JOTA

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Jamboree on the Air 2023

September 15, 2023

Author(s): Simon Bijlsma (PA7SB)

Photo(s): CAMRAS Sigrid Witteveen

Online EME relay station

Friday, 20 October, 2023 and Saturday, 21 October, 2023, the Dwingeloo Radio Telescope will once again function as an online ‘Earth Moon Earth’ (EME) relay station. Scouting groups will also send signals to the moon with their self-built antennas during the international ‘Jamboree On The Air’(JOTA).

Due to its enormous sensitivity, the Dwingeloo telescope is very suitable for receiving the extremely weak EME signals. These signals are offered over the internet by means of the CAMRAS webSDR. Via this link: 70 cm EME you can watch, provided you have installed the special decoder software WSJT-X. The signal from the webSDR enters the said software via a virtual audio cable. You should set the audio level to approximately “30dB” (“green”). In WSJT-X, the scouts use the mode “JT65” and “sub B” and at the same time the option “EME delay” must also be enabled so that the required 2.5 second delay is used. This delay is necessary to account for the duration of the lunar echoes.

Test session

The radio telescope will be online on Friday, October 20, 2023 between 14:00 UTC and approximately 19:00 UTC so that the JOTA participants can test their antennas and equipment again prior to the official opening of the JOTA. Unfortunately, the moon has already set again before this official opening and therefore the real JOTA EME connections will have to wait until Saturday.

On Saturday, October 21, 2023, the radio telescope will be online between 15:00 UTC and approximately 20:00 UTC so that JOTA participants can send messages to each other via the moon. The frequency on which the JOTA groups broadcast is, as last year, 432.050 MHz. Unfortunately, the elevation, that is, the height, of the moon is low during JOTA this year. This only reaches a maximum of 10 degrees above the horizon. This will often make it more difficult to find a good spot where the antenna can ‘see’ the moon. This is necessary because obstacles, such as buildings or trees, can cause additional attenuation of the signal.

Of course non JOTA stations can also use this opportunity to test their equipment, which may normally be not really suitable for EME, for QRP EME. Consider, for example, a single Yagi antenna with sufficient elements with approximately 50W of transmitting power. In many cases this is sufficient in this particular situation because the Dwingeloo telescope is such a sensitive receiver. It’s probably fun to try this too?

We kindly ask the non-JOTA and especially high power “QRO” EME stations to transmit around 432.100 MHz or higher so that the weak JOTA stations will not be hindered!

More info

The CAMRAS crew that provides the online streaming of the JOTA EME signals consists of Michel Arts (PE1NVK) and Simon Bijlsma (PA7SB).

Further information.

Download a report by Frans De Jong (PE1RXJ) of the test session of September 2, 2023 here(in Dutch).

Fifteen years ago, this JOTA-EME project was initiated by Frans de Jong, who wrote a construction description (in Dutch) for the required ’23 elements Long Yagi voor de 70cm band’. See also the page JOTA-JOTI and the blog post about it from 2008 (also both in Dutch).

Dwingeloo Telescope active again this year with the Jamboree On The Air

October 9, 2022

Author(s): Simon Bijlsma (PA7SB)

Friday, October 14, 2022 and Saturday, October 15, 2022, the Dwingeloo Radio Telescope will function again as an online ‘Earth Moon Earth’ (EME) relay station. Scouting groups will send signals to the moon with their self-built antennas during the international ‘Jamboree On The Air’ (JOTA). Due to its enormous sensitivity, the Dwingeloo telescope is very suitable for receiving the extremely weak EME signals. These signals are being streamed over the internet by means of the CAMRAS webSDR. You can watch it via this link: 70 cm EME, provided you have installed the special decoder software WSJT-X. Via a virtual cable, the signal from the webSDR comes into the aforementioned software. You should set the audio level to approximately “30dB” (“green”). The scouts use the “JT65” and “sub B” mode in WSJT-X and at the same time the option “EME delay” must be enabled so that the necessary 2.5 seconds delay is used. This delay is necessary to account for the duration of the moon echoes.

On Friday evening, October 14, 2022, the radiotelescope will be online between 10 PM and midnight. Saturday October 15, 2022 we will be online between 9.00 AM and 1 PM and if there are enough participants, also Saturday evening from 10 PM to midnight. This year’s CAMRAS crew consists of: Michel Arts, Piet Pont, Roel Ovinge and Simon Bijlsma.

Fourteen years ago, this JOTA-EME project was initiated by Frans de Jong, who wrote a construction description in Dutch for the required ’23 elements Long Yagi voor de 70cm band’. See also the page JOTA-JOTI and the blog post about it from 2008 (also both in Dutch).

Dwingeloo Telescope receives Moon echoes for Scouting Jamboree

September 10, 2019

Author(s): Simon Bijlsma (PA7SB)

Photo(s): CAMRAS Cees Bassa

Last Friday and Saturday evening 6 and 7 September 2019, Michel Arts (PE1NVK) and Simon Bijlsma (PA7SB) operated the Dwingeloo telescope to make it act as an ‘Earth Moon Earth’ (EME) relay station for scouting groups who wanted to try out their self-built antennas in preparation for the coming ‘Jamboree On The Air’ (JOTA) on Friday 18 and Saturday 19 October 2019. The Dwingeloo telescope is very suitable for receiving the extremely weak EME signals due to its enormous sensitivity. The signals received are being streamed over the internet via the webSDR developed by Pieter-Tjerk de Boer (PA3FWM).

Eleven years ago this JOTA-EME project was initiated by Frans de Jong (PE1RXJ) who wrote a building description for the required ‘23 elements Long-Yagi antenna for the 70cm band ‘ (in Dutch but with drawings and photos).

On Friday, Frans successfully tested their antennas at the scouting group in Veldhoven and Bart Laarkamp (PD1BCL) at the group in Zutphen. On Saturday Michiel Vonk (PB0MV) from the Scouting group in Uitgeest, together with his father (Fred PE1PAB) and brother (Jeroen PA2JV) was active from Reeuwijk. Peter Ravestein (PE1NLU) was active with a group from Breda. In Eindhoven, scouts watched the broadcasts of the other groups via the webSDR. Unfortunately, both Michiel and Peter, apart from sending the numbers ’73’, the radio amateur code for ‘warm greetings’, failed to make a complete two way connection. The transceiver Michiel had borrowed did not have a TCXO and therefore it’s frequency was drifting. Accidentally he also forgot to adjust the software from HF to UHF with the nescessary 2.5 seconds EME delay time. This has shown that setting up and using the WSJT-X decoder software, designed by Nobel Prize winner Joseph Taylor (K1JT), for the first time is no mean feat. Michel and Simon also had to struggle with the software settings in previous years to be able to decode the signals that we offer via the webSDR. The settings, also the audio level, listen very closely because of the extremely weak moon echo signals that the scouts send with their antennas. However, if it works, the results are great! The software is so sensitive that signals up to -30dB (1/1000) can be detected under the noisefloor. This is so faint that you hear nothing at all by ear, just noise and you hardly see anything in the ‘Fast Fourier Transform’ (FFT) waterfall screen (see photo below).

During the successful test broadcasts from Frans and Bart, their signals in the different passages were between -28dB and -16dB under the noisefloor. These differences in strength were caused by the fact that the antenna must always be aligned with the moon. However, due to the clouds, the moon was often not visible on Saturday evening, and therefore making manual alignment was a difficult job. Just ‘forgetting’ to adjust the antenna for five or ten minutes means that the signal is received much weaker in Dwingeloo. See for this the explanation with the building description of Frans.

Interesting to see was that in addition to the moon echoes, reflections were also seen against aircraft and the ionosphere. Bart in Zutphen had once directed his antenna straight to Dwingeloo and then the + 6dB signal, that is strongly audible, came through. Because there was no delay time (delay time ‘DT’) in the signal, this was clearly distinguishable from the real moon echoes because those signals are received with a delay of approximately 2.5 seconds. The distance from the earth to the moon is more than 385,000 km and you can therefore calculate that, with the speed of light, the echo time is approximately 2.5 seconds.

With this blog post we hope to interest other scouts or radio amateurs who support scouting groups during the JOTA to also watch the activities of the JOTA groups that are working on EME via our webSDR. And hopefully they become so enthusiastic that they will participate next year with their own built antennas. To be able to watch, it is necessary to install WSJT-X and inject the audio from the webSDR into the WSJT-X software via a sound mixer or ‘virtual cable’ so that the JT65 mode B signals can be decoded. Of course we also invite other interested parties to try this with their PC or laptop.

Tag Archive for: JOTA

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Online EME relay station

Test session

JOTA

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