Stewart,
Re : Loran Blankers :
It is not too difficult to build a blanker for Loran. I made one in the
early days of the 136khz band to try it in comparison with antenna nulling
techniques and it did work quite well. It used a diode gate in the RF
signal
input fed by an adjustable width monostable fed in turn by a delay equal
to
the Loran pulse interval triggered via an adjustable signal threshold. The
diode gate was in effect operated by the previous pulse burst to overcome
the problem of circuit delays and rise-time effects. From what I remember,
I
found it just as effective to blank the whole of the pulse burst rather
than
try to blank individual Loran pulses. The technique was similar to that
used
on HF to combat the old Russian "Woodpecker" over-the -horizon radar. The
diode gate reduced the Loran pulses only down to the average background
band
noise level rather than right down the to receiver noise floor so as to
minimise modulation of ordinary band noise. In the end. I actually went
for
antenna nulling as being more flexible in also being potentially able to
null other sources of QRM.such as CFH etc. when it was on.
73, Derek Atter
