Subject: Hand Held Transceivers KE3FL: The opionons expressed here are not those of the webmaster :) I have had good results using good HT's with external (cigar lighter) power, good external speaker-mikes and power amps when needed. "Getting the Most From Your Hand Held Transceiver" Copyright 1997, Nonprofit reproduction permitted with attribution C. Edward Harris, KE4SKY, AEC Fairfax ARES When limited to "barefoot" operation with a "rubber duck" on simplex, HTs are not adequate as a primary rig for emergency communications. I started with an HT when I first got my license, but I now recommend full-powered mobiles as a first rig, although I admit they don't work for everyone. If all you have is an HT, the following will help you "make the most of it." An HT does make perfectly good sense for: 1) Anyone who doesn't drive; 2) Commuters who use public transportation; 3) Controlling a dual-band mobile in cross-band repeat or; 4) As a "spare," backup or loaner. FACTS ABOUT HT ANTENNAS National Bureau of Standards tests of Public Safety high band and amateur 2-meter antennas indicate that a "rubber duck" has -5db "negative gain" compared to a quarter wave held at face level. In terms of effective radiated power (ERP), a 5w HT with rubber duck antenna, held at face level radiates 1 watt. Placing the HT on your belt attenuates the signal -20db further, reducing ERP to only 50 milliwatts! UHF results are little better. This simple helical spring is intended to withstand rough handling, but is not indestructible. Flexible antennas used on Idaho fire lines for several weeks showed a 60 percent failure rate. California RACES recommends that flexible amateur antennas be replaced annually or when they show any apparent kinks or wear to visual inspection. A simple, inexpensive and effective expedient which improves a "rubber duck" is the "tiger tail". You can make one of these using a quarter-wave (18-3/4" for 2 meters) piece of #14 through #20 braided wire, crimped and soldered to a battery clip. Reinforce the soldered connection with shrink wrap or tape to resist flex. Clamped to the outer collar of the BNC connector on your HT antenna, it acts as a counterpoise so that RF from the HT doesn't couple with your body. A tiger tail is directional and can be used to change both radiation angle and direction. It gives best simplex performance when tied to an elastic lanyard, hooked over your thumb, pointing your hand horizontal to he ground in the direction of the station you are trying to "hit." Numerous antennas work much better than the "rubber duck" that comes with an HT. A flexible 1/4 wave or telescoping half-wave antenna are recommended. A 1/4-wave used with a ground plane, or at face level with a counterpoise has "unity" gain, a 5 db improvement over a rubber duck, because most of the signal is radiated. Using an HT at 5 watts with a 1/4 wave mag mount on an improvised ground plane, or telescoping half wave with a "tiger tail" improves simplex readability. In marginal locations a telescoping half-wave is a better performer. A half wave used without a ground plane has the same unity gain as a 1/4 wave when used with a ground plane. Adding an effective ground plane or counterpoise to a half- wave produces 2 db of gain. Telescoping antennas work best when operating stationary or in the open, avoiding side impacts or rough handling. A telescoping half wave can be attached to a coax jumper and pulled into a tree, dangled out a window, attached to a window pane with suction cups or used with a window clip door mount, mobile in city traffic. Avoid prolonged mobile use at high speed, because excessive flexing will loosen the internal electrical connections. Never collapse a telescoping antenna by whacking it down with the palm of your hand. Gently pull it down with your fingers. If you note any wobbling or looseness, replace the telescoping radiator, if possible, or replace the antenna. Flexible antennas are safer when working in close quarters around people and are more durable when walking through dense vegetation during search and rescue operations. They are a good choice for dual-band transceivers because telescoping antennas are usually limited to a single-band. Dual-band flexibles are usually optimized for one band and merely "acceptable" on the others. Most approximate a 1/4 wave on 2 meters and a 5/8 wave on 70 cm, but how efficient a particular antenna is can be determined only by testing. If you want to buy one emergency HT antenna, without risk or experimentation, the telescoping half-wave, flexible quarter wave and quarter wave mobile magnetic mounts offer the best "bang for the buck." A telescoping half-wave boosts practical simplex range of a 5 watt, 2-meter HT from the typical mile or so with a rubber duck to 3 miles or more over suburban terrain. Adding a tiger tail further extends readable simplex range under the same conditions to 5 miles or so. Whatever HT gain antenna you get should be rated for 25W so that it can also serve as an emergency antenna for the HT with a brick amp or a mobile at medium power. A 1/4 wave mag mount with 15 ft. of coax and a female UHF to male BNC adapter can be used with an HT, connected to a brick amp or higher powered mobile rig. It works best on a car, but a suitable improvised ground plane can usually be found around the home or office, such as a metal filing cabinet, metal trash can, rain gutter, refrigerator, window air conditioning unit, balcony railing or other large metal object. An effective, portable improvised ground plane is easily constructed from a pipe floor flange, 1/4" bolts, nuts and lock washers, attaching 20" radials bent from #10 solid steel or aluminum wire. BATTERY BASICS It is highly recommended that you routinely carry two fully charged nicad packs and an extra AA battery case, so you can continue to operate if you can't recharge your nicads. It is important in cold weather to keep nicads warm, not exposed on your belt. Adapter cords enabling you to use DC power taken from an auto cigarette lighter plug or a gel cell battery, are needed for extended operation. The popular cigarette lighter plug power cords are often unreliable because auto lighter sockets are often contaminated and not the best conductors. They also vary in size, so the plug can vibrate loose. As an alternate source of power, everyone should still have one, because they are ubiquitous and in a pinch, much better than nothing. Commercial power packs are excellent, but expensive. Your group can make its own using Yuasa NP2-12 or similar 12-volt, 2 amp-hour gel cells. These fit in a coat pocket, run an HT all day or power a VHF mini-amp for 3 hours at a typical duty cycle. SLA batteries used to power medical diagnostic instruments, alarm systems and UPS are replaced on schedule before they are worn out. They require disposal as hazardous waste unless recycled or reused, so a hospital's "donation" to your ARES group reduces their disposal cost. EC's should write a letter to local hospitals, explaining how gel batteries they discard are useful to provide power for your emergency communications activity. It is often possible to obtain a quantity free for the asking, with no more trouble than signing a hand receipt to satisfy the environmental officer and writing a thank you letter to the hospital administrator. Assemble auxiliary power cords to power your HT and small brick amp following the standard wiring configuration shown in the ARRL ARES Resource Manual. Use twin lead AWG12 to AWG16 gage "zipline" with Molex Series 1545, 2-pin polarized connectors and .093 pins. In ARES practice the female pins are assembled into the male plug which is attached to the power source, and the male pins into the female receptacle which is attached to the rig. The plug, receptacle and pin sets cost $0.99 each from Radio Shack, Part No. 274-222 and are rated at 8 amps, which is adequate to power small brick amps up to 35w output. Electronic suppliers carry the genuine Molex parts in bulk. These are rated at 11 amps and suitable for mobile rigs up to 50w. Wiring is simple. The end of the two-pin Molex plug in cross section resembles a little 2-story house with peaked roof. Remember proper polarity by using the word associations "red roof" and "black basement," or "pointy positive" and "flat black." Crimp the wires in place before soldering to ensure a strong connection. After inserting the pins into the plug and receptacle, check fit of the assembled fitting and reinforce the wires behind the plug and receptacle with heat shrink or tape. On the battery ends attach crimp type .187" female tab terminals to fit the male tabs on the battery. Wire a plug receptacle onto the leads of a 12-15v, 500mah to 900mah charger. A depleted battery is restored in 4 to 6 hours. Gel cells larger than 5 ah may be left on a 12-14V DC "smart" charger of 1 amp without harm. You can rig two sets of cords directly from your car battery to power an HT and your brick amplifier without using the cigarette lighter plug. This is a good arrangement for using an HT in the vehicle during your commute and taking it with you when you park the car. Splice AGC type fuse holders on the red or "hot" leads, as close to the battery as possible. Use a 2 amp fuse for the HT and 10 amp for the small brick. Use a heavier gage wire than needed to reduce voltage drop, and use different sizes, such as AWG 16-18 for the HT and AWG 10-12 for the amp, so the two cords are readily distinguishable by both sight and feel. HAND HELD DUTY CYCLE LIMITS If you subject compact HTs to frequent full power 5w transmissions of several minutes duration they overheat and the final power transistors may fail prematurely. Kenwood and Yaesu state in their service manuals that their HTs are rated for 20% duty cycle at maximum RF output, or 30 seconds of transmit to 2 minutes of standby. After I first got my license, I burned up three sets of "finals" in less than a year with long winded QSOs using a Radio Shack HTX-202 which produced 8w when powered at 13.8V from my auto cigarette lighter plug! When the warranty ran out, I replaced it with a Kenwood TH-22 and soon repeated the same result. Kenwood's Virginia Beach service center politely admonished me that I was "exceeding the recommended duty cycle" and should buy a mobile. I followed their advice and am satisfied with my two Kenwood mobiles, but I sought out other HTs and pass that advice along. Of the popular 2-meter HT's, Standard does not restrict duty cycle on theirs, rating their amateur hand helds equal in that respect to their aviation, marine, commercial and public safety portables. My advice is that unless your HT is a Standard, older Icom or converted commercial gear, it is best to use your HT mostly on medium or low power for long winded rag chews and restrict full power 5w use to short transmissions to save the finals. If you have a need for high power transmissions of several minutes duration and can't replace or supplement your hand held with a mobile rig, my advice is to get a brick amp to do the heavy work. This keeps your HT from overheating, and helps ensure a solid copy signal for simplex operation. ADVICE ON BRICK AMPLIFIERS An ideal amp for HT owners to upgrade portable ARES/RACES equipment, at modest cost should weigh under a 1 pounds, be capable of 10 to 15w output when driven by an HT at 1w, or 20 to 40w output when driven by the same HT at normal 2 or 3w output from its 7.2 volt nicad battery pack. It should draw no more than 8 amps current at its maximum rated output, enabling it to operate safely from the .093 pin Molex Series 1545 connector or fused cigarette lighter plug. An FM-only brick without a preamp is fine, unless you have an all-mode rig or equip your portable station with a notch filter and/or cavity bandpass to suppress intermodulation distortion which a preamp will bring in from paging transmitters, etc. Brick amps which have been satisfactory in our group experience are the Mirage B-23, the dual- band Mirage BD-45, and RF Concepts Mini 144. There are larger amps which produce 100+ watts output when driven by an HT, but their size, 5+lb. weight and 20+ amp power consumption lend them more to base or rover, wide area simplex, than to "backpack portable." Be wary of bargain, "no-name" amps you see at ham fasts or in discount catalogs. Some are not aligned for the entire U.S. 2-meter band, many lack thermal protection circuitry for over voltage, overdrive or high VWSR or simply have an inadequate heat sink and will overheat and quit. A friend bought an amp from MCM Electronics for $69 which worked fine on packet, negative offset repeaters and simplex from 146.415 to 146.585, but would not function above 147 MHZ. MCM took it back and refunded his money. Though aware of duty cycle limitations in small amps having minimal heat sink, I still wanted a tiny amp for my personal kit, for when space or weight constraints required leaving my 16 pound backup bag with dual-band Mirage amp behind. The Maxon CA-1461 is only 1.7"x1.7"x5.5" and weighs 9 ozs. I bought the last remaining demo unit at the Gaithersburg hamfest, but it did not produce rated output. The seller told me to return it to Maxon. Instead, I had K4KXK open it up. John found it was aligned for marine and VHF high bands, but it had an adjustment "pot" and came down to 2 meters. Maxon later confirmed that this accessory for a discontinued commercial product is aligned from the factory for 153-160 MHZ and has a 7 MHZ passband, adjustable from 140-172 MHZ. Because the "Tx" and "Ant" ports were unmarked and the jumper provided had male BNC and UHF connectors, it led me to hook it up reversed, but fortunately, nothing inside was damaged. Using a double-male BNC to connect the HT to the input and putting a dummy load on the UHF output, John soon got it working. It now produces 15w out with 1w drive, 25w out for 2w in, and 35w out for 5w in. and doesn't get uncomfortably warm after five minutes of key- down at 15w into a dummy load, though it does after 5 minutes at 25w or 3 minutes at 35w. It worked well on packet during the Marine Corps Marathon, but a longer shakedown is needed before recommending that you find one to "mod." Unless you know how to modify commercial gear, I recommend that you seek a quality amp of known brand, with ample heat sink, from a dealer who backs up the product, rather than seeking the smallest "box" at the lowest price. For further information see the Virginia ARES web page at: http://www.aresva.org