I'm under the impression that NVIS propagation fails at the higher HF
frequencies - that is frequencies above the vertical Critical Frequency
which pass right through the E and F layers without reflection.

How often does the critical frequency exceed 14, 21 and 28 MHz for NVIS
operation to succeed? Which is better - day or night. Thanks.
----
Reg.


"Bob Bob" wrote in message
...
Hi All

I want to get some ideas on how to feed my horiz 40M loop (NVIS) for
harmonics of 7Mhz. It is sufficiently low to the ground that the feed Z
is close to 50r (which makes 14Mhz - 100r, 21Mhz - 150r amd 28MHz - 200r)

I realise that the radiation pattern may nit be desirable. Space is kind
of limited here and stealth is important

I want it to be "no tune/no ATU" and to avoid switching things in and
out. It is currently fed directly with coax and a 1:1 ferrite balun. I
cant use open wire feeder back to the TX (needing at least 10M of coax)

Cheers Bob VK2YQA

(bcnntp doesnt exist. If important use bcnoop)