Practical question related to db

[Fulcum]

- A radio-receiver receives a signal from a transmittor transmitting at a
certain power level.
- The maximum distance that the receiver detects the signal is 300meter
- Suppose the transmittor signal level would be 25db lower, using the same
antenna's etc.

How much lower would the maximum distance be.

Thanks in advance for your help!

 

[Fred Bloggs]

- A radio-receiver receives a signal from a transmittor transmitting at a
certain power level.
- The maximum distance that the receiver detects the signal is 300meter
- Suppose the transmittor signal level would be 25db lower, using the same
antenna's etc.

How much lower would the maximum distance be.

Thanks in advance for your help!

See your advisor about changing the major to bullshitology- and get lost
while you're at it.

 

[Fulcum]

Didn't your mother teach you manners?

 

[Fred Bloggs]

Didn't your mother teach you manners?

Take your damned punk-ass Dutch self and get the hell off this NG....

 

[Reg Edwards]

- A radio-receiver receives a signal from a transmittor transmitting at a

certain power level.
- The maximum distance that the receiver detects the signal is 300meter
- Suppose the transmittor signal level would be 25db lower, using the same
antenna's etc.

How much lower would the maximum distance be.

==========================

The maximum distance would fall to about 17 meters.

 

[Fulcum]

Thank you reg!

 

[Dbowey]

Fred, behaving as if he was King of the newsgroup instead of merely a rude
jerk, posted

Didn't your mother teach you manners?

Take your damned punk-ass Dutch self and get the hell off this NG....
Say, Fred, having a bad day? You really should cool it lest we think ill of
you.

Don

 

[Philip A. Marshall]

Thank you reg!

the answer isn't any good unless you know how to solve it yourself.
what if it was changed to 20dB lower? then you'd be lost again. much
better to understand how to calculate it.

also, it's dB, not db. and antennas, not antenna's.

 

[Genome]

| > - A radio-receiver receives a signal from a transmittor transmitting
at a
| > certain power level.
| > - The maximum distance that the receiver detects the signal is
300meter
| > - Suppose the transmittor signal level would be 25db lower, using
the same
| > antenna's etc.
| >
| > How much lower would the maximum distance be.
| >
| ==========================
|
| The maximum distance would fall to about 17 meters.
| ----
| Reg
|
|

Spooky..... 25dB is 17.78 times less voltage. 17.78 times less of 300M
is 16.87 meters.

Is it that simple?

DNA

 

[Alan]

| > - A radio-receiver receives a signal from a transmittor transmitting
at a
| > certain power level.
| > - The maximum distance that the receiver detects the signal is
300meter
| > - Suppose the transmittor signal level would be 25db lower, using
the same
| > antenna's etc.
| >
| > How much lower would the maximum distance be.
| >
| ==========================
|
| The maximum distance would fall to about 17 meters.
| ----
| Reg
|
|

Spooky..... 25dB is 17.78 times less voltage. 17.78 times less of 300M
is 16.87 meters.

Is it that simple?

DNA

Distance is proportional to the square root of the power

or alternatively (as power = voltage squared x impedance)

distance is proportional to the voltage


Alan


++++++++++++++++++++++++++++++++++++++++++
Jenal Communications
Manufacturers and Suppliers of HF Selcall
P O Box 1108, Morley, WA, 6943
Tel: +61 8 9370 5533 Fax +61 8 9467 6146
Web Site: http://www.jenal.com
e-mail: http://www.jenal.com/?p=1
++++++++++++++++++++++++++++++++++++++++++

 

[Fred Bloggs]

Distance is proportional to the square root of the power

or alternatively (as power = voltage squared x impedance)

distance is proportional to the voltage


Alan


++++++++++++++++++++++++++++++++++++++++++
Jenal Communications
Manufacturers and Suppliers of HF Selcall
P O Box 1108, Morley, WA, 6943
Tel: +61 8 9370 5533 Fax +61 8 9467 6146
Web Site: http://www.jenal.com
e-mail: http://www.jenal.com/?p=1
++++++++++++++++++++++++++++++++++++++++++

The thing is S/N received = k x Pxmit/ Range^2 so that
Pxmit,1/R1^2=Pxmit2/R2^2 for S/N minimum acceptable level so that
(R2/R1)=SQRT(Pxmit2/Pxmit1)- then since Pxmit2/Pxmit1= 10^(-25/10) this
implies R2=R1 x 10^(-25/20)=300m x 0.0562=16.9 meters.

 

[Activ8]

the answer isn't any good unless you know how to solve it yourself.
what if it was changed to 20dB lower? then you'd be lost again. much
better to understand how to calculate it.

also, it's dB, not db. and antennas, not antenna's.

or antennae<snip>

 

[L. Fiar]

or antennae

Only when referring to the feelers found on the heads of some creatures.
When referring to the devices used for radio, the plural is antennas.

REF: Collins Compact Dictionary.

 

[Activ8]

Only when referring to the feelers found on the heads of some creatures.
When referring to the devices used for radio, the plural is antennas.

REF: Collins Compact Dictionary.

I sometimes go against the grain.