Antenna height question

[WRTK502]

Hello to all as I am a bit new here, but not entirely new to GMRS. I had a question related to the Antenna height.

 

So I personally use GMRS in my adventure vehicle for Touring/Overlanding. I currently have the Midland MXT575(50 Watt Radio) in it and I can say that is a nice radio with the power. I also have the Midland Ghost Antenna as well which is a 3 dB type Antenna. It is mounted on the roof to help clear any instructions on the vehicle, but here are a few things on the roof that are kinda in the way(recovery boards, fuel cans, water tanks and whatever else I may throw up top). 

 

Something I have been looking at and considering is the new Midland Highland and Canyon Edge 3 dB Antenna's(28-28.5 inches tall over the 3.5 inch Ghost). If anything they would be taller and still be mounted on the roof. I would also make sure to have the folding base for when I don't have it in use. My only question is would there be any benefits other than not having to worry about obstructions from item on the roof? Again I would be staying with a 3 dB so the projection pattern and range should be the same if not mistaken.

 

Thanks in advance 

[marcspaz]

I think one thing to be aware of is, the fold down feature is for parking in garags and under covers, not driving. You cannot drive the vehicle with the antenna folded over. The antenna wasn't designed to be used/stored in that condition. Eventually it's will break. The spring will eventually stop pulling the antenna into the socket. The connection and coax will start to fill with water. There will be all kinds of issues. And that is assuming you found a way to stop it from spinning and flopping around, because it free-spins when its laying down.  If you don't want it up when not in use, you have to remove it and put a weather tight cap on the mount to keep it clean and dry.

 

Next, the bigger antennas are just a bunch of small antennas stacked on top of each other and phased, to create a specific radiation pattern. Typically, elongated out to the horizon, deadening elevation above a certain degree above the horizon... usually 30⁰ or less. They also tend to be somewhat directional, depending on where they are physically installed. They are great in places with no significant elevation changes, but in hilly and mountainous areas, they are not a good choice. 

 

So, if it has benefits or is detrimental will be based on where you are using it and where the person you are trying to communicate with is located.

 

[OffRoaderX]

Bigger and higher/above any (metal) obstructions will always be optimal... But unless you are trying to bounce your signal off the moon - ie; you are just talking with your friends on the road and/or using repeaters within 5, 10, 20 miles or so, I would question whether swapping out the antenna and having to fold it up/down all the time would be worth the money or the hassle.

TL;dr: If you are some kind of radio dork that obsessively requires every tiny maximum bit of performance, whether or not you'll ever notice, and at any expense, then get the bigger antenna.  If however you are a normal person that just needs to talk with your group while traveling, then your Ghost antenna is just fine. 

[AdmiralCochrane]

I am aware of all the problems Marc points out, but so far I have had no failures of fold overs.  I was aware of all those potential problems when I selected them and have been prepared to replace them and the coax if/when needed.  Very lucky so far.

[tcp2525]

3 hours ago, OffRoaderX said:

TL;dr: If you are some kind of radio dork that obsessively requires every tiny maximum bit of performance, whether or not you'll ever notice, and at any expense, then get the bigger antenna.  If however you are a normal person that just needs to talk with your group while traveling, then your Ghost antenna is just fine. 

I definitely agree! The ghost antenna is perfect for off-roading and can withstand the force of relatively small low hanging branches. Now, if you're a serious off-roader like me you really need to step up your game and get a higher quality ghost antenna. This is why I use this heavy duty model manufactured by Bird. It's rated at 50 watts and delivers the perfect antenna radiating performance, about equal to the Midland. The best part is the durability, with its DIN connector that adds extra holding power to the vehicle so it can withstand branch strikes up to 6" in diameter.

On a more serious note for the OP. If you're traversing through terrain where you're going to be grazing a lot of tree branches you might want to consider the famous and much loved 1/4 wave whip. It's perfect for rough service, just bend it back to shape after a fun day on the trail. It breaks, replacements are cheap. And you'll get better range than the ghost antenna you're using now.

[OffRoaderX]

39 minutes ago, tcp2525 said:

This is why I use this heavy duty model manufactured by Bird

Don't be mean, and if you are insinuating that the ghost antenna functions as an antenna the same as a dummy-load, you would be very, very wrong.

[SteveShannon]

2 minutes ago, OffRoaderX said:

Don't be mean, and if you are insinuating that the ghost antenna functions as an antenna the same as a dummy-load, you would be very, very wrong.

He’s just not using LMR 600 to connect to it.

[tcp2525]

57 minutes ago, SteveShannon said:

He’s just not using LMR 600 to connect to it.

Nope, this is strictly a task for RG-8x.

[WRYZ926]

I know @OffRoaderX has compared the Midland and Melowave ghost antennas against each other and also against other antennas. 

I also tested the Melowave Shadow (ghost) antenna against my Tram 1184 and the Nagoya UT-72G. The Melowave outperforms the Nagoya. The Tram is definitely the best out of those three.

You can run a longer antenna if you want. You will have to worry about the longer antennas getting damaged easier and also have to deal with them if you park in a garage.

[WSGK834]

Here is something to consider: GMRS is in a UHF band and RF wave is expected to be in a vertical polarization. Bending antenna will produce all kinds of polarization from 90 to 0 degree. This alone will lead to a both reception and transmission getting a very  significant penalty.  
And don't forget, using 15ft of RG8x at GMRS frequency already leads to a 20% of power loss. 

Best antenna would be vertical, unobstructed and at least 1/4 wave length, with a good "ground plane", so mounting an antenna at the edges of a car would be a problem too. 

Physics is brutal, no compromises

Anton

[marcspaz]

8 minutes ago, WSGK834 said:

Here is something to consider: GMRS is in a UHF band and RF wave is expected to be in a vertical polarization. Bending antenna will produce all kinds of polarization from 90 to 0 degree. This alone will lead to a both reception and transmission getting a very  significant penalty.  
And don't forget, using 15ft of RG8x at GMRS frequency already leads to a 20% of power loss. 

Best antenna would be vertical, unobstructed and at least 1/4 wave length, with a good "ground plane", so mounting an antenna at the edges of a car would be a problem too. 

Physics is brutal, no compromises

Anton

 

A great example of the loss you are talking about with bending... for those who have longer steel whip antennas on their vehicle, if you are outside the edge of 100% coverage of a repeater (or a friend you are talking simplex to) listen to how broken and scratchy the receive sounds, and then pullover an see just how much the signal improves.  Some of it is because varying obstacles between the radios is no longer occurring, but most of it is because the antenna is no longer moving around in the wind.

[Soggybottomboy]

Damn!

Ya'll are smart. Great info in this thread.

SBB

 

[OffRoaderX]

1 hour ago, Soggybottomboy said:

Damn! Ya'll are smart

I know.

[marcspaz]

3 hours ago, Soggybottomboy said:

Damn!

Ya'll are smart. Great info in this thread.

SBB

 

 

1 hour ago, OffRoaderX said:

I know.

 

And humble, too!

[WSGK834]

So, I've been thinking: the idea is to have an antenna that is as short as possible and has low wind resistance , while offering high gain and vertical polarization and be omni directional. 

There is a well forgotten antenna design type that will be very short for 70cm/GMRS band , horizontal by nature, but produces vertical polarization and up to 4db gain. 

It's called slot antenna and was invented initially for a TV transmission.

Here is how it looks like for 2m band, square side is 16.5 inches, 3 inches tall.

 

For 65cm GMRS band it will be  proportionally smaller,  likely the side of the square will be around 7 inches, it will be around 1.5 inches tall.

Expected gain around 3db ( twice the power ) in the middle of the band

 

Slap it on the top of the car using  neodymium magnets. 

Enjoy.

This will need to be calculated and tested. 

Some members of this community could make these and offer for sale on this site, for example.

Metal type does not make any difference. You can use aluminum or , if you feel fancy, aluminium. Copper or steel will work just as well. 
Square shape offers better omnidirectional properties, but you can make it look like a bat or a flower.  

 

Is there any interest ? I should be able to figure out dimensions, but will need help building prototypes. 

 

I'm in MN.

Anton

 

 

[AdmiralCochrane]

Radiation pattern is counterintuitive until you realize that the electrical and magnetic features of this type of antenna are reversed.

[WRQC299]

So, I've been thinking: the idea is to have an antenna that is as short as possible and has low wind resistance , while offering high gain and vertical polarization and be omni directional. 
There is a well forgotten antenna design type that will be very short for 70cm/GMRS band , horizontal by nature, but produces vertical polarization and up to 4db gain. 
It's called slot antenna and was invented initially for a TV transmission.
Here is how it looks like for 2m band, square side is 16.5 inches, 3 inches tall.
http://files.mygmrs.com/forums/monthly_2025_01/image.png.e5ff9b70892012d69d05c2843f173606.png
 
For 65cm GMRS band it will be  proportionally smaller,  likely the side of the square will be around 7 inches, it will be around 1.5 inches tall.
Expected gain around 3db ( twice the power ) in the middle of the band
 
Slap it on the top of the car using  neodymium magnets. 
Enjoy.
This will need to be calculated and tested. 
Some members of this community could make these and offer for sale on this site, for example.
Metal type does not make any difference. You can use aluminum or , if you feel fancy, aluminium. Copper or steel will work just as well. 
Square shape offers better omnidirectional properties, but you can make it look like a bat or a flower.  
 
Is there any interest ? I should be able to figure out dimensions, but will need help building prototypes. 
 
I'm in MN.
Anton
 
 

Have you seen this YouTube video about prototyping a slot antenna for ham and gmrs?

Sent from my iPhone using Tapatalk

[tcp2525]

4 hours ago, WRQC299 said:

Have you seen this YouTube video about prototyping a slot antenna for ham and gmrs?

 

 

Sent from my iPhone using Tapatalk

Now that is pretty cool and looks like a fun project to experiment with. This is something I definitely want to build out of aluminum plate and see how well it performs on mobile GMRS. Thanks for posting.

[WRYZ926]

Ham radio rookie has some interesting designs. His latest one is using faraday clothe on a fiberglass pole as a vertical HF antenna. And his faraday cloth j pole antennas are well built and work pretty good.

I have seen others make slot antennas out of old satellite dishes before but never seen one made flat like the one above. It would be interesting to see a flat and horizontal slot antenna looks like in one of the modeling programs.