tx power versus received signal

I can never quite get my head round this. Suppose a transmitter
increases the ERP from 10kW to 20kW. What will the increase in received
signal strength be, expressed in dB? What about an increase from 10 to 15kW?

Bill

"Bill Wright" wrote in message
...
I can never quite get my head round this. Suppose a transmitter increases
the ERP from 10kW to 20kW. What will the increase in received signal
strength be, expressed in dB? What about an increase from 10 to 15kW?

Bill

10kW to 20 is 3dB, so the signal will increase by that much, 10 to 15 is
about 1.6dB
Y.



--- news://freenews.netfront.net/ - complaints: ---

Surely that depends also on the polar diagram of the transmitting aerial as
well. I also used to notice that there were wide variations from day to ay
even with outside aerials at UHF, as presumably, the moisture content of the
intervening air mattered much more at high frequencies.
I'm certainly not going to postulate on this one. I have had too many run
ins with the mythical isotropic radiator..
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Bill Wright" wrote in message
...
I can never quite get my head round this. Suppose a transmitter increases
the ERP from 10kW to 20kW. What will the increase in received signal
strength be, expressed in dB? What about an increase from 10 to 15kW?

Bill

"Brian Gaff" wrote in message
...
Surely that depends also on the polar diagram of the transmitting aerial
as well. I also used to notice that there were wide variations from day to
ay even with outside aerials at UHF, as presumably, the moisture content
of the intervening air mattered much more at high frequencies.
I'm certainly not going to postulate on this one. I have had too many run
ins with the mythical isotropic radiator..
Brian

Yes but...
at any one time and direction, the signal strength will increase by (if the
TX goes up to 20kW from 10) 3dB, (The reading on a FSM in volts will go up
by the square root of 2) even though it will as you say vary over time.
Y.



--- news://freenews.netfront.net/ - complaints: ---

In article , Brian Gaff
wrote:
Surely that depends also on the polar diagram of the transmitting aerial
as well. I also used to notice that there were wide variations from day
to ay even with outside aerials at UHF, as presumably, the moisture
content of the intervening air mattered much more at high frequencies.

there was one genuine wideband aerial which worked absolutely perfectly
when it was dry, but was so tightly designed that it lost all the high
channels when it rained. Droplets of water collected on the ends of the
elements and detuned it.

--
From KT24

Using a RISC OS computer running v5.18

In article , Y Dangle
scribeth thus

"Brian Gaff" wrote in message
...
Surely that depends also on the polar diagram of the transmitting aerial
as well. I also used to notice that there were wide variations from day to
ay even with outside aerials at UHF, as presumably, the moisture content
of the intervening air mattered much more at high frequencies.
I'm certainly not going to postulate on this one. I have had too many run
ins with the mythical isotropic radiator..
Brian

Yes but...
at any one time and direction, the signal strength will increase by (if the
TX goes up to 20kW from 10) 3dB, (The reading on a FSM in volts will go up
by the square root of 2) even though it will as you say vary over time.
Y.


This isn't really answering the question. Bill asked what would be the
increase at the receiver if the TX power or ERP went up by a given
amount. If nothing else is altered then the simple answer and accurate
answer is the RX level will increase by the same so if TX goes up from
10 to 20 kW ERP and NO alterations are made to the receive system then
there will be a simple 3 dB increase or 3.01 dB for the correct
figure..

If you alter the radiation pattern in that instance then you can say
that the RX received level has increased or decreased by x dB which is
in effect the same thing, as at the TX end altering the radiation
pattern is altering the ERP unless you alter summat else!"..

That can also be an alteration in the actual TX power, the feeder losses
the combiner or filtering losses and the aerial gain and or pattern.

Altering any of those will affect the overall ERP and hence the level
received at the receiving end will move the same amount as long as you
don't make any alterations at the RX end..


As to the Isotropic it is mythical in concept as it's only that, you
simply cannot produce one .. it cannot exist in reality...

--
Tony Sayer

In article , charles
scribeth thus
In article , Brian Gaff
wrote:
Surely that depends also on the polar diagram of the transmitting aerial
as well. I also used to notice that there were wide variations from day
to ay even with outside aerials at UHF, as presumably, the moisture
content of the intervening air mattered much more at high frequencies.

there was one genuine wideband aerial which worked absolutely perfectly
when it was dry, but was so tightly designed that it lost all the high
channels when it rained. Droplets of water collected on the ends of the
elements and detuned it.


Which one was that Charles?..
--
Tony Sayer

In article ,
tony sayer wrote:
In article , charles
scribeth thus
In article , Brian Gaff
wrote:
Surely that depends also on the polar diagram of the transmitting
aerial as well. I also used to notice that there were wide variations
from day to ay even with outside aerials at UHF, as presumably, the
moisture content of the intervening air mattered much more at high
frequencies.

there was one genuine wideband aerial which worked absolutely perfectly
when it was dry, but was so tightly designed that it lost all the high
channels when it rained. Droplets of water collected on the ends of the
elements and detuned it.


Which one was that Charles?..

It was a long time ago - came on sale just as the Over Biddulph relay came
into service, when ever that was. Made by Jaybeam. I think it was the JBX5.

--
From KT24

Using a RISC OS computer running v5.18

Well yes, but I have noticed that a lot of the time the power quoted is ERP,
and they have tweaked lobes to make better coverage when they changed the
pwer, if they actually did and not just the gain of aerials in a given
direction.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Y Dangle" wrote in message
...

"Brian Gaff" wrote in message
...
Surely that depends also on the polar diagram of the transmitting aerial
as well. I also used to notice that there were wide variations from day
to ay even with outside aerials at UHF, as presumably, the moisture
content of the intervening air mattered much more at high frequencies.
I'm certainly not going to postulate on this one. I have had too many run
ins with the mythical isotropic radiator..
Brian

Yes but...
at any one time and direction, the signal strength will increase by (if
the TX goes up to 20kW from 10) 3dB, (The reading on a FSM in volts will
go up by the square root of 2) even though it will as you say vary over
time.
Y.


--- news://freenews.netfront.net/ - complaints: ---

Yes, I know, I know, but somehow, reception and the theory do not seem to
have a great correlation, probably due to real world stuff like buildings
and weather.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"tony sayer" wrote in message
news
In article , Y Dangle
scribeth thus

"Brian Gaff" wrote in message
...
Surely that depends also on the polar diagram of the transmitting aerial
as well. I also used to notice that there were wide variations from day
to
ay even with outside aerials at UHF, as presumably, the moisture content
of the intervening air mattered much more at high frequencies.
I'm certainly not going to postulate on this one. I have had too many
run
ins with the mythical isotropic radiator..
Brian

Yes but...
at any one time and direction, the signal strength will increase by (if
the
TX goes up to 20kW from 10) 3dB, (The reading on a FSM in volts will go up
by the square root of 2) even though it will as you say vary over time.
Y.


This isn't really answering the question. Bill asked what would be the
increase at the receiver if the TX power or ERP went up by a given
amount. If nothing else is altered then the simple answer and accurate
answer is the RX level will increase by the same so if TX goes up from
10 to 20 kW ERP and NO alterations are made to the receive system then
there will be a simple 3 dB increase or 3.01 dB for the correct
figure..

If you alter the radiation pattern in that instance then you can say
that the RX received level has increased or decreased by x dB which is
in effect the same thing, as at the TX end altering the radiation
pattern is altering the ERP unless you alter summat else!"..

That can also be an alteration in the actual TX power, the feeder losses
the combiner or filtering losses and the aerial gain and or pattern.

Altering any of those will affect the overall ERP and hence the level
received at the receiving end will move the same amount as long as you
don't make any alterations at the RX end..


As to the Isotropic it is mythical in concept as it's only that, you
simply cannot produce one .. it cannot exist in reality...

--
Tony Sayer