Repeater channels vs simplex channel for a newbie

[breakfasttaco79]

Good afternoon everyone.  I am new to radios and just got my GMRS license a couple of weeks ago.  I purchased a Baofeng AR-5RM.  I plan on checking out some other radios before figuring out which ones I like best.  I have been able to program it with CHIRP and connect it to a repeater close by.  It is my understanding that when I transmit on the repeater frequency, the repeater picks up my broadcast and then retransmits it to extend the range of my radio.  I have noticed that I can transmit from 8-10 miles away from the repeater and it can pick up and retransmit my transmission with no issues.  However, if I am on a regular simplex channel (21 for example) my range is nowhere close to that for a radio-to-radio transmission. When using radio to radio channel 21 if I am more than a mile apart they don't seem to connect. Can someone help me understand how I can broadcast to a repeater 8-10 miles away but not to another radio a little under 1 mile away? Thank you 

[BoxCar]

You have two things to understand here. Repeaters are almost always higher power than your hand held (HH). Repeater antennas are almost always higher above ground than your HH antenna. Power means better coverage for the signal area and height means distance. The higher above the average terrain in your area you put an antenna, the greater area served.

[Raybestos]

24 minutes ago, breakfasttaco79 said:

Good afternoon everyone.  I am new to radios and just got my GMRS license a couple of weeks ago.  I purchased a Baofeng AR-5RM.  I plan on checking out some other radios before figuring out which ones I like best.  I have been able to program it with CHIRP and connect it to a repeater close by.  It is my understanding that when I transmit on the repeater frequency, the repeater picks up my broadcast and then retransmits it to extend the range of my radio.  I have noticed that I can transmit from 8-10 miles away from the repeater and it can pick up and retransmit my transmission with no issues.  However, if I am on a regular simplex channel (21 for example) my range is nowhere close to that for a radio-to-radio transmission. When using radio to radio channel 21 if I am more than a mile apart they don't seem to connect. Can someone help me understand how I can broadcast to a repeater 8-10 miles away but not to another radio a little under 1 mile away? Thank you 

Box car is correct on all points.  In addition to greater power and altitude, many repeaters use land mobile public safety/business grade gain antennas and low-loss feedline (hard line).  All of this contributes to the extended range you enjoy on a repeater, versus ht to ht, ht to mobile, etc.  This is why people who can afford it, spend the extra money on repeaters.

[WRXB215]

If you, or your friend were at the same altitude as the repeater antenna, there is a chance you could talk simplex. Trees could still be a problem but height is the primary variable.

[amaff]

Because oftentimes, this is where repeaters are located:

 

And this is where you and your friends are located

 

Ok, I don't actually know that, but...repeaters are often powerful radios with big antennas located somewhere high up. You're holding a handset on whatever ground you're standing on. I can reach a repeater on a mountain 50 miles from my house, but if I'm hiking in a canyon, I'll be lucky to get half a mile depending on where the other radio is

[Socalgmrs]

So gmrs 460 is totally dependent on line of sight.  My self because of where I live and to a much smaller extent the antennas I use on all my hand  helds I can talk simplex hand held to hand held well into the 30 plus miles at times further.  But when I go into the city, mountains, trees hills, suburbs  ext then not even a mile simplex.  However like already said. Usually repeaters are far up on hills or mountains or towers and at that point line of sight again takes over your your antenna can see the repeaters antenna.   Same thing with good  home base stations.  My base station with location and antena and a 20w radio will do 200 miles. While some one in the city with a 50w radio and a junky little antenna may only get 5 miles.  

[breakfasttaco79]

Thank you guys for the response.  I understand the concept of a repeater broadcasting from a higher point with more power thus allowing it to reach a much greater area.  The part I am wondering about is, doesn't my ht have to transmit far enough to reach the repeater?  If that is the case why can I transmit from 10 miles away to the repeater but only 1 mile to another radio?  Or does the same large net that the repeater cast when transmitting go for when it is receiving my signal as well?

[Socalgmrs]

1 minute ago, breakfasttaco79 said:

Thank you guys for the response.  I understand the concept of a repeater broadcasting from a higher point with more power thus allowing it to reach a much greater area.  The part I am wondering about is, doesn't my ht have to transmit far enough to reach the repeater?  If that is the case why can I transmit from 10 miles away to the repeater but only 1 mile to another radio?  Or does the same large net that the repeater cast when transmitting go for when it is receiving my signal as well?

First a repeater is just 2 radios hooked together with a good antenna up high.  It’s not magic or anytning.  So No it’s more about line of sight.  You’re standing at 6’ off the ground with an 6” rubber duck antenna And your buddy is standing at 6’off the ground with his rubber duck.   It’s much harder to get line of sight. Mean while you’re 6’ off the ground but the repeater is at, let’s say 1000’ higher than your locations    It’s much easier to get line of sight.   While a repeaters antenna is also MUCH better and receives somewhat better it’s again all about line of sight. A 5w hand held on 460mhz will and has reached the space station so it’s a direct line of sight.  That is always why a good antenna up on a tower at home say 30’ up hooked to your hand held will transmit and receive MUCH further than you standing on the ground.  Or even you standing on the roof is better then the ground. 

[WRYZ926]

The coverage radius of a repeater goes for both receive and transmit. With all things being equal, you could be 30 miles away from a repeater and your friend could be 30 miles away in the opposite direction and you two would still be able to talk to each other through the repeater.

[breakfasttaco79]

9 minutes ago, Socalgmrs said:

First a repeater is just 2 radios hooked together with a good antenna up high.  It’s not magic or anytning.  So No it’s more about line of sight.  You’re standing at 6’ off the ground with an 6” rubber duck antenna And your buddy is standing at 6’off the ground with his rubber duck.   It’s much harder to get line of sight. Mean while you’re 6’ off the ground but the repeater is at, let’s say 1000’ higher than your locations    It’s much easier to get line of sight.   While a repeaters antenna is also MUCH better and receives somewhat better it’s again all about line of sight. A 5w hand held on 460mhz will and has reached the space station so it’s a direct line of sight.  That is always why a good antenna up on a tower at home say 30’ up hooked to your hand held will transmit and receive MUCH further than you standing on the ground.  Or even you standing on the roof is better then the ground. 

Thank you.  I think I understand how this works better now.  The radios work great at our ranch in West Texas (a little over a mile apart at the furthest points) but struggle back in the city.  It sounds like I'll be putting an antenna on the roof and getting a base station set up at home soon.  My wife is excited about it. 

[Socalgmrs]

37 minutes ago, WRYZ926 said:

The coverage radius of a repeater goes for both receive and transmit. With all things being equal, you could be 30 miles away from a repeater and your friend could be 30 miles away in the opposite direction and you two would still be able to talk to each other through the repeater.

No it really does not.   The radius is really just a general estimate in transmission area.  And has very little to do with rx as the transmitting station into the repeater has the most to do with the repeater being able to hear the transmission.  Also a repeater could only be 5 or 10 or 20 watts with a bad antenna while a station transmitting into the repeater may have a full 50w and a good high gain antenna up high and radiating over 600 watts.  So in reality just because you are inside the radius does not mean the repeater can hear you and just because you’re outside the radius does not mean you can’t hit the repeater.  Just gotta get out in the field like people used to do before they had interwebby apps that don’t work very well in The real world. 

[WRYZ926]

@Socalgmrs You definitely love to be argumentative don't you.

Two people can be within the range of the repeater and in opposite and equal directions and talk to each other. So if a repeater has a 30 mile radius of receive/trasmitt coverage and both parties can open the repeater, then YES both parties can be 60 miles apart with the repeater in between them and still talk to each other.

[BoxCar]

13 hours ago, Socalgmrs said:

No it really does not.   The radius is really just a general estimate in transmission area.  And has very little to do with rx as the transmitting station into the repeater has the most to do with the repeater being able to hear the transmission.  Also a repeater could only be 5 or 10 or 20 watts with a bad antenna while a station transmitting into the repeater may have a full 50w and a good high gain antenna up high and radiating over 600 watts.  So in reality just because you are inside the radius does not mean the repeater can hear you and just because you’re outside the radius does not mean you can’t hit the repeater.  Just gotta get out in the field like people used to do before they had interwebby apps that don’t work very well in The real world. 

Let's break your statement down. First of all, you are correct in that the radius is an approximation (really, guesstimation) on the coverage area. Some of the best estimations are based on a mathematical model developed by the team of Anita Longley and Phil Rice in Boulder Colorado. Their model, the Irregular Terrain Model, takes the curve of the earth along with its ridges and valleys into play and does a fairly accurate job of predicting if a signal sent from one point reaches another point and at what strength.

The model takes several things into consideration in its projection of coverage. Chief among them are the "big three" of frequency, radiated power, and the height above ground of the antenna. Also playing an important part of the calculation is the radiation pattern for the transmitting antenna. The coverage radius for a repeater is typically based on just two factors, the transmitter power and antenna height. This provides a guess that you should be able to both transmit and receive better than 80% of the time within the area calculated. The only time the model is 100% correct is when there is a clear path between the two stations (line of sight for VHF and UHF).

So yes, you are correct in stating because you are in the radius reception and transmission may not be possible. But other than that, the rest of your statement should not be taken as being fully accurate. The ability to reach a fixed location, the repeater, depends soley on the position and power from the mobile station. We refer to this condition as the "talk out" and "talk in" projections.