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

v

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.

 3-WAY active splitter

This is a 3-WAY splitter with the ability to connect a preamplifier with a large dynamic range and gain up to 18dB. This preamplifier can compensate for split losses. It can also add gain up to 10dB.

Both current and voltage protection are included. The gain of the amplifier can be adjusted from the front panel.

Link to web page with manual

block diagram

Examples

Measurements

 YAESU PTT splitter - RCA output, INH input

Today's standard is PTT output and input on RCA connector. However, the YAESU TRX does not have these connectors. For many users, it is not easy to connect an external device to the TRX that needs a PTT signal. 

For this purpose, a simple box has been created that contains two separate PTT outputs on RCA and one INHIBIT input. These signals are connected to the MINI DIN connector of the TUNER. The signals for the TUNER are also pass-through and will not restrict its connection.

The box includes optical isolation of the PTT and INH signals.

Two versions are available - they differ only in the INH input. The first version has INH active when connected to ground. In the second (MK2) version, an internal jumper can be used to set when INH is active.

There are links for:

MK1 version with simply INHIBIT

MK2 version with INHIBIT jumper

Main functions

• Adapter from YAESU TUNER connector
• Protecting TRX from accessories - opto isolators
• Minimal delay
• Two independent PTT outputs
• PTT output FET switch - DC 30V 1A
• PTT, INH LED indicator
• INH with Jumper for 3 different states
• RCA connectors
• Mini-DIN 8 1.5m cable included
• 4pcs self adhesive feet pads included
• Aluminium enclosure: W x H x L = 58 x 24 x 50 mm
• 
  

Parameters

• Optocoupler isolators protecting TRX PTT out
• Output FET switch 30 V 1A for each port
• 3 states INHIBIT (internal jumper)
• DC power OUT TUNER PTC fuse 1.1A
• TUNER mini-DIN 8 connector
• PCB size 50x50.4 mm

Inhibit (MK2 version)

• Internal jumper to set
• INH active when grounded
• INH deactivated when grounded
• INH activated by positive voltage

MK2 version with INHIBIT jumper

Example to use INHIBIT

An example with a device where RF power is blocked until PTT feedback occurs. Protecting the connected device (here RX Audite) from transmitting into the RX path.

⚠ NOTE: Both jumpers in right position - second jumper settings at picture - jumper settings.

Example of use with Easy Controller 6-2, where the PTT output from the controller unblocks the RF output from the TRX. This watchdog prevents transmissions where the same ANT would be accidentally selected for both TRX - Manual switching and switching from USB or Wi-Fi.

⚠ NOTE: Both jumpers in right position - second jumper settings at picture - jumper settings.

 Tropo DX at LoRa APRS 433 MHz

Late October and early November brought exceptional conditions for long distance DX contacts. The result was not only great result of OL7M guys in MMC contest, but also new and beautiful DX on LoRa APRS. 

The longest two-way contact was achieved from Koruna 1100m asl - isn't that even a LoRa 433MHz world record over land?

F4JPO-10 from JN08wt 1057km

F1ZFC-10 from JN09xi 1039km

And stations which heard me:

RIG there is TTGO LoRa32 with around 30mW and home made 4el. collinear antenna. Installed at the top of the tree in 1100m asl. Solar powered with rest LoRa toys. More there.

The conditions also favoured the lower positions. Here are the weather stations located around the hills in my area. One nice DX came through my apartment window. On the 5th floor with a small 3D printed dipole - OK2ZAW-23.

There is a 3D printed dipole, like on the other weather stations as well. They are all solar panel powered and have RF power around 50mW.

And there were also nice DX for YO gateways... like YO2B-10