Signal Propagation on sea water path
Signal Propagation on sea water path
(OP)
Hi
Is the propagation of a signal on a sea water path faster than that on a all ground path.
I know that conductivity causes this but what is the equation or theory that explains this effect on speed.
All literature I have got explains propagation INSIDE the medium (in water, in air).
My application frequency is 100 KHz.
Thanks
Is the propagation of a signal on a sea water path faster than that on a all ground path.
I know that conductivity causes this but what is the equation or theory that explains this effect on speed.
All literature I have got explains propagation INSIDE the medium (in water, in air).
My application frequency is 100 KHz.
Thanks





RE: Signal Propagation on sea water path
RE: Signal Propagation on sea water path
Mike Halloran
Pembroke Pines, FL, USA
RE: Signal Propagation on sea water path
ofcourse C is the max.
But in my application time is very critical.
a few hundred miles (390 miles) of sea water path as compared to ground path causes a 1 microsecond timing difference
and this is throwing me off in my further calculations.
Does anyone know any papers and stuff.
There is a Milingtons method for calculating this stuff but I cannot find that paper (1949 IEE).
RE: Signal Propagation on sea water path
RE: Signal Propagation on sea water path
I think I will have to dig more into the Loran papers as there is no other good solid source of info.
RE: Signal Propagation on sea water path
RE: Signal Propagation on sea water path
I have found a paper "Geographic information system Loran C coverage modeling".
I think this paper has few equations which may answer the question (I am not sure).
these equations discuss conductivity, path impedance, SNR and TOA (time of arrival varaince).
If anyone is interested you can check it out at
http://ww
RE: Signal Propagation on sea water path
It is possible that the library here could have one in the archives, but I see in this extract that the phase velocity reduces with altitude and frequency and changes with path conductivity (seawater sigma = 5.0 mhos/m, e = 80), so I expect the solution to your issue is going to be quite complex. I see that skywave propogation is also a factor.
Might be time to bring out the Kalman filter.
RE: Signal Propagation on sea water path
Years ago I was involved in a project to grab the phase of a MW groundwave signal before the skywave arrived. One could clearly see on the scope the clean and steady waveform up to the point when the skywave arrived and made a mess of it.
I hope that orcus drops by again with the answer once he finds it - interesting topic.
RE: Signal Propagation on sea water path
Seems like the rf would travel thru the water on long distance over the horizon trips and be 9x slower than in air. On shorter trips, travelling thru air would seem correct. Hence the rf travel speed must transition from standard lightish speed to 9x slower as distance changes from short to long. Throw in the ground travel in shallow water areas and the answer is even more convoluted.
In the reference by orcus above, sea water is 80 dielectric constant and land is 15 dielectric constant. Hence the rf over very long distances is probably 4 to 9 times slower than air travel. No way it's faster.
kch
dielectric constant of sea water reference.
http://ww
RE: Signal Propagation on sea water path
RE: Signal Propagation on sea water path
That fits with the vacuum of space being the fastest.
OP seems to have been asking (backwards) if the speed over land is slower than over the sea. I've never heard about the ~adjacent~ media affecting the speed of light.
RE: Signal Propagation on sea water path
RE: Signal Propagation on sea water path
I too was under the impression that adjacent media does not affect the speed of light. But apparently there is a very very small change in speed (Loran needs a heck of a timing accuracy and 1us corressponds to 300m)
Brian I think 100 Khz is still a high frequency to propagate through the seawater. (skin depth is 0.8m) and I am looking at distances in excess of 100 miles. Hence I do not agree on
"it's not really adjacent as part of the propogation occurs in that media too "
I would definitely recommend to read through those few equations in that paper
http://ww
which discusses the variance in time of arrival. I am still lost in those equations cause I am not sure if they are talking abt adjacent media.
This is definitely a interesting topic and I am getting a good experience with you guys.
RE: Signal Propagation on sea water path
www.eurofix.tudelft.nl/pdf/ion97.pdf
It mentions an "Additional Secondary phase Factor (ASF)" as being the term applied to the propagation difference arising from soil and water conductivity differences. Some references are given. Maybe this "ASF" phenomenon is what you are looking for.
RE: Signal Propagation on sea water path
Yes the ASF tables correspond to variations in conductivity.
the time required for a loran groundwave signal to propagate
comprises of 3 factors
1) primary factor using c = 3e8 m/s. (distance/speed)
2) secondary phase factor (SF), corrects for signal propagation delays over seawater compared to propagation through the atmosphere. (this is what I am looking for)
3)ASFs correct for propagation delay over a mixed land/seawater path compared to an all-seawater path.
These factors show that adjacent medium does affect the speed of light.
RE: Signal Propagation on sea water path
http://w
Interesting topic.
RE: Signal Propagation on sea water path
RE: Signal Propagation on sea water path
I think a lot more research is needed
If I get any solution I will definitely
post it.
RE: Signal Propagation on sea water path
Seems very small the delay, I guess my 4x-9x slower propagation speed was only off by a factor of 1000. I feel more informed now, which is nice.
kch
RE: Signal Propagation on sea water path
I think I know what you mean and I'm sure it isn't 23k miles per second (C/8).
RE: Signal Propagation on sea water path
kch