HF mobile radios

Recognizing the rapid growth in mobile and portable operation, most manufacturers offer small, rugged radios. Each year, more bands and better features are crammed into these amazing radios. These radios are quite capable as base or fixed stations if you want to use the radio at home, too. Many radios include coverage of VHF and UHF bands on the weak-signal modes (SSB and CW) as well as FM.

An excellent website for mobile operators is Alan Applegate (KØBG)’s Web Site for Mobile Operators (www.k0bg.com). The site covers everything from powering your mobile rig to using it effectively.

Because they’re so small, these radios must make some compromises to save space. The operator interface is constructed as a series of menus. This makes some adjustments a little harder to get to, although the most-used controls remain on the front panel. These smaller rigs don’t include internal antenna tuners at the 100-watt output level, as many larger rigs do.

As when evaluating these radios’ larger base-station siblings, you have to consider features and accessories. Because these radios have a minimal set of controls and are menu-driven, I recommend that you try one before you buy it. If you don’t have a friend who owns one, you can often find an owner online, maybe even with a video to share, who will answer basic questions.

The Icom IC-7100 in Figure 14-1 is a typical example of mobile all-band radios. (An earlier version, the IC-7000, is shown later in this chapter.) The IC-7100 is small, but produces 100 watts output on all amateur bands between 1.8 and 50 MHz, 50 watts on 144 MHz, and 35 watts on 432 MHz. The radio’s detachable control head is intended to be securely mounted near the operator. The radio itself is typically installed under a seat or in the trunk. As of late 2017, other popular rigs for mobile operation include the Yaesu FT-891, Kenwood TS-480, and Alinco DX-70.

Connect the radio headphone output to your vehicle audio system’s AUX input with a short stereo audio cable. You’ll find high-fidelity mobile hamming to be easy on the ears.

If you plan to operate from your RV, take a few pointers from the clean layout shown in Figure 14-2, designed by Pete Wilson (K4CAV). When Wilson stops at a campground, he sets up a station right at the driver’s position. The HF transceiver is not only mounted right on the dashboard, but also sitting on top of a mobile amplifier for an extra-powerful signal. When the RV is in motion, all this gear is safely stowed.

Maybe you’d like something less tied to an automobile or RV. Well, how about a bicycle mobile station? The bicycle mobile station shown in Figure 14-3 was built by Ben Schupack (NW7DX) during his senior year of high school. An HF QRP rig mounted on the handlebars of the recumbent bike. A whip antenna and batteries are mounted behind the rider.

Mobile installations

Driving your station creates its own set of unique considerations. Because vehicles come in so many styles, every installation is a custom installation. Leave some of your radio budget for automotive fixtures and wiring. You may find it prudent to spend a few dollars for a professional shop to make recommendations about power wiring, how to route wires and cables in your vehicle, and safe installation methods.

Lease agreements may prohibit modifications to the vehicle or hold you responsible for repair costs. If you share the vehicle, get agreement on where to place the radio before drilling any holes.

Where can you fit a radio in your vehicle or boat? If you have an RV or a yacht, you may not have a problem, but in a compact car or an 18-foot runabout, the space issue can be a challenge. Luckily, many radios designed for mobile use, such as the IC-7000 shown in Figure 14-4, have detachable front panels (these are also control heads). A cup-holder flex-mount designed to hold phones or tablets can also hold a small control head.

Poorly secured radio gear can be lethal in an accident. Please don’t drive without making sure your radios are securely mounted. Anything in motion inside the vehicle is a hazard to you and your passengers.

As you can see, this arrangement provides lots of functionality in a small space. This mobile station can operate on the HF bands and several VHF/UHF bands with all controls right at the driver’s fingertips. (The small unit below the control head is a controller for an adjustable antenna.)

If you can borrow a mobile radio before buying it, make sure that the control head can be mounted in your vehicle where the display is easy to see and the controls are easy to operate. Don’t build in a driving distraction! Use hook-and-loop adhesive tape to try out the mounting locations without drilling any holes.

A detachable control head allows you to put the body of the radio under the dash or a seat or on a bulkhead. The radio is attached to the control head with a special cable available from the manufacturer in several lengths. The combination of cable and mounting hardware for the radio and control head is called a separation kit. The separation kits can be expensive purchased separately but may be available at reduced cost if purchased with the radio.

Make sure that the separation kit cable is long enough to connect the control head to the main radio unit, wherever you decide to mount them. Include for extra length to run the cable under mats and around obstacles.

Don’t install a mobile radio control head (or anything else) on or near a panel that conceals an airbag! If the air bag deploys, the control head will become a projectile. A heavy radio or improper mounting might prevent the airbag from deploying properly, leading to injuries inside the vehicle. Take care to keep cables and microphones away from airbag deployment areas as well. Check the vehicle’s service manual for the locations of all airbags, which may be on the door panels and other unexpected locations. Take caution when working around the airbag systems!

Multimode radios are very popular for the special type of mobile contesting called roving. One of these small rigs and a transverter or two for other bands makes for a lot of fun as you rove from grid square to grid square, racking up points.

It can be “interesting” trying to find a solid connection to vehicle power that can supply enough current for your radio at full power. A 100-watt rig can draw as much as 25 amps at peak output. This is far too much current to use the typical auxiliary power jack, also known as a cigarette or cigar lighter. Those are usually rated at less than 10 amps — check the vehicle’s manual. You will have to find a connection rated for the load.

The most robust power connection is directly to the battery. (Newer cars and trucks have a battery charge control system — see your owner’s manual or consult the dealer for the proper point at which to connect your radio.) To prevent a short circuit from finding a path through your radio, be sure to include a fuse in both the positive and negative leads. Make sure your connections are secure so they won’t come loose in the car’s harsh mechanical environment. Use anti-corrosion compound on the terminals because the connection will be exposed to corrosive chemicals, salt, and water.

Each vehicle is different in the way cables have to be routed. If you can find protected access holes and cable trays, use them because they keep the cables from being abraded or pinched, which can lead to damaging short circuits. Fight the temptation to make a hasty or unsecured connection to vehicle power. Speaking from personal experience, a loose connection or wire can cause a lot of trouble in a big hurry. Be safe and do things right.

Mobile antennas

Obviously, you won’t be able to drive, boat, or cycle around with a full-size HF antenna for most of the bands. Quarter-wave whips for 10, 12, and 15 meters are 8.3, 9.4, and 11 feet long. Mounting the antenna on the vehicle adds at least a foot or two to the overall height. Because maximum allowed vehicle height is 13 feet, 6 inches, longer antennas will exceed that limit and become increasingly impractical.

For mobile operation on the HF bands, many hams use Hamstick-type antennas attached to a mag-mount or a permanent mount attached directly to the vehicle, as shown in Figure 14-5. These antennas consist of wire coiled on fiberglass tubes about 4 feet long, with a stainless-steel whip or “stinger” attached at the top. The antennas work on a single band and are sufficiently inexpensive that you can carry a whole set in the car. You have to change the antenna to use a different band. Another design uses resonators attached to a permanent base section to operate on different bands. The resonators and fiberglass whip antennas use a standard ⅜-24 threaded mount.

An adjustable design that has become popular in recent years allows the antenna to tune over nearly any HF frequency. (Antennas of this type are known as screwdriver antennas because they were first made with DC motors similar to those in battery-powered electric screwdrivers.) The antenna is similar to a Hamstick — its base section is a coil with a whip attached at the top. The coil is adjustable, however, with sliding contacts that are controlled from inside the vehicle. The coil is adjusted for minimum SWR.

The antenna also has a small switch in its base that closes temporarily once with each turn of the motor. Screwdriver antenna controllers, such as the one seen in Figure 14-4, count the number of switch closures as the coil contacts move up and down. This way you can store pre-sets to position the antenna automatically. Advanced controllers can use the radio’s computer interface to read the operating frequency and set the antenna accordingly. This is more convenient than swapping an antenna.

Hamstick-type antennas are least expensive, and screwdriver antennas are most expensive. Performance varies dramatically, depending on mounting and installation, so predicting which gives the best results is difficult. An advantage of the screwdriver antennas is that they can be adjusted to suit the circumstances even if something is close to the antenna or wind is bending the whip section.

Mobile signals are generally stronger at 20 meters and up. The need to keep antennas small makes operating on the “low bands” (10 MHz and below) more of a challenge.

The type of antenna mount you select depends on where it can be mounted and how your vehicle is constructed. HF antennas are pretty large, and it takes a three-magnet design for a mag-mount to be secure at highway speeds. Adjustable trunk-lip and hatch-lip mounts are available, such as the Diamond K400 (www.diamondantenna.net/k400.html), which can hold a good-sized mobile antenna, even one of the smaller screwdriver antennas.

To avoid scratching paint with a mag-mount you can buy circular magnet pads or in a pinch, use a plastic sandwich bag beneath the magnet.

No matter what kind of mount you use, there should be a solid connection from the mount to the body of the car. The connection may be made by the mount itself, such as by set-screws. If a mag-mount is being used, the connection can be made with a heavy wire attached to a body screw somewhere nearby, such as in a door frame.

Mobile antennas depend on the vehicle’s metal body to provide a “ground” or counterpoise for proper operation. Many vehicles are made with plastic or composite panels, hoods, trunk lids, and so forth. These look just like metal, but a magnet-mount antenna will not “stick” to them. Clamp-on or drilled-hole mounts depend on being attached to a metal surface to work. A body shop can help you find a metallic support such as a roof support column or door frame.

To get some good ideas for mounting antennas, go to a hamfest and take a walk through the parking lot looking for mobile antennas. See how they are installed and with what type of mount. If you can find a vehicle like yours, even better! Take photos of good mounting ideas for reference later on.

Your antenna mount may come with feed line attached, typically RG-58 for HF antennas although miniature Teflon cables are another possibility. If not, RG-58 is the smallest regular coax you should use. Smaller cable, such as RG-174, is too lossy, particularly at high values of SWR.

When running the cable between the mount and the radio, be sure it will not be pinched or worn by moving seats or doors. If the mount is on a hatchback or swinging door, leave a loop of cable to allow for the motion. Running the cable underneath weatherstripping helps protect it, as well.

If adjusting your antenna doesn’t produce a low-enough minimum SWR, you will probably have to try adding a matching component or antenna tuner. The MFJ-909 or -910 (www.mfjenterprises.com) may be all you need. They add a small amount of capacitance to your antenna. If that doesn’t do the job, you will need an adjustable antenna tuner, either manual or automatic, for the transmitter to output full power.

Portable Antennas

At VHF and UHF, portable antennas are very small, lightweight, and easy to pack and carry. Even for the 6 meter band, a three-element Yagi or 2-element quad can be quickly disassembled and carried in a gym bag. On higher-frequency bands, longer, higher-gain antennas are practical, as well. Two or three sections of a painter pole or telescoping tubing are sufficient to hold the antenna with a minimum of guying. Three light-duty ropes and some tent pegs are sufficient to hold up most antennas and masts.

At HF, however, the larger antennas are more difficult to deal with. You can try a lightweight wire antenna if you can find a way to support it well above the ground. Trees or lightweight fiberglass masts are your best choices. Vertical antennas need a sturdy base, often a set of guy ropes, and usually a set of wires to make a ground screen.

A more convenient choice may be the portable antennas designed exactly for this type of operation. The Buddipole designs (Figure 14-8a; www.buddipole.com) are well-known and easy to set up. Each of the horizontal sections is adjustable so you can create a dipole for the 40 through 2 meters bands. Turned vertically, the TW vertical dipole (Figure 14-8b: www.dxengineering.com/parts/dxe-tw-2010l-p) can be adjusted to cover several bands. Both the Buddipole and TW designs are supported by a tripod which makes them easy to support, even in the wind.

Small, portable antennas are a compromise, trading performance for convenience. If you can put up a higher, longer antenna, do so. You’ll find the performance to be much better.

Portable Power

In Figure 14-6, K7WA is using a lead-acid storage battery to power his 100-watt transceiver. This certainly enables him to put out a strong signal but it’s not a practical choice for carry-able stations! What other options are out there?

• Lead-acid storage: Large and heavy but these batteries can supply a lot of power. When fully charged, they can run a QRP transceiver for an entire weekend.
• Lead-acid gel-cells: Available in a wide range of sizes, these are still heavy but smaller than car or tractor batteries; can be trickle-charged.
• Li-ion: Multi-cell battery packs are fairly lightweight and can be charged quickly; good for QRP operations; must have a Li-ion charger.
• Li-iron-phosphate (LFP): Better performance than Li-ion and constant voltage output, but expensive; must have an LFP charger.
• Solar panels: Bulky at the size needed to run a radio directly; can be combined with a battery pack and charger; combination panel-charger-battery units available.

When you’re not using an AC-powered supply, you need to use equipment that can operate from a wide range of voltages. Batteries discharge or a cloud can shade a solar panel. Most 100-watt transceivers need to be supplied with 13.8 V plus-or-minus a couple of volts. Low-power QRP radios are more tolerant but you still need to keep the input voltage above the specified minimum. When power supply voltage drops to the minimum, the radio may begin operating erratically or transmit a poor-quality signal.

Field Day

The annual ARRL Field Day (www.arrl.org/field-day) is one of ham radio’s largest events. (See Figure 14-9.) Held on the fourth full weekend of June, more than 50,000 hams from around North America are involved in some years. Clubs, informal groups, and individuals are all involved in this annual exercise.

Field Day operating frequently involves disassembling and moving equipment from a fixed station to a temporary location and operating for the weekend. Assuming you can drive to the site, this kind of portable operation can be approached much like building a fixed station, but with the expectation that it will be disassembled after a couple of days.

Much of a successful Field Day revolves around antenna selection and installation. It’s a challenge to erect effective HF and VHF/UHF antennas using temporary supports. You have to choose between quick-but-low and difficult-but-high antenna systems. Instead of heavy towers, you’ll have to make do with masts. Can you really get a line over that high branch in a tree, and will it stay there for the weekend? Remember that a compromise antenna that can be put up and put on the air makes more contacts than a complicated “Field Day Special” that turns out to be a little too special to stay up!

Field Day is a great opportunity to see if you are really prepared to respond following a disaster or to provide effective public service. Is all the gear ready to go? Can you find all the accessories? Does it all work when away from home or a club station? These are good questions to answer before you need to respond to a real emergency.

Many public service teams treat Field Day as an “incident response,” including organizing the event according to the IMS plan that a real served-agency would require. An emergency operations center (EOC) or communications trailer station can be put to the test during Field Day — there is even a special category for them in the competition.