Dexter, your HBG plot is most interesting and shows a greater stability of
signal strength over the night period than on 136kHz. This implies that a
cross-band QSO/HF would be possible even with the long transmission times
associated with 73kHz experiments.
Furthermore, the way you have made this information available makes it very
useful for real time monitoring of conditions.
What signal strength level on your plot indicates an 'opening' on 72kHz?
Does the Rugby RTTY station on 73.2kHz follow the same pattern?

The HBG plotting is now running on a complete dedicated system.  The
graph is now calibrated and reads actual input power into the 75 ohm
terminated input of the HP SLM.  I finally figured out how to use the
100 db dynamic range of this instrument.  The output tracks perfectly
with Spectrum Lab.  The antenna is a 3.3 meter square loop with no
amplification.

The plot is uploaded every 5 minuets to:

http://www.w4dex.com/75khz/hbg.jpg

Regards,
Peter, G3LDO

e-mail <[email protected]>

Web <http://web.ukonline.co.uk/g3ldo>