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Old July 19th 03, 07:03 PM
Charlie
 
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Default 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?
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Old July 19th 03, 09:22 PM
Scott Unit 69
 
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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?

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Old July 20th 03, 01:18 AM
Jim Hampton
 
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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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Old July 20th 03, 03:34 AM
'Doc
 
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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
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Old July 20th 03, 03:58 AM
Frank Gilliland
 
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Default

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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Old July 20th 03, 05:24 AM
Duh
 
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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.


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Old July 20th 03, 06:10 AM
Jim Hampton
 
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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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Old July 20th 03, 06:42 AM
Jim Hampton
 
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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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Old July 20th 03, 06:44 AM
'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
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Old July 20th 03, 07:06 AM
'Doc
 
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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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