May 2000 QST

DIGITAL DIMENSIONAPRS Digipeater in A BoxAPRS digipeaters come in a varietyflavors. Nowhere near the 28 varieties thatHoward Johnson’s offers, but enough tomake things interestingThe original APRS digipeater flavorconsisted of the requisite radio equipment(transmitter, receiver, antenna, cables andaccessories) and a TNC connected to acomputer running some version of APRSsoftware. You configure the APRSsoftware, which sets the TNC to act as anAPRS digipeater.The second flavor again consisted of therequisite radio equipment and a TNCconnected to a computer. Instead of runningsome version of APRS software, thecomputer ran APRS digipeater emulationsoftware. The TNC simply acted as aconduit for packets that it relayed to andfrom the computer. The APRS digipeatersoftware is called aprsdigi and it runs onthe Linux operating system. AlanCrosswell, N2YGK, created aprsdigi.Around New Year 2000, Kenwoodintroduced its TM-D700A dual band(144 and 440 MHz) transceiver. The TM-D700A has a built-in TNC and APRSsoftware, which can be configured as anAPRS digipeater without a computer. Thenecessary configuration can be performedusing the controls on the front panel of theradio.Last month, Marco Savegnago,IW3FQG, announced the availability ofAPRS digipeater firmware, called UIDIGI.You replace the firmware in a TNC2 orTNC2 clone with the UIDIGI firmware andthe TNC (with the requisite radio equipment)functions as an APRS digipeater. Acomputer is required to configure thesoftware before burning the EPROM thatcontains the firmware.These four flavors of APRS digipeatershave advantages and disadvantages.The ProsThe “original” APRS digipeatersupports the state-of-the-art WIDEn-n and/or TRACEn-n digipeater functions only ifthose functions are supported by the TNCused with the APRS software. (CurrentPacComm TNCs support TRACEn-n, whilecurrent Kantronics TNCs support bothWIDEn-n and TRACEn-n.) The APRSsoftware that configures the TNC isavailable for many computer platformsincluding DOS, Mac OS, Windows, Linux,Palm OS and Windows CE.Stan Horzepa, WA1LOU One Glen Ave, Wolcott, CT 06716-1442 wa1lou@arrl.net, www.tapr.org/~wa1lou88 May 2000Figure 1—A view of the MacDSP Webpage.N2YGK’s aprsdigi supports theWIDEn-n and TRACEn-n digipeaterfunctions.The TM-D700A is a good choice foremergency communications and publicservice events because it is self-contained“APRS in a box” and only requires anantenna and power source. It can be up andrunning very quickly.UIDIGI supports the WIDEn-n andTRACEn-n digipeater functions. It is agood choice for remote sites because theconfiguration is permanently stored inmemory. Power outages will not affect theconfiguration, so a computer is not necessaryto reconfigure the system. It is also themost inexpensive APRS digipeater flavorbecause TNC2s and TNC2 clones areplentiful and cheap.The ConsThe “original” APRS digipeater does notsupport WIDEn-n and TRACEn-n digipeaterfunctions if those functions are notsupported by the TNC used with the APRSsoftware. It is not a good choice for aremote site because you need a computerto reconfigure the TNC whenever it losesits configuration due to power outages andsuch, which are more likely to occur inremote locations.N2YGK’s aprsdigi ties up a computerall the time. It also runs on the Linuxoperating system, which is not the mostcommon, friendly or easy-to-learnoperating system around.The TM-D700A does not support theWIDEn-n and TRACEn-n digipeaterfunctions, therefore, it is not a good choicefor a permanent APRS digipeater installationin a network using WIDEn-n and/orTRACEn-n.UIDIGI requires the equipment and theability to burn EPROMs. Any changes inthe digipeater configuration require burninga new EPROM and installing it in the TNC.Getting ItThere you have it. If you are interestedin getting it, here is where it is available:Various versions of APRS are availablefrom ftp://ftp.tapr.org/aprssig. N2YGK’saprsdigi is available from ftp://ftp.tapr.org/aprssig/linux. The TM-D700A isavailable from your favorite Kenwooddealer. UIDIGI is available from http://gw.ir3ip.ampr.org/~iw3fqg/files/UIDIGI16.ZIP. TNC2s and TNC2 clonesare available at any ham radio flea market.More New Good StuffChris Smolinski, N3JLY, has released apreliminary version of MacDSP. As itsname implies, it is a digital signalprocessing(DSP) program for theMacintosh computer. Feed audio into yourMacintosh’s microphone jack, select thelow and high frequency cut-off, thenMacDSP filters the audio and plays theresults through your Macintosh’sspeaker(s). MacDSP requires a PowerPCMac. Download a copy at http://www.blackcatsystems.com/software/macdsp.html.Rob Wittner, KZ5RW’s, long awaitedAPRS/CE (APRS for the Windows CEoperating system) is now available in a betatest version. Download a copy using thefollowing URL: ftp://ftp.tapr.org/aprssig/wince/aprs-ce.exe. By the way, APRS/CEcan use any APRS (DOS), MacAPRS,WinAPRS, or pocketAPRS map and theymay be obtained at ftp://ftp.tapr.org/aprssig/maps/.