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That looks like me at Point B! Where did you get my picture at?
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UHF Range Question
- Thread starter gman4661
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SkipSanders
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If you really, really want to get an idea of 'range possible' from your home, and aren't afraid of learning a complex program, you can go to Radio Mobile WEB Site to get a program called 'Radio Mobile' that will let you figure line of sight for various antenna heights, to various antenna heights, from your location.
It allows (and requires) you to download digital elevation data for your location from various sites on the web to create actual terrain height maps of your area, and lets you specify antenna locations and heights, then calculate just what is, and is not, in line of sight.
It allows (and requires) you to download digital elevation data for your location from various sites on the web to create actual terrain height maps of your area, and lets you specify antenna locations and heights, then calculate just what is, and is not, in line of sight.
A free web version of that is what I linked to in my previous message (http://forums.radioreference.com/general-scanning-forum/115818-how-far-can-i-receive.html).
OK guys, a lot of good information has been posted and for that I thank you. There is much food for thought. It's obvious that I don't have have the technical background that many of you do. My ignorance is plain to see, and to some degree, has been pointed out to me. I fully realize that there are many variables in radio theory and plan to do some research as time allows. I have a strong interest in GMRS primarily for practical and not so much hobby reasons.
Still, I am seeking answers to my original questions:
What is the approximate range between simplex UFH mobiles (25-40 watts) using quarterwave antennas. What about high gain antennas?
Also, same question, but with a handheld and a mobile?
I really just need estimates. Thanks!
Still, I am seeking answers to my original questions:
What is the approximate range between simplex UFH mobiles (25-40 watts) using quarterwave antennas. What about high gain antennas?
Also, same question, but with a handheld and a mobile?
I really just need estimates. Thanks!
iMONITOR
Silent Key
My post #15 gave you exactly that!
iMONITOR
Silent Key
Yes. To have greater reange you need repeaters, or really high towers!
SkipSanders
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What we're telling you is, there's no way to predict your range, because it's very dependent on your local conditions. The answer in place X is going to be quite different from the answer in place Y.
In urban conditions, anywhere from .5 miles to 20 miles could happen, depending on terrain, foliage, buildings, etc. Most commonly it'll be in the .5 - 2 mile area for HT's or mobile to mobile, regardless of power, once you reach 4 watts, unless you're standing on hills with nothing in between. More than 4 miles would be uncommon, again unless one or both ends is on a hill, with nothing in between the stations.
In urban conditions, anywhere from .5 miles to 20 miles could happen, depending on terrain, foliage, buildings, etc. Most commonly it'll be in the .5 - 2 mile area for HT's or mobile to mobile, regardless of power, once you reach 4 watts, unless you're standing on hills with nothing in between. More than 4 miles would be uncommon, again unless one or both ends is on a hill, with nothing in between the stations.
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Right. Range at anything over about 2W ERP (assuming a decently sensitive receiver) will normally be limited by terrain, not by power or type of antenna. Typical "line of sight" (the distance from a person standing on "flat" terrain to the horizon) is about 3 miles. Two people standing on flat terrain would have a line of sight to each other of about 6 miles. So, that is your range (unless one person is a child or sitting down, or transmitting with the radio on their belt...so their antenna would be significantly lower and their line of sight would be significantly shortened). To get more range, you need more antenna height. And, since terrain is almost never truly "flat" (except in some scrub desert areas), using the application I've linked to in my earlier posts can give you the expected line of sight for a specific area.
Of course, buildings and other major "non-earth" obstructions will also limit a radio's line of sight. In a heavily urbanized area, more power will actually help some, as buildings tend to reflect signals around...more power will allow for more power available in a reflected signal and can improve on range. Foliage is not a very significant factor for UHF, but it does have some effect. So, more power could improve range in heavily forested areas where the signal is being attenuated below the receiver's ability to discriminate the signal even though it is still "line-of-light" to the transmitter.
A mobile mount antenna, if mounted on the roof of a vehicle, is generally taller than a handheld antenna, and so will get a bit better range. But, if the antenna is trunk mounted, the range would be worse than standing handheld.
As pointed out, if you want coverage for an area, you need to use a repeater system (GMRS allows for duplex repeaters, where the repeater receives on one frequency--the input frequency--and simultaneously "repeats" or retransmits the received signal on a 2nd frequency at higher power--the output frequency). With a repeater system, the repeater antenna is normally situated tens or hundreds of feet in the air (depending on your budget) and so has a much greater line of sight than either a mobile unit or a handheld unit. This is what lets police agencies talk on low-power handhelds across an entire city...the handheld only has to "see" the repeater's antenna in order to communicate with any other radio on the system.
Of course, buildings and other major "non-earth" obstructions will also limit a radio's line of sight. In a heavily urbanized area, more power will actually help some, as buildings tend to reflect signals around...more power will allow for more power available in a reflected signal and can improve on range. Foliage is not a very significant factor for UHF, but it does have some effect. So, more power could improve range in heavily forested areas where the signal is being attenuated below the receiver's ability to discriminate the signal even though it is still "line-of-light" to the transmitter.
A mobile mount antenna, if mounted on the roof of a vehicle, is generally taller than a handheld antenna, and so will get a bit better range. But, if the antenna is trunk mounted, the range would be worse than standing handheld.
As pointed out, if you want coverage for an area, you need to use a repeater system (GMRS allows for duplex repeaters, where the repeater receives on one frequency--the input frequency--and simultaneously "repeats" or retransmits the received signal on a 2nd frequency at higher power--the output frequency). With a repeater system, the repeater antenna is normally situated tens or hundreds of feet in the air (depending on your budget) and so has a much greater line of sight than either a mobile unit or a handheld unit. This is what lets police agencies talk on low-power handhelds across an entire city...the handheld only has to "see" the repeater's antenna in order to communicate with any other radio on the system.
hockeyshrink
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There you go. 1 to 5.....1/2 to 2. I personally think 5 miles simplex GMRS over terrain is incredibly optimistic. Let's say 1/2 to 3.
I personally don't think a gain vs. 1/4 wave antenna on a mobile using simplex is going to make any practical difference whatsoever.
Why are you locked into a GMRS solution? I have had much better performance on simplex over terrain with MURS (VHF) rather than GMRS (UHF). That 50 watts of UHF doesn't help a whole lot in the real world on simplex, on the ground. If my need is to communicate simplex over terrain, and can't use a ham radio, I will use MURS if I need portables, or if its just mobile-to-mobile I'll use Class D CB on SSB.
Hockeyshrink, thank you for your response. You have provided a very good summary of what has been said. Here is my motivation for GMRS:
1. My county CERT team is on GMRS.
2. Although the nearest GMRS repeater is about 50 air miles away, I would like to have that option when I am within range.
3. A group has offered to install a repeater in my area, should tower space be located.
4. I could communicate with persons who are using bubblepack radios.
Thanks again.
1. My county CERT team is on GMRS.
2. Although the nearest GMRS repeater is about 50 air miles away, I would like to have that option when I am within range.
3. A group has offered to install a repeater in my area, should tower space be located.
4. I could communicate with persons who are using bubblepack radios.
Thanks again.
RADIOGUY2002
Member
Ref chart
UPMAN,that's pretty accurate tool, compare to my system that I have in play. The actual calibration of my system is 29 ft added on to the physical height, for a good comparison with foliage blockage. Either way still pretty cool utility.
UPMAN,that's pretty accurate tool, compare to my system that I have in play. The actual calibration of my system is 29 ft added on to the physical height, for a good comparison with foliage blockage. Either way still pretty cool utility.
I was also impressed. As I mentioned in that thread, there are a couple of spots on my drive to/from work where Arlington TRS goes dead...and they are both about the only areas on the drive that the app predicts would be dead. I that it was RF swamping...turns out to be earth shielding.
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Just to introduce myself, I live in Pennsylvania and I use 2 way radios for hunting purposes.
We have about a dozen or more radios between the 4 of us.
The terrain in Pennsylvania varies from town to town and woodlot to woodlot and so there is never any one rule of thumb as to how far our radios can transmit.
Basically one thing I will say is that one of my older radios actually transmits better then the new ones.
I have a old 5 Channel Motorola radio that has a antenna that is about 5 or 6 inches long that has both a battery pack and a rechargeable battery that is over 10 years old that works just as good as the day it was new.
With all the options of the newer style radios, as long as the other radios are not on a special side band, it will transmit and receive better then the new radios'.
We also have 4 - T 7400's that my brother bought a few years ago. They are very good on battery life - we can use them for as many as 24 hours without a recharge. They transmit fairly well on every channel and they are good performers out in the woods.
One small comparison is that we were using 7 / 7 for hunting because the older radios did not have as many sub channels as the new radios and I liked using the old radio for transmit and the newer radios for scan and weather channel.
One day I was walking in the ridge my family was hunting on was horseshoe shaped and I was on the one side of the ridge and they were on the other side and there was only about 1/2 a mile between us and I had no reception.
Another time, they were on the ridge and I was at the bottom of the ridge - about 1 1/2 miles away down hill and the radio would transmit up over the ridge, but their smaller radios would not transmit as well down - even though they had a height advantage on me.
Another time, we were in the parking lot and my brother was in the woods about 1/2 of a mile away and they had no signal. I moved to the bottom of the ridge - 1 1/2 miles away and they could hear me and I could almost hear them. That was on one watt.
Well one day we were hunting and I got into a fight with a neighbor over the radio and they were in the Game Lands in a open food plot 3 miles away and they could hear every word I was saying, and there was thick woods between them and me.
Another day, we shot a deer and I took it home and was hanging it in the tree when the door bell went off and it was my brother - up in the woods 3 miles away. I was down in a valley, around the side of a hill, and on top of another hill with less elevation then where the other brother was, and he was on the side of a ridge - where he could look out and see the valley below him to the SW where I was at, and could talk just like as if he was only 100 yards away.
If someone had one of my big radios and was on a ridge 10 miles away and you were on a ridge and there was nothing between you, you would be able to talk with 1 watt with no problem. Maybe even 1/2 a watt if the atmospheric conditions were right.
We have about a dozen or more radios between the 4 of us.
The terrain in Pennsylvania varies from town to town and woodlot to woodlot and so there is never any one rule of thumb as to how far our radios can transmit.
Basically one thing I will say is that one of my older radios actually transmits better then the new ones.
I have a old 5 Channel Motorola radio that has a antenna that is about 5 or 6 inches long that has both a battery pack and a rechargeable battery that is over 10 years old that works just as good as the day it was new.
With all the options of the newer style radios, as long as the other radios are not on a special side band, it will transmit and receive better then the new radios'.
We also have 4 - T 7400's that my brother bought a few years ago. They are very good on battery life - we can use them for as many as 24 hours without a recharge. They transmit fairly well on every channel and they are good performers out in the woods.
One small comparison is that we were using 7 / 7 for hunting because the older radios did not have as many sub channels as the new radios and I liked using the old radio for transmit and the newer radios for scan and weather channel.
One day I was walking in the ridge my family was hunting on was horseshoe shaped and I was on the one side of the ridge and they were on the other side and there was only about 1/2 a mile between us and I had no reception.
Another time, they were on the ridge and I was at the bottom of the ridge - about 1 1/2 miles away down hill and the radio would transmit up over the ridge, but their smaller radios would not transmit as well down - even though they had a height advantage on me.
Another time, we were in the parking lot and my brother was in the woods about 1/2 of a mile away and they had no signal. I moved to the bottom of the ridge - 1 1/2 miles away and they could hear me and I could almost hear them. That was on one watt.
Well one day we were hunting and I got into a fight with a neighbor over the radio and they were in the Game Lands in a open food plot 3 miles away and they could hear every word I was saying, and there was thick woods between them and me.
Another day, we shot a deer and I took it home and was hanging it in the tree when the door bell went off and it was my brother - up in the woods 3 miles away. I was down in a valley, around the side of a hill, and on top of another hill with less elevation then where the other brother was, and he was on the side of a ridge - where he could look out and see the valley below him to the SW where I was at, and could talk just like as if he was only 100 yards away.
If someone had one of my big radios and was on a ridge 10 miles away and you were on a ridge and there was nothing between you, you would be able to talk with 1 watt with no problem. Maybe even 1/2 a watt if the atmospheric conditions were right.
Ok well here is my experience under *average rural* terrains across the country...
FRS-FRS (handheld UHF simplex .5 watts)- 1/2 mile max
GMRS-GMRS (handheld UHF simplex 4/5 watts [not bubble packs but professional quality radios])- 2 miles
GMRS-GMRS(mobile UHF full wave 40watts) 4-5 miles
Take the motorola rule of thumb from earlier and you'll get somewhat comparable results. Lump all the bubble packs in with the FRS radios.
I'd suggest using the programs mentioned earlier to put in a little data, so you're aware of gaps with areas you frequent (neighborhood) or will put added importance on the communication. When it comes to Scouting, I'd also check with a locall ham club to see if they'll offer a class for your group, getting a Troop liscensed at the technical level will open up many more VHF options that are more suitibale for wooded terrain, and the boys can earn a badge for it if I remember correctly.
The general estimates aren't a bad thing, but yes there are variables that can help or hurt those numbers, so don't think of them as binding.
SpringHill
Member
i know this is from forever ago but im just curious about how one goes about getting a tower space..
Thanks!
Step 1 is to have a boat load of money in the bank. Seriously!
Step 2 would be to contact in person any LMR shops in your area. If anyone knows, it would be them.
Step 3 be prepared for probable "sticker shock."
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