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The standard distance for calculating a MUF for a particular path is 4000
km/2485 miles but the digisondes use 3000 km/1864 miles
http://digisonde.haystack.edu/cgi-bin/latest.exe? . The frequency of optimum
traffic (FOT) is approximately 20% below the MUF. The FOT was basically
invented for use by international shortwave broadcasters during the cold war
era and is still in use today.
I personally use the MUF while keeping in mind that minute to minute changes in
ionization via the F1/F2 layer can either refract my signal back to Earth or
let it go out into space.
BTW a nice little piece of software that calculates MUF on a world map is
HFProp v1.3 at http://www.tech-pro.net/g4ilo .
73 & Happy Holidays,
Thomas F. Giella, KN4LF
Lakeland, FL, USA
Grid Square EL97AW
27 57 26.5 N 81 56 46.6 W
kn4lf@arrl.net
PODXS 070 PSK Club #349
Proof Of God Through Science:
http://www.cosmicfingerprints.com/audio/newevidence.htm
KN4LF Amateur & SWL Radio History: http://www.kn4lf.com/index.htm
KN4LF MF Radio Propagation Theory Notes: http://www.kn4lf.com/kn4lf8.htm
----- Original Message -----
From: David Robbins K1TTT
To: propagation@contesting.com
Sent: Monday, November 28, 2005 6:29 AM
Subject: Re: [Propagation] Basic Propgation Question
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Muf maps have to assume a path. I think a common method is to assume a
2000km (or some other fixed distance) centered at the point to be mapped.
This is reasonable for single hop paths going through that point... so yes,
this results in a map that closely resembles the f2 layer characteristics.
another method that my program uses is to fix one end(your qth) and move the
other end around the world and calculate the muf (or mof in my case) for
however many hops the path may result in.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: propagation-bounces@contesting.com [mailto:propagation-
> bounces@contesting.com] On Behalf Of ROBERT CARROLL
> Sent: Monday, November 28, 2005 04:28
> To: propagation@contesting.com
> Subject: [Propagation] Basic Propgation Question
>
> This e-mail posting is from the Radio Propagation Reflector that you're
> currently subscribed to. Refer to the end of this e-mail for directions
> on how to change your subscription options, or to unsubscribe.
> _______________________-start-_________________
>
> Though I had never thought much about it, it seems to me there are two
> views
> of MUF:
>
>
>
> 1) MUF is a prediction of the maximum frequency that can be used at
> a
> given time to communicate between a transmitting site and a desired
> receiving site (lots of wrinkles about 50% statistics, using a month's
> worth
> of data, the need to be maybe 20% below the prediction in the real world
> etc). This says MUF is a two point number, and at a given transmitting
> site
> at a given time will vary with the azimuth of and the distance to the
> desired receiving site. There are many MUF numbers for the transmitting
> site
> because there are many receiving locations on the earth. This is the
> ITU/IEEE definition.
>
>
>
> 2) MUF is a quantity dependent only on the spot on the earth for
> which
> the number is to be computed, i.e. it is similar to a map of critical
> frequency. For the case of a critical frequency map, conceptually you
> pick
> a point on the map, put a sounding device at that point, shoot straight
> up,
> look at the data, and determine the critical frequency and mark that
> number
> on the map at that point (in reality you may use models and a small number
> of actual measurements). Do the equivalent for F2 layer height. At a
> given
> time there is only one critical frequency contour map for the earth, and
> only one f2 layer height map. But as far as I can tell the MUF maps
> generated by many of the propagation programs are independent of the site
> assumed for the transmitter, just as are (and should be) the layer height
> maps.
>
>
>
> Can someone clarify this for me, or point me to a source which is clear on
> this point?
>
>
>
> Bob W2WG
>
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>
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