[Lowfer] The case for DSB or antennae diversity on 500Khz :-)

[Howell, Laurence (Shanghai/Singapore)]

I suppose Ive been around 500kHz for most of my working life but it
wasn't till the advent of SDR/Panoramic that the true nature of the
beast has become apparent to me. They really do show graphically for the
eyes pleasure what the hecks going on.

As an example Ive been doing commercial calibration of NDB's
onshore/offshore here in the Bohai Bay area for a while (OM89) and most
of the targets are just within ground/sea wave range at around 80-100NM
- the far limit of what can be classed as usable in my environment here
dependant on night/day

At night, at this range, we get a mix of both sky and ground with signal
levels of say around -60dBm - watching the beacons, which in my case are
DSB (per se)  with a 400Hz modulating tone its intriguing to look at the
amplitude of the carrier and the sidebands and how you can see one
modulating sideband completely being phased out (>50dBc) whist the other
or carrier remains whole. The Periodicity varies as the dynamics of the
iono change - 

So if I had been looking for that sideband modulated signal at that
instance on a single band radio there was more chance at this range that
I may have missed it......

Laurence
http://kl1x.com



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