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Radio Propagation Basics
Radio propagation on the Primary Frequency* is usually good out to three thousand miles or more from
the MARS station. Between 3,000 and 6,000 miles, propagation is less reliable but is often acceptable. Nighttime
propagation (US time) on the Primary Frequency* is less reliable than daytime propagation, particularly during or around
the winter months.
MARS stations operating at night monitor both the Primary and Secondary Frequency* in order to compensate
for the possibility of poor nighttime propagation on the Primary Frequency. It should be noted that many nights the
Primary Frequency works just fine.
Attempts to contact MARS should always start with several calls on the Primary Frequency. If there
is no answer on the Primary frequency, the Secondary Frequency should be tried. When not classified, include your location
on the initial call. MARS stations use directional antennas that need to be pointed in your direction for best reception.
*MARS Frequencies are not published on this website as per MARS regulations. Frequencies may be obtained
by email from John McGee, AFN4PP at: afn2ac@juno.com. Please make the subject "MARS FREQUENCY REQUEST".
More Detail
Radio Propagation on the Primary Frequency is able to cover long distances because it is reflected
off the ionosphere and back to the ground. Depending on the distance, it may be reflected back and forth between the
ground and ionosphere several times. This type of radio propagation is commonly referred to as "skip". Skip propagation results
in an area of poor reception when you are between 200-500 miles from the MARS station because the radio waves have gone overhead,
and are reflected back towards earth hundreds of miles further out. The MARS Phone Patch Net compensates for the areas
of poor propagation by having several stations in different locations around the US in operation at the same time. If
you are very close (<200 miles) to the MARS station and at cruising altitude, your signal will travel via "line of sight".
The Primary Frequency is the best overall frequency for long distance communication. During the winter months,
the ionosphere tends to be less reflective at night, and this results in the radio waves continuing straight off into space.
During these nighttime periods, the net monitors the Secondary Frequency as well as the Primary Frequency.
Radio Propagation on the Secondary Frequency tends to follow the curvature of the earth via "ground
wave". During daylight hours, this frequency is reliable to 1000 miles or so. At night, the range improves to
3000 miles or more. You will notice the same effect when listing to AM Broadcast radio. At night, you are able
to hear AM Radio stations from around the country, while during the day only stations in nearby cities can be heard.
While the USAF Phone Patch net has two frequencies that it monitors, it also has eight other frequencies
that are available for use when propagation favors a different frequency, or traffic levels require.
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