How far can a antenna see?Highthwise?
 

I seem to recall reading about a 'standard', it went something
like this,,,, a two meter antenna at 100 feet can "see" or be useable
for 17 miles. I don't recall where I read this,,, but would really
appreciate any and all input on the question,,,,,,,,,,,, How far can a
base two meter radio antenna transmit and recieve so as to be
'useable' when the antenn is 100 feet tall above the earth, and the
surronding area is fairly level. (no hills or mountains). I am
talking about a 50 watt base and 50watt mobil. If there is a formula
somewhere, would appreciate the input.
The reason I ask, is on the way by some very tall tv antennas
1000 and 1200feet, I got to wondering,,, they don't work well with
""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are
out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up
my brain'. thanks in advance. cl.73

I seem to recall reading about a 'standard', it went something
like this,,,, a two meter antenna at 100 feet can "see" or be useable
for 17 miles. I don't recall where I read this,,, but would really
appreciate any and all input on the question,,,,,,,,,,,, How far can a
base two meter radio antenna transmit and recieve so as to be
'useable' when the antenn is 100 feet tall above the earth, and the
surronding area is fairly level. (no hills or mountains). I am
talking about a 50 watt base and 50watt mobil. If there is a formula
somewhere, would appreciate the input.
The reason I ask, is on the way by some very tall tv antennas
1000 and 1200feet, I got to wondering,,, they don't work well with
""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are
out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up
my brain'. thanks in advance. cl.73

A rough rule of thumb is to take the square root of the height in feet and
that will give you the miles from the antenna to the ground. YOu do this
again for the other antenna and add the number of miles. This can be
multiplied by about 1.2 to 1.3 for radio waves. For example if the
transmitter antenna is 625 feet high and the receiving antenna is 16 feet
high. YOu get sqrt 625 = 25 miles, then sqrt 16 = 4 miles. YOu add 25+4 =
29 miles for the visual distance. Then multiply this by 1.3 to get 37.7
miles of radio range.

Ralph Mowery wrote:
I seem to recall reading about a 'standard', it went something
like this,,,, a two meter antenna at 100 feet can "see" or be useable
for 17 miles. I don't recall where I read this,,, but would really
appreciate any and all input on the question,,,,,,,,,,,, How far can a
base two meter radio antenna transmit and recieve so as to be
'useable' when the antenn is 100 feet tall above the earth, and the
surronding area is fairly level. (no hills or mountains). I am
talking about a 50 watt base and 50watt mobil. If there is a formula
somewhere, would appreciate the input.
The reason I ask, is on the way by some very tall tv antennas
1000 and 1200feet, I got to wondering,,, they don't work well with
""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are
out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up
my brain'. thanks in advance. cl.73


A rough rule of thumb is to take the square root of the height in feet and
that will give you the miles from the antenna to the ground. YOu do this
again for the other antenna and add the number of miles. This can be
multiplied by about 1.2 to 1.3 for radio waves. For example if the
transmitter antenna is 625 feet high and the receiving antenna is 16 feet
high. YOu get sqrt 625 = 25 miles, then sqrt 16 = 4 miles. YOu add 25+4 =
29 miles for the visual distance. Then multiply this by 1.3 to get 37.7
miles of radio range.


Yep!! That's the way to do it!!

Ht of ant over gd Optical range limit Ht ant above sealevel limit
optical rg

5 ft 3.2 miles 1000 ft 45
miles
20 6.4 2000 63.5
50 10.0 3000 78
100 14.2 4000 90
500 32 5000 100

Horisontal dist calculated from S = 1.42root H
S = miles H = ht of observers eyes in feet above sea level Above table
gives horizon distance for various heights of antenna above sea level

RADIO DATA REFERANCE BOOK
RSGB

aRT







"Ralph Mowery" wrote in message ...
I seem to recall reading about a 'standard', it went something
like this,,,, a two meter antenna at 100 feet can "see" or be useable
for 17 miles. I don't recall where I read this,,, but would really
appreciate any and all input on the question,,,,,,,,,,,, How far can a
base two meter radio antenna transmit and recieve so as to be
'useable' when the antenn is 100 feet tall above the earth, and the
surronding area is fairly level. (no hills or mountains). I am
talking about a 50 watt base and 50watt mobil. If there is a formula
somewhere, would appreciate the input.
The reason I ask, is on the way by some very tall tv antennas
1000 and 1200feet, I got to wondering,,, they don't work well with
""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are
out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up
my brain'. thanks in advance. cl.73

A rough rule of thumb is to take the square root of the height in feet and
that will give you the miles from the antenna to the ground. YOu do this
again for the other antenna and add the number of miles. This can be
multiplied by about 1.2 to 1.3 for radio waves. For example if the
transmitter antenna is 625 feet high and the receiving antenna is 16 feet
high. YOu get sqrt 625 = 25 miles, then sqrt 16 = 4 miles. YOu add 25+4 =
29 miles for the visual distance. Then multiply this by 1.3 to get 37.7
miles of radio range.

Art, KB9MZ wrote:
"Horizontal distance calculated from

S = 1.42 root H----."

The 1.42 is rounded from 1.414 which is the square root of 2. The
formula previously given is:

Miles to the horizon = sq rt 2H

H is in feet.

You can remove 2 from under the radical by expressing it as 1.414. That
is all the RSGB did. I think it is easer to leave the 2 under the
radical, that is just to take the square root of 2x the antenna height
in feet when you are estimating the distance to the horizon in miles.
Usually you can do this in an instant in your head. The results are most
often good enough.

Best regards, Richard Harrison, KB5WZI

See Guide to Transmitter Range From Artsci --- URL:

http://www.artscipub.com/simpleton/simp.range.html

Also see VHF/UHF Line of Sight Calculator
http://www.vwlowen.demon.co.uk/java/horizon.htm

And Calculating the Distance to the Horizon URL:
http://www.wolfram.demon.co.uk/rp_horizon_distance.html

--
73 From The Wilderness Keyboard
-----------------------------------------------------------------
wrote in message
...
I seem to recall reading about a 'standard', it went something
like this,,,, a two meter antenna at 100 feet can "see" or be useable
for 17 miles. I don't recall where I read this,,, but would really
appreciate any and all input on the question,,,,,,,,,,,, How far can a
base two meter radio antenna transmit and recieve so as to be
'useable' when the antenn is 100 feet tall above the earth, and the
surronding area is fairly level. (no hills or mountains). I am
talking about a 50 watt base and 50watt mobil. If there is a formula
somewhere, would appreciate the input.
The reason I ask, is on the way by some very tall tv antennas
1000 and 1200feet, I got to wondering,,, they don't work well with
""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are
out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up
my brain'. thanks in advance. cl.73

Wilderness Keyboard wrote:
"See Guide to Transmitter Range from Artsci---."

See the 19th edition of the "ARRL Antenna Book" pages 23.5 and 23.6.

Eqn. 3:

Dmiles = 1.415 sq rt Hfeet

This can be rewritten:
D = sq rt 2H

Wasn`t it Albert Einstein who wrote something like: "Don`t make things
any more complicated than necessary?"

Solutions to Eqn 3 are plotted in Fig 6.

Example: 20 ft gives 6 miles. The approximate sq rt of 40 is 6 miles.

Example: 50 ft gives 10 miles. The approximate sq rt of 100 is 10 miles.

Example: 200 Ft gives 20 miles. The approximate sq rt of 400 is 20
miles.

Etc., etc., etc..

Best regards, Richard Harrison, KB5WZI

Richard Harrison, KB5WZI, wrote:

See the 19th edition of the "ARRL Antenna Book" pages 23.5 and 23.6.
Eqn. 3:
Dmiles = 1.415 sq rt Hfeet
This can be rewritten:
D = sq rt 2H

Wasn`t it Albert Einstein who wrote something
like: "Don`t make things any more complicated
than necessary?"

I think it was:

"Everything should be made as simple as
possible, but not simpler". -- Albert Einstein

But... whatever. I think Herr Doktor Einstein would
appove of the derivation from first principles found
on:

http://www.wolfram.demon.co.uk/rp_horizon_distance.html

K7JEB
Glendale, AZ

Artsci takes into account
To properly estimate a signals range, you must have a few important figures:
-- Frequency / Band
-- Transmitter power (in watts)
-- Antenna height (from sea level)
-- Antenna gain (net after coax loss)

And that is what the original poster asked for (I thought)
--
73 From The Wilderness Keyboard

"Richard Harrison" wrote in message
...
Wilderness Keyboard wrote:
"See Guide to Transmitter Range from Artsci---."

See the 19th edition of the "ARRL Antenna Book" pages 23.5 and 23.6.

Eqn. 3:

Dmiles = 1.415 sq rt Hfeet

This can be rewritten:
D = sq rt 2H

Wasn`t it Albert Einstein who wrote something like: "Don`t make things
any more complicated than necessary?"

Solutions to Eqn 3 are plotted in Fig 6.

Example: 20 ft gives 6 miles. The approximate sq rt of 40 is 6 miles.

Example: 50 ft gives 10 miles. The approximate sq rt of 100 is 10 miles.

Example: 200 Ft gives 20 miles. The approximate sq rt of 400 is 20
miles.

Etc., etc., etc..

Best regards, Richard Harrison, KB5WZI

K7JEB wrote:
"But....whatever, I think Herr Doktor Einstein would approve of the
derivation from first principles found on---."

No doubt, as that illustrates it is a problem involving geometry. But in
all cases the distance to the horizon is inexact due to constant
variations in refraction of the atmosphere. Most often the earth appears
to have a radius of about 4/3 the actual which means the earth appears
flatter than it is so that radio waves range farther than many
predictions. When propagation for line-of-sight signals gets tough in
the early am under still air conditions, the earth can apper to have 2/3
its actual radius or even less. Bad news out on the fringes!

Terman says:
"Theoretical analysis indicates that the earth curvature reduces the
received signal below the value calculated by Eq. (219) by the factor
given by Fig. 362. This factor takes into account that refraction in the
atmosphere and also the diffraction of the energy around the curved
surface. Under practical conditions the reduction factor of Fig. 362 is
negligible as long as a straight line path exists, but at greater
distances it decreases rapidly and the signals soon become unusable
because of fading, as mentioned below."

Terman also has a height versus distance chart similar to that in the
ARRL Antenna Book. Fact is that the experimentally determined formula is
related to the geometric calculations and is plenty close enough for
practice. I`ve used it commercially many times and for more than half a
century and never been embarrassed by inaccuracy causing excess expense
nor excess outage time. It is a good indicator of the radio distance to
the horizon under "usual" propogation conditions. It is easy to remember
and simple to apply.

Best regards, Richard Harrison, KB5WZI