Eight rovers pause for a photo opportunity near Palmdale, Calif. during the August, 2009 UHF contest.  Five are using 10-band "toolbox" stations mounted on roof racks or, in one case, a truck bed.

This is based on a paper that was prepared for the Proceedings of the 2009 Microwave Update in Irving, TX.

     Ever since N6NB’s 10-band “toolbox” rover stations began to attract attention on the Internet, there has been a stream of e-mail inquiring about them with questions like, “what are they?” and “what’s inside those boxes?”
     The short answer is that these stations cover 10 VHF+ bands in a compact, portable package.  Each station has six UHF/microwave transverters and in some cases small amplifiers, all in a 20” Craftsman steel toolbox from Sears.  Each toolbox has two short masts, one on each side, to support antennas for as many as 10 VHF+ bands. The toolboxes also have cooling fans and remotely controlled switching.  The toolboxes sit atop an antenna rotor on a roof platform that can be adapted to almost any roof rack on a truck or SUV.  Each toolbox station also includes a console that normally rides on the passenger seat of a car.  The console has at least two transceivers (sometimes three) to cover 50, 144, 222 and 432 MHz, plus a rotator control and an inverter to power the rotor, a Rubidium frequency standard, and a remote control head for the equipment in the toolbox.  Fig. 1 and 2 at the end of this article are block diagrams of a typical operating console and toolbox.  These units can be powered by an auxiliary storage battery and charged by a connection to a cigarette lighter outlet.  Of course, better performance is possible with a high-current connection to a car battery.
     I have built seven of these 10-band toolbox stations as well as four larger 10-band stations that can be used in vehicles with more space such as a truck or a van.  One of these larger stations is equipped with vacuum tube kilowatt amplifiers for six and two meters, powered by a 3000-watt inverter and a bank of batteries charged by a heavy duty alternator.  That station also has solid state amplifiers for all higher bands through 10 GHZ.  But even toolbox stations built around transverters that deliver less than one watt of power output are effective over long microwave paths, thanks to their high gain antennas and short feedlines.  With their portability and simple installation requirements, these stations make it easy to promote activity on the microwave amateur bands even in areas that have no tradition of activity on those bands.

THE TOOLBOX ITSELF - Each toolbox station has a combination of Downeast Microwave (DEM) and Kuhne (DB6NT) transverters for 902, 1296, 2.3 GHz, 3.4 GHZ, 5.7 GHz and 10 GHz.  All use DEM transverters on 902 and most use DB6NT transverters on 1296.  The rest of the transverters may be either brand, depending on a number of circumstances.  With either brand, it’s possible to fit six transverters plus one or two small amplifiers into the toolbox.
     Each toolbox has at least one cooling fan; some have two.  Warm air is vented out through a water-resistant port that also provides access for control, power and antenna cables.  There is insulating material in the lid of the toolboxes to reduce equipment heating.  Experience has shown that these toolbox stations are reliable even at summertime temperatures of 110 degrees Fahrenheit in the California desert.  The first toolboxes had insulation but no cooling fans--and it quickly became apparent that more cooling was needed.
     The two masts support antennas for up to 10 bands in a compact, easily transported package.  All of the toolboxes have small (usually 30 cm.) dish antennas for 5.7 and 10 GHz, using W5LUA-type dual band feed horns.  The toolboxes use short loop Yagis on 2.3 and 3.4 GHZ.  Some also have loop Yagis on 902 and 1296.  Others have quad or Quagi antennas for those bands.  Some have a triband 3-element quad antenna for 144, 222, and 432 MHz as well.  Others have omnidirectional loop antennas 144, 222 and 432.  The most common antenna for six meters is also a full-wave omni loop, although two of the larger stations use two-element Moxons for six meters.
     One significant advantage of the toolbox design is that the feedlines can be kept very short, minimizing losses.  Even at 10 GHz, feedline losses are typically below 1 dB.  Because the entire package--including equipment and antennas--rotates together, semi-rigid cables can be used on the microwave bands.  Only a bundle of more forgiving cables (power and control cables  plus RG-58 type feedlines for lower frequencies) needs to be free to rotate.  Even those cables are usually less than 15 feet long.

CONTROL ARRANGEMENTS – Instant, single-knob bandswitching is crucial for these rover stations, even on the microwave bands.  That is accomplished with a remote control head at the operating console and a relay box inside each toolbox.
     Each control head is similar to the one shown in the photographs.  All use the same cabling arrangements for interoperability.  Each has a DC ammeter to allow the current drawn by the toolbox to be continuously monitored.  Since the individual transverters and amplifiers are not visible, the ammeter is used to keep track of what is going on in the toolbox.  If there’s no increase in current when a transverter is keyed, that would most likely indicate a failure in the keying circuitry for that band.  No current drain when the main power switch on the control head is turned on would probably indicate a failure of the DC power connections to the toolbox or perhaps a blown fuse.
     Bandswitching is accomplished with a multi-position rotary switch on the control head.  In the “through” or “2/432” position, a relay at the i.f. transceiver engages to allow straight through operation on the VHF bands.  All keying circuitry in the toolbox is disabled in this position.  When the operator switches to any band from 902 on up, 24 volts is sent to the appropriate contacts on a six-position SMA relay in the  switching box in the toolbox.  The 24 volts also engages a double pole relay for that particular band, transferring the PTT line and the 10 MHz Rubidium reference  signal to the proper transverter.  The Rubidium unit and its 24-volt power supply are housed in the operating console and connected to the toolbox with a single coaxial cable.
OPERATING CONSOLE – Each operating console is similar to the one shown in the photograph, although a variety of hardware is used in various stations.  Each station has a 222 MHz transceiver for intercommunications.  Some use a mobile FM transceiver, while others have a transverter and a separate 28 MHz transceiver for always-on 222 monitoring as well as SSB/CW capability.  Some stations also have a “brick” amplifier on 222.  Having constant liaison is essential for moving quickly through the higher bands.
     Many of the stations use a single 100-watt HF/50 MHz transceiver that also covers 144 and 432.  The transceiver runs straight through for the bands through 432.  In several of the most compact stations, the same transceiver is the i.f. rig for the  transverters on 902 and higher bands.  Some more elaborate stations have a separate transceiver and amplifiers for 6, 2 and 432 and are capable of at least 100 watts output on two meters and 75 watts on 432.  Some have more potent amps for even higher power on the VHF bands.
     The Rubidium unit and its power supply are always located in the operating console.  Every console also has a control unit for an antenna rotator as well as a power inverter to provide 110 volts for the rotor. Although the console is usually strapped to the passenger seat of  a car for single-person operation, it is more convenient to mount the console on the rear seat if a station will have a driver as well as an operator.  Some have tried to operate a station in the passenger seat from the back seat, with consistently bad results.
     Many operators have their own favorite GPS unit that they carry with them.  Some also have a digital voice recorder for logging on the fly while driving.  Some try logging on a personal computer while driving.  The wiser ones soon decide that isn’t a particularly good idea.  Of course, some also have a c.w. paddle that they use for mobile weak-signal operating. 

ROTORS, PLATFORMS AND DC POWER – It has to be possible to mount and dismount the toolbox stations quickly.  With 11 stations to install during the week before a VHF contest, I was forced to come up with easy ways to accomplish the task.  A variety of platforms have been built to allow a toolbox and antenna rotor to be attached to any vehicle that has a roof rack or a truck rack.  Sometimes toolbox stations have been installed in the bed of a truck or inside the rear of an SUV, although that arrangement makes rotating the antennas much more inconvenient if not impossible.  But not everyone who may use one of these stations in a contest owns an SUV or truck with a rack.
     Once a platform with a rotor is secured to a roof rack or some other stable surface, the toolbox is lifted onto the rotor and attached with four bolts.  Experience has shown that this arrangement is quite stable.  No rotor has ever failed because of the weight or windload of a toolbox station.  Yaesu rotors are used for all of these installations because the toolbox can be bolted directly atop the rotor without any mast or pipe bracket.  Mounting the toolbox directly on the rotor body reduces stresses on the rotor, perhaps accounting for the reliability of these installations.
     Providing DC power to the toolbox stations is a more difficult challenge in some cases.  Ideally, a heavy primary cable (at least #10) runs directly from the operating console to the car battery.  Operators are always advised to leave the engine running while on the air for an extended period of time. 
     If a station has to be installed in a vehicle that lacks a heavy cable to the battery, the second-best alternative is an auxiliary battery near the console, recharged by a cigarette lighter plug.  This is not an ideal arrangement because few lighter circuits are intended for this kind of current demand.  Dead auxiliary batteries are a common occurrence when an ambitious operator does a lot of transmitting at the 100-watt (or higher) level, even with the engine running and a recharging circuit properly plugged in. 

STATION PERFORMANCE - The inevitable question about these stations is always, “how well do they work?”  The answer, of course, is “it depends.”  Under good conditions, any of the 11 stations discussed here is capable of working 1000 km. into Mexico on 10 GHz.  Several of them have been in the right place at the right time to do just that.  Under mediocre conditions with typical mobile noise on a freeway, all are capable of working well-equipped stations several hundred kilometers away if the terrain is clear.  What these stations offer is a way to get on 10 VHF+ bands quickly with well-tested setups that are ready to go on short notice.  Considering how much trouble most of us had getting our first 10-band VHF+ station running, these stations have proven to be remarkably trouble free.  It’s not unusual to get through an entire contest with every station still working on every band when it’s over.

Fig. 1.  A typical operating console that mounts inside a car to control a toolbox station.

Fig. 2.  A typical toolbox assembly for auto rooftop mounting.  Thanks to Jim Forsyth, AF6O, for drafting these figures.

About the author:  First licensed in 1957, Wayne Overbeck has been interested in VHF+ operating, and especially portable contesting, for more than 50 years.  He holds Ph.D. and J.D. degrees and is a retired Professor of Communications at California State University, Fullerton.  He is the senior author of a communications law textbook that is now in its 21st edition.  He won the Radio Amateur of the Year Award at the Dayton Hamvention in 1980 as well as the ARRL Technical Excellence Award and the John Chambers Memorial Award of the Central States VHF Society in 1978.  The latter awards were in recognition of his work on the original “VHF Quagi” antenna and his early moonbounce expeditions to Alaska and the Utah-Nevada border.  See www.n6nb.com for more information about many of these subjects.

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