Barefoot LimeSDR Mini Digital TV Transmission over 16 km

LimeSDR Mini has proved particularly popular with digital amateur television (DATV) operators and is at the heart of the BATC Portsdown transmitter — a turnkey solution that makes DVB communication readily available to a wide community of radio amateurs — which is frequently used with QO-100, the world's first geostationary satellite for amateur use. Much closer to earth, however, we are also seeing some pretty impressive uses and we were delighted when BATC Chair, Dave Crump (G8GKQ), got in touch to share a few details of a recent low power achievement:

"On Sunday 26 July, John G7JTT did some TV transmission tests over a 16 km path to the Amateur TV Repeater in Bournemouth, GB3SQ on 1249 MHz. Initially, John used a TV transmitter with a Power Amplifier and his signals were easily received at the repeater and re-transmitted for other radio amateurs in the area (and also streamed on the internet at https://batc.org.uk/live/gb3sq).

The signals were so strong that John decided to try the LimeSDR Mini without a power amplifier. The repeater keeper, Colin G4KLB, reduced the repeater receiver symbol rate to 250 kS, and John was able to get pictures into the repeater over a 16 km path using just 5 mW from the LimeSDR Mini and a home-made 15 element yagi aerial.

The equipment used at the transmit end was a Portsdown 4 Digital Amateur Television transmitter, which is based on a Raspberry Pi 4, and a LimeSDR Mini running the custom DVB firmware. This was connected through a short feeder (about 1 dB signal loss) to a 15 element yagi antenna. The transmission was 250 kS DVB-S2 standard definition TV with 2 audio channels.

The receive end used a British Amateur Television Club MiniTiouner (which includes a Serit Satellite tuner including specialist ICs for forward error correction and DVB-S2 decoding) and a Raspberry Pi 4 feeding composite video into the repeater transmitter system.

You can find more information about the BATC Portsdown TV Transmitter and LimeSDR here: https://wiki.batc.org.uk/The_Portsdown_Transmitter."

John’s picture as received at GB3SQ