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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
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Date: Sat, 4 Mar 2006 19:58:20 -0000
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Subject: Re: LF: LORAN spurious emission levels
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Peter, In one way I think you are right. If you were to select one line you
would not be able to hear it. The effect is a little like FM. If you listen
to a WB FM signal with a narrow band receiver you dont hear anything, but as
you widen the bandwidth to accept more sidebands a signal becomes audible
though distorted. The "Galloping Horses" effect is not so noticable in a
narrow CW filter, but is quite loud in an SSB bandwidth. This is probably
why they dont think it is a problem more than 10kHz away from the carrier !!
Subjectively the individual lines on a 30second dot QRSS screen such as ARGO
are around 30dB below the minimum audible CW signal.

Does that make sense ??
Cheers de Alan G3NYK

----- Original Message -----
From: Peter Martinez <peter.martinez@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: 04 March 2006 19:21
Subject: Re: LF: LORAN spurious emission levels


> From G3PLX:
>
> Some small corrections to the calculation of the erp of a LORAN line...
>
> The mean power of a LORAN transmitter is a little lower than I said. If
the
> published peak power is P and the Group Repetition Interval (GRI) is G,
then
> the mean power will be 74.88*P/G for a master station (9 pulses/group) and
> 66.56*P/G for a slave (8 pulses/group). For example the Lessay (G=6731)
> slave transmitters are radiating 2.45 kW mean power.  Thanks to DF6NM for
> helping me to get this part more accurate.
>
> To simplify the calculation derived from the spectrum measurements I
showed
> in my last posting, the mean erp of spectral lines around 136kHz can be
> calculated as 1.155e-4*M/G where M is the mean power calculated as above.
>
> This makes the spurii from the Lessay slaves (eg Rugby) about 42uW.
> (micro-watts).
>
> Because of the way the pulses interact, individual spectral lines may be
up
> to 3dB higher than this, or they may cancel out completely at some
> frequencies - it would be too complicated to figure out exactly what
should
> be the level of each individual spectral line and the above calculation is
> attempting to give an average level only.
>
> I am still not sure I believe that we can really hear signals this low in
> power!
>
> 73
> Peter
>
>