HF Mobile Installation and Operation

Why HF Mobile? HF Bands are used for Long and Medium haul communications. VHF & UHF for short range or local communications.

Why HF Mobile? With today’s modern compact transceivers it is possible to have portable HF communication in our vehicles.

Components Of A Mobile Station Transceiver Antenna System (radiator + matching network) Power Source

Transceivers There are many HF transceivers on the market made specifically for mobile or portable use.

Transceivers Units designed for mobile work usually have easy to read displays. They should be mounted so that they do not affect the driver’s ability to safely operate the vehicle.

Yaesu offers many models for mobile operating

ICOM has its IC-706 and IC-703 (QRP) models

Kenwood’s TS-480 is available in a 200 watt version

Alinco DX-70 TH HF+6m All Modes

Antenna Systems Mobile antenna Systems are comprised of a radiator and a matching network. Mobile antennas have a low impedance, therefore, a matching network is required.

Antenna Systems Systems can be mono-band or multi-band. Multi band systems can be tuned from inside the vehicle while in motion or from outside the vehicle when stopped.

Antenna Systems: Good, Bad and Ugly All systems have some sort of loading. Center loading is best. Base loading is least effective Because of their skinny coils, helically wound antennas are a compromise of the other two designs.

SWR A good SWR is not an indicator of an effective antenna system. Click your heels and say this three times. Think of a dummy load; it has a good SWR but is not an effective antenna.

BIG NOTE * *An entire program can be had just on the discussion of antennas. All mobile antennas are a compromise of some sort and much consideration should be given to safety and the type of operating that is being done, as well as spouse appeal. End of Big Note.

Multi Band Antennas Motorized Automatically tuned Manually tuned

Center Loaded Antennas Whether motorized or manually tuned, these are by far the most effective type of mobile antenna.

Motorized Antennas Commonly called “screwdriver” antennas because the first designs used cordless screwdriver to drive the screw that adjust the coil. Uses a motor to move a large coil up and down to obtain resonance. System consist of the large coil, whip radiator, shunt coil at feed point and a control unit

Motorized Antennas Advantages Multi band. Can be tuned from inside the vehicle. Hi “Q” Very effective antenna. Computerized control units can be added for quick band changes.

Motorized Antennas Disadvantages Large and heavy; requires strong mounting and support brackets. Hi “Q” make tuning on low bands very touchy.

High Sierra motorized antennas

Lil Tar heel motorized antenna

The Yaesu ATAS-100 Active Tuning Antenna System provides HF/VHF/UHF coverage with automatic motorized tuning. Utilizing control signals from the transceivers microprocessor received via the coaxial cable, the ATAS-100's internal motor adjusts the radiator length for best SWR.

Manually Tuned Center Loaded Multi Band Antennas Some types use taps to tap the coil at a resonant point. Other designs use multiple resonators or change resonators on a single mast.

Bug Catchers Advantages Very effective center loaded antennas. Large coils results in Hi “Q”. Can be tapped to use on multiple bands

Bug Catchers Disadvantages Large and heavy requires strong mounting and support. Band changes have to done while parked.

Large coil and center loading make the Bugcatcher an excellent performer. This unit is shown with a capacitance hat.

Capacitance Hats Loss resistance is lowered by removing turns in an inductor coil. This is then compensated for by adding capacitance above the coil. The more capacitance that is added the less inductance is needed for a given frequency.

CPU Controlled Automatically Tuned Multi Band Antennas Uses a CPU controlled matching network and a whip antenna. Can match almost any frequency. Some models are capable of matching over a million LC combinations in less than a second.

CPU Controlled Automatically Tuned Multi Band Antennas System can be made low profile. Internal memories save settings an allow quick band changes.

CPU Controlled Automatically Tuned Multi Band Antennas When used with a loaded whip designed for the tuner these systems can be extremely effective. When used with a 8 ft. whip the system is less effective than loaded whip or center loaded systems.

Interior view of YAESU FC-40 CPU controlled remote tuner for FT-897 & FT-857 radios

ICOM AH-4 CPU controlled auto-tuner for use with many ICOM radios

ALINCO EDX-2 for USE exclusively with ALINCO DX-70T, DX-70TH, DX-77EQ, DX--77T, DX-701 and DX-707

SGC makes an entire line of reliable CPU controlled auto-tuners that will match almost any radiator with any radio.

SGC’s QMS system is rugged, mounts on any vehicle and includes the CPU tuner and loaded whip antenna.

Mono-Band Antennas Operate on a single band. Can be effective. Can be made low profile. Can be easily mounted. Inexpensive way to enter into HF mobile.

Good results can be had with mono band antennas Good results can be had with mono band antennas. These “sticks” can be easily mounted and are lower profile.

Antenna Mounting Which ever antenna is used the mount has to be solid, strong and safe. No sharp edges or protrusions that could cause injury. Anything flying off a moving vehicle can be deadly. Safety first. Obey DOT laws.

Custom Heavy Duty Mount

Notice the heavy braided ground strap added to this custom mount ensuring a good bond to frame.

Custom Heavy Duty Mount

Don’t Be Afraid To Drill A Hole

Mounting Alternatives

Mounting Alternatives

Grounding A good solid ground connection to the vehicle frame is necessary for good antenna performance. Make ground connections as short as possible and to bare metal. Ground connections can be weatherproofed with undercoating spray.

Bonding Bonding is connecting together loose or moving metal parts of the vehicle with grounding braid. These areas are doors, trunk and hood lids, mufflers and exhaust parts, and any other areas where metal parts may rub. Rubbing metal parts can cause excessive noise in the receiver.

Power Power should be taken directly from the vehicle’s battery. Both positive and negative leads should be fused at the battery. If there is a fault anywhere after the fuse the fuse will do it’s job and break the circuit.

Both leads should be fused at the battery to prevent fire.

Power Drawing power directly from the battery helps eliminate noise. All leads should be 10 ga. or larger stranded wire and be kept as short as necessary. Protect wires with rubber grommets where they pass through the firewall or any metal.

Power Flexible conduit and wire ties make the job neat and also protect wires form accidentally being cut or shorted. If using an auxiliary battery, make sure that it is securely mounted with proper electrical connections and change over charging circuits.

Grommets and conduit protects wires. Cable ties keeps things neat.

Flexible conduit and wire ties keeps all wires dressed and neat.

Wires and cables Keep all wires and cables as concealed as possible. Not only does it make the job look neat but, it also protects them from damage and prevents anyone from tripping as they enter or exit the vehicle.

Mounting The Radio The radio should be mounted in such a way that it does not interfere with the driver’s ability to safely operate the vehicle. Period.

Mounting The Radio Say it again. The radio should be mounted in such a way that it does not interfere with the driver’s ability to safely operate the vehicle. Period.

Mounting The Radio The mount should… Be secure. Not obstruct the driver in any way Keep the unit within easy reach and view. Allow proper air flow and not be in a heat source such as heat ducts.

Mounting The Radio Unsecured objects in a vehicle are potential hazards in an accident. They can be thrown about, hitting the occupants with deadly results.

Mounting The Radio A lot of the mobile HF radios today offer a detachable remote control head that allows to “face” of the radio to be mounted in a safe and convenient location while the main unit is mounted out of the way under a seat or in a trunk.

Pedestal mounts work well in pick up trucks…

…or SUVs

An aftermarket visor shelf makes a convenient and safe mount for this ICOM IC-706 control head.

Gooseneck allows control head to be adjusted.

Control head of this YAESU FT-100 is mounted safely and securely and allows the driver to view it at a glance.

YAESU FT-857 control head mounted on gooseneck and radio mounted under passenger seat. A neat and secure installation.

Noise Grounding and shielding should eliminate most noise in your receiver and on your transmitted signal. Ferrite on speaker leads and other leads to electronics and CPU modules can remedy RFI in the vehicle.

Noise Previously mention bonding of metals parts can prevent unwanted receiver static noise. A large capacitor from the positive lead to ground will eliminate AC noise on DC power cables.

Noise RFI to your vehicle can be a problem. Some fuel pumps or other devices have been known to shut down in the presence of strong RF signals. Consult your vehicle manufacturer for any Technical Service Bulletins (TSB) regarding these issues.

Publications “Your Mobile Companion” http://www.arrl.org/catalog/?item=5129

Publications ARRL Handbook http://www.arrl.org/catalog/?item=9280

Publications ARRL Antenna Book http://www.arrl.org/catalog/?item=9043

Resources ARRL on the web: http://www.arrl.org/tis/info/HF-Mobile.html http://www.arrl.org/news/features/1999/11/05/1/

Contributors Thank you to all who supplied pictures of their mobile installations: AB1ER, N1RWY, W2WJO, K3CAV, W3IZ, N5PR, K6OWL, W6PW, WØWEB

Contact Norm Fusaro, W3IZ ARRL Affiliated Clubs/Mentor Program Manager 225 Main St. Newington, CT 06111 860-594-0230 w3iz@arrl.org