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.