WA5MLF: Graphs of Maximum Usable Frequency from Ionosonde Data

In support of a forthcoming article on 40 m propagation during the daily East Coast RV Service Net, data has been collected for two ionosonde sites: one at Eglin AFB in Florida and one at Wallops Island in Virginia. The locations of ionosondes around the world can be seen at this web page.

Thanks to Dan KC4GO for collecting data on

critical frequency (foF2)
MD = MUF(3000) / foF2
Maximum Usable Frequency (MUF)

from both sites, spanning 16 months. Data are available in plain text format from the Digital Ionogram Data Base.

The Eglin ionosonde provided 96 data sets for each day, and the Wallops Island ionosonde provided even more. Data were collected for propagation distances of 300 and 500 miles, which were chosen to represent some common distances among regular RV Net participants. The longest distance among regular participants appears to be about 1200 miles. A review of past ionogram data shows that the MUF at 900 miles or beyond is typically about 7 MHz at the start of the 2-hour net. Shorter distances are likely to have poor to marginal propagation that improves gradually during the Net time frame.

Eglin Graphs

Below are some graphs developed from the Eglin ionosonde data. Click on any graph for a full size view.

The above graph shows the variation of MUF(300) [MUF at 300 miles] over the past 5 months, using data from 1200 UTC each day.

The above graph shows the MUF(300) at 1300 UTC on each of the dates.

The above graph shows the MUF(500) at 1200 UTC on each of the dates.

The above graph shows the MUF(500) at 1300 UTC on each of the dates.

The above graph presents the variation of MUF(500) values during the 2-hour time frame of the RV Service Net. The data points are taken from the same calendar period as the previous four graphs: 9/1/2019 thru 1/15/2019. The bottom curve shows the minimum value of MUF(500) for each time-of-day point among the 137 days. The middle curve shows the average or mean value (across the 137 days) of MUF(500) for each time-of-day point. The top curve shows the maximum value of MUF(500) for each time-of-day point among the 137 days.

I plan to produce the same type of graph for MUF(300) [MUF at 300 miles].

Wallops Island Graphs