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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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,

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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