Like on satellites?

Operation via amateur radio satellites is a good option for VHF DX operation even from otherwise unsuitable QTH. And there are so many of them in Slovakia. In addition, compared to other types of VHF DXing, there is no need for high power and antennas at all, it is also possible to work successfully with simple or portable equipment.

The most accessible satellite transponders are currently on VO-52, FO-29, AO-27 (just turned off) a SO-50. The first two are linear, t.j. designed primarily for CW and SSB, the other for FM operation.

Satellite transponders work as crossband converters. T.j. we transmit the signal on one band and receive it on the other. This apparent disadvantage is actually a great advantage, because with two devices we have the opportunity to hear our own signal. The setup for SO-50 can look like this, for example:

2m uplink 145,850MHz FM CTCSS 67,0Hz: Alinco DR-130 + X300 antenna
70cm downlink 436,795MHz (+/- doppler) FM: Yaesu VX-3R + 10el.yagi

So how to start?

Start with a satellite prediction program. Such a program can calculate and display satellite crossings. It is simple and understandable for fun, which is free and Slovak and Czech are also available. He is also clever Gpredict . And HamRadio Deluxe is also popular, which also has a satellite interface. It is especially important to enter your QTH data correctly and to update the Keplerians. That's track data, which are needed to calculate the satellite's motion.

On the world map, we can see the current position of the satellites and the signal coverage area around the selected satellite. It is theoretically possible to establish connections within this territory. A frequently used function is the flyby forecast - it allows you to know when a satellite will fly by.

If you know flights, you can try the reception during a flight. Achieving a good income is the key to a successful operation. What makes him difficult?

1, RF performance of a satellite transponder with respect to a limited energy source (solar panels, batteries) not usually big, only in hundreds of milliwatts
2, the satellite uses small, low-gain antennas
3, the distance between the ground station and the satellite is large
4, the satellite rotates, thus changing the position of the antennas (imagine a centrifuge)
5, doppler effect
6, QRM

The website is an excellent tool for income verification http://oscar.dcarr.org/ , where you can look, what other radio amateurs heard in the given flight. With some satellites, the mode is switched, so it may not be possible to capture the signal, which you are tuning - the satellite had a downlink on a different band, whether it was only transmitting telemetry data.

Practical guide for QSO with SO-50

Setup consists of 2m FM Alinco DR-130 + X300 antennas and 70cm Yaesu VX-3R with headphones + 10el.yagi with rotator.

• I tune the Alinco DR-130 to 145.850MHz, I turn on CTCSS 67Hz and power 50W. I do not change this setting during the entire flight
• the Gpredict software displays the approaching SO-50 satellite. As it approaches, due to the Doppler effect, I correct the RX frequency upwards, t.j. I tune to 436.805MHz and listen without squelch
• according to the data from the Gpredict program, I set the rotator to azimuth, where the satellite appears above the horizon
• Gpredict reports the rise of the satellite above the horizon
• only noise can be heard from the headphones
• a fragment of an incomprehensible signal appears
• don't hear anything for a minute, a signal appears at once, but it seems distorted. I change the RX frequency and clearly hear "you, 59 in JO31BA, roger?“
• I am waiting, because the message was not yet intended for me
• I hear the reply “Thanks PA3ABC, 73! – QRZ EA3XYZ?“
• i call “EA3XYZ OM0AAO!” and at the same time I hear my signal from the headphones
• „OM0AAO good day, 59 IM??T name José" is the answer
• „Hello Jose, 58 JN99DA JN99DA, your locator?" I answer
• „IM99FT IM99FT, 73!“
• „73!“
• I move the RX frequency to 436.795MHz and rotate the antenna to azimuth according to Gpredict

And the QSO is complete. So that other stations have a chance to make a connection, data exchange is brief. There is not always room to make a QSO during the flyby, sometimes QRM will make the connection impossible.

Portable operation via AO-27

A practical guide for QSO via VO-52

The setup consists of 2m TR-9130 + X50 antennas and 70cm Yaesu FT-790 + 10my el.yagi s rotator.

• I will pre-tune TR-9130 to 145.900MHz USB and FT-790 to 435.242MHz LSB
• the Gpredict software displays the approaching VO-52 satellite
• according to the data from the Gpredict program, I will set the rotator to azimuth, where the satellite appears above the horizon
• Gpredict reports the rise of the satellite above the horizon
• I start tuning the TR-9130 around the center frequency of the transponder, from 145.890MHz to 145.910MHz
• a fragment of an unintelligible signal appears on 145.903MHz
• the signal improves slightly, but it is still frequency unstable and needs to be fine-tuned
• I adjust the antenna according to the data from Gpredict
• I emit a drawn-out "ooooool" and tune the FT-790 upwards, when I'm already on 435.246MHz, my faint "ooooh" appears from the headphones next to the station's signal
• still understand those signals little, only managed to hear "FAV JN70ET"
• I adjust the antenna according to the data from Gpredict
• the satellite descends below the horizon

QSO failed, the signals were very weak. Well, I heard my own signal! How to improve it? The following is the production of a 2m directional antenna according to the DK7ZB version 50 ohm. Follow-up QSO with UA9CS goes well, signals are max. according to S-meter. S4, but readability is good. Another significant improvement was the installation of a GaAs FET preamplifier, and the signals are real S9.

VO-52 reception on TS-700

Setup OM0AAO

Satellite antennas: 5el.DK7ZB na 2m a 10el.DK7ZB na 70cm, filming in both azimuth and elevation
28MHz: antenna Diamond W-8010, These are a key factor determining properties such as the selectivity and durability of the receiver + MF SDR Softrock Ensemble + PowerSDR/GenesisSDR
144MHz: antenna vertical 5el.DK7ZB 50ohm version + FT-290R alebo home made XVRT 2m/10m. Preamp HA8ET, PA home made 4CX250B
432MHz: antenna vertical 10el.DK7ZB 28ohm version + FT-790RII. PA modified V-ULA 50
Software GPredict, PstRotator a ERC interface to AZ/EL rotator according to DF9GR.

Try it too!

Several decades have passed since the time of Sputnik, however, radio amateur satellites are still a field, which hides a lot to discover. However, it is an excellent combination of operation and technical complexity and gives the radio amateur a lot of enriching knowledge.