📡 DXLook Propagation Interpretation Cheat Sheet

How to Read SSB, CW & Digital Conditions Using SNR, MUF & Real Paths

DXLook shows real reception reports, not predictions.
To use it correctly, it’s important to understand how SNR, MUF and real paths translate into actual operating success for different modes.

This guide is written for typical home stations (roughly 50–100 W and a dipole or vertical), not contest super-stations.

🔊 1) SSB (Voice) — “Is it worth calling?”

Practical SNR requirements for SSB

• ✅ Good: ≥ 15 dB → Comfortable copy, casual QSOs, relaxed ragchew
• ⚠️ Marginal but workable: 10–14 dB → Weak but readable voice, more tiring to listen to
• ❌ Below 10 dB: Usually not usable for SSB, even if digital is decoding just fine

On DXLook, a lot of the underlying data comes from digital networks (PSK Reporter, etc.), so we use SNR-based mode augmentation:

• When digital reports from your area show SNR ≥ 10 dB, that path is reclassified as SSB-capable.
• That means the SSB filter in DXLook is not limited only to native SSB spots; it also uses strong digital reports as evidence that SSB should work.

Key idea:
A band full of –5 to –20 dB digital spots does not mean SSB is open.
SSB needs comfortable SNR, not just “a decode.”

SSB also depends on:

• Your local noise floor
• Antenna efficiency and takeoff angle
• Stability of the ionosphere (fading, QSB)

One single high-power “big gun” getting through does not mean the band is “open for everyone.”

🔔 2) CW (Morse) — “Weak signal but still human-copyable”

CW is more forgiving than SSB, but still has limits.

Practical SNR ranges for CW

• ✅ Good: ≥ 5 dB → Easy copy
• ⚠️ Readable with effort: –5 to +5 dB → Copyable but may require focus
• ❌ Below –5 dB: Often unreliable, even for skilled operators

On DXLook:

• CW paths include native CW spots, but also
• High-SNR digital spots that are reclassified as CW-capable when SNR is high enough.

CW often:

• Opens earlier than SSB on a given band, and
• Stays usable longer after SSB has become too weak.

So if:

• SSB looks marginal or dead,
• But CW-classified paths are active around your grid,

…there is a good chance CW will still be workable.

💻 3) Digital (FT8, FT4, WSPR, etc.) — “The canary in the coal mine”

Digital modes are designed to work well below the noise floor. That makes them ideal for detecting propagation long before SSB and CW become practical.

Decode capability (rough guide)

• ✅ Strong digital signals: ≥ 0 dB
• ⚠️ Weak digital: –10 to –20 dB
• ✅ Extreme weak-signal (FT8 / WSPR): down to about –28 dB

Important:

• Digital activity ≠ SSB usability.
• Digital shows:
  • The ionosphere is ionized enough for RF to get through
  • There is a valid path between two stations
  • Timing and geometry are working

But you might still have no chance on SSB at the same moment.

Think of digital as your:

“Early warning system for band openings.”

It tells you something is happening — then SNR and MUF tell you whether that “something” is usable for voice or CW.

☀️ 4) MUF — “What bands can physically work?”

MUF (Maximum Usable Frequency) tells you the highest frequency that can be refracted over a given path right now.

On DXLook, MUF zones are built from real reported paths, not a pure theoretical model. That helps keep it grounded in reality.

How to use MUF in practice

• If your band is above MUF for a path → it’s very unlikely to work.
• If your band is well below MUF → the ionosphere can easily support it.
• If your band is just below MUF → you are near the edge: openings can be spotty and time-dependent.

Example

• MUF around a path ≈ 18 MHz:
  • ✅ 20m (14 MHz): very good chance
  • ⚠️ 17m (18 MHz): conditional, short openings possible
  • ❌ 15m (21 MHz): likely closed

Remember:

MUF only tells you “this frequency can refract.”
It does not guarantee SNR good enough for SSB.

You still need to look at SNR and recent spot density to judge real-world usability.

🧭 5) Real paths matter more than global blobs

On DXLook you can center everything around your grid square. This matters because propagation is not uniform worldwide.

Two things can be true at the same time:

• The band is wide open from North America to Europe
• The same band is almost dead from Southern Europe to South America

So when you evaluate conditions:

1. Prioritize paths that start or end near your grid (your QTH).
2. Treat global “clouds” of activity as context, not as a guarantee.
3. Combine MUF zones + your perspective grid + SNR.

This is exactly why DXLook uses real paths and geometry instead of a single global “band open/closed” flag.

✅ 6) Practical “Should I call now?” decision tree

Here’s a simple way to combine everything when you’re sitting at the radio.

For SSB

1. Is MUF for your region at or above your band?
2. Do you see SSB-classified or high-SNR digital paths (SNR ≥ 10 dB) from or to your grid area?
3. Is your local noise floor reasonable?

If yes to all three → it’s worth calling on SSB.

For CW

1. Is MUF at or above your band?
2. Are there CW-classified or high-SNR digital paths (SNR ≥ –5 dB) around your grid?

If yes → CW is likely workable, even if SSB is marginal.

For Digital

1. Do you see any spots on your band from or to your grid in DXLook?

If yes → it is usually workable for FT8 / FT4 / similar modes.
If no spots appear at all in your region, the band is likely actually dead, not just quiet.

⚠️ 7) Why DXLook doesn’t blindly trust a single station

One of the design goals of DXLook is to avoid black-box “band open” claims based on a few outliers.

• A single 1.5 kW station on a tower-top Yagi doesn’t define the experience of a 100 W station with a wire.
• DXLook:
  • Applies SNR sanity filtering,
  • Uses mode reclassification based on real thresholds (SSB / CW / Digital),
  • Builds MUF and zones from actual reported paths, not just generic models.

This is why sometimes DXLook may look more conservative than other tools that simply mark a band as “open” when any path exists.

📌 Final summary table

For quick reference:

If you have suggestions or real-world examples that don’t match what this cheat sheet suggests, I’d love to hear from you.
DXLook is built around real data and real operators, and feedback from actual use on the air is what keeps improving it.

73,
Rodrigo (AK6FP)