Video: Modes of Propagation on 50 MHz by K9LA

In June of 2021, Carl Luezelschwab K9LA gave a presentation to the Madison DX Club titled 'Modes of Propagtion on 6 meters'.

There are plenty of guides and explanations about propagation on the 50 MHz band in books and on websites and they tend to be pretty basic. In this video, K9LA looks at propagation modes in more detail and as expected, things are often not as simple as they seem.

It's very easy to look at long distance contacts on the 50 MHz band and just blindly assume it has to be multi-hop Sporadic-E. As you will see in the video, we should all keep an open mind and accept that it may be due to other propagation modes. This is especially true now as the FT8 digital mode is showing that weak signal paths exist that weren't so obvious in the past with SSB or CW.

The 51 minute video can be seen below...

Some timestamps and items of interest...

00:00 to 02:20 Introduction

02:20 to 04:20 Old 50 MHz radios

The talk is then broken down as follows...

Review of all these modes
Antenna considerations
Solar Cycle 25
References

04:50 to 09:30 Fundamentals of the atmosphere and ionosphere.

It's interesting to note that K9LA questions if PMSE (Polar Mesospheric Summer Echoes) at 85kms above the Earth plays a part in bending radio signals slightly before they reach the higher Sp-E and F2 layers.

In the slide for trospheric ducting, there is an error in that it should read 450 metres as opposed to 450 kms. As K9LA observes, tropo ducting at 50 MHz is very unusual in temperate regions.

At 15:45, K9LA talks about SSSP - Short-path Summer Soltice Propagation which is linked to PMSE. It may well be that this propagation mode is responsible for many of the openings from Europe to Japan on 50 MHz as opposed to the standard 'it must be multi-hop Sporadic-E explanation'.

At 27:30, there are charts suggesting that Sporadic-E may be changing over the years.

At 32:00, Carl suggests that equatorial Sporadic-E may be a significant factor where signals are crossing the equator at local noon.

At 36:00, the video looks at Chordal Hop modes. As the image below shows, there can be a lot more going on than just simple hop Sporadic-E...

At 41:00, skewed paths are examined.

45:20 Antenna considerations

46:50 Cycle 25 status

Links...

1) I have some examples of unusual long distance paths on the 6m band on my 50 MHz page.