[Lowfer] Dead of the night signal enhancement

[craig wasson]

Given the diverse frequency range you are seeing this effect over, I'm
doubting it's caused by changes in propagation.

Since the strip chart application is looking at S-meter output have you
confirmed it's not a local noise source kicking in?  I used to see a
similar effect when doing a similar plot with my SDR-IQ and spectran.  I was
plotting longwave broadcast station carriers in 1 to 5  hz wide windows for
24 hour periods and had some light dimmers causing broadband noise.
The plotted carriers would drop about 10db when the room with that dimmer
was in use, then jump in strength about 10 db when the lights were shut
off.

Another possibility is a very strong local source such as an AM broadcast
station causing desense.  Maybe it shuts down for maintenance just before
dawn?  However I'd be surprised that you would see desense from an AM
station all the way up to 10 MHz.

It might be worth setting the alarm to listen to this live, or set up
something to record the audio during that time range to see if that gives
any clues.

Craig

(N6IO, beacon IO down for antenna work)





On Wed, Nov 24, 2010 at 8:52 AM, Dick Goodman <wa3usg at verizon.net> wrote:

>        Over the last several years of monitoring signals on L.F. I've
> noticed that
> the reception seems to always be the best about halfway between midnight
> and
> dawn. For the last 2 nights, I've plotted the signal strength of AM740 (740
> KHz) and WWV on 10 MHz. I saw a definite enhancement of signal strength in
> that time period. I'm going to run this for a few more nights to see if it
> is  repeatable.
>
>        http://mysite.verizon.net/wa3usg/AM740.jpg
>        http://mysite.verizon.net/wa3usg/WWV10.jpg
>
>
>        I had forgotten that I even had the software to do this. It's a
> Strip Chart
> program called "RadioSkyPipe" available from Radio Sky Publishing (there is
> a free version there):
>
>        http://www.radiosky.com/skypipeishere.html
>        http://www.radiosky.com/
>
>        It's a pretty flexible program. It's getting its input from a 12 bit
> A/D
> converter plugged into my parallel printer port. The analog end of the
> converter is connected to the S-meter in my old Kenwood R2000. You can also
> configure the software to use any input to your soundcard (or the output of
> your soundcard) as input instead of an outboard A/D converter. Radio Sky
> Publishing offers the A/D converter in kit form that will  plug into a
> parallel printer port. They also offer one that plugs into a USB port. This
> system won't detect really weak signals (eg QRSS) but it's cool for
> plotting
> signals that are stronger.
>
> Happy Thanksgiving!
>
> Dick, WA3USG
> Mechanicsburg, PA.
> FN10LE
>
>
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