Topband: Inquiring minds want to know....

[David Olean]

Hello Carl

     All very interesting! I still see a huge increase in distances as 
nightfall moves in, but all of the extremely distant stations are picked 
up at the upper end of the NDB allocation close to 400 kHz. During the 
day a good haul is Schenectady, NY to the west. For 25 watts that is a 
good overland distance. At night I hear maybe another 200 miles into 
Ontario. Once you go above 400 kHz, things change and I start hearing 
stations much farther away at night. IY in Iowa also with 25 watts at 
417 kHz has a pretty fair signal at night and is in audible during the 
day.  I will do some more listening in the 200 khz range to see if I can 
hear more distant stations during daylight. DIW in Dixon NC is on 198 
kHz, but it is running QRO so that can be heard a long way off. Thanks 
for the information. This sure is fun.

73

Dave K1WHS

On 2/8/2020 8:19 PM, Carl Luetzelschwab wrote:
>> What the heck happened that I could hear a
>> long wave signal over 2000 miles away at mid day?
> For a given electron density profile, the amount of refraction incurred by
> an electromagnetic wave is inversely proportional to the square of the
> frequency.
>
> The result of that is the lower the frequency, the less high the wave gets
> into the ionosphere. LF hardly reaches the absorbing region (the D region
> during the day), and thus LF suffers minimal ionospheric absorption. The
> wave refracts between the lower ionosphere and Earth - also known as the
> Earth-ionosphere wave guide.
>
> NO3M has heard VK4YB on 2200m (137 KHz) many times. I'm sure there are
> other examples like that out there.
>
> Carl K9LA
> _________________
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