Thanks to IU2EFA (William) for writing in and letting us know about his success in decoding telemetry from the moon orbiting satellite known as DSLWP-B / LONGJIANG-2. LONJIANG-2 is a Chinese lunar microsatellite (45kg) that was launched in May 2018. It is designed to perform ultra long-wave radio astronomy observations. It also has an on board camera and took some nice photos of the Earth back in June.
While the satellite is still being tested, William notes that it is transmitting telemetry data to Earth during it’s scheduled days at 435.4 MHz and 436.4 MHz, and the signal can be received with an RTL-SDR and Yagi antenna. William writes:
“[LONJIAN-2] transmits with a little linear antenna and a little power of just 2 Watts.
In other sessions, I used a professional radio to have the maximum performance.
But this morning I wanted to test the reception, just using my RTLSDR V3 and my antenna yagi 15 elements pointed to the Moon. No other options (as filters, pre aplifiers, or other stuffs. Zero of these)
Well, the result was great. I received the signals and also i could decode them!
So I think people can be happy to know, that with a very little setup, they can receive incredible little signals from great distances.
When I received these signals, the Moon distance was about 378500 km.”
LONGJIAN-2 transmits telemetry with GMSK and JT4G, and JT4G can be decoded with WSJT-X or WSJT 10. There is also a GNU Radio program called gr-dslwp that can be used to decode the telemetry. JT4G is a weak signal coding that can be decoded with signal levels down to -17 dB. Therefore anyone with modest hardware can decode the satellite. More information about the coding can be found on this post by Daniel Estevez.
On the Lilacsat page for LONGJIANG-2 if you scroll down you can also see reports from several other amateur radio operators who have managed to receive the satellite with RTL-SDR dongles and other radios. Below is an image of an example for SP5ULN who was able to receive and decode the JT4G signal with an RTL-SDR, LNA, and 19-element Yagi.
Source:RTL-SDR.COM
Equipment
The ZN-9CRB IAMBIC KEYS by N3ZN
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The L3Harris AN/PRC-117G delivers breakthrough wideband data speed and legacy narrowband performance in a form factor 30% smaller and 35% lighter than... Read more
Ameritron AL 811
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Icom IC-R8500 Communications Receiver
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YAESU FT-8900R
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Review
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Antenna
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ANTENNA CAROLINA WINDOM ® 160
Specifications Frequency Coverage 160 – 6 meters + 30, 17, 12 WARC Gain As much as 10 dBd* reported at most installations Radiator Length Horizo... Read more
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VHF
Signal Stick Super Elastic Antennas | Every HT Needs One
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ntroducing the ComLink™ BCR FM Repeater System by BridgeCom Systems, Inc. The BCR Repeater provides a feature rich, extremely reliable repeater/base s... Read more
Trial for transatlantic VHF QSO this weekend
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