Current Ionospheric Status
G3CWI Station Details
Location (GPS antenna) N53:15:47.963 W2:08:48.426 (+159.68m MSL). This is a long-term GPS averaged position. All of the antennas that I use will be within 30m of this location.
Receiver - IC-737 (measured delay 1.82ms)
Receive antenna - 100ft doublet at 10m agl.
Chirp Plots - How Do I Do this?
Chirp plots are one of many original ideas from Peter Martinez, G3PLX
The following plots were made using ChirpView by Andrew Senior.
Latest Chirp Plot Results from G3CWI
Previous Results - Click on dates to view
For Doppler experiments I recommend the use of Spectrum Lab by Wolf, DL4YHF. Awesome!
Multiple Paths - Random Ramblings
Some thoughts on multiple paths. Several of these Chirp plots show multiple paths, with Inskip arriving by one, two, three or more hops. These have some interesting characteristics and perhaps have something to tell us. At the beginning of a period of multiple path propagation the starts of the paths slopes forward in time and at the end of the period they slope backwards. This is illustrated on the plot below but is a common characteristic of all the plots that I have done so far.
If we think about these multiple paths is it clear that the lowest return is the single hop path and the next one is two hops and so on. The lowest path enters the ionosphere at the lowest angle if incidence and thus has more chance to be refracted, thus it need the lowest amount of ionisation. As the hop numbers increase so the angle of incidence rises until the incidence is nearly vertical. Great theory which seems to make sense if the ionisation increases and then falls with time - but wrong. Because what we are seeing in the plot above the the recombination of the E layer allowing the waves to penetrate through to the F layer. Therefore following the same logic that I explained above, one might reasonable expect the multihop paths to appear first. thus my logic would be that the slope should be in the opposite direction...
Another thing to think about it what might be learned from the signal levels of the respective paths. The one hop path has a single refraction. The two hop path has two refractions and one reflection and a longer path length. Thus a table can be constructed:
ChirpView allows the measurement of signal levels so it is possible to attach rough signal levels to the various hop numbers. Thus it may be possible using simultaneous equations to draw conclusions about the reflection and refraction losses.
It is tempting to think of multipath effects as a problem - especially for data modes. In fact the really sophisticated data modes use multipath effects to improve their performance. This is one of the tricks that will be used by the third generation mobile networks.