K1YW wrote:
"Artsci takes into account:
To properly estimate a signal`s 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)

As a practical matter, first you must have a line-of-sight path. Then
you can worry about path attenuation, gains, losses, transmitter power
and receiver sensitivity.

Attenuation between stations with an obstructed path (including earth
bulge) rises so rapidly with the obstruction that non of the other
factors matters except in the case of brute force communication, such as
atmospheric scatter.

Best regards, Richard Harrison, KB5WZI

Terman also says the radio horizon as seen from a ground-mounted vertical
antenna is at distance of -

50 / Cuberoot(FreqMhz) miles.

This does not mean the ground wave suddenly weakens at this distance but
that Earth curvature and atmospheric refraction begin to have a significant
effect on ground-wave propagation.

At MF and LF, useful ground-wave propagation can occur at distances
considerably greater than the radio horizon. At HF the skywave can provide
stronger signals.
----
Reg, G4FGQ

Well -- the original post was from he asked:
"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."

So Artsci should help him.

--
73 From The Wilderness Keyboard
--------------------------------------------------
"Richard Harrison" wrote in message
...
K1YW wrote:
"Artsci takes into account:
To properly estimate a signal`s 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)

As a practical matter, first you must have a line-of-sight path. Then
you can worry about path attenuation, gains, losses, transmitter power
and receiver sensitivity.

Attenuation between stations with an obstructed path (including earth
bulge) rises so rapidly with the obstruction that non of the other
factors matters except in the case of brute force communication, such as
atmospheric scatter.

Best regards, Richard Harrison, KB5WZI

K1YW wrote:
"So Artsci should help him (KC5CQA)."

50-watt radios will talk with plenty of exess fade margin over any
line-of-sight path from a 100-foot tower to any land mobile in the
two-meter band.

Beyond line-of-sight, VHF propagation is kaput because the signal does
not follow earth curvature as Reg`s low and medium frequencies do.

Over smooth earth or sea, the horizon is sq rt of 200 from a 100-foot
high antenna. That is about 14 miles. Add 4 or 5 miles of range due to
the mobile antenna height and that is near the maximum range. 5 watts,
100 watts, or 500 watts make very little difference in range. Range is
extended with increased power very slightly. There is some noise
reduction. In my experience, I found it advantageous to use 50-watt
mobiles and 500-watt base stations. This is because the mobile is often
in a noisier environment than the base station. Obviously the path
length is the same in both directions in this VHF application.

The dominant requirement in VHF communication is a line-of-sight path.
Once that is obtained, all else is secondary.

Most of the microwave stations I`ve put in have 100-milliwatt
transmitters and these produced 30 dB fade margins on paths of more than
20 miles. For land mobile VHF service, you usually have no significant
antenna gains, but you also have significantly lower path and
transmission line losses, higher receiver sensitivities, and higher
transmitter powers. Received carrier power to produce full quieting in a
good receiver is very small indeed. This makes line-of-sight the only
significant requirement for single-channel, single-hop VHF
communications. Noise is cumulative, so for a multi-hop system, big
signal surplus is required on each hop to supress noise to make the
cumulative total acceptable.

Best regards, Richard Harrison, KB5WZI

There is almost always some kind of enhanced propagation. With 50W SSB to a
10 element 2 meter beam at 40 feet, 90% of the time my range is 75 - 100
miles when talking to another base station. I don't think they all have 1000
foot towers.

Tam/WB2TT
"Richard Harrison" wrote in message
...
K1YW wrote:
"So Artsci should help him (KC5CQA)."

50-watt radios will talk with plenty of exess fade margin over any
line-of-sight path from a 100-foot tower to any land mobile in the
two-meter band.

Beyond line-of-sight, VHF propagation is kaput because the signal does
not follow earth curvature as Reg`s low and medium frequencies do.

Over smooth earth or sea, the horizon is sq rt of 200 from a 100-foot
high antenna. That is about 14 miles. Add 4 or 5 miles of range due to
the mobile antenna height and that is near the maximum range. 5 watts,
100 watts, or 500 watts make very little difference in range. Range is
extended with increased power very slightly. There is some noise
reduction. In my experience, I found it advantageous to use 50-watt
mobiles and 500-watt base stations. This is because the mobile is often
in a noisier environment than the base station. Obviously the path
length is the same in both directions in this VHF application.

The dominant requirement in VHF communication is a line-of-sight path.
Once that is obtained, all else is secondary.

Most of the microwave stations I`ve put in have 100-milliwatt
transmitters and these produced 30 dB fade margins on paths of more than
20 miles. For land mobile VHF service, you usually have no significant
antenna gains, but you also have significantly lower path and
transmission line losses, higher receiver sensitivities, and higher
transmitter powers. Received carrier power to produce full quieting in a
good receiver is very small indeed. This makes line-of-sight the only
significant requirement for single-channel, single-hop VHF
communications. Noise is cumulative, so for a multi-hop system, big
signal surplus is required on each hop to supress noise to make the
cumulative total acceptable.

Best regards, Richard Harrison, KB5WZI

Tam, WB2TT wrote:
"There is almost always some kind of enhanced propagation."

True. It is also true that a 10-element beam and high power extend
transmission range.

Terman has eqn. (22-7b) on page 820 of his 1955 edition:

"Radio horizon distance in miles = sq rt 2h
Again, h is in feet."

Terman also says: "In the special case of the standard atmosphere, k =
1.33 and the horizon distance becomes, miles = sq rt 2h."

1.33 means the earth`s radius appears as 4/3 the actual value.due to
atmosphere causing the radio horizon to be more distant than the optical
horizon.

On page 825, Terman says:
"Fading is most pronounced when the received signal is much weaker than
the free-space value for the distance involved. Thus fading is usually
greatest near the radio horizon and in the shadow zone, and tends to be
small when a "good" optical path is present."

My experience agrees with Terman. We all know that VHF propagation does
not always follow the simple rules.

My contention is that path clearance outshines other considerations in
determining "How far can an antenna see?". Terman`s eqn. (22-7b) is the
usual answer.

Best regards, Richard Harrison, KB5WZI

O.K. CAN YOU HEAR ME NOW ?









"Tarmo Tammaru" wrote in message ...
There is almost always some kind of enhanced propagation. With 50W SSB to a
10 element 2 meter beam at 40 feet, 90% of the time my range is 75 - 100
miles when talking to another base station. I don't think they all have 1000
foot towers.

Tam/WB2TT
"Richard Harrison" wrote in message
...
K1YW wrote:
"So Artsci should help him (KC5CQA)."

50-watt radios will talk with plenty of exess fade margin over any
line-of-sight path from a 100-foot tower to any land mobile in the
two-meter band.

Beyond line-of-sight, VHF propagation is kaput because the signal does
not follow earth curvature as Reg`s low and medium frequencies do.

Over smooth earth or sea, the horizon is sq rt of 200 from a 100-foot
high antenna. That is about 14 miles. Add 4 or 5 miles of range due to
the mobile antenna height and that is near the maximum range. 5 watts,
100 watts, or 500 watts make very little difference in range. Range is
extended with increased power very slightly. There is some noise
reduction. In my experience, I found it advantageous to use 50-watt
mobiles and 500-watt base stations. This is because the mobile is often
in a noisier environment than the base station. Obviously the path
length is the same in both directions in this VHF application.

The dominant requirement in VHF communication is a line-of-sight path.
Once that is obtained, all else is secondary.

Most of the microwave stations I`ve put in have 100-milliwatt
transmitters and these produced 30 dB fade margins on paths of more than
20 miles. For land mobile VHF service, you usually have no significant
antenna gains, but you also have significantly lower path and
transmission line losses, higher receiver sensitivities, and higher
transmitter powers. Received carrier power to produce full quieting in a
good receiver is very small indeed. This makes line-of-sight the only
significant requirement for single-channel, single-hop VHF
communications. Noise is cumulative, so for a multi-hop system, big
signal surplus is required on each hop to supress noise to make the
cumulative total acceptable.

Best regards, Richard Harrison, KB5WZI