Thanks to everyone who commented on "Is anyone planning any propagation
experiments on136kHz or there abouts during the eclipse next week".
After your comments I decided to study it, visually and by radio
techniques at home (ON5OO software).
Thanks Rik for the detail on the ON5OO software. Its working out very well.
I used the software to record the strength of the German station on 138 kHz
during the eclipse.
Location Yeovil , Somerset , England
50deg 56.5 mins North and
2deg 39mins West
I am using a 54 turn 38cm diam. square loop with 0.5cm spaced turns and
feeding into a lowe 225 Rx set to SSB and 2200 hz filter. This receiver
has a very good AGC system which cannot be switched off. For 2days before
the event I experimented to find the linear section of the AGC before the
signal hit the noise floor. I needed 30dB's switched in between antenna and
Rx tto acheive reasonable results.
On the 10th I took a recording which shows an 8dB increase during the
evening over the daytime figure with some qsb nulls. Recording was stopped
at appox 2130 GMT.
After the recording I left the RX on all night for stability but switched
off the
computer.
In the morning to my horror no signal from Rx on138kHz.
Eventually I retuned to another station to prove Rx working.
Some time later 138 kHz signal returned, but seemed to be at least 20dB down
on my previous measurements.
Recalibrated the sound card and the software.
I was concerned about the station level would be switched during the
measurements. So the eclipse data file had a calibration switching in and
out of -/+ 10dB at both the start and finish of the recording.
Eclipse results
0951 GMT 138 kHz increase in level starts
1002 GMT signal variable average about 3dB up, peaking 6dB up
1025 GMT signal variable average about 3dB up, isolated peak 9dB up
1033 GMT signal returns to the pre eclipse level
The follow up must be to find time to build a RX with no agc.
Regards
Peter G8AFN
|
