wrote:
Several months ago we had a thread about RF going through the
ionosphre if the angle was accute enough. IE 90 degrees.
I wrote the fine people at www.spacew.com/proplab.
This is my original question to them and their response.
I would suggest that anyone who is interested in this
subject download and read thier manual, it is educational.
Now if I just had a spare $150 kicking about......

Terry
--------------------------------

This may be a silly question, but does any RF penetrate the
ionosphere even at the MUF? Can you suggest any online links
for info on thsi subject?


Sorry for not responding earlier on this.

Assuming we are speaking strictly of RF that has a known trajectory
(elevation angle with respect to the ionospheric layer), and we aren't
including effects of reflected/scattered RF energy that may reach the
ionosphere at an angle different from the primary RF energy, then the
answer is no - no RF energy penetrates the ionosphere, even at the MUF
- provided all the RF energy is below the critical reflection frequency

of the ionospheric layer in question. If a 20 MHz signal is
omnidirectionally transmitted, there WILL be RF energy penetration at
near vertical incidence because that frequency will exceed the critical
plasma frequency of the F-layer (even during the day).

We don't have any specific links to sites on the Internet for this
particular subject. Our Proplab-Pro manual is available online (a link
under www.spacew.com/proplab) that includes a fairly comprehensive
discussion concerning ray reflection and may help (it's a PDF
document).
--------------------------

Gentlemen,

It all depends on: the time of day; the critical angle; and the
frequency of interest. The best thing is to get one of the free
propagation programs, and play with it to fully understand the
implications of the three variables working together.

In reality, unless you are in the business of SIGINT, or going for all
DX awards, it is of little use to most SWL or operators.

Joe