[TowerTalk] NVIS (not exactly towers, but HF)

[jimlux]

On 6/9/20 7:39 AM, Rob Atkinson wrote:
> I didn't see anything in the abstract that made me want to read it as
> far as ham radio is concerned.   A number of hams over the past years
> have cited military work with cloud burners as a justification for
> their usefulness in ham radio.   I don't contest a horizontal antenna
> that has its highest field intensity straight up, but I do contest the
> argument for ridiculously low hanging antennas because that's what
> other services do.   There are several differences between ham and
> other services that have to do with power limits, frequency
> exclusivity, transmission modes, battle conditions, and radiation
> efficiency.



what's interesting in the article isn't so much the NVIS stuff, but the 
modeling approach. They're doing some ionospheric ray tracing using 
ionosonde measurements.  For what it's worth, the antennas they are 
using are at 0.2 wavelength, which isn't one of those knee high wires. 
At frequencies from 4-11 MHz it seems.

They're using Coleman's ray tracing approach
21] C. J. Coleman, “Point-to-point ionospheric ray tracing by a direct 
variational method,” Radio Sci., vol. 46, no. 5, pp. 1–7, 2011.
Here's a report on it
https://apps.dtic.mil/dtic/tr/fulltext/u2/a271058.pdf

These days, there's a lot more real-time ionosonde data available - it's 
sort of the next step beyond NCDXF beacons or various reverse beacon 
networks.


Of particular interest is a paper I want to track down

[17] P. J. Coetzee, “A technique to determine the electromagnetic 
properties of soil using moisture content,” South Afr. J. Sci., vol. 
110, no. 5/6, pp. 1–4, 2014.