Thoughts About Birds

Satellites, that is.

This post is a follow up to my LEO Learning Curve post from earlier this month. I think of this as sharing some notes, providing context, and trying to make them readable for others.

One thing you can’t rush is experience. You can prepare, study, make notes, organize information, and so on, but nothing is a substitute for putting in the time. In my case it is about 6 months since my first satellite QSO, so I’m not speaking from great authority. I am speaking to others who are starting to work sats, are thinking of it, or are frustrated by it.

Here are a few things that have helped me:

  • Take a Listen-First approach to your satellite passes: Running two VFOs on a sat pass can be like juggling at first. Just like juggling it helps to start simple before adding balls in the air. Track the doppler shift of a satellite for fun, listen to the stations they are working and how on-frequency they are/are-not. Having some practice with the receive side makes it easier to find yourself and track shift during a QSO.
  • There is no “One True Rule”: Correcting for Doppler shift isn’t done the same way by all operators. I have had some odd experiences where the other station is off frequency but copying me, and when I retune to hear them they chase me. I assume they are using RIT, which is weird on SSB, but . They could also be using computerized doppler correction and adjusting both uplink and downlink at the same time. I understand the approach, but it only works if both stations are doing it the exact same way. (I assume these are computer control guys who are warm in their shack while I am shaking in the cold and trying to tune with numb fingers.)It is difficult to make a contact a contact if the other station isn’t tracking Doppler shift the same way. Leaving the 2m side alone and tuning the 70cm side to correct for Doppler is how I roll. Either way, listen and you can hear one or both stations fine-tuning.
  • Start with more passes and then find better passes: When looking for an operating location, start by finding a convenient spot to where you live/work and try that first. An easy location with just-ok horizon can be an excellent spot to build technique. I use an app like Theodolite to document the cardinal directions and the height of the horizon due to obstructions. Make a little map, maybe. You can now use that to decide whether a pass will be worth setting up for. Or find a pass on the edge and see what you can hear and how well you can hit the satellite (or hear yourself).
  • Satellites Helping Satellites: Use a tool like Google Earth to scout locations with a clear horizon, especially to the east or west. Piggybacking on the previous item, I have found some excellent spots precisely because I needed to work a low-elevation pass to work a station in Europe or on the West Coast of the US. GE has Street View, and the line tool generates a terrain profile. Draw a line from your spot to the direction you want to work and see what it looks like. You can also drop to ground level and see the estimated horizon. It’s usually very close. I use Google Earth (or other mapping if you want) to scan for good locations.
  • Refine your portable locations: I have fine tuned one of my Greencube/IO-117 operating locations for Northwest-AOS passes this way and have a good number of JA stations to show for it. Here is the Google Earth Screenshot:

Both of these lines show a 320-degree bearing at Ninigret Park in Charlestown, Rhode Island FN41ei. The line from Location 1 has a radio tower right on the 320-deg bearing, and some higher/closer trees. I used GE to find Location 2, where 320-deg is on the right side of some trees, but there are fewer obstructions, the radio tower is comfortable off to the north, and the trees are further/lower. This small change of just a few hundred yards got me into IO-117 earlier/lower in the pass and allowed me to contact more JA stations on these passes starting between 220-230 degrees AOS and running overhead to south-east to about 160-degrees at LOS.

  • All Is Not Equal: The correlation between how loud you are hearing yourself on the downlink and how loud the other station is hearing you on the downlink is “loose”. I often hear myself at true 59 on RS-44 and the other stations is not able to copy me. That could be polarization and antenna selection, the location of the other station, receiver type, preamps… That situation works both ways. A weak station might be hearing you very well while you can barely hear yourself. Just try to make the QSO. I record my passes and have exchanged recordings. It is interesting to hear what the other station is hearing.
  • Make skeds! I’ve been able to help other ops get closer to WAS because they needed Rhode Island, or FN41. It doesn’t seem rare but I have had plenty of European ops interested/scheduled. This little state has plenty of hams but not many on the sats. I went a long time with only one contact in FN41 and it took me a while to get it confirmed! Likewise, look for operators or rovers in grids and states you need. Many grids are only available this way as they have no resident operators.
  • Keeping track of uplink and downlink pairs: I have a document in a notes app on my phone with just the basic transponder info and it is very handy. If you use a downlink radio with a waterfall display you can get away with only keeping a note of the uplink and downlink center frequencies, transponder bandwidth, inverting/not, and doppler shift direction. You will use the waterfall to spot yourself, and if you correct manually for doppler you will be only tracking the 70cm radio most of the time. I use GoSatWatch or one of the other iOS apps for tracking passes, so having a transponder reference document on my phone is super helpful.
  • Keep an open mind about everything: I would like to finish this list with a shout out to Dragan, 4O4A, who tweeted this super helpful doppler correction procedure. Knowing the upper and lower limits of the uplink and downlink, plus the doppler offsets, is all you need. My mind is still a bit blown, but it is changing how I will approach the previous tip. For 2023 I will be making a passband-edge and offset document for the linear sats I like to work.

How I approach a typical pass, and some other considerations:

Take RS-44, an inverting V/U satellite with decreasing doppler tracking, for example: My uplink is a Yaesu FT-817ND, set to 2M LSB, and I run it in VOX mode with a headset. My downlink is an Icom IC-705, in 70cm USB mode, and the waterfall set at 50KHz wide. I have a pretty good idea of UL/DL frequencies at or near AOS. Once I hear the bird well enough I will whistle and look for my signal on the waterfall. When I find it I move my DL frequency to a quiet section and move my uplink to match. That’s a good place to start calling CQ. I also might start by listening to the frequencies I “see” on the IC-705 waterfall. It gives me a quick idea of who is active and who they might be working. At that point I can call one of those stations, or move to a quiet spot to call CQ. I might do that several times over 5-10 minutes. I might make three or four CW calls, then scan the stations again.

When I need to QSY I know my TX has to move the same amount (in reverse) as my change in downlink frequency (and v-v). If I move my receive frequency from 435.650 to .655 I have to move my uplink down (inverting) by 5KHz.

On an overhead pass it is important to remember it’s a low elevation pass for someone. In my area that can be the Rockies and upper Midwest USA, through central Canada, or could also be Mexico and Central America. It’s easier for me to work those stations on a pass with a 35-50 degree W or S max elevation, especially since my home has a bad western view.

So that’s what I have found useful as I started operating more satellite passes, and putting time into optimizing my routine. Drop a comment or an email if you find this useful, or have something to add. Best 73 and see you on the birds, Pete N1QDQ

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