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Date: Wed, 12 Apr 2006 10:27:50 -0400
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From: markusvester@aol.com
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To: rsgb_lf_group@blacksheep.org
Subject: LF: Wishing LORAN away?
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Dear Stewart and Peter, LF Group,
 
in view of LORAN-C as a complementary backup to satellite based navigation, I do not think that European interest will die away completely with the advent of Galileo, which would have the same potential failure modes as GPS (such as susceptibility to low power jamming). For timing applications, narrowband LF systems suffer from variable skywave components, which limit carrier-frequency measurements to about 1e-8 at night across a couple of 100 kms. These can be suppressed to a large extent by sampling the phase early in a Loran pulse, improving precision by at least one order of magnitude.
 
Personally, I found in LORAN a fascinating means of monitoring global LF propagation, with the ability to resolve multiple skywave propagation modes in time domain, analyse their phase evolution, or see solar disturbances (and perhaps even strong gamma ray bursters) in real time. For example, a recent ten-day observation of 58 Loran stations is on http://people.freenet.de/df6nm/LoranView/LoranView_Mar2006.htm .
 
So I would not really wish for LORAN to disappear altogether, but rather try to work towards convincing the operators that it's out-of-band emissions definitely have to be cleaned up. Technically, a transmitter filter with a passband from 90-110 kHz should be quite feasible, and finally result in an enhanced Loran system which could be called compatible to other LF users like us.
 
73 and kind regards
 
Markus, DF6NM
 
_________________________________________________
>>
From: Stewart Bryant 
To: rsgb_lf_group@blacksheep.org 
Subject:  Re: LF: Rugby LORAN measurement? 
Date:  Mon, 10 Apr 2006 13:19:02 +0100 
 ....
> I understand the Rugby site must close in a year or so and they are > looking for an alternative site for the 60kHz MSF transmitter. The > question becomes whether the LORAN transmitter will also move to that > new site or whether it will close down. The long term future of LORAN > has always seemed shakey but it doesn't look as if it will be > killed-off until there is a European second-source for satellite-based > position-finding, and that seems some years away yet. 
> 
I am not sure what is going on in Navigation circles, but in timing circles LORAN 
is being sold in the US (by the LORAN providers) as an alternative source of 
time reference/frequency reference. 
 
Contra to the US position, European service providers do not want to rely 
off-air frequency service for reference - they are very vocal on this. The 
telecomms industry is therefore persuing: synchronous ethernet, IEEE-1588, 
timing over packet and possibly NTPv5 to address this and the signs are 
that we can get to the required 10ppb using packet network technology. 
 
One can but hope that the absence of interest in LORAN by the 
telecommunications industry in Europe will limit the economic viability 
of LORAN over here and assist its early demise. 
 
73 
 
Stewart G3YSX 
<< 

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<HTML><BODY><DIV style='font-family: "Verdana"; font-size: 10pt;'><DIV>Dear Stewart and Peter,&nbsp;LF Group,</DIV>
<DIV>&nbsp;</DIV>
<DIV>in view of&nbsp;LORAN-C&nbsp;as a complementary backup to satellite based navigation, I do not think that European interest will&nbsp;die away completely with the advent of Galileo, which would have the same potential failure modes as GPS (such as susceptibility to low power jamming). For timing applications, narrowband LF systems suffer from&nbsp;variable skywave components, which limit carrier-frequency measurements to about 1e-8 at night&nbsp;across a couple of 100 kms. These can be suppressed to a large extent&nbsp;by sampling&nbsp;the phase early in a Loran pulse,&nbsp;improving precision by&nbsp;at least one&nbsp;order of magnitude.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Personally, I&nbsp;found in LORAN&nbsp;a fascinating&nbsp;means of monitoring global LF propagation, with&nbsp;the ability&nbsp;to resolve&nbsp;multiple skywave propagation modes in time domain,&nbsp;analyse their phase evolution,&nbsp;or see&nbsp;solar disturbances (and perhaps even strong gamma ray bursters) in real time. For example, a&nbsp;recent&nbsp;ten-day observation of 58 Loran stations is on <A href="http://people.freenet.de/df6nm/LoranView/LoranView_Mar2006.htm">http://people.freenet.de/df6nm/LoranView/LoranView_Mar2006.htm</A>&nbsp;.</DIV>
<DIV>&nbsp;</DIV>
<DIV>So I would&nbsp;not really wish for LORAN to disappear altogether, but rather try to work towards convincing the operators that it's out-of-band emissions definitely have to be&nbsp;cleaned up.&nbsp;Technically, a transmitter filter with a passband from 90-110 kHz should be quite feasible, and finally result in an enhanced Loran system which could be called compatible to other LF users like us.</DIV>
<DIV>&nbsp;</DIV>
<DIV>73 and kind regards</DIV>
<DIV>&nbsp;</DIV>
<DIV>Markus, DF6NM</DIV>
<DIV>&nbsp;</DIV>
<DIV>_________________________________________________</DIV>
<DIV>
<DIV>&gt;&gt;</DIV></DIV>
<DIV>From: Stewart Bryant <BR>To:&nbsp;<A href="mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org</A> <BR>Subject:&nbsp; Re: LF: Rugby LORAN measurement? <BR>Date:&nbsp; Mon, 10 Apr 2006 13:19:02 +0100&nbsp;<BR>&nbsp;....<BR>&gt; I understand the Rugby site must close in a year or so and they are &gt; looking for an alternative site for the 60kHz MSF transmitter. The &gt; question becomes whether the LORAN transmitter will also move to that &gt; new site or whether it will close down. The long term future of LORAN &gt; has always seemed shakey but it doesn't look as if it will be &gt; killed-off until there is a European second-source for satellite-based &gt; position-finding, and that seems some years away yet.&nbsp;<BR>&gt;&nbsp;<BR>I am not sure what is going on in Navigation circles, but in timing circles LORAN&nbsp;<BR>is being sold in the US (by the LORAN providers) as an alternative source of&nbsp;<BR>time reference/frequency reference.&nbsp;<BR>&nbsp;<BR>Contra to the US position, European service providers do not want to rely&nbsp;<BR>off-air frequency service for reference - they are very vocal on this. The&nbsp;<BR>telecomms industry is therefore persuing: synchronous ethernet, IEEE-1588,&nbsp;<BR>timing over packet and possibly NTPv5 to address this and the signs are&nbsp;<BR>that we can get to the required 10ppb using packet network technology.&nbsp;<BR>&nbsp;<BR>One can but hope that the absence of interest in LORAN by the&nbsp;<BR>telecommunications industry in Europe will limit the economic viability&nbsp;<BR>of LORAN over here and assist its early demise.&nbsp;<BR>&nbsp;<BR>73&nbsp;<BR>&nbsp;<BR>Stewart G3YSX&nbsp;<BR>&lt;&lt;&nbsp;<BR></DIV><!-- end of AOLMsgPart_0_8d8c150c-de16-4113-a952-3cc9ff3cd60c --></DIV></BODY></HTML>

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