VHF/UHF (incl. GMRS range) Mobile 1/2 Antenna

[ytechie]

I know this is a big ask, but I'm wondering if such a beast exists, that allows:

• GMRS send/receive
• Decent UHF receiving
• Decent VHF receiving
• 1/2 wave / No ground plane (will be mounting opposite of factory radio antenna near the hood)

On my previous car, I roof mounted a Comet CA-2x4SRNMO when I wanted all of those capabilities, but that was with a ground plane. It's not an option on my new truck.

If it doesn't exist, I'll stick with GMRS-only (1/4 wave on the roof or 1/2 wave hood), but I'll be a little sad that I might not be able to receive VHF decent.

[kidphc]

You didn't mention if the vhf/uhf bands were for amateur or lmr services. So I will assume for this post you are talking about amateur vhf/uhf.

To be honest not really many options and you have one of them. Gmrs is skewed to lmr/commercial frequencies. Amateur bands are just far enough from those bands, as you saw you end up with more comprimises.

Part of the comprimises on he 2x4sr (not a terrible antenna) are it doesn't get the best swr for gmrs. It's a thick not forgiving antenna, this is to try and stretch the bandwidth.

I had one mounted, where you plan on mounting. Mine was mounted to a ditch mount. The weight of the antenna shook the mount violently over any bump. So much so I went back to the 2/70b. Both the 2/70b and 2xsr, where better on the roof, on the fender mount expect about 65%-75% on the fringes of what you had on the roof. With some skewing of signals due to a pillar.

Marc had mentioned the diamond version did better with the swr. We have a thread in the amateur section.

Btw, current setup is a 5/8 wave on the back of the roof and the 2/70b on the fender. I am currently tossing up the idea (cheaper route) of putting up a vhf/uhf/7-800 antenna or a triplexer ($200+ for triplexer alone) with each band tuned.

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[SpeedSpeak2Me]

49 minutes ago, ytechie said:

I know this is a big ask, but I'm wondering if such a beast exists, that allows:

• GMRS send/receive
• Decent UHF receiving
• Decent VHF receiving
• 1/2 wave / No ground plane (will be mounting opposite of factory radio antenna near the hood)

On my previous car, I roof mounted a Comet CA-2x4SRNMO when I wanted all of those capabilities, but that was with a ground plane. It's not an option on my new truck.

If it doesn't exist, I'll stick with GMRS-only (1/4 wave on the roof or 1/2 wave hood), but I'll be a little sad that I might not be able to receive VHF decent.

Take a look at the Laird antennas, the models that end with an "N", which stands for "No Ground Plane Required".  I have the BB4502N (1/2λ) with a mag mount, and use it regularly for GMRS, and it receives UHF (amateur 70cm) just fine.  I have used it for listening to NOAA weather reports on VHF (162 MHz) and it hears "ok".  I haven't Rx tested it on local amateur 2m (144-148 MHz) to see how it does. Its primary design is for 450-470 MHz.

[Lscott]

48 minutes ago, ytechie said:

I know this is a big ask, but I'm wondering if such a beast exists, that allows:

• GMRS send/receive
• Decent UHF receiving
• Decent VHF receiving
• 1/2 wave / No ground plane (will be mounting opposite of factory radio antenna near the hood)

On my previous car, I roof mounted a Comet CA-2x4SRNMO when I wanted all of those capabilities, but that was with a ground plane. It's not an option on my new truck.

If it doesn't exist, I'll stick with GMRS-only (1/4 wave on the roof or 1/2 wave hood), but I'll be a little sad that I might not be able to receive VHF decent.

I'm looking for one too. I have an old Comet CA-2x4MB. The tested SWR was good for the above bands. I had one on my old Jeep. Other than the fold-over spring it's still in good shape. I have a spare that's never been used outdoors. If the current one is destroyed I have a backup. So far I haven't found a no ground plane antenna that works as well. Unfortunately the two I have have not been manufactured in over 20 years.

https://forums.mygmrs.com/gallery/image/259-ca-2x4mb-jeepjpg/?context=new

https://forums.mygmrs.com/gallery/image/282-ca-2x4mb-scansjpg/?context=new

I think Comet made a mistake when they discontinued this model.

I have the CA-2x4SR too. However for some reason it just doesn't work as well. Also requiring a ground plane is another negative for my usage requirements.

 

[ytechie]

Thanks all for the input. Yes, good assumption on the amateur frequencies.

I think I've narrowed my options down to these - basically optimizing for GMRS and living with whatever VHF performance I get:

1. Find a good 1/2 wave GMRS antenna and hood mount it (symmetrical to the radio antenna) - this would actually look pretty cool on the truck.
2. Go with the 1/4 wave antenna and roof mount it - I will have a power moonroof, but I think I can find enough room for this option. This would basically be the most stealth option but performance outside of GMRS wouldn't be great.

Alternatively, is there a device (is it a diplexer?) that would allow me to have a hood mount 2m/70cm antenna and the GMRS roof antenna? I even toyed with the idea of a physical switch, but something automatic would be even better.

[kidphc]

Thanks all for the input. Yes, good assumption on the amateur frequencies.
I think I've narrowed my options down to these - basically optimizing for GMRS and living with whatever VHF performance I get:

1. Find a good 1/2 wave GMRS antenna and hood mount it (symmetrical to the radio antenna) - this would actually look pretty cool on the truck.
2. Go with the 1/4 wave antenna and roof mount it - I will have a power moonroof, but I think I can find enough room for this option. This would basically be the most stealth option but performance outside of GMRS wouldn't be great.

Alternatively, is there a device (is it a diplexer?) that would allow me to have a hood mount 2m/70cm antenna and the GMRS roof antenna? I even toyed with the idea of a physical switch, but something automatic would be even better.

A diplexer will not work real well, 70cm and gmrs are too close.

With the right diplexer (most stop at 450MHz, the ones that go up to 500MHz can get expensive and sometimes difficult to find). You could use a bcn4503 (5/8th) or similar tune it to 450mhz, get most of 70cm band and all of gmrs on one antenna. Then install a separate vhf antenna.

Generally, for dual service 70cm/gmrs the 1/4 waves work really well. They are for the most part, pretty wide banded. Watch out for some of the ghost types, because of the matching network they might not be widebanded enough.

Any particular reason you are keep going with 1/2 vhf antennas?





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[ytechie]

Sounds good, I'll optimize for GMRS and live with what else I can hear.

Quote

Any particular reason you are keep going with 1/2 vhf antennas?

The stock radio antenna on the passenger side is ~32 inches. I was just hoping to keep the drivers side roughly symmetrical.

I'm attaching a pic (not mine) of someone that went with this symmetrical setup using an MFJ-1412.

This is all easier in the Ham world because I think there are a couple of dual-band antenna options covering 144-148/440-450. However, I need the best performance when I'm camping with my friends and we've settled on GMRS. I helped my dad install a 6" antenna on his truck roof.

[BoxCar]

15 minutes ago, ytechie said:

Sounds good, I'll optimize for GMRS and live with what else I can hear.

The stock radio antenna on the passenger side is ~32 inches. I was just hoping to keep the drivers side roughly symmetrical.

I'm attaching a pic (not mine) of someone that went with this symmetrical setup using an MFJ-1412.

This is all easier in the Ham world because I think there are a couple of dual-band antenna options covering 144-148/440-450. However, I need the best performance when I'm camping with my friends and we've settled on GMRS. I helped my dad install a 6" antenna on his truck roof.

 

Take a look at this antenna. It does work well on GMRS a is a 20" length. Super-Elastic Signal Stalk — Signal Stuff

[kidphc]

Take a look at this antenna. It does work well on GMRS a is a 20" length. Super-Elastic Signal Stalk — Signal Stuff

I tested (in the amateur section of the forum) it optimized for 70cm/ gmrs. Wasn't messing with the vhf side. It worked but for gmrs/70cm it's a 3/4 wave design, so it was just a shade above 1/4 as far as transmission and reception.

I would NOT recommend it for gmrs if that is the primary service. Might be good for vhf, as well almost look like a factory antenna.

My recommendations doe antennas.

1/4 gmrs/uhf for repeaters.
5/8 over 5/8 for fringe repeater and simplex. B4505 series.
5/8 b4503 series for mixed simplex/repeaters for those with clearance issues.
Slim jim roll up ( toss it as high up a tree as you can) for base camping simplex/repeater work.


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[N0GX]

What vehicle do you have that you're worried about the ground plane? I have this same Comet antenna on my Ram 1500, and my wifes Wrangler, both with aluminum hoods. It's worked on my truck right out of the box. I can cover 2 meters, on up to our farm channels at 159 Mhz easily. Same with 70cm and GMRS. On the wife's Jeep it was a little more finicky. I trimed the botton section of the antenna to raise the resonant point on UHF to have coverage on 70cm, and GMRS. Doing this appeared to have no effect on VHF, or if it did, it didn't matter because it's so broadbanded, because I can still cover 144-159 and then some, easily.

[wrci350]

2 hours ago, kidphc said:

With the right diplexer (most stop at 450MHz, the ones that go up to 500MHz can get expensive and sometimes difficult to find). You could use a bcn4503 (5/8th) or similar tune it to 450mhz, get most of 70cm band and all of gmrs on one antenna. Then install a separate vhf antenna.

I have a diplexer and a triplexer and they are both good to 500 MHz or above.  I checked The Antenna Farm's website and all the ones they carry that are VHF/UHF split (no HF or 220) go to at least 470 MHz, with most going to 540.  Cost is around $50 or so 

[kidphc]

I have a diplexer and a triplexer and they are both good to 500 MHz or above.  I checked The Antenna Farm's website and all the ones they carry that are VHF/UHF split (no HF or 220) go to at least 470 MHz, with most going to 540.  Cost is around $50 or so 

Good to know. A lot of stuff just barely works for gmrs and the other frequencies.

I will have to check again.

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[ytechie]

10 hours ago, N0GX said:

What vehicle do you have that you're worried about the ground plane? I have this same Comet antenna on my Ram 1500, and my wifes Wrangler, both with aluminum hoods. It's worked on my truck right out of the box. I can cover 2 meters, on up to our farm channels at 159 Mhz easily. Same with 70cm and GMRS. On the wife's Jeep it was a little more finicky. I trimed the botton section of the antenna to raise the resonant point on UHF to have coverage on 70cm, and GMRS. Doing this appeared to have no effect on VHF, or if it did, it didn't matter because it's so broadbanded, because I can still cover 144-159 and then some, easily.

My 2023 Superduty shows up any day now. It's built and being shipped from the factory.

I'm not concerned about the type of hood, it's that it will be mounted right at the corner of the hood by the cab. In one direction, I'll have the cab blocking it. Another direction, there will be no ground plan. For signal going forward and to the right, it would be a fantastic ground plane.

I'm including a top down picture with "x" marking the spot where I would mount an antenna. That same pic shows that I *might* be able to install an NMO mount on the roof between the moonroof and the bed light. My plan is to remove that light and see how much room is in there.

[SpeedSpeak2Me]

26 minutes ago, ytechie said:

My 2023 Superduty shows up any day now. It's built and being shipped from the factory.

I'm not concerned about the type of hood, it's that it will be mounted right at the corner of the hood by the cab. In one direction, I'll have the cab blocking it. Another direction, there will be no ground plan. For signal going forward and to the right, it would be a fantastic ground plane.

I'm including a top down picture with "x" marking the spot where I would mount an antenna. That same pic shows that I *might* be able to install an NMO mount on the roof between the moonroof and the bed light. My plan is to remove that light and see how much room is in there.

There is a company, Diesel Power Products, that makes an NMO mount that sandwiches between the cab and HMSL (High Mount Stop Light).  Josh from Ham Radio Crash Course installed one on his new 2023 Ford F-150 Lightning.  They're not cheap, at $360.  They also make a dual NMO for $436.

https://www.dieselpowerproducts.com/p-bulletproof-diesel-third-brake-light-antenna-mount-17-21-superduty?variant_id=19192&gclid=CjwKCAiAmJGgBhAZEiwA1JZolr5krfYYI3FLAQpq4JQItmmOf3GdAd-GxnoAgbdszuyTFw5P9gPShRoC8y0QAvD_BwE

 

[gortex2]

Drop a NMO in between sun roof and HMSL and be done with it. I installed a UHF and VHF in that location for a SAR member. His is a GM Denali but same setup. Running 1/4 wave on both with no issues at all. 

[Sshannon]

6 hours ago, SpeedSpeak2Me said:

There is a company, Diesel Power Products, that makes an NMO mount that sandwiches between the cab and HMSL (High Mount Stop Light).  Josh from Ham Radio Crash Course installed one on his new 2023 Ford F-150 Lightning.  They're not cheap, at $360.  They also make a dual NMO for $436.

https://www.dieselpowerproducts.com/p-bulletproof-diesel-third-brake-light-antenna-mount-17-21-superduty?variant_id=19192&gclid=CjwKCAiAmJGgBhAZEiwA1JZolr5krfYYI3FLAQpq4JQItmmOf3GdAd-GxnoAgbdszuyTFw5P9gPShRoC8y0QAvD_BwE

 

As you say, they’re not cheap, but compared to the pricing of a new truck the pricing is minuscule.  

[kidphc]

One of my fireman buddies has about 4 nmos in the camper top on his super duty.

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[ytechie]

1 hour ago, gortex2 said:

Drop a NMO in between sun roof and HMSL and be done with it. I installed a UHF and VHF in that location for a SAR member. His is a GM Denali but same setup. Running 1/4 wave on both with no issues at all. 

My hope is that there is room to drill a hole between that light and the sunroof. I would have a proper ground plane in every direction. I already have the drill bit.

[ytechie]

BTW, here the video that @SpeedSpeak2Me was referencing indirectly - thanks!: 

 

[WRUU653]

1 hour ago, ytechie said:

BTW, here the video that @SpeedSpeak2Me was referencing indirectly - thanks!:

Thanks for putting that up here. I like his videos but had not seen this one. This product may be pricey but it sure is a clean install and that would be worth it to me. I have a question about the version that has two antenna mounts, is there any issue with having a ham antenna and a GMRS antenna so close to each other? 

[kidphc]

Thanks for putting that up here. I like his videos but had not seen this one. This product may be pricey but it sure is a clean install and that would be worth it to me. I have a question about the version that has two antenna mounts, is there any issue with having a ham antenna and a GMRS antenna so close to each other? 

Yes, mobile installs are all comprimises. You want about 1/2 wave length of the longest minimal separation, if you can. But that is not always possible.

I have about 8 feet from my 2m/70cm antenna and gmrs/70cm antenna. I noted the other night even when transmitting at 5watts on the 2m/70cm antenna (I was using 70cm fusion at the time). It was tripping out the xtl5k (gmrs/70cm) really badly. Like opening squelch on a frequency, i was scanning gmrs repeaters on the xtl5k. From my calculations, it was about 30MHz difference.

The physical radios are some 6 feet apart. One in the glove box. The other on the third row molle panel.

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[AdmiralCochrane]

Deacdes ago I discovered by accident that my 11 meter equipment propagated best across my ground plane.  Physical heights of the vehicle sections did not seem to affect the signal strength as much as placement relative to the ground plane. This was determined with a signal strength meter. 

In layman's terms, propagation in all directions was optimized when the antenna was centered on the vehicles.  Propagation straight foreward was best when centered on the rear of the vehicles.  When placed on a rear corner, the strongest signal was observed foreward to the opposite corner. 

[ke6atj]

I have had great luck with this comet antenna on a NMO hood mount on my Toyota Tacoma...  Works awesome on both vhf/uhf ham and GMRS.

Comet B-10 NMO

 

https://a.co/d/59paNDT

 

 

[WRWD707]

I have had good luck with this Diamond antenna mounted on the front fender. It has very usable SWR values on VHF, UHF, and GMRS frequencies when measured on a NanoVNA.

https://diamondantenna.net/az507rsp1.html


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[ytechie]

I got the truck, took off the rear light/camera on the cab. There's only a tiny cavity behind that light. I sent in my borescope to look behind the metal "wall" in there, and it's really messy behind that with the sunroof. Basically, I've ruled out the option of drilling a hole in the roof.

I've narrowed it down to 2 options:

1. Use the NMO mount that goes on the rear light. I would use my 1/4 wave, 6" tall antenna (I don't want to risk hitting the antenna on my garage door). The downside is the cost of the mount ($359!) and the fact that I'll only have half a ground plane (forward-facing essentially).

2. Use the fender mount and find a good 1/2 wave GMRS antenna that doesn't require a ground plane.

Feel free to weigh in. I'm curious if you think one would perform better over the other.