FRS/GMRS radios
 

I hope that this is the right newsgroup for posting this question. I
wasn't sure where else to post it.

I am looking for a single FRS type radio to communicate with a group
of people who already have a radio. They are using motorola talkabout
radios, and I think the model number is t5620. I know that the model
number doesn't matter, just as long as the radio that I get has the
subchannels that they are using. It is my understanding that these
radios require a license. I found a single motorola talkabout radio at
Best Buy, but it has a 5-mile range capability. I ended up buying a
2-pair pack of the talkabouts that have a 2-mile range. If I return
the 2 pair pack and get a single at the 5-mile range, will I need to
apply for a license even if I am going to be communicating with
someone at 2 or 3 mile range?

GMRS requires a license. You won't notice much, if any, difference
with a 5 mile radio, the built in antenna is the limiting factor.

Get the two-pack, you'll have one to share.
A single two-way radio is no fun . :

You may need to get a radio with PL or CTCSS (same thing). These are
subaudible tones that activate the squelch in their radios.

Charlie wrote:

I hope that this is the right newsgroup for posting this question. I
wasn't sure where else to post it.

I am looking for a single FRS type radio to communicate with a group
of people who already have a radio. They are using motorola talkabout
radios, and I think the model number is t5620. I know that the model
number doesn't matter, just as long as the radio that I get has the
subchannels that they are using. It is my understanding that these
radios require a license. I found a single motorola talkabout radio at
Best Buy, but it has a 5-mile range capability. I ended up buying a
2-pair pack of the talkabouts that have a 2-mile range. If I return
the 2 pair pack and get a single at the 5-mile range, will I need to
apply for a license even if I am going to be communicating with
someone at 2 or 3 mile range?

Charlie,

Scott has an excellent reply. I'd like to point out that any handheld radio
will start running out of steam at 5 or 6 miles. This is due to the lack of
height of the transmitting antenna. As you know, a lot of folks put base
station antennas up on towers. The reason being is that it gets the signal
up away from nearby objects and also increases their distance to what is
called 'radio horizon'. Radio horizon is the distance over flat ground (or
water) from the transmitting (receiving) antenna to the point where the
radio wave hits the ground/water due to the curvature of the earth. A
simple formula to figure your range is take the height of the antenna from
the ground (on an HT, 5 feet would likely be good as you're holding it up to
your face) in feet (5 in this example). Double that number (10) and then
take the square root (a bit over 3). That is the range of the radio to
radio horizon. This will give you a bit over 3 miles. Now, as long as a
second station's radio horizon overlaps or touches yours, you will have
communications (assuming no big obstruction between you). The other station
will have a bit over 3 miles. Added together, that means 6 miles is likely
the limit (unless you climb a tree or something like that :)

FRS is a bit more limited, but the batteries will last longer at lower power
and the difference isn't going to be large under any normal circumstances.


73 from Rochester, NY
Jim

"Charlie" wrote in message
m...
I hope that this is the right newsgroup for posting this question. I
wasn't sure where else to post it.

I am looking for a single FRS type radio to communicate with a group
of people who already have a radio. They are using motorola talkabout
radios, and I think the model number is t5620. I know that the model
number doesn't matter, just as long as the radio that I get has the
subchannels that they are using. It is my understanding that these
radios require a license. I found a single motorola talkabout radio at
Best Buy, but it has a 5-mile range capability. I ended up buying a
2-pair pack of the talkabouts that have a 2-mile range. If I return
the 2 pair pack and get a single at the 5-mile range, will I need to
apply for a license even if I am going to be communicating with
someone at 2 or 3 mile range?


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Jim,
In your example about range, the range wouldn't
be 6 miles, it would 3 miles. The radius of the
coverage area has to overlap the transmitter/receiver.
So, if two radios each have a range of 3 miles that
does not mean the total range between radios is 6 miles.
'Doc

In , 'Doc wrote:



Jim,
In your example about range, the range wouldn't
be 6 miles, it would 3 miles. The radius of the
coverage area has to overlap the transmitter/receiver.
So, if two radios each have a range of 3 miles that
does not mean the total range between radios is 6 miles.
'Doc

In his example the range is limited by the curvature of the earth. That means if
a person's eyes are five feet above the earth he can see the feet of someone
three miles away, but he can also see the eyes of someone six miles away peeking
over the horizon. So if the radios will talk line-of-sight, the range between
them is six miles when they are both held five feet above the ground.





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"Frank Gilliland" wrote in message
...
In , 'Doc wrote:



Jim,
In your example about range, the range wouldn't
be 6 miles, it would 3 miles. The radius of the
coverage area has to overlap the transmitter/receiver.
So, if two radios each have a range of 3 miles that
does not mean the total range between radios is 6 miles.
'Doc

In his example the range is limited by the curvature of the earth. That
means if
a person's eyes are five feet above the earth he can see the feet of
someone
three miles away, but he can also see the eyes of someone six miles away
peeking
over the horizon. So if the radios will talk line-of-sight, the range
between
them is six miles when they are both held five feet above the ground.


Sorry Frank, you are wrong. Check the books again.

Sorry, Doc. Frank's reply is exactly correct. As long as the two radio
horizons touch or intersect, communications will be established (assuming,
of course, that the receivers work properly, the transmitters work properly,
and the antennas work properly). My former neighbor now lives in
Wellsville, some 80 miles away (110 or so by car) and can hear me just fine
on the local repeater. Her elevation is around 2200 feet, which translates
to a radio horizon of roughly 66 miles. One has to add the radio range of
the repeater (which, incidentally, is located in the *opposite* direction
from her) - the elevation is something like 500 feet (31 miles to radio
horizon).

73 from Rochester, NY
Jim

"'Doc" wrote in message ...


Jim,
In your example about range, the range wouldn't
be 6 miles, it would 3 miles. The radius of the
coverage area has to overlap the transmitter/receiver.
So, if two radios each have a range of 3 miles that
does not mean the total range between radios is 6 miles.
'Doc


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Doc,

I've yakked with another handheld user. He was about 5 miles from the
repeater; I was around 100 miles from the repeater and was running 3.5 watts
to the handheld. Oh, I happened to be on the 21st or 22nd floor of a
high-rise :)

73 from Rochester, NY
Jim
ps - not sure how far Massena is from Rochester, but it ain't close!



"'Doc" wrote in message ...
I didn't get 'Sparky's post, but...

Sparky,
You're right, and you're wrong. Besides the curvature of
the earth you also have to remember that the output power of
the transmitter also controls the distance at which the signal
can be heard. The signal has to have a certain minimum strength
to be heard at all. At UHF, 'line of sight' isn't the only
range limitation, but it is one of them...
'Doc


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Jim,
If you both were using the repeater, then you were
both in range of the repeater. You weren't talking
direct, so not the same thing.
'Doc

Jim,
So, are you saying that range is unlimited at UHF as
long as it's 'line of sight'?
Assuming that the transmitter's output for both radios
are the same, and both receiver's sensitivity is the same,
and both have a usable range of 3 miles. That means for
the two stations to hear each other they have to be within
three miles of each other. At 6 miles neither will be able
to hear the other because they would both be out of each
other's usable range. Wouldn't matter what the 'line of
sight' distance was. Propagation will make a difference,
but we're talking about the 'normal', every day state of
propagation.
'Doc

Doc,
He was 5 miles from the repeater. I was around 100 miles from the repeater.
I also opened (and tried a quick call) over a repeater in Pennsylvania.
This was from Rochester, NY (almost at Lake Ontario). In other words, I was
transmitting successfully to another repeater in another state(and that one
was *well* over 100 miles away) :)

BTW, two folks could well be on opposite sides of the repeater. Should the
other guy happen to have a high elevation (as did I), then communications
approaching 200 miles between the HTs (100 miles to the repeater plus
another 100 miles to the other guy) are possible (but only in *unusual*
circumstances). My former neighbor lives on a 2200 foot "hill" and I am
certain she would have one heck of a range. I am only considering the range
I can obtain to a repeater. Granted, the repeater antenna gain is pretty
high, but it would likely not be more than 10 dB over my 36 inch gain
antenna. So, between similar HTs, cut the distance 1/3 (1/9th the power)
and I'd still expect well over 30 miles (and not need as much height, but
still both would have to be located fairly high above average terrain).
Simple math, as long as you've got a clear shot. The satellites are not
running kilowatts either, you know :)

73 from Rochester, NY
Jim


"'Doc" wrote in message ...


Jim,
If you both were using the repeater, then you were
both in range of the repeater. You weren't talking
direct, so not the same thing.
'Doc


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Doc,

Normally, HTs will be limited to line of sight. The problem is that normal
line of sight is only about 3 miles to radio horizon for a person standing
on level ground. Get up on a ladder, and the horizon stretches out farther.
We're not talking propagation enhancements, just a simple formula which
takes the station's height above average terrain (in feet), double that and
take the square root. The answer is the range to radio horizon. 5 feet (to
a handheld antenna) times two is 10. SQR(10) is a bit over 3 miles. 6 or 7
miles max. Get in the second story of a house. Figure 11 feet (up a few
feet to the first floor, another 8 or so to the second floor) and add that 5
feet from that floor to the HT. Now 16 doubled is 32. The square root of
that is somewhat over 5. I would suspect a range of 10 to 12 miles between
two handhelds equally elevated over average terrain in that case. I was on
the 21st or 22nd floor of a high rise. Figure over 200 feet up, plus 600
feet above average terrain (yes, it was on a hill). 800 feet and I won't
add the extra 5 feet. SQR(1600) yields 40 miles to radio horizon. Now
figure in the repeater height. Should that repeater be up a total of 2000
feet (including hill, tower, antenna, whatever), it will have a range over
60 miles to its' horizon. As long as my horizon intersects its' horizon
with no obstruction, I can use that repeater. The 3.5 watts on my HT is not
a problem; my antenna gain is around 6 dBi and I'm sure the repeater antenna
gain is way over 10 dBi. Plenty of power. I'm talking 24/7 communications.
I've had a few chats over (and can raise at any time of day) the Toronto
repeater. Definitely more than a couple of miles. Way more than a couple
of dozen miles too :)


73 from Rochester, NY
Jim


"'Doc" wrote in message ...


Jim,
So, are you saying that range is unlimited at UHF as
long as it's 'line of sight'?
Assuming that the transmitter's output for both radios
are the same, and both receiver's sensitivity is the same,
and both have a usable range of 3 miles. That means for
the two stations to hear each other they have to be within
three miles of each other. At 6 miles neither will be able
to hear the other because they would both be out of each
other's usable range. Wouldn't matter what the 'line of
sight' distance was. Propagation will make a difference,
but we're talking about the 'normal', every day state of
propagation.
'Doc


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