Miniature Rigs

Caveats

Here is the best advice you'll ever receive when you're in the market to purchase a new (or used) transceiver; Don't ask anyone for their opinion! Instead, go to your nearest dealer and play with the radio(s) first hand. No matter the brand, no matter the model, there are always drawbacks to every transceiver. Whether these drawbacks present a problem for you personally, depends on the type of operating you do. I'll give you a typical example.

The Icom IC-7000, stock out of the box, does not send live TouchTones^®. Rather, it uses one of just four, preprogrammed memory locations. If you operate through the MegaLink^® system, this is a big drawback. For me personally, it isn't, as I do very little FM work. Remember the old adage; it is always better to buy right, than twice!

Another very important caveat with respect to the IC-7000 (and older IC-706), is to make sure the grounding screw for the remote cable is installed. It is very small (2 mm x 6 mm), and is depicted on page 16, center drawing, Figure 2, in the Owners Manual (reproduced at left). Leave it out, and you're in for major RFI problems. The 706 cable is slightly different (see page 10), but the same caveat applies.

Although not strictly a caveat, a lot of folks deem is necessary to install an additional cooling fan. While it might make you warm and fuzzy, there is no need to do so. This brings up another point. All miniature radios require good ventilation. This means cubby holes, center consoles, DIN slots, and similar tight places should be avoided.

I mention this in my Audio Transmit article, but it bears repeating here. There are at least three enterprising amateurs modifying stock microphones (primarily the Icom HM-151) with the supposition of improved audio quality, and output level. If you use the stock microphone correctly as described in the article, there is no need for any modifications. If you're buying a used radio, you always want to ask about these types of mods, as returning the radio to factory specs often requires a new (≈$100) microphone.

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Basics

The first mobile transceivers, like the Heathkit HW32 should left, were often bulky in size, heavy in weight, and not very efficient overall. Most were all tubes, but by the mid 70s, all solid state models, like the Atlas 180 shown right, were becoming the norm.

Today's transceivers are often smaller than yesteryear's DC power supplies, certainly lighter, and best of all, much more compact! They're certainly more popular. Icom has sold over 75,000 IC-706 models in several iterations, and Yaesu's FT-857 has been almost as popular.

Modern transceivers are more capable, in that their frequency coverage is often 160 through 450 MHz. Most models are remotable. The light weight control head makes mounting easier, while 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. If you do remote yours, read this article on cabling, and this one on wiring.

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.

Impedance matching can present a problem too, as all solid state transceivers are designed for 50 ohm, non reactive loads. When decent quality HF mobile antennas are used, impedance matching becomes a necessity. The subject is covered in the Antenna Matching article.

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.

The IC-706 in its various iterations has become the most popular amateur transceiver, ever! After the introduction of the IC-7000, many thought Icom would drop the 706 from its product line. However, it has remained so popular, Icom was still manufacturing it in its latest form, the IC-706MkIIg. That is, until March of 2010 when it was finally discontinued. Its ≈$900 price tag replete with remote mounting kit, is certainly one reason for its popularity.

It covers 160 meters through 450, has extended general coverage receive, and supports both FSK and AFSK. One interesting feature with obvious benefits is its separate power output adjustments for HF, 6 meters, 2 meters, and the 70 cm bands. It even has a built in CW keyer, which can be keyed by the microphone's up and down frequency buttons. It has the usual complements of FM, AM, splits, auto-repeat off sets, ninety nine memory channels, and a very capable audio-based DSP. Like a lot of miniaturized radios, it requires an interface buffer to key a power amplifier (except for the SG500 and THP 450HL). The IC-706 has one unique feature, and that is a BFO offset (-200 to +200 Hz). This allows tailoring the transmit frequency to one's voice characteristics.

The IC-706 also gets very warm during use, and good ventilation is a necessity. As a result, some enterprising amateurs have added fans to the heatsink, and there has even been an article or two on the subject. Nonetheless, there is no concrete proof this elongates life.

The Icom IC-7000 has innovations that place it a head above the competition in many ways. Aside from its advanced IF DSP, Icom has done a good job of answering the common complaints with respect to menu selection and the buttons used there in. It is slightly smaller in length than the 706, has a color display, a built-in speech synthesizer, and enough memories for to keep anyone happy. The street price is $1,299 which is a bargain considering its overall capabilities. The remote kit is $110 (currently included).

If you believe the retailers, the IC-7000 is selling at about the same pace the IC-706 did. If the trend continues, it could become the best selling radio, ever. However, it's got a long way to go to catch up with its stable mate IC-706 in its various configurations.

The power cable is is the newer style four pin, and the matching power supply is a PS126. There are adapter cables from Icom (and the after-market) available, so interfacing to the PS-125 is easy. The fuses for the DC power cable have been moved to the far end (battery) where they belong.

The PTT keying capabilities of the 7000 is now 200 mils (the 706 is just 20 mils). While this fact still requires a buffer interface to key most amplifiers (the SGC SG500 and THP HL-450B are exceptions), it is a step in the right direction. Incidentally, the 13 pin accessory plug shipped with the Icom comes equipped with pigtails for some odd reason. However, late-model Kenwoods use the same plug, so most amateur suppliers carry them. It sells for about $7.

If you're one of the Golden Screwdriver types, you might want to take heed to the following. Unless you're adapt to working on micro-sized surface mounted devices, I wouldn't attempt it to do the popular extended coverage mod. If you do, be warned; the band edge warning beeps no longer work. Worse, most warranty repair stations will not work on modified radios, so you're really on your own here.

A lot of amateurs are adding video input devices to their Navi units as a means of displaying the front panel. It works, but if the display is larger than 7 inches, the lettering starts to be rather blotchy looking, especially if you use the alternate fonts. If you're in the market for a Navi video adapter, I suggest you look at the TV&Nav2Go system. It retails for $225 plus shipping, or about half what competing brands sell for. It's a small box about 4 inches square, and about 1 inch thick. The instructions are nearly worthless, but the unit is so simple it isn't difficult to install. Just remember to solder the green wire to its companion ground, and not to the parking brake as indicated. It requires 13.8 VDC even if you aren't using it to display the front panel, so some form of power switching will be necessary.

The TV&Nav2Go supports a backup camera too (see Soundstorm^® camera right), and models for just about any Navi are available. By the way, the Soundstorm^® camera displays the image as if you were viewing via a rear view mirror. It's a little disconcerting at first, but you get used to it fairly quickly. You can't complain too much, as the camera costs less than $25, and it's full color no less! It's available from a variety of on line sources.

Pin three of the microphone jack used to be audio out which allowed the use of a headset like the Heil Traveler^® without resorting to an adapter cable. On the IC-7000, pin three is a sense for the HM-151 microphone supplied with the radio. Since the IC-7000 has internal solder pads incorporated in the microphone circuitry, it is possible to change the microphone configuration to that of the IC-706, where as Pin 3 becomes an audio out. Icom does not mention this in their Owners Manual, but the pads are clearly shown in the Service Manual and the included schematic. Be advised, there may be a warranty issue if you do change the pads.

The HM-151 microphone has another drawback, in that you cannot send live TouchTones^®. You have to use one of the four presets. This makes accessing autopatches, IRLP, echolinks, and megalinks much more difficult and restrained.

The HM-151 does have some good points, however. The microphone has 25 buttons on its face, and while it looks busy at first glance, once you get used to it it's very easy to access the various buttons with your thumb. You can change frequency, bands, filters, VFO or memory, modes, the tune function, and a few other most-used functions. There is also two programmable function keys. Each button can be programmed for one of 21 different commands. Most all of the function would otherwise require accessing the various menus. This is not only a time-saver, it's also less distracting, thus safer.

If you use an Icom 2KL amplifier, or an Icom AT-500 tuner, or one of the many after-market devices which use the band select voltage for control, you'll have to open up the radio and solder a jumper to activate it. I removed the cover to look at the pad, and I can tell you it won't be easy to do. The fact that Icom states in their owners manual, "Performing this modification is the customers responsibility. Icom does not guarantee the modifications results" speak volumes!

The IC-7200 is a 160 through 6 meter, 100 watt, base station transceiver, but small enough to be used mobile in some (larger) vehicles. While available in Japan for nearly three years, it just recently received its FCC certification here in the US. Specification-wise, it is almost identical to the IC-7000 (IF DSP for example), but lacks video out, a color screen, and no VHF/UHF capabilities.

It has a real PTT relay capable of handling most modern amplifiers (16 vdc, 500 mils, maximum). Its street price is hovering around $1,200, and the mobile mounting bracket is about $30.

Contrary to some popular press, the IC-7200 does indeed have a 6 kHz roofing filter. From a personal (read that as mobile) standpoint, the roofing filter needs to be closer to 3 kHz, and perhaps as low as 2.4 kHz. In any case, it is a step in the right direction. Perhaps Icom will do the same for the 7000.

The IC-7200 is not waterproof, but considering what's being said about it, it's splash proof (what ever that means). Unlike the 7000, it uses a standard 8 pin microphone jack, and will accept a SM-8 base microphone without an adapter cable.

One interesting feature is a USB port on the rear panel. Icom (America) says it's a future interface for audio input, etc. It's that etcetera which leaves most folks wondering what Icom is up to. However, if you take the time to download the user's manual from their Japanese web site, some information is evident (?), but you need to read between the lines. If you click on the owner's manual verbiage at left, you can view a full-sized version (note the difference in procedures depending on the version of Windows you have). I suspect it will be just a matter of time before someone comes up with the necessary (after-market) software interfaces. One thing is apparent, and that's its lure for all things Field Day. A requisite laptop, a little software, and viola! Sadly, all is not want! The IC-7200 doesn't have voice or CW memories, like the IC-7000 (and later Icom transceivers). However, considering the street pricing, it is still a decent bargain.

Regardless of its size, a few folks are buying the IC-7200 to use mobile. Be advised, most antenna controllers designed for the IC-7000 will not work with the IC-7200.

Lastly, whether folks like the militaristic look (a departure for Icom), only time will tell. From strictly a personal standpoint, I don't like the looks, but I just may buy one as a backup radio. After all, the price is right, and it has a lot of bang for the buck!

One of the latest entries from Kenwood is the TS-480, which comes in two iterations; a 100 watt version with a built in auto coupler, and a 200 watt version without the coupler. It's poor man's amplifier, as no other mobile radio offers this much power. The Hx version sells for $1,100, and the Sx (SAT) sells for $999. Of late (Spring-Summer 2010), the Hx version's street price has been as low as $899.

The head, and the main body cannot be connected together (remote only). As with other Kenwood transceivers, the microphone plugs into the main unit, not the head. The cables (control and microphone) have pre-installed split beads to minimize RFI problems. This brings up another potential problem. The option cable extension kit might be needed in some installations. Rather than use CAT5 cables, buy the real deal. If you don't, you'll be plagued by RFI problems.

Calling it a miniature radio is a bit of a misnomer. It's approximately 7 x 2.5 x 10 inches, and weighs in at just over 8 pounds. Its 16 bit DSP is AF based, but Kenwood has done a decent job of designing out some of the problems that have plagued most AF based DSPs. There are optional filters available, and if used mobile the 1.8 SSB filter is almost a necessity. The others are a 500 Hz and 270 Hz CW filters.

Speaking of optional devices, here's a good suggestion. Order the optional VGS-1 voice guide and storage unit. Like the Icom IC-7000, it reads out all of the vital settings in the radio, and it also allows recording up to 90 seconds (3 x 30 seconds) of audio. The audio can be used to record, and play back any transmission, as well as CQ and CW messages. It is well worth the $80 it sells for.

The funny looking serrated plate shown in the photo is the mobile mounting bracket for the head, which is attached with double-sided sticky tape (and optional self-tapping screws). For some, this could be a drawback. If you use this type of mounting, remember this: Some automotive surfaces can be damaged and/or stained by the tape. Wherever you mount it, make sure is well out of reach of any SRS device. That virtually rules out the top of the dash as shown in their advertising brochures.

The 200 watt (Hx) version requires two power hookups (or two separate factory power supplies if used as a base). These can be combined into one feed, but users should remember the radio draws about 40 amps, so heavy duty wiring is a necessity.

Both versions have two cooling fans, so full power, key-down operation is possible (30 minute limit, 25°C ambient). I've not heard folks complain about the noise they make when operating mobile, but to me they are a bit noisy. One thing to keep in mind, the main body of the radio requires good ventilation clearance on both ends which might negate some mounting locations, under seat for example. The Hx version also gets very warm, hot actually, in normal SSB operation, so don't be alarmed if it does.

The manual has an interesting comment, which proves not everyone understands the origins and cures for mobile egressed RFI. It states in part; If there is excessive noise, use suppressor spark plugs (with resisters), and/or DC line filters to reduce the electric noises. While the former suggestion might help, if you have to resort to using brute-force DC line filters, you haven't installed your equipment correctly.

The TS-480 sports a CAT interface similar to those on the TS-2000, and there are quite a few after-market accessories which will work with this radio. Lastly, the two coax connectors are installed on dongles, rather than hard-mounted on the chassis. This fact could be a drawback for those who R&R the transceiver regularly.

The Yaesu FT-450 is a 160 through 6 meter, 100 watt transceiver. It's a bit large for a mobile (9 x 3.3 x 8.5 inches), cannot be remoted, and it doesn't have VHF capability. Whether the size and these missing features are a drawback, depends on your needs.

It has about the same attributes most of its competitors have, including an excellent IF-based DSP. There's also a 10 kHz bandwidth roofing filter located in the first IF, right after the first mixer. This not only increases selectivity, it improves the performance of the DSP. It has two voice memories, but they're both just 10 seconds long, as compared to 30 seconds times four for the Icom IC-7000.

There are a couple of features that are very unique. One of those is the PTT TOT (timeout timer), a feature every transceiver should have! If you happen to sit on your microphone and key the radio, the TOT will shut down the transmit. It's adjustable from 1 to 20 minutes. The other is the automated CW beacon. I can't imagine someone using it mobile, but if you're into 6 meters, you just might.

All is not rosy, however. The microphone gain is a menu-selectable LOW, NOR, HIGH, and the latter two automatically turn on the speech processor. While there are menu adjustments for the DSP microphone equalizer, finding the right setting isn't easy, especially if you close talk your microphone. If you use a Heil Traveler^® headset, you'll also find the lack of fine settings exacerbating. There is an internal adjustment, but it's not something you want to play with unless you have the right equipment, but the golden screwdriver folks probably will mess with it anyway.

As stated elsewhere, transceiver manufacturers seemingly have a hard time designing menu settings to be intuitive, and ergonomically easy. Although the FT-450 is better than some, it still lacks ease of use, especially in a mobile setting. Again, the best way (read that as safest way) is to learn the settings verbatim, or at least keep the manual handy.

Unlike it's little bother the FT-857, the FT-450 has a complete set of CAT commands, which makes computer interfacing a breeze. In fact, a lot of the existing Yaesu, after-market accessories which use the CAT commands will work with this radio. Incidentally, the commands are virtually identical to those of the FT-950.

Like most current models, the cooling fan is temperature controlled, and a bit noisy when it's on high speed. The LCD display is pleasantly large, and easy to read. Street price is about $699. There is a version with an internal auto-coupler ($770), and a mobile bracket is available.

The Yaesu FT-857 certainly has a popular following, in spite of several drawbacks. The main one is its small, orange-tinged display. Contrary to to the popular press' claims, it isn't any easier to see in daylight than its competitions.

Because, in part, to its decade-old design, the front end sensitivity takes a back seat to every other current offering. To be honest, in a mobile scenario this fact isn't particularly important, but could be under the right (wrong?) circumstances.

The power cord is actually a dongle, and an extension cable with the fuses included which might be a drawback if you R&R the radio frequently. there is another, potential drawback, if you use one of the many after-market devices which draw power from the radio (i.e. antenna controllers). The rear panel ports are protected with a 3.5 amp, surface-mounted fuse. It is not an easy task to replace, and requires special tools.

There are several others in popular use, albeit in legacy form. Certainly the Yaesu FT-100D, and SGC 2002 are in this category. If you're still using one of these transceivers, and it's giving you good service, there's probably no reason to upgrade (if you're satisfied). However, like the Atlas, finals for these transceivers are getting scarce, and in some cases, nonobtainium. If cost is an object (it should be), if and when they fail, you're much better off junking the radio, rather than attempting to repair it. It is, after all, a cost-benefit equation with no clear solution.

While the next few sections are pointed towards the Icom IC-706 series, and the IC-7000, the caveats can be applied to every miniaturized radio sold.

The port on the rear apron of the IC-7000 designed to interface with the AH-4 auto coupler is configured differently than the IC-706 series. Pin 1 (TKEY) input is shared internally with the temperature control circuitry. This pin MUST be left floating. If it isn't, the fan may not come on as required, which can lead to failure of the final transistors!

If you own, or plan to purchase, an Icom IC-7000, please read this paragraph carefully. Devices used to mimic the AH-4, and trick the IC-706 into transmitting 10 watts of carrier are not compatible with the IC-7000. This includes the suggested circuitry from SGC, at least one of the older model screwdriver controllers, and most small tuner modules. In other words, just because it appears to work correctly, it might not. Before using any interface designed for an Icom IC-706, ask the manufacturer if it is fully compatible with an Icom IC-7000.

The only US made one known to work correctly is from BetterRF, and designed specifically for the IC-7000. Their older IC-706 model is not compatible. There is also an Australian one designed by Owen Duffy, VK1OD, which is compatible. If you are using one of Bob Lewis' (AA4PB) Ham-Kit interfaces for the SGC couplers, remove R1 (33k) entirely, as it is not needed.

It is also important to mention the power handling capability of both the tuner port and the accessory jack. A lot of after-market devices, including some screwdriver controllers, antenna tuners, and digital interfaces, use the tuner port (or Accessory jack) for power. Icom states you can draw power up to one amp from pin 8 of the accessory jack. Although no specs are published about the current draw from pin 3 of the tuner port, most folks assume up to one amp is okay as this is what the AH-4 draws when it's tuning.

Both of these ports are fused (4 amps for the 706, and 5 amps for the 7000), and both are switched on and off by a switching transistor and/or a small relay. If you short either of these ports to ground, there are three failure scenarios.

First, the fuse will blow which doesn't happen often. Secondly, the switching transistor will fail (usually open). And lastly, and most likely, the circuit board trace will melt. The latter two failures are costly ones to repair.

Further, the voltage drop across these ports with a one amp load imposed on them, is just over 1 volt less than the supply voltage. While this might be okay for short durations like the tuning cycle of an AH-4 or other tuner using the port for power, long term draw means that 13 watts or so of heat is being absorbed by the radio's circuitry. I'm of the opinion that if you need the radio to supply switched power to an ancillary device, that you use a properly buffered relay to do the task. Or, use a PowerWerx APO3 as described below.

I've also discovered, the hard way, that the rear panel jacks on the 7000 are surface mounted. Even a minor bump can dislodge them from their circuit board. In my case, just a small, dropped screwdriver did the trick. It takes about 2 hours to fix because you have to R&R the main board too. Assuming, of course, that you're adept at working on surface mounted devices, that you have the tools to do so, and the circuit board hasn't been damaged. Luckily, mine wasn't. If you're not adept, this is a costly repair (about $150). Forewarned is forearmed, so even if you have the main unit hidden under a seat, protect the rear apron from impact. It's also advisable to use angle plugs (90°), rather than straight ones, as Icom suggests.

If you use the front jack to power a speaker, and the audio level is very low, check to make sure the switch on the back of the head is set for speaker. If it is set for headset, there is a 100 ohm resistor in series with the output, resulting in low audio.

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. But, before you dismiss the APO3 because your radio has an auto-off feature, who says you have to use it to control your radio?

As I said above, there is just so much power you can safely draw from the radio itself. Since the APO3 is equipped with Anderson Powerpole connectors, expanding the device is easy. For example, you could use it to feed power to their 4005 RigRunner, and automatically switch all of your ancillary devices (wattmeters, powered speakers, etc.). This results in less wire, wiring, switches, and a lot of headaches.

Here's how it works. 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, 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.). It switches 20 amps, and can handle up to 30 amps, making it compatible with almost any radio. At $60 (MSRP) it is also affordable. Visit their web site for more information.

One caveat. Some radios are switched on electronically. Once the APO3 powers up, you'll still need to push your radio's on button.

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.

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. A trunk-mounted, second battery will alleviate 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.

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.

All miniature radios have built-in temperature controlled fans. They typically run anytime the heatsink exceeds ≈150°F. If you have the transceiver mounted in the trunk under the package shelf, the heatsink could easily exceed 150°F even when the outside temperature is moderate. If your transceiver doesn't have an automatic off feature, you might come back to a vehicle with a dead battery. For example, with the fan running, an Icom IC-706 draws nearly 5 amps. Over time this will drain the hardiest of batteries

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, or buy a PowerWerx APO3.

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 dissipating up to 250 watts of heat. Obviously, good ventilation is a requirement, especially if the amp, and the transceiver are collocated.

There is a lot 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.

Not all headsets are created equal. Modifying a telephone headset is a questionable project. The impedances are not correct, and the audio quality is substandard as a result. Proper matching is especially important for Icom radios. Heil Sound makes a mobile headset designed to perfectly match the Icom's input requirements (models are available for Yaesu, Kenwood, and many others). It has a single earpiece, an adjustable microphone boom, and a PTT button in the cord.

I use my Heil Traveler^® frequently around town, and it's standard fare on trips. Because of the differences in audio quality and gain offered by the Heil Traveler^®, it maybe necessary to readjust your microphone gain, and perhaps the carrier offset (Icom menu G6) to achieve all of the benefits it offers.

Another item to watch is the receive audio level. Headsets require far less amplification than speakers do. Being so close to your ear, excessive volume can and does cause hearing loss. Just as a sidelight, here is an interesting site about noise pollution.

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 (with two exceptions; SG500, and THP HL-450B).

This shortcoming is also inherent in Yaesu radios. The voltage drop problem is there too. Even with no load, the accessory jack 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 3.5 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.

With the aforementioned in mind, it is always best to power ancillary equipment directly, via a RigRunner or similar power tap device.

Hands-on experience is worth more than a thousand opinions. Make sure you go through all of the menus, and all of the manuals. Spend extra time on the memory entry portions, and then try and program the demo units. If you can't do it in the store, how are you going to do it when you get home?

Now is the time to buy accessories. Most dealers (not all) discount accessories if you buy them with the radio. Don't scrimp on extra filters, audible readouts, digital boards, or what ever extra cost accessories are applicable. They make the radio easier to use, and easier to sell when the time comes to upgrade.

I don't like eBay and other on-line auction houses. If you buy a radio sight unseen, you're at the mercy of the seller. While a lot of eBay sellers are honest people, some are not, and you cannot tell by reading the reviews.

If you are buying your first radio, don't buy a handheld! They're nice and geeky, but their utility wears off very quickly. Always think about license upgrades when buying. You'll never regret it.