There's also the "9pm at the transmitter" enhancement, written about in
detail in an early-1990s Fine Tuning's "Proceedings" publication in an
article by John Bryant. This phenomena apparently results from a region of
aligned, parallel "bumps" or rollers in the ionosphere in the 2 to 3 hours
after sunset. John's article has the data and background information on the
studies that were done which showed the existence of these aligned regions.

I've seen the enhancement on the tropical bands many, many times myself, but
less often on TP mediumwave. For instance, the Indonesian stations often
rise up from the background noise at their sunset, then level off or fade
away a few hours until roughly 9pm at their transmitter, then the signals
level off again until another boost is found at receiver sunrise.

The Fine Tuning group once published a set of charts and maps based on
John's article (I think it was a reprint of what was in the Proceedings
article). These charts helped the DXer to easily visualize the regions in
world experiencing "9pm at the transmitter" periods.

This form of signal enhancement sounded very weird to me the first time I
heard of it, but it truely works. Not all of the time of course, but it's
definitely a phenomenon that can help the DXer log good DX. It's been over
10 years since the article appeared, and I've had many DX sessions when I've
the boost, right around 9pm, transmitter time.

Guy Atkins
Puyallup, WA USA


"dxAce" wrote in message
...

Grey line dx'ing implies that it is sunset at the transmitter site and
sunrise at
the receiving site, or vice versa.

There is also the effect of sunset and or sunrise enhancement at either
the
receiving or transmitting site, but that is not true grey line.

dxAce
Michigan
USA