Radio Distance Question discussion

[rfradioconsult]

Ok guys, it's cold and raining here and will stick around for a few days, so how about a lively discussion to warm thing up.

Q. What is the ultimate range limiting factor of a radio signal from a given transmitter to a given receiver?

Hint: There are two factors, either one or the other. The question contains all the information that you need to answer.

 

[Shortwavewave]

Noise?

 

[N_Jay]

Signal

 

[jhooten]

Atmosphere and curvature of the earth.

 

[N_Jay]

Or more correctly;

Signal to Noise ratio

 

[N_Jay]

Atmosphere and curvature of the earth.

Nope!

 

[zz0468]

s/n ratio is the correct answer, but I'm under the (perhaps mistaken) impression that the question isn't looking for that simple an answer.

I'm going to say the two ultimate factors determining range are receiver noise temperature and bandwidth... which boils down to s/n.

 

[N_Jay]

s/n ratio is the correct answer, but I'm under the (perhaps mistaken) impression that the question isn't looking for that simple an answer.

I'm going to say the two ultimate factors determining range are receiver noise temperature and bandwidth... which boils down to s/n.

But to that you would have to add desired signal level.

You got the noise part but forgot the signal part.

 

[zz0468]

Didn't forget, really. It's an incomplete answer to an incomplete question. But yes, you're right - it's only part of the story...

 

[rfradioconsult]

Ok guys, it's cold and raining here and will stick around for a few days, so how about a lively discussion to warm thing up.

Q. What is the ultimate range limiting factor of a radio signal from a given transmitter to a given receiver?

Hint: There are two factors, either one or the other. The question contains all the information that you need to answer.

Good going guys! One answer is noise. Ambient noise, thermal noise, internal noise generated within the receiver. As we know volumes have been written on antenna theory, radio propagation and others on the "black art" of radio. As student's (all of us are student's) and practactioners of the art we all know it's all FM i.e.: Fucxxxx Magic.

Now part two what is the second factor?

I'm posting these to perhaps impart the years of knowledge and experience that some of us have to those that have developed an interest in all things radio. After WW-II many ex. GI's were the innovators and developers of the radio field. I know I was lucky enough to start my radio career in the 60's while many of these innovators were still around.

 

[N_Jay]

Now part two what is the second factor?

We covered them both. :roll: :roll:

All a receiver cares about is signal and noise. A transmitter just generates signal and noise, and the path just adds noise and takes away signal.

 

[zz0468]

All a receiver cares about is signal and noise. A transmitter just generates signal and noise, and the path just adds noise and takes away signal.

That's actually a nice, elegantly simple little summary of the whole process. There really isn't much more to discuss about it.

 

[N_Jay]

That's actually a nice, elegantly simple little summary of the whole process. There really isn't much more to discuss about it.

So true, but since (according to some here) my posts are worthless, I guess this one is also.:roll: :twisted: :roll: :twisted: :roll:

 

[jhooten]

Nope!

Been a long time since I actually had to to path planning.

 

[N_Jay]

Been a long time since I actually had to to path planning.

But the question did not say or even imply it was for a specific path or that it was a terrestrial system.

 

[rfradioconsult]

External interference also enters into the question. Co-channel, adjacent channel, intermod products, man made noise, solar noise.

Back when, DecibelProducts published an intermod product finder in a sprial notebook, you could look up simple intermod problems.

 

[N_Jay]

External interference also enters into the question. Co-channel, adjacent channel, intermod products, man made noise, solar noise.

Back when, DecibelProducts published an intermod product finder in a sprial notebook, you could look up simple intermod problems.

That is all "noise".

It's been discussed.

 

[obijohn]

But to that you would have to add desired signal level.

You got the noise part but forgot the signal part.

As an example- NBFM requires about 20 db more signal to be readable than SSB.

 

[prcguy]

Not true. SSB has a slight advantage on paper due to the narrower BW but with many years of testing this specific topic from HF through UHF, I have never had signals readable out of the noise on one mode and not the other. Any major difference would be from a bad implementation of one mode over the other by a specific radio manufacturer. CW is another story and can be copied well beyond the point SSB or FM is not usable.
prcguy

As an example- NBFM requires about 20 db more signal to be readable than SSB.

 

[rescuecomm]

I guess S/N is the main thing for propagation through a vacuum. Something like the Voyager/Pioneer transmissions from a billion miles away. For us laypersons on earth, it might be path loss, since S/N could be affected by man-made (or woman made) interference.

Bob