HF.txt 6.11 HF APRS BOAT AND RV TRACKING NET (see new TUNING section) HF FREQS: MFJ/KAMS AEA'S Mode NORMAL USAGE 10.151 10.1515 LSB Mostly East Coast so far (Calif late eves) 7.085 7.0855 LSB Mostly West Coast 14.0963 14.0958 USB Proposed new APRS DX freq 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. Please note the SIDEBANDS used. These are important and here's why: By using 10.151 Lower Sideband, the packet signal RF energy is 1.7 Khz lower and is inside the band edge by 700 Hz. The sideband energy is down by 40 dB which meets the FCC requirements for band edge operation. I use the LSB convention in specifying the freq to be compatible with other packet channels on the band. Of course, you can operate on 10.147.6 USB which is exactly the same frequency, but you will have just as hard a time trying to explain to the Guys on 10.147 that you are NOT interfering with them!. ALSO PLEASE NOTE that these freqs assume an audio modulation center frequency of 1700 Hz. The AEA- PK232 uses tones centered at 2210 Hz and some others may use tones centered at 2125 Hz. Radios connected to a PK-232 need to be tuned 510 Hz higher using LSB and 510 Hz lower on USB. The other TNC's which use 2125 need an offset of 425 Hz. On 20 meters, by selecting the frequency of 14.0963 UPPER SIDEBAND we are in effect radiating on 14.098 MHz. This frequency is a full 2 KHz away from the international CW Beacon frequency of 14.100 which SHOULD NOT BE USED FOR PACKET. The advantage of this 14.098 frequency is that it can also be described as 14.0997 LSB for 1700 HZ packet or 14.1002 for LSB with 2200 HZ tones. These are exactly the frequencies that all other packet stations might be trying to avoid if they do not understand the LSB offset! In effect, we are taking advantage of their missunderstanding. To further clarify this nuance, it is important to note that a packet station desiring to avoid the CW BEACON frequency of 14.100 should actually never operate within 500 Hz of 14.1017 LSB with 1700 HZ tones or 14.1022 LSB with 2210 Hz tones! Putting it a third way, we would be crucified if we announced that we are operating on 14.100 LSB by all those who do not understand LSB offsets. So we are just calling it 14.0963 USB to avoid the controversy. In any case, we are 2 KHz away from the TRUE CW BEACON FREQ! If we use this 20 meter freq for casual APRS DXing and new user familiar- ization, then we will remove some of the QRM from the 10.151 LSB national APRS tracking frequency. I expect this summer, 1994, to see a big increase in the number of boats and RV's tracked. In the future, we should also find a single APRS frequency on 18 and maybe 24 MHz. Any pioneers? TUNING: To aid in tuning into an APRS HF net, I am suggesting that ONE station on each frequency be designated as the frequency CZAR. That station should set his HF alias to TUNE. Any newcommer on frequency that desires to lock onto that station, simply sets his UNPROTO path to go via TUNE temporarily. Then he hits several PINGS. As each Ping is digipeated bcak, he can tune his receiver right on frequency. This is the normal netting procedure, but by using the generic alias of TUNE, a newcommer does NOT have to know who the CZAR is in order to find the exact frequency. To avoid excess digipeating, the station must remove TUNE as soon as he is finished. Others should keep an eye on the DIGI page and remind anyone that forgets and leaves TUNE in his path. It may be possible to have additional slave TUNE's on freequency (TUNE1,TUNE2), as long as they make a DILLIGENT effort to zero to each other. A new user getting no response from TUNE can then try TUNE1 and TUNE2 in turn. Obviously these other slaves should be very widely separated. HF OPERATIONS: The HF/VHF modes in APRS only change the packet timing to account for the slower channel. As of version 5.05 toggeling this mode also can switch the KAM between HF and VHF. For other dual band TNC's, you must do this manually using the OPS-COMM dumb terminal mode to set change bands according to your TNC instructions. When you configure APRS for HF instead of VHF, it simply multiplies all timing routines by 2 to make up in the difference between 1200 and 300 baud (and the factor of two improvement when not using a digipeater on HF). So the net cycle time on HF is twice as long as on VHF. One other thing it does is to change your default ALIAS from the generic callsign of RELAY to the generic callsign of ECHO. Read the info on the UNPROTO command and in the README.RPT file to fully understand the implications of the generic ALIAS of RELAY used by all VHF APRS stations. Obviously, for a nationwide HF net, we do NOT want everyone digipeating everyone else's packets! So the change to the alias of ECHO is only important in that it REMOVES the generic ALIAS of RELAY! Of coure you can still digipeat your HF packets off of another station under critical or emergency situations, but now you should specify exactly who, by callsign, NOT by the generic call of ECHO. (In real emergencies where you want to maximize the chance of your signal being heard at the expense of nationwide collisions, then digi via ECHO) GATEWAYS: APRS has great applications through HF/VHF gateways. By assigning the generic APRS alias of GATE to the gateway function in any of the dual port Kantronics or AEA TNC's, then any HF station can gateway into your local net. HF stations can probably use the VIA path of GATE 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 caution. This is of course because there will probably be more VHF users in a single VHF net than there will be HF users across the whole country. So the HF net would be totally clogged. I am concerned about over-using the VHF side of the gateway, and have included a mechanism to discourage the use of the GATE via path on VHF. That way a user will have to intentionally specify the GATE function each time he wants to use it and there will be no way for him to forget about it and accidently contribute to un-necessary QRM! To repeat: The purpose of HF/VHF gateways is to permit VHF local area APRS nets to see the movements of nationwide RV and BOATER mobiles. For example, when I go GPS mobile, I do not want to, and cannot leagally leave my HF station running at home so my wife can follow my status. But If I send my HF mobile APRS reports via the local HF GATEway, then my wife can see me on our computer which only needs to have a VHF TNC. Please DO NOT GATEWAY from VHF through a gateway ONTO HF! (Unless you have good reason.) TYPICAL DUAL PORT GATEWAY SET UP: So here in Annapolis, I have the two KAMS each with an HF radio on the two HF frequencies. The audio of their VHF sides are tied together into a 1 watt radio on 145.79. 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 145.79 APRS net. The purpose of this gateway is to support the big picture APRS objective of allowing any mobile station anywhere in the country to report his position back to his home QTH. If I am driving through ANY area in the country that is using 145.79 for APRS and that has a GATEway station on either of the two APRS HF frequencies, my 2 meter APRS position report has a good chance of making it all the way back to my PC display. All I have to do is to set my mobile TNC outgoing path to WIDE,GATE, GATE,W3XYZ. This way the closest generic APRS WIDE digipeater will digipeat my report to the nearest GATEway. It will in turn digipeat the report out onto the HF APRS net. My Annapolis HF GATEway will then see the second GATE and repeat the packet onto the local VHF net through the local W3XYZ digipeater, which will then reach my home. Notice that all of the other gateways will also transmit the packet, but only the Annapolis packet will get digipeated via the W3XYZ digipeater. For this reason, an APRS gateway should have a low power VHF radio only capable of hitting the nearest VHF APRS digi so that it does not QRM a large area. Neat huh! SETTING THE UNPROTO PATH WITH THE DUAL PORT KAM: The HF and VHF parameters for the KAM Unproto command are separated by a slash character as follows: UNPROTO APRS VIA HFDIGI1,HFDIGI2/APRS VIA VHFDIGI1,VHFDIGI2 etc To set up your KAM using the APRS UNPROTO-VIA command, you need to remember to include the second half of the command as noted above. If you omit the second half of the command, then the KAM applies the Unproto command identically to both ports. Since I want my KAM to go out on VHF via the local WIDE area digipeaters (WIDE,WIDE) but I want the HF packets to go via any HF GATEway node (GATE), I can do that via the APRS UNPROTO command with the following: ... Enter new VIA path: GATE/APRS VIA WIDE,WIDE Notice that APRS automatically inserts the UNPROTO APRS VIA ... for the first part of the UNPROTO command and all I have to do is type the DIGI address (GATE here), but for the dual port KAM, that I must type "APRS VIA" again myself after the slash for the second half of the command (for the VHF port). CAUTIONS: Obviously the shared HF APRS net cannot handle a lot of such cross band position reporting, but if you are far enough away to have to use an HF link to report your position, then nobody really cares exactly where you are minute by minute, simply which town you are in is fine. So mobile stations using this gateway function should probably not beacon any more often than once every half hour. Similarly, HF stations such as boats and RV's I would not expect to routinely report any more often than that either. We will just have to see how APRS grows. OTHER BANDS: I only have two HF radios, which is why I have not looked for other APRS packet frequencies on the other bands. I would avoid the QRM on 20 meters and would look next on the 18 MHz band for a good permanent APRS report- ing frequency for the long haul round-the-world boaters. Of course, the 20 m frequency would be fun for just working APRS HF DX and seeing where those foreign stations are! Remember that APRS can also plot stations using only grid squares. Any BEACON packet with the grid sq enclosed in brackets at the beginning of the BText will be plotted. HF TRACKING DEMONSTRATIONS: To see the results of some actual APRS HF tracking events, use the FILES-REPLAY command to replay the ACADEMY.HST file. The boats were transmitting once every 10 minutes or so. My first HF mobile excursion was over Xmas 93 holidays. When I returned 2 weeks later the file XMAS93.hst showed me all that was received in Annapolis of my journey (before the computer crashed). 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 hours!