Jim, thanks for this interesting plot. As the trace is still on my screen here, I decided to follow your footsteps, and generated the attached plot. It shows Ossi's frequency offset (mHz from
8970 Hz, blue), signal level (arbitrary dB units, red), and approximate noise (dB in 1.5 x 0.95 mHz, green). The ascii data are also attached.
As Mal and Rik say, we would expect some ERP variation from a balloon antenna, equally affecting all receiver sites. Ossi does run a local grabber about 10 km from his transmitter (screenshot attached). Unfortunately the spectrogram
colourscale does not differentiate minor ERP variations. The outage at 11:20 had been reported yesterday.
The interesting large variations in Jim's plot (about 6 dB pp) do not seem to appear here. This would hint towards a propagation effect, which seems odd as the timescale (half hour period) is a bit too fast for ionospheric Doppler
at that range. As the signal at M0BMU was apparently not too far above the noise, some fluctuations might have been contributed simply by the stochastic noise vector addition.
Today Ossi is transmitting again. He is about 10 dB weaker than yesterday so probably running "barefoot" without the balloon.
Best 73,
Markus (DF6NM)
Sent: Tuesday, February 08, 2011 12:09 AM
Subject: LF: Re: OE5ODL over different paths
Dear Ossi, Markus, LF Group,
I was quite interested to notice the sharp dip in OE5ODL's signal at around
1430utc today, and in light of Markus' comments, I used the cursor
facilities in SpecLab to manually read off the signal levels, avoiding the
noise bursts. I also did a quick field strength calibration of the
loop/receiver - the resulting plot of field strength vs time is shown in the
attachment (the vertical axis should say "dBuV/m"). As well as the deep null
around 1430, the signal level seems to rise several dB during the day,
peaking around 1800 - 2000, and now starting to fall off. Also, a downwards
drift in frequency of about 1.5mHz can be seen.
Cheers, Jim Moritz
73 de M0BMU
