In his setup, Zoltan uses a QRP Labs U3S WSPR transmitter kit that was configured to transmit WSPR at 2m (144 MHz). It is not designed for transmitting the 2.4 GHz QO-100 uplink frequency. To get around that limitation, the moRFeus is used to upconvert the 144 MHz frequency into the QO-100 uplink band by mixing it with a 2,255,634.309 kHz signal. The resulting 2.4 GHz output signal from moRFeus is sent to an amplifier, 2.4 GHz band pass filter, and finally into a 5-turn LHCP helical feed mounted on a 1m parabolic dish.
Successful uplink was confirmed by a UK based WebSDR receiving the QO-100 downlink. Zoltan estimates that the total output power was only 4mW, and actually more like 1-2 mW due to losses in the coax feed.
The LimeNet Micro is a is a $329 board that combines a Raspberry Pi 3 (compute module) together with a LimeSDR radio. The LimeRFE is an amplifier and filter board accessory designed to be used with LimeSDR units. When a LimeNET Micro and LimeRFE are used together, it is possible to create a transmit capable radio system that can be used for amateur radio.
In terms of software, Daniel is using a Python script that communicates with the Limesuite API for PTT control. For transmitting IQ data generated by GNU Radio he uses limesdr_send. So far he's been able to successfully test a CW beacon, SSB voice and waterfall text generated by gr-paint.
Over on his YouTube channel Adam 9A4QV has uploaded a short video that demonstrates his 2.4 GHz homemade helical feed designed to be used with a reflector (prime feed satellite dish) for QO-100/Es'Hail-2 satellite reception. The antenna is made from an old can, 2-turns of copper wire, and a plastic insulator to hold the turns in place. The two turns are wound in left hand circular polarization (LHCP), because when used with a satellite dish reflector it will result in right hand circular polarization (RHCP), which is the polarization QO-100 uses.
One of the most important parts of the video is when Adam shows how he matches the antenna to 50 Ohms. He notes that without matching the antenna won't work properly, and the return loss will be about 8 dB or even less, resulting in poor performance. With matching he obtains 30 dB return loss.
Over on YouTube user [Radio Electronics] has uploaded a useful video showing how to install your own personal SDRplay or RTL-SDR based WebSDR for QO-100 (aka Es'Hail-2) reception. Es'Hail-2 is the first geostationary satellite with amateur radio transponders on board, and is positioned at 25.5°E which covers Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia.
The idea behind a WebSDR is to run your RTL-SDR QO-100 receiver on a remote Raspberry Pi (perhaps mounted close to the antenna on your roof etc). The Pi runs custom WebSDR software that has been created from scratch by [Radio Electronics] specifically for monitoring Es'Hail-2. Then you can access your QO-100 receiver from any device on your network that has a web browser (computer/phone/tablet etc). The interface of his WebSDR appears to be quite slick, which multiple QO-100 specific options and labels.
Quite a lot of work must have gone into this software which looks to be of high quality, so it is definitely worth checking out if you are interested in QO-100/Es'Hail-2 monitoring.
In the first video he first talks about various methods for downconverting the 10489.550 MHz QO-100 CW signal into a range receivable by the RTL-SDR or SDRplay. He then goes on to show the exact steps to install and run his WebSDR software on a Raspberry Pi 3.
In the second video he goes on to demonstrate the web browser interface highlighting the QO-100 specific features that he has implemented such as being able to compensate for any LNB frequency drift via a feature that can lock to the QO-100 PSK beacon.
Es’hailsat, otherwise known as QO-100 is the first geostationary satellite with an amateur radio payload on-board. The satellite contains both a Wide Band transponder for experimental modes and DVB-S Digital Television and a Narrow Band transponder used mostly for SSB voice and some digital mode contacts with other amateur operators. If you’re unfamiliar with this satellite we’ve covered it in previous articles, like in [Es’hail Transponder Now Active]
While many choose to use a transverter connected to a traditional amateur transceiver, others have turned to use Software Defined Radios to complete their satellite ground stations.
[Radio Innovation] posted a video back in March showing his contact on QO-100 using a LimeSDR Mini as the 2.4 GHz transmitter and a 10 GHz LNB for the downlink.
Calling cq on QO-100 with LIMESDR
The PlutoSDR has been frequently seen used for QO-100 satellite operation on the Wide Band transponder due to its ease of DVB-S transmission utilizing software such as [DATV Express] but more recently there have been more and more operators turning to SDR for their day to day satellite operation.
It will be interesting to see how these stations evolve, perhaps by the time North America has access to a similar satellite, we’ll be prepared to operate it.