Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org)
Message-ID: <011501c63fe0$c454e500$0300a8c0@LAPTOP>
From: "Peter Martinez" <peter.martinez@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <PAEFLMFGBDKKCONLMLBIKEOMCFAA.ganymede444@btopenworld.com> <01cd01c63d73$69bc4f80$0300a8c0@LAPTOP> <4407287F.8000306@freenet.de> <029801c63e22$bb20b190$0300a8c0@LAPTOP> <003a01c63e33$08290cc0$67b0fea9@lark> <02a101c63e36$cf0e6120$0300a8c0@LAPTOP> <7.0.0.10.2.20060302213743.0383a228@spin-it.com> <02b901c63e4c$38a127c0$0300a8c0@LAPTOP> <030401c63ea8$6a6b90e0$0300a8c0@LAPTOP> <00fa01c63fc0$e082d860$0300a8c0@LAPTOP> <000a01c63fc6$10b045e0$67b0fea9@lark>
Date: Sat, 4 Mar 2006 23:10:02 -0000
MIME-Version: 1.0
Subject: Re: LF: LORAN spurious emission levels
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-1";
	reply-type=original
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

Alan:

Yes, it's true that if the signal is wider than your receiver and is 
coherent (like a pulse), then the SNR will increase if you widen the 
bandwidth, inspite of the fact that the noise increases in proportion to the 
bandwidth. This is because, with a transmission like a pulse, all the 
separate spectral lines add IN VOLTAGE, so the peak voltage increases faster 
than the noise level as you make the receiver wider.  This explains why you 
can hear the galloping horses in a 6kHz wide AM receiver by ear (at least in 
the south of the UK - I can't hear them up here)  but not hear anything by 
ear in a narrow CW filter.  The latest version of my GPS-locked receiving 
idea works in the same way - I can copy these LORAN spurii 25dB better by 
adding-up the voltage of all 300 of them across the SSB passband than I can 
by trying to see a single line in a narrow passband.

But that isn't really what I find surprising about the 42uW figure I have 
just calculated. These LORAN lines, when seen on Argo or similar software, 
are around the same sort of level as the weak TA signals we are exchanging 
these days. We choose to do the TA tests on frequencies which avoid these 
lines, so they must be around the same level if they annoy us to that 
extent.  If 42uW is a typical erp of a LORAN line, are we only transmitting 
signals of that order ourselves? Surely most amateur stations would like to 
think they are transmitting a few hundred mW. Something doesn't make sense. 
I really don't mind if I have made a mistake here!

73
Peter G3PLX