[Lowfer] Re: Hifer reception this week

[Ed Phillips]

Johan Bodin wrote:
> 
> Jim, Lowfers,
> 
> Jim Moritz wrote:
> > The waterfall traces are often blurred, and at one point last
> > night, the signal from GA split into 2 distinct traces running parallel a
> > couple of Hz apart.
> 
> That is interesting. I guess it must be a combination of multipath and
> doppler shift. The trace separation tells the rate of change of the
> difference between the distances of the two paths
> 
> One Hz of doppler shift on a 13.555 MHz signal corresponds to a
> speed of about 22 m/s.  Those "heavenly mirrors" seem to be moving
> fast...
> 
> I have been looking at the carriers from various HF broadcast stations
> and they are more or less blurred. Quite interesting, the "line width" varies
> from one day to another. One station may be less than 1 Hz wide one day
> and as much as 20 Hz wide at the same time the other day. The reflecting
> properties of the ionosphere seem to vary from calm to extremely shaky.
> 
> > SM6LKM's 14.1011MHz beacon has been harder to copy here - it is usually
> > visible in the mornings, but generally much weaker than the trans-atlantic
> > signals. Perhaps this is due to our antennas not being favourably aligned,
> > or just that propagation at 14MHz works better over several 1000s of km
> > than it does at 1000km
> 
> I think it has something to do with propagation.
> My dipole wire runs N-S and should have its max lobes E-W. However, at a
> height of 9m it is quite omnidirectional although the radiation pattern varies
> somewhat with elevation angle.
> 
> 73
> Johan Bodin, SM6LKM
> 
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	The instability in the transmission path can be demonstrated very
easily by beating a precision local RF source with incoming signals such
as WWV.  If you form a lissajou pattern on a scope you can see the phase
twisting and turning, often at quite a rapid rate and the use of VLF
standard frequency stations like WWVB is intended to minize that effect.

Ed

Ed