QO-100 systems

After getting my LEO satellite system up and running, I looked into collecting and assembling the equipment needed for using the QO-100 satellite. QO-100 has a downlink in the 10 GHz band and uplink to the satellite is at 2400 MHz. Antenna is a Triax 100 cm dish, an LNB from DXPatrol and an "Ice Cone" feedhorn from DC8PAT.

At the operator position I used "SDR Console", an excellent application with LOTS of nice features!

Early on, I choose to make the station "remote", all the RF stuff is located close to the antenna, the only cables from the system into the shack is a power cable (230VAC), an Ethernet cable and a 4 wire control cable.

The control cable is used for 2 things:

1) Switching the remote system on, a 24 VDC relay i mounted in the remote box, when energized, 230VAC is turned on in the remote box.

2) PTT line, this is not needed as such, but I though that it would not hurt to have the possibility (just in case ;) The 20W PA in the remote box is VOX controlled (hang time about 1 second), so it should take care of PTT itself.

The system consists of the following components:

1) Triax TDS 100LG 100 cm dish

2) LNB from DXPatrol with 25 MHz ref input

3) Feedhorn from DC8PAT

4) 20W 2400 MHz amplifier from SG-Lab

5) 10 cm wide piece of heatsink for 20W PA

6) Driver for 20W PA from SG-Lab

7) ADALM-Pluto SDR transceiver

8) GPSDO from Leo Bodnar (outputs 25 and 40 MHz)

9) 24VDC 120W (5 Amp) power supply (adjusted to 27V)

10) 2 x Buck voltage regulators (one for 5VDC and one for 12VDC)

11) Bias-T for injecting 12VDC to LNB
12) TMate-2 for controlling SDR Console

13) USB to Ethernet adapter for ADALM-PLUTO

14) Various RF adapters, cables, RG405 semirigid etc.

I issued a couple of commands to the Pluto SDR to get external clock working (from GPSDO) and to correct the TX from the pluto (these notes are here mostly for my own sake :)

fw_setenv refclk_source external

Set CW TX to 437.500 on Pluto-SDR, received on IC-9700 (not GPSDO controlled!)

fw_setenv xo_correction 40000000 437.499.61
fw_setenv xo_correction 40000010 did not write down
fw_setenv xo_correction 40000020 437.500.35
fw_setenv xo_correction 40000040 437.500.15
fw_setenv xo_correction 40000055 437.500.00 <-- Good enough for now

Update: The system works perfectly and is a real joy to use :)

Portable setup

I also made a setup for portable operation. Much of the equipment are the same, except the dish and the PA. The dish is a small 35 cm dish, and the PA is from JKElektronic in Germany. The PA does not require a preamp from the Pluto and is VERY nice.
Pictures below of the box/setup

The pipe

A lot of projects starts with a hole :) So did this! As I needed to have the 100 cm dish a little out of the way (so it would interfere with my future 7 meter EME dish, I choose to place it in a corner of our garden. I installed a 2 meter long 40 mm galvanized steelpipe 90 cm in the ground. I poured 40 kg of concrete around the pipe, I think it will stay there!

The antenna

The antenna is a Triax 100 cm dish. I could probably have gone away with a smaller one, but why :)

Installation

I needed to install 230VAC, Ethernet cable and a control cable from the shack to the dish. All the RF equipment is installed in a water tight box close to the antenna.

In the corner the box with all the RF equipment will be installed. The cables on the floor is:

From shack:
1) 230VAC supply

2) Ethernet (RJ45)

3) Pwr-on/PTT cable

From Dish:

1) IF from LNB (739 MHz)

2) 25 MHz Ref to LNB

3) 2400 MHz TX cable

First light

After installing the dish and the LNB (TX antenna not yet installed at that point), it was hard not to do a little test :)

So I took most of the modules, a powersupply and a laptop with me out to the dish.

I hooked everything up, I had just installed the dish on "eyesight". With the beamwidth of a 1 meter dish at 10 GHz, I did not expect to hear anything from QO-100. I was wrong! I heard the beacons at around -75 dBm, faint but very easy to read! By luck, I had pointed the dish almost spot on! It was just a matter of doing some small adjustment in azimuth and elevation and QO-100 was coming thru with very good signals!

Video from the test, sorry for the shaky hands, part of it because I had to adjust the dish with one hand while holding a labtop in the other hand, part because I was exited :)

Equipment and next steps

Currently the remote box is being finilized. I have mounted most of the equipment on the steel plate that goes into the box. I'm waiting for the driver for the power amplifier, I have tested so far with a CN0417 from Analog Devices. I was able to get around 19 Watts out of the SG-Lab power amplifier, this is way too much for the uplink on QO-100 (I estimate 4 or 5 watts will be enough).

Below is a slideshow of the equipment as it is right now.

Finishing the outdoor box

As all the equipment for the QO-100 station will be located outside at the dish, I decided to mount everything into a "Fibox" box (58 x 28 cm). All the equipment is mounted on a steel backplate. This backplate can then easily be mounted inside the box once this is mounted.

Below is a picture of the finished setup. I made most of the interconnections with RG405 semi rigid cable and SMA connectors. The outdoor unit will have 230VAC power connection, 100 MBit Ethernet cable and a 4 wire control cable. The control cable can enable the 230VAC in the box (to the 27V SMPS module), it can also control the PTT signal on the PA module (probably not needed as the PA has a good VOX circuit). A spare wire is also present in the cable, you never know ;)

The outdoor box was mounted close to the 1 meter dish, I needed approx 3 meter cable for the 2400 MHz transmit signal, I measure a loss of 1 dB for this cable including connectors.

Before mounting the setup in the outdoor box I did some testing of the complete setup. It worked absolutely perfect, I ended up in a small pileup on QO-100, I think it was the fact that I was a "new station" on the satellite :)

The completed setup was then mounted in the box and tested again. The GPS antenna for the Leo Bodnar GPSDO was mounted in the top of the box, not the most optimum mounting (would like to have some groundplane), but it seems to work fine (quick GPS lock, stable frequency etc).