VU2EXO QO100 Setup

VU2EXO QO100 Setup

About My QO-100 Setup:

Description : The QO-100 project was executed in two phases

Step 1: Reception

As the first step towards the QO100 setup, we need to have a dish focussed to the satellite. This dish can be used for uplink and downlink with the satellite. Towards this, the location identified on the terrace which has the open space towards the satellite, in fact the closest location was 35 meters from the shack. The dish antenna installed at this location and focused to the satellite using the compass and protractor. Once the dish antenna is almost focused to the theoretical location of the satellite, a satellite dB meter used to identify the signal from the satellite.

Once the signal trace detected by the dB Meter, the LNB replaced with a SHARP LNB having the crystal replaced with 25.78125 MHz to peak the signal from the satellite using my Kenwood TS-2000 operating in satellite mode (UHF CW mode). The rig connected to a laptop using ARCP-2000 application to view and control the rig remotely from terrace via team viewer app using mobile.

This helped me to listen to QO-100 QSOs using my radio without an SDR. The LNB reference clock was not stable, the frequency used to vary time to time and I have to tune again and again to listen to long QSOs.

This varying reference signal made me to think about the use of an external reference signal to the LNB from a comparatively temperature stable environment i.e., from My Shack 😊. I have decided to use the already available home brewed DDS VFO (AD9851 with PIC controller) as the reference signal generator and made necessary changes to the VFO to drive the signal over 35 meters of RG6 cable.

The next step was to modify a dual channel LNB to give reference signal from VFO. It is found that few LNBs are not designed in such a way that the modification is not easy or in fact sometimes practically not possible to modify. Later found Solid SKU-FS-255 twin LNBF is suitable for my purpose. The LNB opened and the 25.000 MHz crystal was carefully removed from it. The clock-in of the PLL is fed from a 1:1 transformer wounded over an old radio IF former to isolate it from the ref clock generator and also to avoid the unwanted noise injection to the reference clock. This turned to be a success and the IF frequency of the LNB could change by adjusting the Reference signal from DDS VFO. Later adjusting the reference frequency to 25.782051 MHz the start beacon is received at 434.500 MHz in the rig.

Step 2: Transmission

The Rx was active for a while and then my company Ham radio club of Germany unit arranged a net including different location of the company clubs via QO-100, which triggered me to make my Tx ready in 9 days. Then started collecting parts from different sources and made the 3.5 turn helical antenna at home and tuned to a low SWR 1.12.

To reduce the transmission loss the unregulated DC taken to the terrace from my shack and the DC regulators, the upconverter and the RF Power amplifier are placed near to the Dish. 1.2 Meter away from LNB)

By overcoming multiple hurdles of transportation, connectors on the last moment, the first QSO via QO-100 was made just 3 hrs before my targeted time 😊 (The time of the planned net on QO-100)

QO100 Setup Details :

Dish : 90cm Offset Dish

LNB: Solid Dual port LNB modified by to have external Reference Signal input. The AD9851 DDS/DAC Synthesizer located in the shack providing stable reference frequency of 25.782051 MHz to the LNB and which in turn brought down the IF frequency of the LNB (434.500 MHz to 435.000 MHz) corresponding to the QO-100 downlink frequency of 10489.500 MHz to 10490.000 MHz

Tx Antenna: 3.5 Turn Helical Antenna made up of brass welding rod

TRx : Kenwood TS-2000 in Satellite mode as my transceiver. The QO-100 reception is done on the Kenwood TS-2000 by feeding the IF of the LNB which is shifted to 434.500 MHz to 435.000 MHz by changing PLL reference frequency.

Up converter: The LARC make up converter used to generate 2.4 GHz signals from VHF input. The VHF band (144.500 MHz - 145.000 MHz) of the Kenwood TS-2000 in satellite mode is giving input to the upconverter. A homemade power splitter is reducing the output power (5W is the minimum power of the TS 2000) to the up converter which needs less than 1W to produce 2.4 GHz upconverted output.

RF Final Amp: 4W Wi-Fi booster amplifier, powered with 12V DC input is feeding the Helical Antenna

For details of this project, please feel free to contact me on my mail id