Hi Dimitrios,
Depending on what you are doing it may be inverse cube law (9 dB).
73 John F5VLF
On 12 Oct 2011, at 11:20CEST, Dimitrios Tsifakis wrote:
> Hi John,
>
> 2011/10/12 John Rabson <[email protected]>:
>> Amongst other things, it depends on the geology. G3XBM has managed 5.6 km
>> with 5 W RF at very low frequency. On 87 kHz with 4W SSB (cave radio) in
>> limestone, the best I know of is 1.6 km two way and 2.5 km one way in the
>> French alps.
>
> Well, the S/N required for voice is much higher than that of QRSS30.
> With a puny 3 W of RF and QRSS30 it seems I can cover a distance of
> about 30 km and still have a S/N of 30 dB! Which implies that possibly
> (if the signal received is normal ground wave, similar to that from an
> above-ground antenna), with a spreading loss of 6 dB per doubling of
> distance and with a bit more juice, much greater distances may be
> covered.
>
>> It is always worth trying.
>
> That's the spirit in the amateur world of LF! :-)
>
> 73, Dimitris VK1SV
>
>
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