Hi Rick,
I use a 68 foot base loaded vertical on 160 meters, but I also use 3
different pennant RX antennas. Unless it's ground wave, my 160 meter TX
vertical is often deaf for stations in adjacent states that are in close to
me (say 100 to 200 miles away). Sometimes I can barely hear these stations
on my TX antenna, but when I switch to one of my pennant RX antennas they
are booming in. What's also interesting during these period of time is
that I can hear the stations pretty good regardless of what pennant I'm
using (pennant pointed 40 degrees, pennant pointed 160 degrees or pennant
pointed 270 degrees) even though my pennants have very good front to back
ratio at low elevation angles (but not at very high elevations angles), and
this is a good indication that NVIS is at play. The modeled elevation
pattern of my TX vertical compared with my RX Pennants appears to explain
this phenomena (certainly does not contradict it). Therefore during
stateside contests it sure appears I could benefit by using an NVIS TX
antenna for working these stations that are in close (adjacent states).
I have never observed this phenomena when copying DX stations, or stations
US stations far away.
I posted the following information on my pennant website many years ago,
and it still holds true based on massive amounts of time I spent on 160
meters.
--------------------------------------------------------------------------------------
*Typical skywave signal to noise improvement on 160 meters using my
pennants compared with my TX vertical*
0 to 1500 miles = 6 dB (and often much more for stations within 200 miles
depending on NVIS)
2000 miles = 3 dB
4000 miles or more = 1 to 3 dB (Note : most often 2 dB, but sometimes only
1 dB) Revised Jan 25, 2016
(The above numbers are just approximations based on many hours of
comparison testing of my pennants versus my TX vertical antenna on 160
meters.)
----------------------------------------------------------------------------------------------
Just FYI, and 73,TX
Don (wd8dsb)
On Sun, Mar 1, 2020 at 8:38 PM Richard (Rick) Karlquist <
richard@karlquist.com> wrote:
> On 3/1/2020 5:26 PM, Mike Waters wrote:
> > However, during stateside contests such as the ARRL 160, not having some
> > NVIS would be a disadvantage.
> >
> > 73, Mike
> > W0BTU
> >
>
> How come AM broadcast stations don't need NVIS?
>
> Rick N6RK
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