QO-100 at CN3A

Together with Vasek OK1VVT during CQ WW SSB 2024 on CN3A we talked and thought about what could be done on VHF. Besides future plans with 2m EME I thought about the QO-100 satellite. Since I have been building LNBs for several years, not only for this satellite, it was "just" enough to finish the rest :)

For several years I have been using an Adalm pluto SDR TRX with additional front end boards for VHF remote control (70 MHz, 144 MHz, 433 MHz). So I decided to use this SDR together with a great SDR program - SDR Console. For the RX I used my LNB ext OSC - that is an LNB with the ability to hang a PLL using an external 10 MHz normal. This GPSDO also serves as a reference signal source for the Adalm Pluto. I also found a nice 10W PA in China. I just had to add some more parts like LAN and PoE filters, DC-DC converter with filters and mount it in a box with a heat sink. 

I printed an ice cone feed as an antenna. Outdoor box is connected only with one CAT-5 FTP cable. There is common power supply with LAN filter and PoE injector - all in one enclosure.

LNB: LNB ext OSC MK3

Adalm Pluto: with EXT REF

LAN and PoE filter: with protections LAN PRO-FIL

ICE CONE FEED: web of author

Common 24V power supply with filters

GPSDO board with LNB bias tee, Adalm Pluto PA and DC converters

Testing output power

First test at CN3A without the dish

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The first test on CN3A was done without dish antenna in January 2025. Despite the opposite polarization of the transmitting antenna and simple support of the antenna on an improvised table, it was possible to listen to the beacon. After tuning to the FT8 frequency, I was surprised that I easily decoded several stations. I tried transmitting with 6W RF power into the wrong polarization and it worked :) The first QSO was very easy and thanks to Libor OK1ALX for the test! After the first CQ an avalanche of calling stations came down.

After a month it was time to go again for 14 days of working relaxation on CN3A. Apart from work and CQ WPX SSB I planned to finish the equipment for QO-100, buy a dish and holder and mount everything.

After a couple of days, Jirka OK1RI and I went to get some food and drink supplies and also visited the local “hardware” street in Safi. After an exchange of greetings and a commented (in Czech) demonstration of photos of the antenna on a mobile phone, the seller brought us the antenna and the wall mount. Even a first year engineering student would be ashamed of this mount... but better than nothing :)

After installing and pointing the antenna, the increase in signal strength was significant. The gain was around 30 dB and our own signal is at S9 level. When there is more time, we will sit down to SSB, where it will be much more fun compare to FT8...

All QSOs are confirmed over LOTW.