May 2000 QST

other radio operation. The chatter from themystery radio station indicated that it wascoming from some kind of governmenthousing authority. I assumed it had to beout of state—I doubted that another in-stateradio service would be assigned the samefrequency as our local police force.The nearest state is Massachusetts andthe nearest populated area in Massachusettsthat would likely have a housing authorityis the Springfield area. I started keepingtrack of the street names that were mentionedby the users. At one point, the intersectionof X and Y streets was mentioned,so I ran Delorme Street Atlas on my computer,searched for that street intersectionand, voilá, Springfield was indeed the sourceof the mystery radio transmissions.Nice detective work, but more importantlyit gave some indication of the radio’sUHF sensitivity. Springfield is approximately40 miles away from my radio shackas the RF flies and the signals emanatingfrom the housing authority were S-9. But,there’s more! Pushing the envelope, Istarted monitoring the Springfield housingauthority while mobile and I was shockedhow well I was able to hear that operationwhile traversing the hills and dales aroundtown. This was very impressive!For a weekend, I replaced the WA1LOU-15 APRS digipeater radio equipment with theTM-D700A using its built-in APRS software.None of the users noticed any difference inthe digipeater’s operation. (At least, no onecomplained and, as they say, “No news isgood news.”)The TM-D700A may lack some stateof-the-artAPRS digipeater protocol featureslike TRACE N-N and WIDE N-N, butit can still serve as a suitable APRSdigipeater in a pinch.The Ultimate TestMy wife has never been interested in anyof my ham radio toys. When she saw theTM-D700A installed in my Oldsmobile, shethought it was actually “neat!” I believe thatearning that response from her qualifies thisradio as a major milestone in Amateur Radioequipment design!I am the administrator of the HTAPRSSpecial Interest Group (SIG), which is ane-mail list devoted to the discussion of technologytopics related to APRS—includingthe TM-D700A. The SIG is sponsored byTAPR. If you have questions concerning theoperation of this transceiver, this list canprovide a good source of information.You’ll also discover how other owners areusing the radio. You can subscribe to theHTAPRS SIG by visiting http://www.tapr.org/tapr/html/sigf.html. Selectthe “Join APRS HT” link.Manufacturer: Kenwood CommunicationsCorp, 2201 E Dominguez St, LongBeach, CA 90801; 310-639-5300; fax 310-537-8235; http://www.kenwood.net.Manufacturer’s suggested retail price,$780. Typical current street price, $660.PG-4X Extension Cable Kit, $70; VS-3Voice Synthesizer Unit, $40.ACOM 2000A HF Linear AmplifierReviewed by David Sumner, K1ZZExecutive Vice PresidentIt would be very easy to get used to havingan ACOM 2000A in your shack. In fact,you might get so used to having it that youmight forget it’s there! Operation is almostthat transparent.The ACOM 2000A amplifier consists ofa large, heavy, black box and a small, separateremote control unit (RCU) that’s abouthalf the size of an 8 1 /2 × 11 sheet of paperand about a half-inch thick. The main unitcan be stowed in any out-of-the-way cornerwhere there is adequate ventilation. In normaloperation you never have to touch it oreven see it, although the manufacturer recommendsusing the master power switch (theblack box’s only control) to turn the poweroff between operating sessions. What littleoperator interface is required is provided bythe remote control unit, which can be as muchas 10 feet away using the supplied cable.The amplifier is shipped in two cartons—the transformer is boxed separately. Thetubes come installed, but special supports areincluded to keep them from shifting duringshipping. These, of course, must be removedprior to use. Two small screws through theback panel also temporarily secure theblower assembly and are likewise removed.The control head comes packed in a boxnestled within the amplifier in the locationwhere the transformer is installed.The desired ac line voltage must be setbefore the transformer is installed. Ratherthan a terminal strip, the 2000A uses a PCboardwith 9 metal posts arranged in a grid.64 May 2000Bottom LineThe operation of the ACOM 2000A isso transparent that you might forget it’sthere. After initial set up and programmingwith it connected to your particular antennasystem, the amplifier will sense your transmittingfrequency and automatically tuneitself for the band segment of interest.Three movable shorting bars are positionedto allow a wide variety of supply line voltagesfrom 100 to 240 volts. As with mostHF amplifiers, the user must supply theappropriate plug for the power receptacle.The complete assembly process takesless than an hour. As the finished main unitis quite heavy (79 lbs), it’s a good idea toput the amp together in a location close toits final operating position.Hooking up the amplifier is straightforward.For full-power operation, a sourceof approximately 240 V ac at 20 A is required.On the rear panel there’s a groundingstud, one SO-239 coaxial connector forthe input from the transceiver, and anotherfor the output to the antenna or antennaswitch. Three RCA phono jacks provideconnections for KEY IN, KEY OUT and ALC.KEY IN is the usual “ground on transmit”control line that puts the amplifier into theline when your transceiver switches totransmit. KEY OUT allows you to inhibit theoperation of the amplifier at times whenyou might want to, such as when you’reswitching antennas and you want to avoidinadvertently “hot switching.” The manufacturerrecommends against using the ALCconnection—it’s better to adjust the driveto the amplifier with the “RF power” controlthat is almost universally available onthe front panel of HF transceivers thesedays—but it’s there if your particular installationrequires it. Finally, there are twoDB-9 connectors, one for the cable to theRCU and the other for an RS-232 interface.The most common use for the RS-232 interfaceis to control the accessory ACOM