Est. MUF
16.9
MHz
Global snapshot
MUF and LUF Explained
Learn what sets the usable range in HF propagation.
Propagation estimate
Using built-in snapshot
Est. LUF
5.9
MHz
Global snapshot
160m
N/A
80m
Good
40m
Good
30m
Good
20m
Good
17m
Fair
15m
Poor
10m
Poor
This is a path estimate, not a guarantee. Use it to choose your first checks, then confirm by listening before you call.
Best HF Bands Right Now
MUF 16.9 MHz · LUF 5.9 MHz
mid-latitude estimate
Built-in snapshot
Band
Status
6m
Above MUF (Unreliable)
10m
Near MUF (Marginal)
15m
Best now
20m
Best now
30m
Best now
40m
Near LUF (Marginal)
80m
Below LUF (Absorbed)
160m
Below LUF (Absorbed)
How to use the HF window in practice
Treat this as a decision aid: pick a likely band fast, then validate with actual activity.
- Start with bands in the middle of the usable window.
- Treat edge bands as marginal, especially when conditions are changing.
- Before transmitting, listen for real path activity and adjust one band up or down.
- Then map your mode and segment with US Band Plan and Digital Mode Frequencies.
MUF vs LUF: what each number means
Both values are path-dependent estimates for current HF propagation, not fixed global limits.
Maximum Usable Frequency (MUF)
The highest frequency likely to refract back over the path at that time.
Lowest Usable Frequency (LUF)
The lowest frequency likely to overcome absorption and noise enough to be usable on that path.
Why the usable HF window changes
Time, solar conditions, season, and path all shift which bands work best.
Usually raises MUF
Solar flux and ionization
Higher ionization often supports higher HF bands, especially 20m through 10m when geomagnetic conditions stay reasonable.
Often lowers MUF
Kp and geomagnetic disturbance
Unsettled geomagnetic conditions can rough up higher-frequency paths, shorten openings, and make promising bands less reliable.
Day raises MUF and can raise LUF
Day vs night
Daylight usually improves ionization for upper HF, but D-layer absorption can also push the practical floor upward.
Changes both floor and ceiling
Path distance
Shorter, regional paths and longer DX paths can behave very differently even when the overall solar picture looks the same.
Can raise or lower support
Latitude
Lower and mid-latitude paths often keep better high-band support. Higher-latitude routes are more exposed to geomagnetic instability.
Raises LUF
D-layer absorption
More absorption makes lower frequencies harder to hold, especially in daylight and during flare-related conditions.
Raises practical LUF
Local noise
A noisy station can make a lower-frequency path unusable even if a propagation model says the band should work.
Can improve some paths
Gray line
Routes near the terminator can briefly favor long-distance work, especially on lower and middle HF.
Check the inputs behind the estimate
MUF and LUF only make sense in the context of solar and geomagnetic conditions.
Check Solar Conditions
Review SFI, Kp, A index, and the other space-weather inputs that influence HF support.
View Propagation
See how those inputs turn into band recommendations and operator guidance.
Compare planning scenarios
Use the simpler predictor when you want to test a time window or target type before you operate.
FAQ
No. MUF is path-dependent. A route from your station to one region may support 20m or 15m while another direction does not, even at the same time.
Daylight often raises D-layer absorption, which can push the practical lower-frequency floor upward. At night that absorption usually relaxes, helping 40m and 80m.
No. They are operating estimates. Antennas, power, takeoff angle, local noise, and fast-changing ionospheric conditions still decide whether a contact actually completes.