, you will get a ground plane with that mount unless you our mounting it on fiberglass or plastic..  Make sure you get the hole punched out to exact size and if using a step drill bit, be very slow and careful,  They can get away from you pretty quick.   I actually prefer to using a gauged hole punch

[Socalgmrs]

Yes the ground plane has zero to do with the mount type and everything to do with location.  If your location has 8-12” all the way around it if steel or aluminum then your golden.  
 

I understand you have a garage hight issue but I’d stay as far away from the ghost antennas as possible. With that cable run, your radio and the ghost antenna you’re only going to radiate about 40w.  With something like an mx26 your going to radiate over 80w. 

[WRXR374]

3 minutes ago, WRXP381 said:

Yes the ground plane has zero to do with the mount type and everything to do with location.  If your location has 8-12” all the way around it if steel or aluminum then your golden.  

Thanks.

Any recommendations for antennas?  70cm/2M with decent GMRS coverage.

[dosw]

2 hours ago, WRXR374 said:

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.

There are not a lot of dual band options that cover GMRS while also being stubby.

The full length monster of a mobile antenna, the Comet CA-2X4SR-NMO covers 2m, 70cm, MURS, and GMRS. It even has reasonable SWR in Marine VHF and 1.25m. But it's 40 inches long. However, it can be folded down when you need to get into a garage, as it has a folding hinge.

 

Some say it's not super in GMRS range. I would say its ears aren't quite as good as my MXTA26, but that's a tradeoff you might need to make to get a multi-band antenna. I have used it to achieve impressive distances, though. I like it. But you'll have to fold it down to get into the garage.

 

There are some very good reviews for it online, and a few mixed. I guess I'm in the thumbs up group.

 

A ground plane for GMRS needs to be metal, with a radius of about 6.4 inches or more. More doesn't hurt anything. Less hampers signal propagation. It doesn't need to be electrically grounded to the antenna, it just needs to be directly beneath the antenna.

 

Ground plane radials are common for fixed (immobile) installations, while using a vehicle body for the ground plane for mobile antennas is common in that application.

[wayoverthere]

One other option that comes to mind is the tram 1181, which is rated to cover both services, plus MURS ranges (140-170 & 430-470 MHz) and is on the less expensive side (under $25).

Some members have reported good results. My experience showed reasonable SWR numbers (1.3 or so), but in terms of "getting out" it didn't seem to work so well for me.

[gortex2]

I run the Larsen NMO Tri Band antenna on my truck. It works quite well on UHF GMRS as well as VHF frequencies in the range of MURS. Its 16.5 inches tall and have no issues.

https://theantennafarm.com/shop-by-categories/antennas-mounts/mobile-antennas/vhf-uhf-dual-band/451-commercial-dual-band/219-high-gain-dual-band-antennas/8932-larsen-nmo150-450-758-detail

 

[WRQC527]

21 hours ago, WRXR374 said:

Thanks.

Any recommendations for antennas?  70cm/2M with decent GMRS coverage.

I have a Jetstream JTM3B that covers 2 meters, 70 cm and GMRS. It also doesn't need a ground plane. It's a bit long at about 40", so I use it on a Comet RS520 lip mount that I can lay down so I can pull in my garage. It does have a built-in fold-over feature but I find it easier to just loosen the mount and fold it over. You'll need an nmo to uhf adapter to run it on an nmo mount.

 https://www.ebay.com/itm/235219942423?epid=1342624531&hash=item36c4337c17:g:VwkAAOSwarpbcflx&amdata=enc%3AAQAIAAAA0Hx7RUSLBzH%2Bmrp08JcdEUeMHTGRDHp6vveWBqPE9F8gmNlwFUZ%2B2TntICLwtxxRx%2BqD5K6yy%2B9cangZOpvWMWTBH4dIgoH%2FaB8PPAkg7DGhBUTAVUT8qlRCx16%2B5COXhbEEhULJ4PujiBt5zoY6sr9yvjPHOrnMwlhOkt5vOKL%2B5w7kbcGAsOzNQ5REk43P%2F91SyLSKk0ZeQ8fUbny2gwRItB%2Fc2f8l2GrPeyutqmL6pPLqAjHRHp4PU%2F6Fjucw9oqgFZdt%2F%2F5mo3zqlRY38W0%3D|tkp%3ABk9SR4Sqke-jYw

[WRZX493]

On 9/29/2024 at 2:12 PM, dosw said:

 

A ground plane for GMRS needs to be metal, with a radius of about 6.4 inches or more. More doesn't hurt anything. Less hampers signal propagation. It doesn't need to be electrically grounded to the antenna, it just needs to be directly beneath the antenna.

 

I think you just answered a question I have, but I'll follow up to make sure:  I'm going to set up a temporary base station in my garage using a mobile unit and a magnet mount antenna.  My plan is to place the antenna on the top of a steel tool drawer cabinet that's about 2'x2'.  The cabinet top has a thin (~1/16") rubber mat on top.  Based  on the quote above it sounds like I don't need to remove that mat before placing the magnet base on the cabinet. Correct?   Thanks!

[SteveShannon]

3 minutes ago, WRZX493 said:

I think you just answered a question I have, but I'll follow up to make sure:  I'm going to set up a temporary base station in my garage using a mobile unit and a magnet mount antenna.  My plan is to place the antenna on the top of a steel tool drawer cabinet that's about 2'x2'.  The cabinet top has a thin (~1/16") rubber mat on top.  Based  on the quote above it sounds like I don't need to remove that mat before placing the magnet base on the cabinet. Correct?   Thanks!

Maybe, but keep in mind that the magnetic mount is designed to stick to the metal with a designed in separation for the rubber pad that’s part of the magnetic mount base.  Adding an additional sixteenth of an inch might be enough to reduce the effectiveness of having a ground.  Try it and see.  Or you might be able to remove the rubber pad that’s part of the mag mount base to make up for the additional rubber pad.

[WRYZ926]

I have used a magnet mount on top of a small 9" x 20" tool box inside the house and it worked fine. Getting the antenna outside of the house will definitely work better. While the antenna worked on the tool box inside, things vastly improved once I moved that antenna outside. I used a couple of shelf brackets and an old 9x13 cookie sheet to set the antenna on. I did not have a rubber mat onto of my toolbox to deal with. Try it with or without the rubber mat to see how it does.

I did this with both a dual band 2m/70cm antenna and a GMRS antenna. Using a mobile mag mount antenna is fine for a temporary setup. You will want to eventually get a base antenna up for a permanent base setup. 

[WRZX493]

49 minutes ago, SteveShannon said:

Maybe, but keep in mind that the magnetic mount is designed to stick to the metal with a designed in separation for the rubber pad that’s part of the magnetic mount base.  Adding an additional sixteenth of an inch might be enough to reduce the effectiveness of having a ground.  Try it and see.  Or you might be able to remove the rubber pad that’s part of the mag mount base to make up for the additional rubber pad.

Would I be able to tell if there’s a loss by using a power/swr meter, or only by actual comm results?

[SteveShannon]

1 minute ago, WRZX493 said:

Would I be able to tell if there’s a loss by using a power/swr meter, or only by actual comm results?

You might see a change to SWR, but comm results are the only thing that matters. 

[WRXR374]

Thank you everyone for the great responses!  I'm aware that a shorter stubby antenna is a huge compromise.  Looks like I'm getting my install done on Friday!