Antenna Questions

[WSGI548]

So I have currently been using an UV5G plus a UT72G stuck to a pizza pan on the end of an extension pole at about 12ft high. This has worked ok for simplex to a buddy about 3 miles away, as well as hitting a couple repeaters, though a little scratchy on the farther repeater(30miles +/-). Kind of a pain to set up, but it works. I currently set it up and down when I want to goof around.
 

I am wanting to start upgrading things a little with the ultimate goal being a base, probably 25 watt, lmr400, and a better antenna. Due to how my house is, shallow backyard with overhead power lines directly over the back fence, I was looking at doing an umbrella base with an extension pole so I can raise and lower when not in use. I  live in the desert, so no trees, most houses 1 story, but high winds during the year.

So my question is primarily about antennas. I understand dbi vs dbd and gain, but what, if any, is the difference between a base (ie: Comet Ca-GMRS) vs a nmo mobile (MXTA26) with a ground radial adapter. I ask because it seems like the base/repeater style antennas are heavy and large , vs the mobile antennas are light and slim. I was concerned about 2-3 lbs antenna on a 16-20 ft extension pole vs a 1/2 lb mobile, thinking about wind load, or am I over thinking this. If all else is equal, is there a difference between a 6 dbi Base antenna vs a 6 dbi Mobile antenna?

 

Any help or insight is appreciated!

 

(sorry if this has been asked before. I tried searching, but didn’t find much)

[BoxCar]

16 hours ago, WSGI548 said:

So I have currently been using an UV5G plus a UT72G stuck to a pizza pan on the end of an extension pole at about 12ft high. This has worked ok for simplex to a buddy about 3 miles away, as well as hitting a couple repeaters, though a little scratchy on the farther repeater(30miles +/-). Kind of a pain to set up, but it works. I currently set it up and down when I want to goof around.
 

I am wanting to start upgrading things a little with the ultimate goal being a base, probably 25 watt, lmr400, and a better antenna. Due to how my house is, shallow backyard with overhead power lines directly over the back fence, I was looking at doing an umbrella base with an extension pole so I can raise and lower when not in use. I  live in the desert, so no trees, most houses 1 story, but high winds during the year.

So my question is primarily about antennas. I understand dbi vs dbd and gain, but what, if any, is the difference between a base (ie: Comet Ca-GMRS) vs a nmo mobile (MXTA26) with a ground radial adapter. I ask because it seems like the base/repeater style antennas are heavy and large , vs the mobile antennas are light and slim. I was concerned about 2-3 lbs antenna on a 16-20 ft extension pole vs a 1/2 lb mobile, thinking about wind load, or am I over thinking this. If all else is equal, is there a difference between a 6 dbi Base antenna vs a 6 dbi Mobile antenna?

 

Any help or insight is appreciated!

 

(sorry if this has been asked before. I tried searching, but didn’t find much)

Base station antennas will have wind load information as it is critical in many installations. It may not be readily available on a retailer's site, but the manufacturer will list it in their brochures for the product.

Yes, there is a difference between a mobile and base antenna. The radiation patterns will most likely vary with the base having a more defined pattern closer toward the horizon. The antenna length also comes into play as most mobiles are base loaded while base antennas tend to be center loaded.

[GrouserPad]

548, that is awesome improvised setup. Props to you for getting on the air. Crutches and all  

[SteveShannon]

On 2/2/2025 at 3:37 PM, WSGI548 said:

If all else is equal, is there a difference between a 6 dbi Base antenna vs a 6 dbi Mobile antenna?

6 dBi is 6 dBi, but with the base antenna you usually have a larger radiator and need less inductance. Higher inductance causes steeper troughs and narrower dips in SWR (called high Q). That means that SWR might be lower across a wider range of frequencies. Also, a larger radiator is usually better than a smaller radiator, if it's tuned correctly, because it has more area to gather RF and because it sticks further up. 

But in actuality, you might never notice a difference. If what you have works for you, I don't think I would change it.

And I agree with @GrouserPad, nice setup!

[WSGI548]

Thanks guys!

It does work pretty well, but is more of a “lets see what I got that will work before we ask the wife for more money for nicer setup”.  
It was definitely an inexpensive way to get a HT some more range. Luckily I am at about 600ft asl but the big repeater is 30 miles away at 8600asl so I can clear the mountains between me and it(about 3000-3500). I will probably go to an umbrella base with a 16-24foot extension pole, maybe with something like a Comet 2x4sr on top. That would give me an easy 4-7 feet taller, but still maintain a fairly light antenna on top. Then I need to decide whether I want a 25w, or 40-50w mobile, but paying 3-4 times the price for about 10% more signal kind turns me off.

Here is the plot for the big repeater I can hit on 5w. I am the blue pin. But this repeater has huge range. We heard a guy last weekend hit it with a 7 element yagi and 50watts iirc from N. Las Vegas, about 110 miles away!! He was scratchy, but readable.

[GrouserPad]

Can you enlighten me as to what app that is showing your “radio path study” ? Looks cool. 

[SteveShannon]

2 minutes ago, GrouserPad said:

Can you enlighten me as to what app that is showing your “radio path study” ? Looks cool. 

It’s a website called scadacore.com. The tool is RF Line of Sight.  https://www.scadacore.com/tools/rf-path/rf-line-of-sight/
 

[GrouserPad]

6 minutes ago, SteveShannon said:

It’s a website called scadacore.com. The tool is RF Line of Sight.  https://www.scadacore.com/tools/rf-path/rf-line-of-sight/
 

Nice! After messing with it on my cell I think I’ll have to fiddle with it on a home computer. The site is hard to navigate with an iPhone. 

[WRYZ926]

The Comet 2x4SR is an excellent multi band mobile antenna. Since you said that you can get into that repeater with an HT then yes going to 20/25 watt radio will improve things. Stepping up to a 40/50 watt radio will definitely improve things.

I have a repeater that is about 50-55 miles away that I can get into with a 20 watt radio but the other people hear a lot of static on my transmission. Everyone can hear me clearly when I use a 50 watt radio.

Basically you have to quadruple the power output to notice any big difference.

I am still going to suggest going with the Comet CA-GMRS for a few reasons. One is that it is light enough at only 2 pounds. Second, it has a wind load of 135 mph. And you can also get rid of the pizza pan that will definitely act as a sail in high winds.

The CA-GMRS is lists at 5.5 dBi which is 3.4 dBd. The 2x4SR is listed at 6.2 dBi ( 4.1 dBd). Plus you would still have to use a metal pan for your ground plane which is a wind sail.

I can't tell in your photo if your roof is fairly flat or has a ridge. Getting your antenna up some more and going with a mobile radio will improve performance for you.

[SteveShannon]

19 minutes ago, GrouserPad said:

Nice! After messing with it on my cell I think I’ll have to fiddle with it on a home computer. The site is hard to navigate with an iPhone. 

It’s a very good tool, but while line of sight is great for vhf and uhf radio work, it’s not absolute.  For instance, here’s how it analyzed the path between my friend’s house and my cabin.  He and I can communicate via 2 meter simplex, but according to the chart we shouldn’t expect to:

[WSEZ864]

The Scadacore site is interesting, but without antenna height input, I don't think it's as accurate as it could be.

NVM, I just figured out how to input antenna heights.

Edited 40 minutes ago by WSEZ864
Correction