theoretical radio range....

i have a radio rated at 10W and a radio rated for 5W output. mine 5
watter isn't a handheld but this is typical output for that genre.

assuming they are using the same antenna what is the theoretical range
difference between the two and what is the practical range
difference? it seems the price difference is 2X to 3X. is the price
difference justified?

i guess i'm asking "should i ebay the 10W unit and find a better use
for the remainder?"

Andy wrote:

i have a radio rated at 10W and a radio rated for 5W output. mine 5
watter isn't a handheld but this is typical output for that genre.

assuming they are using the same antenna what is the theoretical range
difference between the two and what is the practical range
difference? it seems the price difference is 2X to 3X.

is the price difference justified?
No.... you will get similar range... If you want the best range you can,
just install a "perfect" antenna.

I may acheive a 40Nm range with 2500' above grouns with an old Icom A20.
The "secret" is a good and large ground pannel inside the wood and
fabric fuselage. It's made from metalic mosquito mesh.

by
--
Volem rien foutre al païs! minicab F-PRAZ
Philippe Vessaire Ò¿Ó¬

"Andy" wrote in message
oups.com...
i have a radio rated at 10W and a radio rated for 5W output. mine 5
watter isn't a handheld but this is typical output for that genre.

assuming they are using the same antenna what is the theoretical range
difference between the two and what is the practical range
difference? it seems the price difference is 2X to 3X. is the price
difference justified?

i guess i'm asking "should i ebay the 10W unit and find a better use
for the remainder?"

My recollections from physics 20+ years ago is that radio wave strength is
determined by the cube root of the transmitter strength. So, a 10w radio
has twice the power of a 5w radio. The cube root of 2 (twice the power) is
1.26, meaning that the higher powered radio should have 26% more range than
the low powered radio.

One thing to consider is that a 10w radio will have an easier time
overpowering a distant signal, so your transmissions get "stepped on" less.

KB

"Kyle Boatright" wrote

One thing to consider is that a 10w radio will have an easier time
overpowering a distant signal, so your transmissions get "stepped on"
less.

But it will receive no better than the 5w radio.
--
Jim in NC

"Kyle Boatright" wrote in message
...

My recollections from physics 20+ years ago is that radio wave strength is
determined by the cube root of the transmitter strength. So, a 10w radio has
twice the power of a 5w radio. The cube root of 2 (twice the power) is 1.26,
meaning that the higher powered radio should have 26% more range than the low
powered radio.

Another way of saying the same thing is that to double the range, you must
quadruple the power.

I think Kyle has stated the theoretical difference. The actual difference
is that you likely won't notice any difference caused by the difference in
output power. The antenna and the modulation quality probably matter more than
the output power.


One thing to consider is that a 10w radio will have an easier time
overpowering a distant signal, so your transmissions get "stepped on" less.

That is a small (but valid) consideration. Another valid consideration is
that the higher power radio will cause more interference. Particularly when
transmitting on Unicom channels that are reused by nearby airports.

In article .com,
Andy wrote:
i have a radio rated at 10W and a radio rated for 5W output. mine 5
watter isn't a handheld but this is typical output for that genre.

assuming they are using the same antenna what is the theoretical range
difference between the two and what is the practical range
difference?

I know a ham who used to routinely work moon-bounce on VHF, with a rig
powered by a single 9v transistor radio battery. I think he had something
like 60 _milliwatts_ on transmit.

Good antenna's (and proper installations) make a bigger difference than RF
power. Years ago, I had a base-station installation that outperformed
virtually every other installation in the territory -- who were almost all
running 2-4.5x the power I was.

Now, "all else being equal", and for the same recieved RF signal level,
range will chage proportionally to the square-root of the change in
power level.

Caveat: 'all else' is *rarely* equal. wry grin

That said, the 10-watt rig would be expected to have an approximately 40%
greater working range than the 5-watter. *Assuming*, of course, that the
transmitter on the _far_end_ has sufficient power to reach _you_ at that
distance.

it seems the price difference is 2X to 3X. is the price
difference justified?

Depends on 'how badly' you need the extra range, doesn't it? *grin*

Only -you- can evaluate your needs/requirements.

i guess i'm asking "should i ebay the 10W unit and find a better use
for the remainder?"

"Vaughn Simon" wrote in message
...

"Kyle Boatright" wrote in message
...

My recollections from physics 20+ years ago is that radio wave strength
is determined by the cube root of the transmitter strength. So, a 10w
radio has twice the power of a 5w radio. The cube root of 2 (twice the
power) is 1.26, meaning that the higher powered radio should have 26%
more range than the low powered radio.

Another way of saying the same thing is that to double the range, you
must quadruple the power.

I think Kyle has stated the theoretical difference. The actual
difference is that you likely won't notice any difference caused by the
difference in output power. The antenna and the modulation quality
probably matter more than the output power.

The real limiting factor is that VHF is line-of-sight. Over relatively flat
terrain either radio is capable of reaching the horizon until you get above
8500-10000 feet. In mountainous terrain, the horizon is typically much
less.

At 10000 feet the horizon is a little over 100 nm which the 5W radio is
capable of reaching. If you get above that, you'll get more range out of
the 10W, but practically, it will be about 10-20% more. And even it will
max out at about 130-140 nm, regardless of altitude. The 5W will max out
around 105-115 nm.

Most of the time, you'll be talking to someone less than 50 nm away.

Gerry

"I know a ham who used to routinely work moon-bounce on VHF, with a rig
powered by a single 9v transistor radio battery. I think he had something
like 60 _milliwatts_ on transmit."

Although the statement does not give all of the facts, I am sure there is an
error. The moon is 250,000 miles away - which means a total distance
travelled of 500,000 miles. The signals must refect off a less than perfect
reflecting surface (moon dust).

I am an amateur operator and have heard signals off the moon. With modern
digital modes, there is an improvement in single signal performance - and if
the station on the other end has a giant antenna (such as the giant radio
telescope in Puerto Rico, used on occasion by amateurs having fun), it is
possible to work moonbounce with a 100 watt rig and a long single yagi.

That is a far cry from 60 milliwatts. There is about 32 db difference
between 60 mw and 100 watts. That would mean the antenna, instead of 15 db
gain for a long yagi would need to have 47 db gain. An antenna that size
might raise some neighbor's objections (blocking the sun). And, operating
it would not be routine, as an antenna with such high gain needs to track
the sun. Might need something about the size of a locomotive to move it.

Colin

Assuming a 1 microvolt (pretty numb these days) receiver at the other end
and quarter wave vertical whips at both ends, a 5 watt transmitter has a
THEORETICAL range of about 3000 miles. Doubling the power increases the
range by (sqrt(2)) or a THEORETICAL range of about 4300 miles for the 10
watter.

Now since most of us will operate somewhere below the oxygen limited 12000
MSL altitude, and presuming you are over the ocean, your range will be
horizon ("line of sight") limited by the old familiar equation that horizon
(in miles) is equal to 1.4 times (sqrt (altitude in feet)) or something on
the order of 150 miles. You may get a BIT of refraction, but not enough to
make a difference in the basic equation.

The real answer is that 5 or 10 watts really doesn't make a difference in
quiet spectrum range. It only helps "punch through" when there is a lot of
interfering garbage on the frequency.

Jim



"Andy" wrote in message
oups.com...
i have a radio rated at 10W and a radio rated for 5W output. mine 5
watter isn't a handheld but this is typical output for that genre.

assuming they are using the same antenna what is the theoretical range
difference between the two and what is the practical range
difference? it seems the price difference is 2X to 3X. is the price
difference justified?

i guess i'm asking "should i ebay the 10W unit and find a better use
for the remainder?"

Square root.

jw


"Kyle Boatright" wrote in message
...


My recollections from physics 20+ years ago is that radio wave strength is
determined by the cube root of the transmitter strength.