Contents: Basics; Important Caveats; Ic-7000; Kenwood TS-480; Yaesu FT-450; Common Problems; Voltage Problems; Used Gear Boon; Menus & Options; What To Do About Heat; Headsets; Accessory Jacks; Odds & Ends;

The first HF mobile transceiver I ever used was a Heathkit HW32, 20 meter monobander. It was approximately 12" wide, 8" high, and 14"deep including the back panel connections. In addition, there was the power supply which I mounted on the right kicker panel. Nowadays, the transceivers are smaller than the old Heathkit power supply.

I digress. Back during the late 70s when I worked for CW Electronics in Denver, I had an opportunity to meet Dr. Inoue, the founder on Icom. This was just after the introduction of the IC701, one of the first truly all-solid-state, synthesized transceivers. He ask me what I thought Icom should make. I told him I'd like to see an HF transceiver small enough to fit into a DIN-sized slot in the dashboard. I'm sure my comments didn't influence him one way or the other. However, large-scale use of LSI and surface mounting technologies certainly did. In fact, the Icom 706 can easily fit inside a DIN slot with room to spare.

Although there are several other miniaturized mobile transceivers, Yaesu and Kenwood both make one, Icom has the market with nearly 75% saturation. Although what I say here is pointed toward the Icom, in general the topics are applicable to the other brands on the market.

There are several drawbacks to miniaturization. The controls are also miniaturized making it difficult for large fingered folks to do the adjusting, which says nothing about doing it while under way. The front panel real estate is at a premium which means some controls serve multiple purposes and readouts become difficult to see. All of this requires the use of menus further frustrating the average user. There are some technical drawbacks which I'll cover later on.

However, they have lots of advantages. Most all of the new miniaturized transceivers are remotable. That is to say, the control head and the main part of the transceiver can be separated, and in some cases up to 20 feet away. If you do remote yours, read this.

The control head is light weight and small in size, which makes mounting easy. The rest of the transceiver can be mounted out of the way under a seat or even in the trunk. Trunk mounting adds complexity to the DC and control wiring, but is preferred in most cases. So it all seems like a win-win situation. But is it?

One of the drawbacks to miniaturization is heat dissipation. Heat is the bane of solid state electronics, and it can be a problem in mobile installations. In the case of the IC-706 (and others) there is a heat sink fan. This fan can and does run during receive, and anytime the transceiver is in transmit. While it is not very noisy it does increase the power draw by about 1 amp.

The various Icom models, and most all of the other miniature radios on the market, use the same basic circuitry to control several functions. The power out, SWR, and ALC meter readings; the SWR power fold back protection; the ALC fold back protection; and the over-temperature, two-speed fan control are all part of one basic module. Aside from the fact that the built in meter's accuracy is suspect to begin with, when any of the other functions are doing their individual protection bits, the metering becomes virtually useless. For example, when the fan is running, I have seen the SWR read higher than the power out when transmitting into a dummy load. At the same time the ALC will read full scale on one band and have no indication on another. This regardless of the control settings. The long and short of this is obvious. Don't rely on the internal meter for any indication unless the transceiver is (dead) cold and the output is into a dummy load. Even then, it's suspect.

Due in part to their size, a lot of manufacturers use modular jacks and plugs for both microphone and remote cables. While they look similar to RJ45 telephone jacks and plug, they aren't! Here is some more information on Cabling.

Some radios don't have an automatic off feature, which can lead to a dead battery. The PowerWerx APO3 is the best solution to this problem. However, the APO3 is more than just a timed (0, 5, 10, 20 minutes), auto off device.

There are four pre-programmed voltages (11.8, 12.1, 12.7, 13.05 volts) settings. Properly programmed, the APO3 will turn off, and on (with some exceptions), your radio just by monitoring the battery voltage! Remember, static battery voltage is about 12.4 volts, and at least 13.5 volts when the engine is running. Since it monitors the voltage, it knows when to turn the radio off and on. There's also a 10 minute off delay which avoids unnecessary operation (cold weather, heavy accessory load, etc.).

Almost without exception, every solid state rig out there has a low voltage limit. Under this limit and the rig will reset or shut down. For the average Icom, this is 11.6 volts, which is about nominal for the rest of these small wonders. If the rig is on when you start your vehicle (usually in cold weather), the battery voltage can momentarily drop to 8 volts or less. While the duration isn't very long, it is enough to cause the aforementioned problems. I have a trunk-mounted second battery which alleviates the problem.

First, don't be fooled! A Farad capacitor can be very dangerous. When fully charged and subjected to a dead short, the instantaneous current can exceed 500 amps! This dictates proper fusing and wiring. Nonetheless great care should be used when charging them, so following the manufacturers instructions is imperative.

If you ever need to jump start the vehicle, remove the capacitor's fuse first! If you don't, and the capacitor gets hooked up backwards, or the input voltage rating is exceeded (+20 VDC), the capacitor will fail catastrophically. Please use extra care if you take this route.

There is another voltage related issue that should be mentioned, and that is voltage in, versus power out. At a nominal 13.8 VDC, most of the aforementioned radios will output their rated power. Lower the input voltage to 12 VDC, and none of them will. Driving them harder to make up for this loss is not the solution. I also discuss this in my VHF Options article.

A lot of existing IC-706s are being upgraded to the IC-7000, creating a large number of used 706s. These can be bargains if you watch what you buy. Street prices should be in the neighborhood of $300, with later models with the DSP and optional filters command a little higher price, but not $700+ a lot of people think they're worth. I'd avoid older IC-706s without the DSP, unless you have a decent external DSP like an SGC ADSP2, or a similar model from Heil Sound.

There are a few of things to avoid when buying used gear. One is factory unauthorized modifications. If the unit you're thinking of buying has been moded to open up the transmit for example, my advice is simple; DON'T buy it! Further, unless you like to gamble, don't buy radios that you can't operate in person. eBay maybe all the rage these days, but before you buy read very carefully both eBay's return policy, and (especially) PayPay's return policy; they protect the seller more than the buyer.

Another major drawback is the menuing system (by no means is this an Icom-only scenario). Are they intuitive? You've got to be kidding! In all fairness I must say this is a personal opinion. I'm sure some folks like the way the menus are set up. Thankfully there are so many variables it actually fulfills the desires for almost every operator. But wouldn't it be nice if they made the menus user adjustable? Of course if they did, who would be able to program it? And isn't that the point? It's hard enough now I suspect. In the final analysis the real problem is learning the menus. If the users would just take the necessary time to learn them verbatim, things would be easier. Incidentally, Nifty Accessories (see photo) has a line of mini-manuals for all of the popular mobile radios. They contain all of the programming information that the owners manuals do, but with out the size and heft. They're a great mobile tool.

I have a few suggestions for buyers of these small wonders regardless of brand. Buy the narrowest SSB filter you can buy. For the Icom IC-706, this is a 1.9 MHz (the IC-7000 uses DSP). If you're into CW, opt for the 250 Hz filter. While this may seem extreme at first glance, just remember you're not dealing with a base transceiver environment, you're dealing with a mobile environment. One in which you'll need all the signal definition you can get! One more thing. If the transceiver has an optional voice synthesizer to read out the frequency, buy it! You'll be glad you did.

One more thing every reader should keep in mind. Although these miniaturized wonders are the answer to many prayers, they can be a double edged sword. Just because they are light, small, and easily mounted, cutting corners with respect to mounting could be a disaster in waiting. In other words, just because they're small doesn't mean you should use Velcro or double-sided sticky tape to mount the various parts. Like any other object inside a moving vehicle, if it isn't tied down properly, it can become a flying missile during a crash. A missile which can cause great physical harm. It pays to take your time, and do the job correctly.

One menu item you want to avoid using, and that's compression. There are several reasons why you shouldn't, not the least of which is covered in the following section about heat. If you just can't help yourself, you best be using a headset, and that's covered below as well.

Heat is the bane of electronic equipment. Too little heat, better yet a lack of it (read that as cold), can cause stability problems in oscillators and in some cases cause failure of a liquid crystal display (LCD). Too much heat and the life span of solid state devices fall like a rock, and LCDs to blanch out or fail altogether. In any case, it's not something most amateurs loose sleep over. However in a mobile scenario it is something we have to address.

We would all like to think that transceivers designed for mobile operation take into account the wide temperature extremes encountered. I'm sorry to burst your bubble, but this is isn't necessarily so. For example, the Icom IC-706 is rated at a usable frequency range of +14°F to +140°F. While one would think this is adequate, the fact is there are lots of places where temperatures are much lower and can be much higher too. I'll give you two specific examples.

I was in Cutbank, Montana in late 1973 and the outside temperature was -40°F. At the time I had a Heathkit tube-type transceiver. When I switched it on, nothing worked! Even with the heater on full blast, it took nearly an hour before it would receive. Ten years later I found myself in Phoenix, AZ where the temperature was 112°F. After sitting in the sun for 2 hours, the temperature inside my parked vehicle was easily over 160°F. The IC730 I was using at the time would receive, but the high-speed fan came on as soon as I hit the PTT. No permanent damage was done in either case, but there are times when these extremes can and do cause problems.

As an example, the Icom IC-706 has a built-in temperature controlled fan. It will run anytime the heatsink exceeds 160°F. If you have the transceiver mounted in the trunk under the package shelf as I once did, the heatsink will easily exceed 160°F even when the outside temperature is moderate. If you have left your IC-706 turned on and have not set the automatic off feature in the setup menu, you might come back to a vehicle with a dead battery. With the fan running, an Icom IC-706 draws nearly 5 amps and over time will drain the hardiest of batteries. While I'm referring to an Icom IC-706 here, the same can be applied to numerous other mobile transceivers regardless of brand.

Pay attention to your ALC meter reading. Any ALC indication (especially an Icom IC-706) is too much. If it starts to rise off the peg, you're driving it too hard. In either case the transceiver is in a protection mode. This situation can and does cause excessive IMD products to be generated and should be avoided.

Heat rises so it is always better to mount the main unit under a seat or on the floor of the trunk rather than under a package shelf or where the sun can shine directly on it. This will help minimize any heat related problems. Make sure you set the auto-off function as well. A delay of thirty minutes is ideal.

Any piece of electronic equipment should be well ventilated. A common mounting scheme is to use an unused DIN slot or ashtray receptacle to mount the transceiver into. This makes them convenient, but in some cases, the requisite ventilation is inadequate. Worse yet, in some vehicles this allows the heater vent to exhaust directly on to the heatsink with predictable results. In one case I'm aware of, the heatsink of a 65 watt 2 meter transceiver got hot enough to melt the plastic sides of the center console. This could have been disastrous. Thankfully it wasn't.

Mobile amplifiers get hot too. The average 500 watt PEP output solid state amp is only 50% efficient so with average speech patterns the amp is dissipating about 250 watts on transmit (SSB). This heat has to go someplace. On a recent trip I mounted an indoor/outdoor digital thermometer in the trunk of my Acura coupe. With the air conditioning on and the outside temperature hovering around 90°F, the trunk temperature was a reasonable 85°F due in part to the flow-through ventilation. While talking, the temperature rapidly increased. On two occasions it exceeded 130°F and both the IC-706 and the SG500 fans came on.

I have said many times; there is more to mobile installations than throwing the rig in the car and taking a trip. It requires safety mindfulness, forethought, diligence, attention to detail, and it takes time to do it correctly. Heat considerations are only part of the equation. You might not have ever had a problem (or were aware of one) with heat in your mobile installation. This means just one thing; Murphy hasn't discovered you're operating mobile.

The accessory jacks in most transceivers are typically designed for ancillary equipment from the same manufacturer. In the case of the Icom 706 this could be the PW1 amp, or a AH-4 auto-coupler. They can be used for other purposes, but due caution is in order as the current limits are small. For example, the keying line (HSEND) in an Icom will only sink a maximum of 20 mils (200 mils for the IC-7000). This is inadequate for directly switching an amp. This shortcoming is also apparent in Yaesu radios. There's a voltage drop problem too. Even with no load, the output voltage will be approximately 1 V less than the actual supply voltage. Under the maximum load of 1 amp, they're nearly 2 volts less. If you're using these jacks to power ancillary equipment, due caution is necessary. If you exceed 1 amp limit, you either blow the internal fuse (it's a mess to replace), or worse burn a circuit trace. If you power an external device, it's prudent to use a small transistor driven relay with proper fusing to minimize the risks. If you're using a mobile amp, read my Amplifiers article.

There is another problem with them when the units are operated mobile; voltage stability. Unlike a regulated base power supply, mobile DC input voltage can range from 11 to over 14.2 VDC while transmitting, and the accessory output voltages vary accordingly. This fact negates the use of some of the functions. For example, Icom and Yaesu both have outputs which can be used to automatically band switch an amp (or antenna switch). Because the reference voltage and the band select voltage are unstable in mobile operation, they cannot be used for their intended purposes. Ameritron's ARI-500 remote band switching accessory uses these reference voltages, but thankfully ignores them during transmit.