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I am afraid preemphasis and deemphasis are beyond my present knowledge :-)<div><br></div><div>David</div><div><br></div><div><br><div><div>On 19 Feb 2010, at 08:38, Richard Hoskin wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PlaceType"> <o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PlaceName"> <o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"> <o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"> <o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> <o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PersonName"> <!--[if !mso]> <style> st1\:*{behavior:url(#default#ieooui) } </style> <![endif]--> <style> <!-- /* Font Definitions */ @font-face {font-family:Tahoma; panose-1:2 11 6 4 3 5 4 4 2 4;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0cm; margin-bottom:.0001pt; font-size:12.0pt; font-family:"Times New Roman"; color:black;} a:link, span.MsoHyperlink {color:blue; text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {color:blue; text-decoration:underline;} pre {margin:0cm; margin-bottom:.0001pt; font-size:10.0pt; font-family:"Courier New"; color:black;} span.EmailStyle19 {mso-style-type:personal-reply; font-family:Arial; color:navy;} @page Section1 {size:595.3pt 841.9pt; margin:72.0pt 90.0pt 72.0pt 90.0pt;} div.Section1 {page:Section1;} --> </style> <!--[if gte mso 9]><xml> <o:shapedefaults v:ext="edit" spidmax="1026" /> </xml><![endif]--><!--[if gte mso 9]><xml> <o:shapelayout v:ext="edit"> <o:idmap v:ext="edit" data="1" /> </o:shapelayout></xml><![endif]--> <div class="Section1"><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Ray / All,<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Several years I did some extensive testing on the effects of deemphasis on received AX25 signals at APRS digipeaters.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">I found that the digipeaters reception and decoding of data worked best (1 to 2 db better) when the deemphasis was bypassed. This was the case for both preephasised and non-preephasised transmitted signals. This is partly explained by the fact that most TNC (especially the MFJs) require the high tone of the received audio to be louder than the low tone for correct decoding. Especially for weak signals.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">I also looked at the output of the Kenwood D7 & D700 and found that they only used a 3db per octave preephasised / deemphasis on the data TX / RX.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">All VK3 digipeaters have been modified to bypass the preephasised / deemphasis to obtain the better receive performance. The other advantage of this is that we bypassed the audio volume control and squelch circuitry which makes the digi on the hill less prone to accidentally adjustments.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Cheers<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Richard<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">VK3JFK<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p> <div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt"> <div> <div class="MsoNormal" align="center" style="text-align:center"><font size="3" color="black" face="Times New Roman"><span lang="EN-US" style="font-size:12.0pt; color:windowtext"> <hr size="2" width="100%" align="center" tabindex="-1"> </span></font></div><p class="MsoNormal"><b><font size="2" color="black" face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma;color:windowtext;font-weight:bold">From:</span></font></b><font size="2" color="black" face="Tahoma"><span lang="EN-US" style="font-size:10.0pt; font-family:Tahoma;color:windowtext"> ozaprs-bounces@aprs.net.au [<a href="mailto:ozaprs-bounces@aprs.net.au">mailto:ozaprs-bounces@aprs.net.au</a>] <b><span style="font-weight:bold">On Behalf Of </span></b>Ray Wells<br> <b><span style="font-weight:bold">Sent:</span></b> Thursday, 18 February 2010 1:15 PM<br> <b><span style="font-weight:bold">To:</span></b> <st1:personname w:st="on">Australian APRS Users</st1:personname><br> <b><span style="font-weight:bold">Subject:</span></b> Re: [OZAPRS] Setting up TT4 Tx on 2m</span></font><font color="black"><span lang="EN-US" style="color:windowtext"><o:p></o:p></span></font></p> </div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">David/All,<br> <br> I'm not suggesting your problem is tone level related but failure to grasp the following is arguably responsible for more TNC decode issues than any other cause.<br> <br> The need for "twist" adjustment depends on the radio hardware involved so a brief discussion is probably in order.<br> <br> The "norm" for an FM/PM radio is to apply 6dB (x2) per octave of preemphasis in the transmitter. For packet, this results in the high tone (2200Hz) having twice (near enough) the deviation as the low tone (1200). In the receiver deemphasis is applied which restores the audio to a "flat" condition, i.e. both tones going to the TNC have the same level.<br> <br> If TNC audio is fed into the microphone socket you can depend on 6dB per octave preemphasis. However, if the TNC audio is fed in further down the tx audio chain, such as the audio injection point for tone signalling, preemphasis will not be applied in the tx and should be applied externally - with twist, in the case of the TT4.<br> <br> Going to the receiver again, if it receives a signal without preemphasis, it will still apply deemphasis (assuming audio is taken after deemphasis), resulting in the high tone being just half the level of the low tone when fed to the TNC. FSK demodulators based on the the exar pair 2206/2211 will not decode if the high tone is lower in amplitude than the low tone, by even a very small amount.<br> <br> If rx audio is taken from the demodulator in the radio, i.e. before deemphasis, the preceding is not a problem because audio that is transmitted "flat" will be decoded "flat".<br> <br> The exar chip set (found in genuine TNC2 TNC's) is not disturbed by high tone being considerably higher in amplitude than the low tone.<br> <br> In summary, every tx should employ preemphasis, regardless of it being generated internally, or externally. That will eliminate any decode problems in TNC's with finicky chip sets because high tone will always be the same level as, or higher than, the low tone coming out of the rx.<br> <br> David, is TXD 60 60mS or 600mS? Although TXD provides time for your tx to stabilise before valid data is sent, it can also have an impact on the remote rx in cases where muted audio is being used for the TNC. There are some very sluggish receivers kicking about and TXD needs to be long enough for that rx to unmute. My Icon handheld scanner is pathetic in this regard, with the mute being so slow that I can miss at least half of the digi beacon, even when I'm at the digi site.<br> <br> Get that CRO working and save your hair, lest you should end up like me <span class="moz-smiley-s1">:-) </span><br> <br> Ray vk2tv<br> <br> <br> <br> David and Justine Olsen wrote: <o:p></o:p></span></font></p><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">I am presently running TxD of 60 and TXTWIST of 50. I've tried a range of TXTWIST but none sound too different <o:p></o:p></span></font></p> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">David<o:p></o:p></span></font></p> </div> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><o:p> </o:p></span></font></p> <div> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">On 18 Feb 2010, at 00:36, Scott Evans wrote:<o:p></o:p></span></font></p> </div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><br> <br> <o:p></o:p></span></font></p><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><br> ABAUD is just the speed set for serial port 1 ... what TXDELAY are you running? because depending on how quick you radio is you may need to lengthen the delay a little, also check the TXTWIST setting too, this controls the level between the 1200Hz & 2200Hz tones.<br> <br> On Wed, 2010-02-17 at 21:51 +1000, David and Justine Olsen wrote: <o:p></o:p></span></font></p> <pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">ABAUD is set to 19200<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">On 17 Feb 2010, at 21:37, Norm, VK3XCI wrote:<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> Sort of like 9600 baud?<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> 73 de Norm, VK3XCI<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> <st1:place w:st="on"><st1:city w:st="on">Mildura</st1:city>, <st1:country-region w:st="on">Australia</st1:country-region></st1:place><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> The <st1:place w:st="on"><st1:placename w:st="on">Wintersun</st1:placename> <st1:placetype w:st="on">City</st1:placetype></st1:place><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> QF15bt.<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> David and Justine Olsen wrote:<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> I've gone through all of the TT4 audio adjustments as explained in<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> the help docs by listening on another set, but still no success being<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> received by any digis.<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> One thing that has me curious, is the the squak from my Tx sounds<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> nothing like those from others. The others are a deehdaaah kind of<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> sound with two distinctly different tones ate the beginning and end<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> tone, whereas mine is a sqaaaark :-) of mixed tones at the same time.<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> David<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> VK4MDX<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> _______________________________________________<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> OZAPRS mailing list<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> <a href="mailto:OZAPRS@aprs.net.au" moz-do-not-send="true">OZAPRS@aprs.net.au</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> <a href="http://lists.aprs.net.au/mailman/listinfo/ozaprs" moz-do-not-send="true">http://lists.aprs.net.au/mailman/listinfo/ozaprs</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> --------------------------------------------------------------------- <o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> ---<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> No virus found in this incoming message.<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> Checked by AVG - <a href="http://www.avg.com" moz-do-not-send="true">www.avg.com</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> Version: 9.0.733 / Virus Database: 271.1.1/2692 - Release Date: <o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>> 02/17/10 06:35:00<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">>><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> _______________________________________________<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> OZAPRS mailing list<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> <a href="mailto:OZAPRS@aprs.net.au" moz-do-not-send="true">OZAPRS@aprs.net.au</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">> <a href="http://lists.aprs.net.au/mailman/listinfo/ozaprs" moz-do-not-send="true">http://lists.aprs.net.au/mailman/listinfo/ozaprs</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">_______________________________________________<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">OZAPRS mailing list<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><a href="mailto:OZAPRS@aprs.net.au" moz-do-not-send="true">OZAPRS@aprs.net.au</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><a href="http://lists.aprs.net.au/mailman/listinfo/ozaprs" moz-do-not-send="true">http://lists.aprs.net.au/mailman/listinfo/ozaprs</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"> <o:p></o:p></span></font></pre><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><o:p> </o:p></span></font></p> <table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="100%" style="width:100.0%"> <tbody><tr> <td style="padding:0cm 0cm 0cm 0cm"><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">-- <br> Scott Evans <<a href="mailto:scott@vk7hse.hobby-site.org" moz-do-not-send="true">scott@vk7hse.hobby-site.org</a>> <o:p></o:p></span></font></p> </td> </tr> </tbody></table><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><br> -- This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. If you are not the intended recipient you are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited. <o:p></o:p></span></font></p> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">_______________________________________________<o:p></o:p></span></font></p> </div> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt">OZAPRS mailing list<o:p></o:p></span></font></p> </div> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><a href="mailto:OZAPRS@aprs.net.au" moz-do-not-send="true">OZAPRS@aprs.net.au</a><o:p></o:p></span></font></p> </div> <div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><a href="http://lists.aprs.net.au/mailman/listinfo/ozaprs" moz-do-not-send="true">http://lists.aprs.net.au/mailman/listinfo/ozaprs</a><o:p></o:p></span></font></p> </div> </div><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><o:p> </o:p></span></font></p> </div> <pre wrap=""><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><o:p> </o:p></span></font></pre><pre style="text-align:center"><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">
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</span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><o:p> </o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">_______________________________________________<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt">OZAPRS mailing list<o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><a href="mailto:OZAPRS@aprs.net.au">OZAPRS@aprs.net.au</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"><a href="http://lists.aprs.net.au/mailman/listinfo/ozaprs">http://lists.aprs.net.au/mailman/listinfo/ozaprs</a><o:p></o:p></span></font></pre><pre><font size="2" color="black" face="Courier New"><span style="font-size:10.0pt"> <o:p></o:p></span></font></pre><p class="MsoNormal"><font size="3" color="black" face="Times New Roman"><span style="font-size:12.0pt"><o:p> </o:p></span></font></p> </div> </div> </o:smarttagtype></o:smarttagtype></o:smarttagtype></o:smarttagtype></o:smarttagtype></o:smarttagtype><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">_______________________________________________</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">OZAPRS mailing list</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="mailto:OZAPRS@aprs.net.au">OZAPRS@aprs.net.au</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a href="http://lists.aprs.net.au/mailman/listinfo/ozaprs">http://lists.aprs.net.au/mailman/listinfo/ozaprs</a></div> </blockquote></div><br></div></body></html>