|
I have been using space diversity reception for a
while on 137 khz and it is interesting to watch the signals that appear on
screen using QRS.
The system consists of a 90 metre loop antenna,
resonated on 137 khz and fed to RX type Hagenuk Blu EE 430, which is very
sensitive on LF and does not need a RF Preamp, the audio from the RX goes to a
DSP filter and from there to the computer audio card and the signal displayed
using ARGO s/ware.
The other antenna is my vertical system consisting
of 4 x inv L antennas each one at present around 100 ft vertical and 400 ft
horizontal all converging at the bottom of the vertical drop to the loading coil
about 0.5 mh inductance, where the antenna is resonated and matched to 50 ohms,
then fed to the shack via coax to the RX which is an IC706 at present ( I have
other receivers that I use at times) the audio from this also goes to a DSP
filter and the output to the computer as above.
The audio to the computer is optimized at 650 hz in
both receivers but one RX BFO is set on the high side and the
other on the low side, this way each signal can be observed for QSB and any
other changes. The BFO outputs are variable and can be arranged in a
variety of ways, eg both signals exactly on the same
frequency.
The loop is positioned for optimum signals
E/W where most of the activity takes place across EU and to the
USA/Canada.
If necessary I could install a similar loop N/S if
there was an abundance of activity from Africa to the South and Japan to the
North. I have had enquiries from Japan about LF qso possibilities, having worked
scores of JA stns on 160 Metres.
73 de Mal/G3KEV/IO94SH
.
.
| 