Scenario 3 - Wrong-Handed
Session: Saturday, 16:24 UTC
Station: BKYD-YAGI — crossed yagi, feed harness “improved” since last night
Operator: You
Riley: Present, suspiciously casual
Riley’s Note
Section titled “Riley’s Note”I rewired the feed harness on the yagi this morning. Cleaned up the phasing lines, shortened a run, made it tidy. It is objectively a nicer piece of work than it was yesterday.
Tonight’s pass is a sixty-three degree monster — the best geometry you’ve had. Same bird, same frequency, same everything as last night, and the bird is closer and higher.
So this should be the easiest contact of your life.
If it isn’t, don’t start yanking connectors. Read the numbers, work out what KIND of loss you’re looking at, and tell me what you think happened.
— Riley
Tonight’s Pass
Section titled “Tonight’s Pass”| Satellite | AOS | Max Elevation | LOS |
|---|---|---|---|
| CUBEHOP-1 | 16:28 | 63.4° at 16:35 | 16:41 |
Link Reference
Section titled “Link Reference”| Signal | Frequency | Bandwidth | Mode | Polarization |
|---|---|---|---|---|
| CUBEHOP-1 FM downlink | 435.250 MHz | 15 kHz | QPSK 1/2 | RHCP |
Reading a Loss
Section titled “Reading a Loss”When a link comes in worse than predicted, the shape of the loss tells you where to look before you touch anything:
| What you observe | What it usually means |
|---|---|
| Loss varies with pointing | Antenna aim, tracking mode, or a beam too narrow |
| Loss varies with time / fades in and out | Multipath, obstruction, scintillation |
| Loss appears only at low elevation | Trees, terrain, atmosphere |
| Large, constant loss with everything else nominal | Something systematic in the RF chain |
That last row is the interesting one. A big flat number that doesn’t care about geometry, doesn’t fluctuate, and doesn’t improve at high elevation is not a propagation problem. It’s a configuration problem.
Circular Polarization Reference
Section titled “Circular Polarization Reference”The crossed yagi has a switchable feed: it can be configured for right-hand or left-hand circular polarization. That switch is in the RADIO section of the console, marked POL.
| Situation | Loss |
|---|---|
| Feed handedness matches the signal | ~0.5 dB |
| Feed handedness is opposite the signal | ~18 dB |
One More Thing About Handedness
Section titled “One More Thing About Handedness”A circularly polarized signal that reflects off something — a metal roof, a car, a wet street — comes back with its handedness reversed. RHCP goes in, LHCP comes out. That’s worth remembering the first time a signal is strong in a direction where there’s nothing but a building.
Tonight’s Checklist
Section titled “Tonight’s Checklist”- Rotator in program-track on CUBEHOP-1 before AOS
- Confirm the downlink is on the waterfall where it should be
- Diagnose the loss before changing anything
- Fix it
- Prove the fix: lock held 60 seconds at 10 dB C/N or better
Note that last line. Riley does not accept “it looks better now” — the console reports C/N, and the number has to hold.
End of Briefing
Section titled “End of Briefing”Riley did not sabotage the rig. Riley made an honest improvement and introduced one wrong assumption while doing it, which is precisely how this happens to real operators on real equipment.
The lesson isn’t “check the polarization.” The lesson is that the size and shape of a loss tells you which subsystem to suspect — and that a signal you can see is not necessarily a signal you can use.
Sixty-three degrees. Don’t waste it.