The Mode-S Beast in London

I was invited to give a presentation of work towards the Mode-S decoder at the Martlesham Microwave Round Table in London. I took this as a chance to visit long time friends in the UK and of course I had the complete Mode-S equipment with me. Tests were done close to Andover, at the Adastral Park BT site in Martlesham-Heath and last on a decent free location close to Felixtowe. And in the program parallel, my friend Peter showed me the Stonehenge monument. I will surely never forget the moment when we came across the highway and I suddenly spotted the huge construction far away in the middle of the Salsbury plain.

You can download the presentation here.

 The autor in front of a stack of stones

The Mode-S Beast next to Andover

This test was done by placing the G7RGQ omni antenna reverse into the feed point of Peter's (G3LTF) 6m parabolic dish antenna, so the dish was only used as a mechanical fixture of the antenna, and we were able to use the low loss transmit coax (below 3dB attenuation) for feeding the signal into the house.

This is the dish antenna, pointing upwards, and the G7RGQ antenna placed reversee into the feed holder. Despite screening of the antenna against ground noise, the dish did not have any worth for the Mode-S signals.
A closer look at the feed point installation.
Low loss coax cable and the beast directly connected through a chain of adapters.

Peter's location has a very good visibility into all but one directions, just the south-east is blocked by a few nearby trees, that is why we did see no aircraft over the Netherlands or Belgium (where I then placed the CRC driver screen). In the overnight shot there were a few planes towards east in 225nm distance. Yes, I agree to comments that I have received, the London area surely is one of the most busy in Europe. The major difference between London and my Munich home is that at home and at about the same time of the week I have will have about 260 aircraft showing up on Planeplotter, while I just got 160 in London. In difference, the number of frames per second in London is markably higher than the one in Munich (with one antenna)


This is the visibility range of the installation in Andover shows some planes up to 200nm distance (outer ring) at the same time when there is a cloud of aircraft over London.
The CRC driver output gives a nice overview of the history, so there are up to 209 DF11/DF17 frames per second (averaged over a minute, this is the same value as it would have been showed by ModeSCompare from jetvision.de). I am somewhat astonished that the 1-Bit-Error rate at this test was just 10% (we've even seen values of 6% in the night). This is the lowest rate I've ever seen. In comparison to the test done at a presentation at my company's open house, with a transformer station close by, I even went up to 35%, and at home and at F5ANN we both see regularily 25%. This has to be followed up once there is time.

This is a long term recording of Saturday morning traffic across London. The 4 big London airports are marked. Nicely seen how they started stacking. Frame rate history shows up to 246 DF11/DF17 frames per second. The speed meter shows 678 frames per second at the moment of screenshot, which is about 80% of the 3rd column of the CRC driver, as usual.

The Mode-S Beast in Martlesham-Heath

After my presentation at the Martlesham Microwave Round Table, I set up the system in the "Measurements" room. The antenna was at the corner of the table, held by a pastic box, about 1.5m cable and the Mode-S beast. The room is located little above the ground floor, with its windows towards South-West. With this set-up planes were observed up to the french channel coast.

 Picture to come

Clicking on the picture will also display frame rate information.

The Mode-S Beast close to Felixtowe

Finally I went on the late Sunday afternoon towards a good position close to Felixtowe (N 51° 58.577 E 001° 21.660°). I had my antenna on top of the Zafira's open boot cover, about 2m above ground level. With just this I saw the highest frame rate ever on a single antenna by reaching sometimes 1050 frames per second (remember: pre-checked frames). But, we still saw some drawback into directions where we had the horizon covered by the houses of the village.

This picture shows the overall range up to a distance of 200nm. Remember that the antenna was just 2m above ground!

Note that the speed meter is showing above 1000 frames per second (pre-checked by CRC driver)

  This is as we saw the traffic over London.