Technical Articles

Satellite Basics (Part 2): Making QSOs via Satellite


Ruth Willet, KM4LAO, operates FM satellites using a dual-band HT and a hand-held Arrow directional dual-band yagi while on vacation in North Carolina’s Outer Banks, in grid square FM25. [Sharon Willet, KM4TVU, photo]

In my first blog covering Ham Radio satellite basics, we went over the mechanics and logistics of hearing amateur satellite passes. In this blog, we’ll take you to the next step: making QSOs through an FM satellite! This entry assumes you are comfortable with the terms and techniques in my first post and can reliably monitor a satellite pass. If you need a refresher, feel free to review before working on this material.

While it is possible to work FM satellites with a single dual-band HT, using two HTs will allow you to operate in full-duplex mode, meaning you can hear your own signal from the satellite’s downlink in real time as you transmit. Remember, FM satellites function just like an orbiting repeater, so only one person can transmit through it at a time. As a beginner, using two HTs will improve your success rate significantly, and also help avoid unintentional interference to other satellite users during the pass.

Currently, all FM satellites in orbit require a CTCSS (PL) tone of 67.0 Hz on your transmit frequency. If you don’t have that properly programmed, the satellite will not hear you.

These instructions assume you are using a hand-held directional antenna. If you’re using your standard dual-band vertical antenna at home or on the roof of your car, you can ignore those instructions. If you are using an extended whip antenna on your HT, keep the whip broadside to the satellite as it passes over head. This will require some practice.

Know what grid square you are in.

Before the Pass Starts

For best success, operate from a place where you have an unobstructed view of the horizon. Buildings, trees, and other obstacles can interfere with your ability to receive the satellite. If you live in an urban area, try the roof of a parking garage or a large park.

You will need to be able to adjust your 70cm frequency to compensate for the Doppler effect. Whether this is the transmit or receive frequency will vary, depending on which satellite you’re trying to use. Many people program several 70cm frequencies into their HT’s memory channels for ease of operation during a pass. A suggested frequency list of the three active FM satellites at the time of this writing (May 2019) is in Figure 1.

Confirm the time and path over the horizon of the satellite you want to use. Several options for predicting passes are listed in the first part of this blog.

Finally, observe the Cardinal Rule of Satellite Operating: Do not transmit if you do not hear the satellite. It is very common for new satellite operators to transmit before they confirm they can hear other stations during the pass. This often leads to unintentional interference to other users of the satellite, disrupting ongoing QSOs or preventing others from using the satellite at all. Do not transmit until you can reliably hear other users on the pass.

During the Pass

  1. Open your squelch. Most FM satellites don’t transmit with a lot of power, usually less than half a watt. You will need to open your squelch to hear the signals from the satellite, especially when the satellite is close to the horizon.
  2. If all is going well, you should start to hear signals break through your squelch. Adjust the position of your antenna to get the best reception. Remember to aim your antenna at the satellite’s position as it passes overhead, not in the direction of the station you hear. Remember you will need to adjust your 70cm frequency throughout the pass.
  3. Listen for a QSO to end, then give your callsign and your grid square, using standard phonetics. Example: “Kilo X-Ray Nine X-Ray, Echo November Five Zero.”
  4. Repeat this process, being careful not to interrupt an ongoing QSO, until you get a reply.

Somebody Answered Me! Now What?

Because satellite passes typically have many users, contacts are generally very short. A simple exchange of callsigns and grid squares is common, taking only 15-20 seconds for a complete QSO. A sample QSO goes like this:

KX9X: “Kilo X-ray Nine X-ray, Echo November Five-Zero.”

W1AW: “Kilo X-ray Nine X-ray, here is Whiskey One Alpha Whiskey, Fox November Three One.”

KX9X: “Whiskey One Alpha Whiskey, thanks, Echo November Five Zero, Illinois, QSL?”

W1AW: “QSL, Fox November Three One, Connecticut, QSL?”

KX9X: “QSL, thanks and 73.”

It may take a few tries before you are able to get a QSO in. This is normal, so keep trying! There are some things you can do to increase your chances of making that first contact:

  1. Try passes that are in the middle of the day during the week. Lots of folks are at work, so there will be fewer operators on, making gaps between QSOs more frequent. Weekend passes during the day are the busiest.
  2. If you live near a coast, try a pass that is mostly over water. If the satellite pass doesn’t cover a lot of land, there will be fewer operators that can access it.
  3. Try during late-night hours. Fewer people will be awake, so you’ll have a better chance to get in to the satellite.
  4. Schedule a contact with another operator for a specific date, time and frequency (known as a “sked”). There are plenty of satellite enthusiasts who would be thrilled to make a sked with you. You can find lots of helpful people in the AMSAT Facebook Group.

Helpful Tips and Best Practices

  1. Like repeaters, don’t call CQ on an FM satellite. Simply give your call and grid. “Kilo X-ray Nine X-ray, Echo November Five-Zero.”
  2. Use standard phonetics. Some letters like B, C, D, E and G sound quite similar, especially in a weak-signal environment like a satellite. Phonetics reduce errors and save time.
  3. Five watts is generally more than enough power to work a satellite, especially with directional antennas that have gain. Using too much transmit power can damage the satellite’s batteries and shorten the life of the satellite. Please use the minimum amount of power needed to complete a QSO.
  4. Be sure to let QSOs in progress finish before making a call. Remember, only one signal can get transmitted at a time on an FM satellite, so we need to share the time wisely and cooperatively. Don’t make any calls until a QSO in progress has completed.

Refined Techniques

Many satellite operators mount directional antennas on a tripod for ease of use. While this does free up your hands a bit, having your directional antenna in a fixed position makes your station more susceptible to a phenomenon called polarization fading. As the satellite orbits overhead, it is also pitching and tumbling, which causes the satellite’s fixed-position vertical antenna to change polarity, relative to your position on the ground As a result, the receive signal can dip and fade as the polarities between your antenna and the satellite’s antenna get mismatched. Holding your antenna in your hand allows you to quickly adjust for the polarity shift, minimizing signal fade.

With one hand holding your radio and the other holding your antenna, how are you going to log your QSOs? Many operators use a digital audio recorder to record the pass, then log it after the fact. Many models are available on Amazon or other retailers for around $30-$50. Turn on the recorder and put it in a shirt pocket, or buy a passport pouch and wear it around your neck during passes. Be sure to record a brief description of the pass you’re working when you first turn on the recorder: “AO-91 pass on May 19, 2019 at 1546 GMT from grid EN50 in Urbana, Illinois” is quick and gives you all relevant information about the pass you’re working to ensure proper logging of QSOs later.

If you are using two HTs, you will need a diplexer, which isolates your transmitted signal from your receive radio. Without it, you will likely overload the front end of your receive radio, which will make contacts impossible. Several manufacturers such as Comet and MFJ offer diplexers; the Arrow antenna has an optional diplexer that is stored in the antenna handle.

A Community of Friends

The satellite community is one of the friendliest groups of people you will ever meet. Their enthusiasm for this aspect of Ham Radio is intense, and they are eager to help newcomers succeed. The Radio Amateur Satellite Corporation (AMSAT) is the national organization of satellite operators and is largely responsible for getting new satellites in orbit. You can connect with them in their Facebook group or visit their website, AMSAT.org.  

I hope this gets you excited about trying satellite operating. Feel free to contact me if I can help; I always enjoy working new satellite operators! 73 and see you on “the birds!”

Figure 1: FM Satellite Frequency Guide (current as of May 2019)

AOS = Acquisition of Signal (start of pass) ; LOS = Loss of Signal (end of pass)

Frequencies are listed in megahertz (MHz)

SO-50 (2-meter uplink, 70 cm downlink, 67 Hz CTCSS tone)

Part of Pass        TX Freq                RX Freq

AOS                       145.850                 436.805

                                145.850                 436.800

Midpoint             145.850                 436.795

                                145.850                 436.790

LOS                        145.850                 436.785

AO-91 (70 cm uplink, 2 meter downlink, 67 Hz CTCSS tone)

Part of Pass        TX Freq                RX Freq

AOS                       435.240                 145.960

                                435.245                 145.960

Midpoint             435.250                 145.960

                                435.255                 145.960

LOS                        435.260                 145.960

AO-92 (70 cm uplink, 2 meter downlink, 67 Hz CTCSS tone)

Part of Pass        TX Freq                RX Freq

AOS                       435.340                 145.880

                                435.345                 145.880

Midpoint             435.350                 145.880

                                435.355                 145.880

LOS                        435.360                 145.880

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