[HCARC] Total Electron Count (TEC) of The Ionosphere
Kerry Sandstrom
kerryk5ks at hughes.net
Fri Aug 26 20:55:13 EDT 2016
Gary,
Yes, very interesting. The TEC delays electromagnetic waves depending
on frequency. The ionosphere made up of charged particles is a plasma
and this frequency dispersion is characteristic of a plasma. One of the
big differences between civil GPS and Military GPS was the military used
2 frequencies which allowed the calculation of TEC and then the removal
of the excess delay due to TEC from the position measurements. It looks
like this data is based on the GPS measurements.
Another effect of the TEC is its distribution - its not a constant value
from ground to space. It has small irregular volumes of higher electron
density. Certain areas of the ionosphere have a lot of small volumes
which disrupt the signal. Instead of a clean signal the patches break
up the wave front and different parts of the wave arrive at the receiver
at different times. This is a bad multipath problem and limits the
total bandwidth that can be used. It also causes some slow deep fading,
sometimes several seconds between peaks. High rate digital signals, 1
Mb/s and up require extensive error correction coding and large amounts
of memory to continue operating. On 6 meter TE scatter paths we see
this multipath problem. Often it is difficult to use SSB because the
bandwidth of the propagation path is so low only CW is really useful.
Kerry
On 8/26/2016 10:38 AM, Gary Johnson wrote:
> NOAA released an interesting bulletin regarding a new site for watching Total Electron Content (TEC) of the ionosphere. TEC is the total number of electrons present along a path between a radio transmitter and a receiver. The Space Weather Prediction Center (SWPC) has deployed an updated and expanded version of its US Total Electron Content (US-TEC) model.
>
> Interesting.
>
> Gary J
> N5BAA
> ______________________________________________________________
> HCARC mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hcarc
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HCARC at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
More information about the HCARC
mailing list