An example of how little RF output power matters

[SteveShannon]

Yesterday a guy called out on our 2 meter repeater. He was driving up I-15 and had a pretty good signal. He said he was at Barret, which is an exit from I-15 that’s about 70 miles away from Butte. I asked him what radio and antenna he was using. He was using a Baofeng UV5R connected to a 5/8 wave mobile antenna.

During our 2 meter net tonight a friend checked in from Bozeman using his handheld radio (4watts output).  His signal was crystal clear. Bozeman is 80 miles away from our repeater here in Butte and on the opposite side of the continental divide. I assumed he was using a mobile antenna at his house, but he was not. He was using the factory handheld antenna.
After the net he asked if we would listen while he transmitted at low power, 50 milliwatts. He transmitted and although the signal to noise was audibly worse (static in the background) his transmission was very easy to hear and understand. 80 miles on 1/20th of a watt. 
 

[WRYZ926]

A good antenna and coax along with good line of sight makes more of a difference.

I'm 22.5 miles away from our repeater. I did some tests with my faraday clothe j pole antenna using couple of HT's With the top of the j pole at 21 feet I got into the 2m, 70cm, and GMRS repeaters just fine from my yard. I was full quoting into the 2m repeater. I had a slight bit of noise on GMRS and a little bit more on 70cm.

I decided to go inside and test with my base radios. I am using a Comet GP9 and Comet CA-712EFC. both antennas are at 22 feet at their base. I turned my 2730 and KG-1000G down to low power. Low power on both radios is around 5 watts. I did a little better on GMRS and 70cm since the base antennas have more gain. But 5 watts was enough to get into all three repeaters and be completely understandable.

I've talked on 2m simplex with a couple of guys that are 19 miles away. One uses a Comet GP-9 and the other uses a yagi antenna. The one with the yagi is running a Kenwood TS-2000 and the other is running an Icom IC-9700. I can hear the one using the yagi when he is transmitting at 1 watt as long as he has his antenna pointed directly at me (with a bit of noise). The other running the GP-9 has to turn his power up to at least 10 watts for me to hear him clearly above the noise. I have a clear line of sight to both but just barely to the guy running the GP-9.

We have to pretty much run at least 25 watts to talk and be heard clearly on 70cm and GMRS simplex. A third guy lives 24 miles away and it takes us both running 40-50 watts to talk on GMRS simplex.

The trees and rolling hills around us definitely has its effect.

[WRUU653]

A week ago I took my morning coffee out to the back patio, I had my KG-935H (stock antenna) on scan of ham repeaters and simplex just incase there was some early morning chatter. I heard someone calling out CQ on 2 meter simplex (146.580 I think). He and another station were doing a SOTA about 45 miles away from me. It was great line of sight so I guess it shouldn't be a complete surprise that I heard them. I responded with my call sign and "can you hear me" thinking they wont hear this. I was amazed at how clear I could talk to them on an HT (5-9 reports both ways). You would have thought they were 45 feet away not 45 miles.  

[marcspaz]

Yep... height is might. 

I also found that once terrain closes the path, there is no amount of power that can help. I was testing and 2m repeater. I was using 5w on my mobile. I dropped below the horizon by just a few feet. I inched back into range, and then rolled at an idle until I lost the repeater. Switched on the amp to 300w and it made exactly zero difference. 

 

Just how it is. Talk to someone in space with 1w, can't talk 1 mile through or around a hill or obstructions with 100,000w.

 

NVIS.  Now that's my favorite. 250-300 miles of continuous local coverage with 1 or 2 watts. Good times.

[WRUE951]

i have talked to hikers on Mt. Whitney using HT's on my repeater several times. As a crow flies, that's about 70 Miles line of site.  They come in loud and clear.. 

[WRHS218]

I heard an interesting analogy, the other day, regarding radio signals (the guy was talking specifically about HTs).

Imagine you are in the desert after dark and you have a buddy who is 1 mile away with an unobstructed line of sight. He turns on his flashlight and points it in your direction. You can see the light clearly. Now imagine you are in a forest and your buddy is 1 mile away with the same flashlight with the only obstruction being trees. Chances are you won't see the light and if you do see it, the light is severely diminished.

I had never thought of it that way, and it is a useful mental visualization for me.

 

[WRYZ926]

@WRHS218 that is a good analogy.

[WSEZ864]

19 hours ago, WRYZ926 said:

@WRHS218 that is a good analogy.

Yes, that IS a good analogy, and it pays to think of radio signals as behaving more and more like light as frequencies increase.

[WRYZ926]

I find that I have the exact same dead spots when mobile on our 70cm and GMRS repeaters. The 2m/70cm antennas are at 900 feet and the GMRS antennas are at 400 feet on the same tower. We get an average of 30-35 mile radius of coverage from our 70cm and GMRS repeaters. Our 2m repeater has around 80-85 mile radius of coverage. That shows you the difference between VHF and UHF

The UHF dead zones are either in low spots or where trees, especially cedar and pine trees, are located close to the roads.

[73blazer]

Heavy trees/forest put the hurt on it. Power helps in heavy cover. I've tested numerous HT's and none go past 2mi radio to radio with both being in the same many square miles heavy forest. at 3w 0.75mi is about all you can hope for. at 5 or 5.5w 1.5-1.75mi is what you get add a good antenna and you can get to 2mi or a little more. Out in the open, or in most sparsely populated with homes or trees areas, doesn't matter. You can get to the ISS on .5w or less. Heck, the Voyager space craft used 23w transmitters at launch in the 70's, , now currently tuned down to about 2.5w to save power and 16billion miles from earth in interstellar space, no problems. You don't need much when nothing's in the way!

[WRUE951]

41 minutes ago, 73blazer said:

Heavy trees/forest put the hurt on it. Power helps in heavy cover. I've tested numerous HT's and none go past 2mi radio to radio with both being in the same many square miles heavy forest. at 3w 0.75mi is about all you can hope for. at 5 or 5.5w 1.5-1.75mi is what you get add a good antenna and you can get to 2mi or a little more. Out in the open, or in most sparsely populated with homes or trees areas, doesn't matter. You can get to the ISS on .5w or less. Heck, the Voyager space craft used 23w transmitters at launch in the 70's, , now currently tuned down to about 2.5w to save power and 16billion miles from earth in interstellar space, no problems. You don't need much when nothing's in the way!

Actually, its all about the antenna..   I do a lot of RV traveling with 3 other RV traveling friends.  We all have the same 40W mobile radios.  Two of us have the normal UHF whip antenna two have the Midland Ghost antenna..  When we travel in areas like Route 1 in the Redwoods,,  we are lucky to get out two miles if that..  The two of us with the whips do a lot bettter in distance than the two with the ghost antenna..  Get out in open space and the chost antnnas work as good as the whips...

[Blaise]

1 hour ago, 73blazer said:

Heavy trees/forest put the hurt on it.

This is the use case.

If there's a lot of "semi-permeable" terrain between units (trees, foliage, wood structures, etc.), power increases range proportional to the square root of the power increase, which sounds useless, but it means a 5 watt radio should transmit more than 50% farther than a 2 watt radio, all other things being equal.  That said, I'm generally operating inside the largest "forever wild" forest preserve in the US, so I may focus on this more than most!

[Jaay]

On 9/30/2025 at 8:40 AM, WRUU653 said:

A week ago I took my morning coffee out to the back patio, I had my KG-935H (stock antenna) on scan of ham repeaters and simplex just incase there was some early morning chatter. I heard someone calling out CQ on 2 meter simplex (146.580 I think). He and another station were doing a SOTA about 45 miles away from me. It was great line of sight so I guess it shouldn't be a complete surprise that I heard them. I responded with my call sign and "can you hear me" thinking they wont hear this. I was amazed at how clear I could talk to them on an HT (5-9 reports both ways). You would have thought they were 45 feet away not 45 miles.  

That stock antenna is surprisingly efficient when measured on a Analyzer ! 

[GreggInFL]

2 hours ago, 73blazer said:

Heavy trees/forest put the hurt on it. Power helps in heavy cover. I've tested numerous HT's and none go past 2mi radio to radio with both being in the same many square miles heavy forest. at 3w 0.75mi is about all you can hope for. at 5 or 5.5w 1.5-1.75mi is what you get add a good antenna and you can get to 2mi or a little more.

These are the numbers we had when a group of neighbors tested HTs in our wooded area in preparation for hurricane season. We were able to coordinate passing messages over a 2.7 miles distance but could not cover that distance directly. On a whim I hooked my 25W mobile to a good antenna atop a 16' tripod mast in a central location and could connect with everyone.

[WRYZ926]

Power has to be increase by 4 times to see any actual noticeable improvement. So yes going from 5 watts to 20 watts will show an improvement. For a 50 watt radio, you would have to increase the power output to 200 watt, and for a 100 watt radio, increase the output to 400 watts.

You definitely won't see improvements going from 5 watts to 10 watts or 40 watts to 50 watts. Going from 25 watts to 50 watts can help get though/around obstructions but it will not get you any farther range.

A good antenna with good coax will make the biggest difference. The other thing that makes an improvement is getting the antenna up in the air.

As I mentioned in an earlier post, using my faraday clothe j pole with the top up 21 feet with my hand held made a big difference. 

 

[AdmiralCochrane]

25 watts to 50 watts often makes a difference in clarity and readability even when it doesn't push a dB meter very much.

 

All in all I am still a Tim Allen fan

[WRYZ926]

6 minutes ago, AdmiralCochrane said:

25 watts to 50 watts often makes a difference in clarity and readability even when it doesn't push a dB meter very much.

Yes it will. But don't expect your range to increase much.

I tested that with a repeater 50 -55 miles away from me. I could get into it at 25 watts but others had a hard time fully understanding me. They could hear me clearly once I went to 50 watts. But that still didn't get me any more range past that.

[LeoG]

Probably because you can't get through the mountain that repeater is on.

[WRTC928]

18 hours ago, WRYZ926 said:

You definitely won't see improvements going from 5 watts to 10 watts or 40 watts to 50 watts.

I respectfully disagree. I occasionally see an improvement in penetration of foliage going from 5 watts to 10 watts. Just last week, I had a RT97L repeater set up while some friends and I were operating in undulating terrain, some of which was heavily wooded. There were places where 5 watts wouldn't open the repeater, but 10 watts would get through pretty well. They were generally areas where the terrain would have made transmission borderline, and the trees apparently put the last nail in the coffin. That's a pretty specific set of circumstances, but I don't think you can make a blanket statement that you won't see an improvement going from 5 to 10 watts. That's why I like to have the option to increase the wattage, although I rarely run a radio at maximum power. Even my 50 watt mobiles are usually running 12-15 watts. 

[WRYZ926]

@WRTC928 I'm glad to hear that you did see an improvement going from 5 watts to 10 watts. I have not seen any improvement going from 5 watts to 10 watts. I did see a difference going from 25 watts to 50 watts.

Generally speaking, you do have to quadruple the power output to see a noticeable difference that you can actually hear. Quadrupling the power gives a gain of 6 dBd/ one S unit

[WRTC928]

3 minutes ago, WRYZ926 said:

@WRTC928 I'm glad to hear that you did see an improvement going from 5 watts to 10 watts. I have not seen any improvement going from 5 watts to 10 watts. I did see a difference going from 25 watts to 50 watts.

Generally speaking, you do have to quadruple the power output to see a noticeable difference that you can actually hear. Quadrupling the power gives a gain of 6 dBd/ one S unit

I know that, but radio waves don't always follow the rules we were taught.  Sometimes it's worth bumping up the power to see if it helps, especially if you think there may be partial attenuation due to obstruction. 

Also, of course, the difference may have had to do with the fact that it was the repeater that had to "hear" the signal, not a human ear. If I understand correctly, sometimes a repeater may be an "all or nothing" phenomenon; i.e., just above the threshold of detection does pretty well while just below means it doesn't get picked up at all. HT-to-HT in that location is pretty much useless, so I'm not sure how I'd test that hypothesis.

[WRXB215]

From my house, on 4 watts, I can't activate the GMRS repeater I use. With 8 watts I can. It's the difference between talking to someone and not.

[amaff]

Adding power can definitely help in those real edge case scenarios.
But most of the time, without increasing by an order of magnitude? Yeah, not really much noticeable difference.

[LeoG]

Whatta ya gonna trust?  That S meter or your lying ears?

 

[WRTC928]

1 hour ago, WRXB215 said:

From my house, on 4 watts, I can't activate the GMRS repeater I use. With 8 watts I can. It's the difference between talking to someone and not.

Again, I wonder if that may have something to do with it being a repeater. Above the threshold of reception gets retransmitted, below the threshold of reception gets bupkus.