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[aprssig] APRS, caves! & More HF

Ray Wells vk2tv at exemail.com.au
Thu Nov 22 06:27:48 UTC 2012


This is becoming an Aladdin's Cave of (technical) treasures.

Sorry, I'm off my medication!!

Ray vk2tv

On 22/11/12 17:18, Steve Noskowicz wrote:
> I did some back of the envelope calculations...Well... Excel anyway.
> Looking at the Skin depth chart for 'earth' in the Speleonics 
> newsletter #1 gave me an idea.
> Calculate the path loss of earth on 160 meters using skin depths.
> Given that one skin depth has 8.7 dB of loss...
> And assuming you can get a full 5 watts power into the ground at the 
> Tx surface...
> And assuming you can get all the energy out of the ground at the 
> receive "end".
> Looking at the Skin depth chart for 'earth' in the Speleonics 
> newsletter #1...
> The middle curve of .01 mhos/meter of ground conductivity shows a skin 
> depth of about 4 meters at 2 MHz.
> With a receiver sensitivity of -110 dBm (0.7 uV) this is a path loss 
> capability of 147 dB.
> Which translates to 17 skin depth or 222 Feet.
> Using the "best" conductivity curve (0.001 mho/m) I get 888 feet.
> These must give a rough estimate of some sort of an upper limit for 
> through-earth radio ... in rough numbers, very rough, of course....
> There is also a lot of info on low freq Magnetic communications in 
> those newsletters.
> 73, Steve, K9DCI
>   Fun exercise.
>
>
>
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