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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>Dave,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>How did you decide which type of traffic to move to the ALT frequency?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>It would seem to me that the primary traffic on 144.39 MHz 1200 baud should indeed be mobile traffic. According to WB4APR’s plan (I think), the thought is that APRS should be an information mode largely for mobiles who should see other mobile traffic but more importantly objects such as the local voice repeater, ham events, etc.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>Also, how would mobiles coming into your area know to make the switch to the ALT frequency/ALT baud rate?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>So if the mobiles are off 144.39 MHz 1200 baud, what stations are left?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>I agree that WX stations and pilot-less home stations would seem to be good candidates for the ALT frequency… not as critical to mobile information exchange.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>You also mention cross-banding back and forth between the channels. Doesn’t this just add the congestion back in?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>Just asking .. I commend you and the group for your active experimentation. I think it’s terrific.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>One question, you signed as “Spokane” Area but say “Puget Sound” in the note. They’re pretty far apart! </span><span style='font-size:11.0pt;font-family:Wingdings;color:#1F497D'>J</span><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>Ralph NM5RM<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'>Santa Fe NM<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:Consolas;color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> aprssig-bounces@tapr.org [mailto:aprssig-bounces@tapr.org] <b>On Behalf Of </b>David Dobbins<br><b>Sent:</b> Tuesday, November 16, 2010 8:29 PM<br><b>To:</b> TAPR APRS Mailing List; nwaprssig@nwaprs.info<br><b>Subject:</b> [aprssig] THOUGHTS ON RELIEVING APRS CONGESTION ON 144.39<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hello fellow APRS enthusiasts. I’m curious to know what the rest of the world is doing to relieve some of the congestion of APRS traffic on the primary freq 144.39? In my wide travels, my experience has been the larger metro areas are suffering from APRS indigestion, meaning if you turn the volume up on 144.39 and listen, it’s uncommon to hear any break in the packets the closer you get to the big cities.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>I’d like to share what we’ve been doing about this oversaturation of the primary freq in the Puget Sound area. For the past couple years we’ve been experimenting with, and done some implementing of APRS at 9600bd on both UHF and VHF. The initial alternative frequency/speed experimentation began on UHF 440.800MHz at 9600bd by Bob King, K7OFT. We have several UHF APRS digipeaters around the Seattle area. The typical digi setup is an Icom IC-207 and Kantronics KPC-9612, using the same configuration settings found on the primary frequency. The biggest group of users are mobiles, typically those with TM-D700/D710 or the Yaesu FTM-350R and similar handhelds. Those tracking on the UHF frequency are gated to the APRS-IS, and those with an internet connection at their home station will see both the VHF primary, and UHF secondary APRS activity. Our VHF 9600bd effort commenced a little later than the UHF interest, but has grown significantly over the past year, with several high level digipeaters serving the alternate VHF frequency 144.35MHz. Scott Cronk, N7FSP has been leading this effort. We eliminated the possibility of interference between the two freqs (144.39 and 144.35) by replacing an existing APRS digipeater VHF radio with a Kenwood TM-D700 or D710, and retaining the existing KPC-3 (or an Argent TNC). The internal radio TNC operates at 9600bd on 144.35, and the other side of the radio is set to 144.39 and uses the external 1200bd TNC. No change to the filter solution has been necessary, or need to add or change antennas, since the two freqs are close together. We’ve had three arguments presented why this solution wouldn’t work, and all three have been dismissed. First, folks said 9600bd won’t work on VHF. It does, and quite well. Second, folks said the two freqs were too close together and would cause interference. Not so, as the D700 becomes “deaf” on one side of the radio when the other side is transmitting, thus no issue. Third, while one side was transmitting, there would be packets not digipeated on the other side. We’ve found this to be not much of an issue, and the increase in packet loss at the digipeater is insignificant. We have a growing number of mobile users throughout Puget Sound using the 144.35 APRS @ 9600bd with very good results. With several iGates, including direct IGating from the mountaintop digipeaters with internet access, everyone trying to get their data to the APRS-IS is getting through. We’re encouraging home and other fixed stations to make the switch to the alternative frequency to further relieve some of the congestion on the primary frequency. It’s too early to tell just how much relief we’ve seen on the primary frequency, and difficult to measure. We've also been experimenting with cross-banding of data, feeding packets and messages back and forth between the VHF 1200bd, VHF 9600bd, and UHF 9600bd channels.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>We’re also encouraging makers of the VHF trackers to add 9600bd capability to their products. For those folks in areas oversaturated by APRS packets, I suggest the next time you make the mountaintop digipeater run to replace the existing VHF radio with a Kenwood TM-D700/D710 and give dual-APRS ops at 1200bd and 9600bd a try.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Dave K7GPS<o:p></o:p></p><p class=MsoNormal>NWAPRS Spokane Area Coordinator<o:p></o:p></p></div></body></html>