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Hey folks. I have been helping someone here with questions about getting more power out of their radio and into the antenna. I thought the discussion could help many new people, so I am sharing some of that conversation here. This is a really long post. Sorry about that, but I think it's worth it. If you have any questions, just ask. I am sure myself or one of the other experienced operators or engineers can help. ----------------------------------------------------------------------- I think, to help make sense of power vs performance in GMRS, I'll explain how the signal strength is impacted by output wattage. UHF (where GMRS lives) is a Line of Sight service. This means exactly what it sounds like. If it's in the RF line of sight, you can talk to it. When we talk to radios on the surface of the earth, you can only talk to the visual horizon, plus about 15% (aka the Radio Horizon). The higher both antennas get, the further the horizon and the further you can talk. From the roof of a 15 story building, I can use 0.5w from my handheld to talk on a repeater over 50 miles away. I talk to satellites in orbit, 240+ miles above Earth, with only 0.25 watts because there is nothing but empty space between us. There is some very minor benefit to more power. One of the reasons why the GMRS radio waves can be heard past the visual horizon on earth is because some of the signal gets bent / refracted, as well as scattered in all directions while it travels, creating the referenced RF horizon. Some of this signal scatters back to earth while the rest travels out into space. It's a very small percentage and it varies depending on the atmospheric conditions. That said, if you have 100w out and only 1% of your signal gets scattered back to earth (example only), someone can hear that 1 watt and you may be able to talk if the other person's signal scatters about the same, coming back to you. Scatter is extremely unreliable, however. I'll explain why getting the antenna as high as possible is for the best, compared to adding more power. In the radio world we use a quality scale to define how well your signal is being heard. This is called the RST System. RST stands for Readability (how intelligible your words or information is), Signal Strength (how strong your signal is heard by the receiving station), and Tone (mostly used in Morse Code communications). For the voice side of things, we typically only use the RS portion. R is on a scale of 1 to 5, with 1 being aware that someone is transmitting voice, but can't make out anything. An R5 means, regardless of signal strength, your words are 100% intelligible. For the S, we use an S-meter and provide the total number of S-units read on the meter. This indicates how strong your signal is. This is a picture of an analog S-meter scale. The letter S on the left represents one (1) S-unit. The largest S-unit reading on s-meters is the 9 or S-9. I'll explain the +10, +30, +60 in a moment, So, just referencing the RST system and the meter above, the best signal report would be a 5/9 (pronounced five nine) or 59. This means your voice is completely understandable and your signal is strong enough that the needle moves to 9 s-units, the maximum value on the number scale (normally there is zero static or noise heard at this level). The commonly accepted minimum signal report that is considered "usable" is a 2/1, 2 for voice quality and 1 S-unit. However, that is absolute worst case, if it was an emergency and you can repeat information over and over to get the communications out. There is a tremendous amount of noise and your voice is barely being understood when it is heard. Conversational minimal signal reports are going to be about a 3/2, but that is still aggravating and most people give up quickly due to the static and missing every other word or every third word. It's mostly "call me on the phone" or "almost there" kind of stuff. And then there is what most people tolerate for chit-chat, and that is a 4/3. Meaning, I can hear everything you say. There is much less static, and the signal is strong enough that you have established reliable communications. So, to understand what an S-unit is and how it impacts the quality of communication, I have to explain what the meter is actually measuring. One s-unit is equal to 0.2 microvolts detected at the receiver antenna input. Regardless of how much power the transmitter is and regardless of how far that station is, if 0.2 microvolts makes it to your radio, that radio is hearing 1 s-unit of signal. Lets say you have 10w going into the transmit antenna and the receiving station is fairly far from your radio, only receiving 1 s-unit. 10w We really want to get to 3 s-units for reliable communications. Well, in order for the received voltage to climb 1 s-unit, you need to multiply your power by 4. That means to move 1 s-unit on the receiver, you need to increase your transmit power to 40 watts. 40w However, we already know that 2 s-units isn't really usable. To get to 3 s-units, you need to multiply your power 4 times, again. That's 160w into the antenna to go from "I know you're there" to "I can actually talk to you" (assuming your audio is good). 160w Lets assume you wanted to try to get the s-meter to swing to 9 s-units. Well, that will take 655,360 watts. 655,360w Now, the + scale is even more fun You need to double your power for every 3dB increase in measured power. You need go up 4 times the power to increase by 6dB. Those + readings are for strength in dB over the s-9 signal strength. Since in our specific example we know you need 655,360w to go from s-1 to s-9, to get to +30dB over s-9 you need to increase your transmit power to 655,360,000w. That's 655 million. Not a type-o. 655,360,000w So now, lets go back to the original limit of GMRS being a Line of Sight service. That 160w you needed to get to 3 s-units, basically netted you zero distance compared to the 10w, because the horizon didn't change. All you did was make it so that those who could hear you, now understand what you are saying... maybe. To make things even more bleak, if you are communicating due to scatter and 1% or less of your signal is being heard, the amount your transmit power would need to increase is unfathomable. And did I mention that all that transmit power did absolutely nothing for your receive capability? So, you can see why it's not practical to chase power output. If you get your antenna 30 or 40 feet higher, you would actually improve your communications range and quality of reception much more than if you can increased your power from 10w to legal limit.

Great question! If you have walls of a canyon that are high in iron and other conductive material, there can be some tunneling or directional impact, but its rare for it to be in high enough concentration to work. Most natural barriers, such as the trees and hills/mountains absorb UHF signals... however, UHF penetrates man-made structures, like buildings, much better. More power would be more beneficial in urban areas than in other types of areas. More power is going to be a benefit in rough terrain for other reasons, though. RF shadowing is like shadows from the Sun. There is never complete darkness behind a rock or mountain. Same with radio waves. Refraction and scatter places the radio waves behind stuff... the sharper the angle, the less scatter. So, the more power you have, the less you are going to be impacted by shadowing, but only to a limited degree. HF signals will bounce off of stuff pretty well, and goes through trees and foliage with no issues.

Great post! Is not more power also helpful in penetrating objects like walls, and bouncing the signal through canyons, etc, for example when off-roading?

Uh, you didn't answer my question (if I had one) because I'll already knew other radios would work if you want to do that. I don't mod anything or break the rules for now. If the whole system collapses then that is the time.

did you mean "without" the drama BS, because we certainly don't need that on HAM

Thank you! My pleasure, truly. I'm no expert, but I try to be as accurate as possible and deliver it in a way that everyone can understand, regardless of the reader's experience level. My goal is to help as many people as possible, because if it wasn't for the community, I would have been lost.

...but this goes to eleven. In all seriousness though Marc thanks for this post, good stuff sir.

The point of the restrictions on MURS, FRS and GMRS was to limit the range so they could be generally practical for families to use on their block. Allowing repeaters was letting a genie out of the bottle that made a lot of people consider uses beyond the original limiting method/device. My worthless opinion is if you want something more, just get it. "It" being a business or ham license. All the great imaginings of what might be possible with changes already exist in the ham world. Stop trying to make GMRS into amateur radio. Sorry for the musings of a "sad ham"

If the HT is capable of exceeding 2W output or is capable of accessing repeaters, it WILL require a license. The 2017 FCC reorganization granted FRS radios up to 2W output (likely ERP, so fixed antenna to prevent adding a gain antenna -- except for the 0.5W ERP 467MHz channels). Radios sold after that reorganization must specify either FRS or GMRS -- no more bubble-pack FRS/GMRS radios.

I know my 50 cents don't mean squout, but I haven't really heard anything about the FCC not allowing any more repeaters to be errected. However I do think if you're gone to have more then two repeaters on the frequency with a 5 to 20 mile range from another, they should be on different repeaters pairs. After all we only have 8 repeater pairs. I've notice that some repeater owners can act like children fighting over who had their repeater on the first when using the repeater pair and tone.

From the FCC FAQ page: Can I change the licensee name by filing a request to update administrative information on a license? Yes, but only if the name change does not involve a change in ownership of the license or licensee. Otherwise, a transfer of control or license assignment application needs to be filed. Additional information about these types of filings is available at the Transactions Topic page. https://www.fcc.gov/wireless/support/knowledge-base/universal-licensing-system-uls-resources/updating-administrative

The difference being, I suppose, that I actually acknowledge the need...

So what did you come to GMRS for then ? I'm curious because I see more and more hams going to GMRS when they have it already in HAM. I think in some part that's what's messing up GMRS. Its almost become a "ham light" to me. I get more and more baffled daily on the wants and needs of GMRS users. Ive been a ham for years and use ham radio when i want linking or data or other things it provides, but when i want simple point to point stuff GMRS is what I use. Yet the UV5R is not certified for any of this....so why state the reqs when you dont follow them ?

FCC regs: Part 95(e) would prohibit a manufacturer of a GMRS radio to transmit on MURS as well. So you have to look outside of GMRS radios to get one radio to do both. I achieved this on my original Baofeng UV-5Rs and later on my Anytone AT-779UV a/k/a Radioddity DB20-G after "opening" up its ability to transmit on more than just GMRS (to Ham 2 meters and 70 cms and MURS).

I'm guilty too. specially when in a group and no one uses their call sign (CS). We usually have an intro going to trails early in the morn. Names are mentioned etc. Would actually be a wonderful time to start the effort and use their CS just to stay in practice (and legal). Kinda like running through intersections in the woods and not looking both ways for cross-traffic. It becomes a relaxed atmosphere and no one pays it any mine... Yes there are those that do not have a license too. A cool shoulder might be enough to push them in the right direction. And why can't JJAMUSA require it as a part of their entry requirements? I'll ask. I think I know what the answer is all ready.

I'm new to GMRS so I may see it differently than y'all because of that. It was the linked repeaters that piqued my interest (and the club is going to add more). I was discouraged from joining in before because the repeater closest to me is closed (paid members only, not accepting more). Coming from the HAM world the idea of having to be in multiple clubs just to use 2 repeaters close to me did not sit well. Without repeaters I would have almost no use for GMRS because family members aren't interested. The comment above about using MURS if you want VHF seems odd to me. Wouldn't we need yet another radio for that? I've just about hit my limit on buying more radios just because of complicated regulations, especially when one radio is technically capable of doing them all. But if it didn't take buying dedicated equipment first just to experiment, I would have been interested in experimenting with what MURS could offer. I like the 150MHz VHF (or lower) range better than 400+.

Sadly thats what GMRS is becoming. Linking and nets and all that is not the original focus but its out of the bag as ones say so nothing that will change. Only way to seperate is keep them not linked and don't advertise them. I a bit on the fence over listing vs not but since I removed all my repeaters from the interwebs they have been quite. Prior it was non stop squelch noise, static and test test test but never any real conversations. Mostly radios that could not really hit the repeater or were programmed wrong. I removed them all from online sources changed the PL/DPL and its been good since.

Yep, anyone that want the ability to Rag Chew with the Drama BS of 11m CB, GMRS isn't the solution. Amateur Radio is the solution, because GMRS is intended for semi privite communications between family members or organizations, such CERT or Neighborhood Watch Programs. Of course, there are GMRS systems that are design to be what Amateur Radio Systems are.

ok, I want to be cool so i'll order one.

Post the Morse Code ID

Well, yes and no on repeaters and channels. In GMRS there are channels set aside for repeater operation however it is not true that only repeaters may operate on these channels. FRS (and GMRS) can operate simplex (using the same frequency to transmit and receive) on the output frequency of a repeater pair. In the amateur world the channels are a little more structured in there are ranges for repeater channels and these are coordinated by regional volunteers to limit interference. In the part 90 world, the only band with repeater frequencies specifically limited is in the UHF spectrum but the LMR coordinators will and do assign repeater frequencies in any part of their spectrum they can.

If what that person said is "the FCC does not allow new GMRS repeaters", then that person lied to you or is an idiot - likely both.

Not that I am aware of. GMRS Repeaters are not coordinated by anyone. The FCC doesn't even manage Amateur Radio Repeaters. I'm not sure why someone would say that they are not allowing any new repeaters, when the FCC never processed approvals in the first place.

There are already illegal cross band repeaters operating between MURS and GMRS for exactly the reason above. I think it would be a better bet going digital, DMR. There are SFR, single frequency repeaters that take advantage of the dual time slot nature of DMR. The repeaters don’t need expensive tuned cavity filters. No new frequencies are necessary either. Being narrow band, 12.5KHz wide channels, it might be possible to spilt one or two of the existing wide band repeater frequency pairs into two channels. One or two SFR’s could operate on one of the existing analog input frequencies and the same with the output frequencies. Thus one old analog repeater frequency pairs could accommodate up to four digital SFR systems. One could “sell” this to the FCC as making better use of the current spectrum while simplifying the the system hardware making it more accessible to the general public.