[Lowfer] LF Prop Question

[John Davis]

>Question:
>Is the enhanced propagation in the winter solely due to the absence of
>QRN, or does the cold WX in general provide better propagation?


Given only a choice of these two options, the decrease in QRN (certainly not
a total absence, but a really significant reduction) is the logical answer.
It makes a huge difference when listening.

There has been some debate over the effects of cold temperature on
groundwave propagation, but it seems to differ with the type of soil, and
there is some uncertainty how much of that effect is really propagational
and how much is local influence of the cold temperatures at the transmitting
and/or receiving end (i.e., less sap in trees causing less local resistive
loss).

One other factor to take into account, though: solar radiation.  The daytime
absorption of the D-layer doesn't abruptly end at 530kHz, but continues well
below LowFER frequencies.  You can measure it quite readily on WWVB skywave
at 60kHz.  Even a good solar eclipse between you and a distant LF station
will reduce that attenuation.  In winter, therefore, the lesser UV reaching
the D-layer makes many LowFERs more audible for a greater part of the
day--not just late night--and especially at upper-middle latitudes.

John