marcspaz

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.

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.

And.... now we know. LOL

Fine, I'll do it. I'm just saying, you aren't living until you used an amateur cross-band repeater to connect a MURS handheld to a GMRS repeater.... allegedly.... Now we see who has a sense of humor. LoL

I think he picked up on this...

So, is it a good location? Sure, but up high on the lift gate will work better.

Everyone loves a good MURS repeater. Oh.... wait.... never mind.

There is zero chance my team and I are doing all the different site surveys, designing a system, creating all of those plot maps, and proof of concept for $500. At $3,000, we were losing money and finally stopped doing them completely. Now I only assist with Ham club and ARES stuff as part of the hobby.

I ran mine at a 50% duty cycle for close to half an hour. Tried to stress it on purpose. Good point. Hopefully he'll see this and let us know. I have a 300w dummy load that is good from DC to 500MHz.

Mine is an M20RM. 438MHz to 482MHz. Testing on a dummy load on 460MHz. We can always make them run cooler. The question (I think) is if its broken or normal.

The expected behavior is, if the transmitting radio is on narrow and the receiving radio is on wide, than the voice will sound quiet and possibly static-filled. It will also sound tinny due to how the audio filters are tuned. Where the processor normally pulls audio for bass, there is no voice to sample. This is because, best case, only half of the receivers channel space is occupied with data. The rest is noise. In the opposite case, if the transmitting radio is on wide and the receiving radio is on narrow, than the voice will sound overly loud, possibly distorted and possibly have a lot of bass. This is because only half of the transmitter's signal is being heard on the receive side, making is sound over-modulated and the audio segment where he treble is sampled is missing. Based on that understanding, mismatching bandwidth should not cause a variation, starting out loud and shifting quiet. Its either loud and bassy or quiet and tinny, depending on which side of the mismatched bandwidth setting you're on.

Wow... yes, Sir. That is a bit hotter than mine. Looking forward to how the mobiles compare. The owner's manual says the high-side operating temperature is +60* C (140* F). They have to expect the radio will get hotter than the environmental temp, but I can't find anything about it. I have a friend or two who may know. I'll ask around.

It's It's common phrase around my circles. Figured it was a radio thing. Basically it's the guy/gal you is talking extremely loud into their phone/radio because they think you can hear them better. Some of them sound like their mic is in their mouth, too.

Better than hearing "the scream talker". LOL

Understand. Like I said, I'm glad it helped. I would love to know the root cause, but it's good to know that there is some goofy thing out there with an easy work-around.

This makes zero sense to me. I mean, I am glad that picking another code helped you, but there is zero correlation between a digital binary code being injected into your carrier and your audio quality and audio level. Something else is wrong. Just a quick explanation, if you are interested... Digital Code Squelch is a non-audible digital square wave that is injected in between the the audio deviation in the radio waves. It is literally zeros and ones. Injecting different combinations of zeros and ones doesn't change how any of it works, at all. It doesn't matter who originally thought of the binary combination. The radio creates and deciphers the digital code using the exact same process, every time, regardless of the code. There isn't different software or circuitry or methods used if a combination of zeros and one were originally packaged in Motorola radios or not. These are what the square waves look like... This is an actual image from a signal analyzer showing the square wave mixed in between the voice deviation...

60 feet of LMR400 will almost cometely attenuate 5g. (Like 60db)

Nice!

I bought mine from Harbor Freight for $25 when I was building a custom trans cooler for my GT350. I figured it would be "close enough". I compared it to my friend's thermometer that he used for his restaurant, and it was only 0.5⁰ lower on the reading of the pizza oven. I was happy to see that.

I'm curious if you had time to run some IR thermometer readings yet and how it compares to mine?

Try swapping radios. You will get to experience what she hears, to help better understand, or establish if it's environmental interference. Let us know what the firsthand experience is. If you can use your phone to share a video, we may pick up an indicator, too. You may just have a defect in that radio.

I agree with Steve and Randy. If you want a light weight explanation on how this stuff works, you can read about it here... Good luck and have fun.

The XTL5000 is a commercial mobile vhf/uhf radio that was used privately and by first responders. It's pretty sturdy and comfortably goes up to about 850MHz, depending on the version. It was discontinued about 10 years or so. I really like it, especially because it can be remote mounted, but I have many other modern radio with a lot more features. So, like my icom 7000, it just sits in a drawer just waiting for the occasional test ride

I was iffy about mentioning this, since it wasn't asked by Randy, but the last three 30 second transmissions on high power, the amp meter on my power supply was showing the radio current draw was starting to waiver. It would dip about 2 amps and pop back up. I was loosing confidence toward the end, but it survived. LOL

This is what I got. Have to be honest... it's hot, but it "feels" hotter. LOL The IR was a good idea. 5 min Standby = 71.5 (room temp) 10 min Low Pwr (30 sec on, 30 sec off) = 95.7 10 min Hi Pwr (30 sec on, 30 sec off) = 124.4