HF.TXT HF APRS BOAT AND RV TRACKING NET 13 July 2012 Author(s): Bob Bruninga, WB4APR ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Updated 13 july to clarify that it is only GENERIC digiepating that is bad. Selective digipeating by choosing the strongest station heard LIVE and digipeating by callsign has always been OK. Updated 11 Jul 2012 because GENERIC DIGIPEATING on HF is just as bad now as it was in 1992 when APRS first began! In fact, it is even worse, since today we have IGATES listening everywhere acting like the worlds largest Diversity Reception Receiver. Some IGate somewhere will hear each packet, and it only takes ONE to get in. THEREFORE not only does it make no sense to use GENERIC digipeating, it also makes no sense to be burdening EVERY packet with the old GATE,WIDE1-1 adding 14 bytes to every packet just in case it hit a dual-port Kantronics HF-to-VHF TNC. Since packet length on HF is the number 1 packet killer, it only makes sense to drop all path bytes and strive for the shortest packets for reliability. Previous version of this file was Jan 2000 with some tweaks in 2004 Since 1992, we have been operating the National APRS HF tracking frequency on 10.151 LSB (using 16/1800 Hz tones) providing reliable APRS coverage between 100 to about 1500 miles during daylight hours. We chose that channel because we had been using it since 1983 for my original VIC-20 and Commodore dual-port VHF/HF BBS system which had for a decade had hundreds of nodes all over the world. But as BBS's faded, we switched over to APRS. The purpose of the channel is for tracking boats, RV's and portable stations cross country. Notice that the MARK frequency is your actual RF energy transmitted so your DIAL frequency will depend on the exact tones of your TNC. HF FREQS: MARK MFJ/KAMS AEA'S Mode NORMAL USAGE 10.149.2 10.151 10.1515 LSB National HF tracking freq 7.083.2 7.085 7.0855 LSB Regional HF tracking nets 14.098.2 14.100 14.1005 LSB Recommended DX tracking freq 14.103.2 14.105 14.1055 LSB Packet Keyboarding freq 28.187 1200 baud LSB FEED Channels every 2 KHz *Note, these were the recommendations back 8 years ago, other than the original 10.149.2, they may not be the current ones (2004). The 7 MHz frequency has a lot of QRM, but is good for shorter range APRS mobile during the day. Both the 10 and 14 MHz frequencies were very carefully chosen to minimize interference to all present users of the band and to provide some measure of QRM reduction to ourselves. The 10M band during Solar Max allows full 100% gating of regional traffic on to HF from 144.39 in many areas if needed (not needed anymore due to IGates). PSK-31 and other EXPERIMENTS: Notice that in an SSB receiver, the APRS signal only occupies about 1300 Hz of bandwidth. Thus there is room within the passband for some PSK-31 experimentation as well. I propose that such activity be centered on 10.148.3 plus or minus 300 Hz. This places it more than 600 Hz away from the APRS mark tone, yet still within the passsband of a receiver operating in USB. Operators that do not run narrowband CW filters on APRS may be impacted by the PSK-31 work... FREQUENCIES: 30 METERS: By using 10.151 LSB, and the 1600/1800 Hz tones of the KAM, the MARK RF energy is 1.6 Khz lower and is inside the band edge by 600 Hz. The sideband energy is down by 40 dB which meets the FCC requirements for band edge operation. We use the LSB convention in specifying the freq to be compatible with other packet channels on the band. Of course, the actual frequency is 10.149.2 FSK or you can tune down to 10.147.6 USB! If your TNC uses tones centered at 2210 Hz or 2125 Hz, then you will need to tune 510 Hz higher using LSB. 20 METERS: We have suggested 14.098.2 since it is a full 1.8 KHz below the International CW beacon freq BUT your dial freq will typically be about 14.100. Many HAMS who do not understand the LSB offset hopefully will avoid this frequency making it relatively clear channel. The real PACKET LSB freq to AVOID for the sake of the CW ops, is 14.102 +/- 500 HZ! At times there is some APRS activity on the 14.105 LSB keyboarding frequency. APRS is a GREAT monitoring tool, to see who is on freq and who wants to chat... This frequency would be good for casual APRS DXing and new user familiarization. This will remove some of the QRM from the 10.151 LSB and 14.100 LSB tracking frequencies. In the future, we should also find a single APRS frequency on 18 and maybe 24 MHz. Any pioneers? REGIONAL FEEDS on 10M. (*** OBSOLETE after 1998 due to IGates ***) During solar max when the band is open, we can use the spacious band- width of 10m to accomodate 100% FEED channels which simply extend a regional 144.39 frequency onto a dedicated 10m frequency. Thus DX stations can tune into any of these FEED channels and join the LAN as if they were local on 144.39. THese FEED stations simply act as WIDE digipeaters. These stations should be spaced every 2 KHz to avoid mutual interference and on integer KHZ "channels" since many rigs tune in 1KHz steps. Also since we are using 1200 baud standard VHF TNC's here, then the tones are ALWAYS 1200/2200, so the TUNING convention is to simply state the FREQ in LSB... TUNING on 300 Baud Channels: To aid in tuning into an APRS HF net, I am suggesting that ONE station on each frequency be designated as the TUNE station and he sets his HF alias to TUNE. Then anyone can tune to that station, by simply setting his UNPROTO via TUNE temporarily and sending several packets to optimize his success. To avoid excess digipeating, the test station must remove TUNE as soon as he is finished. It may be possible to have additional slave TUNE's on frequency (TUNE1,TUNE2) when band conditions cannot reach the primary TUNE station. But these slave TUNE1, TUNE2 stations must make a DILLIGENT effort to zero to TUNE. HF OPERATIONS: The HF/VHF command in APRSdos changes the packet timing by a factor of 2 to account for the slower channel. Althought HF is 1/4 the speed at 300 baud, it does NOT use digipeaters, so the APRS periodicity timers are only changed by a factor of 2 between bands. In HF, APRSdos also changes your default ALIAS from the generic WIDE1-1 to ECHO. *** This is to make sure we don't get un-intentional digipeats on HF. *** Digipeating on HF is considered bad practice. KAM DUAL PORT OPERATIONS: When APRSdos is configured for HF using the KAM, and the 2PORT command is given, the KAM will not only send out packets on the selected HF port, but APRS will also send out duplicate packets on the VHF port by using the ~ and | stream switch characters. Only the STATUS, POSIT, OBJECTS, MESSAGES, and ACKS are duplicated. All other packets are only sent on the selected port. For the KAM, APRS properly initializes MYalias command to ECHO/WIDE1-1 for both ports. Please do not use 2PORT while chatting on VHF! You will kill the HF band. *** THE FOLLOWING IS OBSOLETE now that we have IGATES! *** *** Therefore use a DIRECT path & save 14 bytes in every packet!*** *** SHORTER packets is always going to be better on HF always! *** GATEWAYS: By assigning the generic alias of GATE to the gateway function in the dual port Kantronics or AEA TNC's, any HF station can gate-way into the local VHF net. HF stations can probably use the VIA path of GATE,WIDE1-1 most of the time, because the slow HF operation could hardly clutter up any local VHF APRS networks. But users on VHF APRS networks should NEVER use GATE on the VHF side of their gateways except under extreme circumstances. This is because there are hundreds of times more VHF users than there are HF users and the 1200 baud users would totally saturate the HF net! Also HF stations should -never- use GATE,WIDE2-2 because the packets will go TWO HOPS on every VHF network in the country and will not only cause duplication but more importantly it makes it impossible for VHF users to know where the packets are coming from! We want to keep the effect of a gateway well within the operating area of just one WIDE1-1. CAUTION: The purpose of HF/VHF gateways is to permit VHF local area APRS nets to see the movements of nationwide RV and BOATER mobiles. Please DO NOT GATEWAY from VHF through a gateway ONTO HF except under very unusual circumstances! Similarly, if you are on HF, only use ONE WIDE1-1 after the GATE so as not to clutter up everyone's VHF nets. KAM GATEWAY SET UP: You may connect two or more KAMS, each with an HF radio on different HF frequencies. The audio of their VHF sides are tied together into a low power VHF radio on 144.39. Both KAMS run with the GATEWAY callsign of GATE so that any HF APRS packets using the VIA path of GATE will be seen on our local 144.39 APRS net. This is for bringing both HF bands onto VHF, NOT for QRMing 2 HF bands by VHFers NOR for ANY back- to-HF gating! The HF and VHF parameters for the KAM Unproto command are separated by a slash character as follows. THis sets the HF path to VIA GATE,WIDE1-1 and the VHF path for this same station to VIA WIDE2-2. *** REEMEMBER THIS IS OBSOLETE! THE PATH NOW IS SIMPLY "UNPROTO APRSHF" *** OBSOLETE: UNPROTO APRS VIA GATE,WIDE1-1/APRS VIA WIDE2-2 HF TRACKING DEMONSTRATIONS: To see some actual APRS HF tracks, use the FILES-REPLAY command to replay ACADEMY.HST where the boats transmit once every 10 minutes on a military frequency. My first HF trips was over Xmas 1993 holidays. When I returned 2 weeks later the file XMAS93.hst showed all that was received in Annapolis of my journey. It shows good tracking from Knoxville TN to Florence Alabama. In fact, N2CZF (then in NJ) was able to track me all day, just about everyday, for the two week period, during daylight! SINGLE FREQUENCY XTAL CONTROLLED 40 WATT HF PACKET TRANSCEIVER FOR $199 Got your attention didn't I! But it is entirely possible to make such a black box for your trunk using recently published MOSFET amplifier designs and a direct conversion receiver. We need to talk the MFR's into making such a box. Why have a $1500 transceiver at risk at home to lightening or mobile to theft when a $199 box can do it? de WB4APR