MUF maps

Discussion in 'The DX Zone' started by M0YRX, Sep 24, 2019.

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  1. M0YRX

    M0YRX Ham Member QRZ Page

    The MUF map below shows that for a 3000km (1864miles) hop from my location in IO81 the refraction point ,mid point, would be over Southern Spain if beaming South and that the MUF would be 22/23MHz.Howerver the Ionosode at Fairford FF051 which is just under 80km ( sub 50 miles) to the North West of my location ,with the same time stamp, puts the MUF at around 16MHz.
    As I've been comparing the MUF map and the FF051 Ionogram for sometime now and that the closest the readings have come is to 3MHz and have been anything upto 7MHz apart my query is to the accuracy of the MUF map shown or is my interpertation of the two sources incorrect ? FireShot Capture 366 - PROPquest - Graphs - http___www.propquest.co.uk_graphs.php.jpg FireShot Capture 367 - Ionogram_ - https___lgdc.uml.edu_common_ShowIonogramPage.jpg FireShot Capture 365 html#hfprop.jpg
     
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Well the ionosondes don't agree with the map, but an F2 of 3-4Mhz is typical for our recent era. I would suspect the map of being out of date. Your screen shot is cutoff and doesn't show source or date.
     
  3. M0YRX

    M0YRX Ham Member QRZ Page

  4. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Those sites seem up-to-date at the moment and pass the reasonable value test.

    Rather than use middle man sites which can have bad links or out of date displays, I usually go directly to the Australian source:

    http://www.sws.bom.gov.au/HF_Systems/6/5
     
  5. WB3BEL

    WB3BEL Ham Member QRZ Page

    Most Ionosondes measure the reflection directly overhead. They send RF straight up and measure the reflection. This measurement basically represents the state of the ionosphere right above the measurement location. However, this measurement is not like a laser beam and so covers a fairly wide range of angles depending on the details of the station. But it will not usually represent the state of the ionosphere above a surface location much more than a few hundred miles away. There are ionospheric radars that can make lower angle measurements, but these are not basic ionosondes.

    If you beam a signal straight up and measure the foF2, it looks like 4.6 MHz at the time the measurement was made in your location. If the signal arrived at the same region of the ionosphere above your station, at a lower angle, at the same time, it would reflect/refract at a higher frequency. So if it came from about >1500 km away (half of the hop distance), it would still reflect/refract at ~15 MHz from the region of the ionosphere above your station. It would ultimately arrive at around the same angle, 1500 km the other direction from your station.

    To compare with ionospheric measurements of other locations, you would need ionosonde data from those ground locations.

    It looks like the data sets are reasonably consistent. The plot from spaceweather is showing about 15-16 MHz F2 above your grid which represents the reflection/refraction maximum frequency above your location for signals arriving at low angles. This data for ionospheric conditions above your location is really only useful for high angle communications. If you want to know what bands might be open you need to look at the ionospheric conditions at the points between your location and the desired location where ionospheric hops are likely to be taking place. (Thousands of km away)
    These would be measurements from ionosondes in those locations. Or could be a composite map made up of many location's ionosonde measurements.
     
    W5BIB likes this.

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