Message-ID: <001701c4c0fa$9429c960$48657ad5@derekm3uttnxf9>
From: "Derek Atter" <datter@btinternet.com>
To: rsgb_lf_group@blacksheep.org
References: <E1COlI9-0000WZ-3f@post.thorcom.com> <4186F5A2.9080706@zen.co.uk>
Date: Tue, 2 Nov 2004 16:39:10 -0000
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Subject: Re: LF: Rugby Loran station
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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


----- Original Message ----- 
From: "Stewart Bryant" <zen27607@zen.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, November 02, 2004 2:49 AM
Subject: Re: LF: Rugby Loran station


>
>
> Stewart G3YSX wrote:
>
>
> How diffiicult would it be to make a Loran gate to put in front of theRX?
> After all the station is fixed so you must, in principle, know when the
> pulses are due.
>
> Stewart G3YSX
>
>
>