The RF Seismograph

a live, off-air HF propagation tool created and maintained by Alex Schwarz VE7DXW

The "Scanning RF Seismograph" is a real time propagation tool developed by the MDSR Team and Alex VE7DXW. Alex is a member of the North Shore Amateur Radio Club, North Vancouver BC, Canada.

How to read the graph:
When the line goes wide there is propagation but not necessarily a man-made signal. The absolute value of the noise level is not important for propagation, but it is interesting to watch how the noise changes over time. Slow changes are usually made by the ionosphere (5 min and longer). The slower the rise of the signal the further away it originated. Fast changes are man-made signals and earth-quakes, hence vertical lines. The black bottom graph is easier to read when it comes to propagation. The grayscale indicator shows propagation for all the bands according to color codes as in the sig/time graph. White is best propagation.

How does it work?

It monitors JT65 frequencies on 6 HF bands for 8 s each, repeating the scan every 52 s. The recorders log the background noise of the band and display the result in six color-differentiated long-duration time graphs. The total displayed time is 6 h.

Where is it located?

The monitor station is located in Lynn Valley (GS: CN89li), North Vancouver at 130 m (500 ft.) ASL. The transceiver used to monitor the HF spectrum is a Yaesu FT-950 connected to an omni-directional multiband antenna (Hy-Gain Hy-Tower 18HT Jr., 36 ft in height). The transceiver is connected to the computer via an MDSR BiLiF converter. The software running on this computer is MDSR V3.1 and Java SA 1.6. (the Windows version of the software).Signals are present when the graph resembles a tiny filled square. The up/down movement of the graphs is caused by changes in noise level, and by the reflection of noise off the D-Layer in the ionosphere.For more information, and a guide to setting up the RF Seismograph on your website, please e-mail:

Thanks to Adam VA7OJ/AB4OJ for setting up this page.

Local RF-Propagation at the MDSR Test Site in Vancouver, BC (UTC)

(real time; updated every 10 minutes)

RF-Seismograph ImageRF Seismo Legend

If you want to set-up your station for monitoring propagation, please go to our website and contact us.

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RF Propagation List (updated every 10 minutes)

Measuring Propagation with your own Transceiver V.1 (presented at SeaPac 2017, Seaside OR. 5 MB PDF)

Copyright  2016-2019  A. Schwarz VE7DXW. Page last updated: 25 September 2019.