From: Ed Harris

To: va.ares@ares.org

"Getting the Most from Your Hand-Held Transceiver"

Copyright 1998, Virginia ARES, Nonprofit reproduction is 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. I now recommend 50w mobiles as a first rig, but admit they don't work for everyone. If all you have is an HT, the following will help you to "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), this means that a 5w HT with rubber duck, radiates only 1 watt. Placing an HT on your belt results in another -20db attenuation, reducing ERP to 50 milliwatts! UHF results are no better...

    This simple helical spring is intended to withstand rough handling, but is not indestructible. Flexible antennas used on fire lines for several weeks showed a 60% failure rate. The California ACS recommends that flexible antennas be replaced annually or more often if they show any apparent kinks, abrasion or other wear to visual inspection.

    A simple, inexpensive and effective expedient to improve a "rubber duck" is a counterpoise or "tiger tail. Make this from a quarter-wave piece (19.5" on 2m, 11.5" for 220 and 6.5" for 440) of stranded wire, crimped and soldered to a battery clip. Always reinforce the soldered connection with heat shrink tubing or tape to resist flex. When clamped to the outer collar of the BNC connector on your HT antenna, the counterpose prevents RF from coupling with your body, so your antenna acts like a center-fed dipole instead of an end-fed dummy load! In marginal conditions extending the counterpoise horizontally, pointing your hand to steer the radiation pattern where you need it, produces a dramatically stronger signal than letting it "droop."

    Several HT antennas are commonly available which perform much better than the standard helical "rubber duck." Flexible 1/4 wave and telescoping 1/2 wave antennas work very well. A quarter wave provides unity gain when used with a "tiger tail" or counterpoise and held at face level. This simple device represents a 5 db improvement over a typical rubber duck, because most of its effective signal is radiated. If using the HT in a vehicle, use a mobile mag-mount antenna to provide an RF path outside the vehicle. This overcomes the -20db attenuation which otherwise results from operating your HT with a rubber duck antenna inside a metal vehicle. Always carry a male BNC to female UHF adapter so that you can attach your HT to a base or mobile antenna, when one is readily available.

    In marginal operating locations a telescoping half-wave is a better performer, because it provides the same unity gain without a ground plane that a 1/4 wave does when used with a ground plane. A 1/2 wave antenna can be pulled up into a tree, dangled out of a window, attached to a window pane with suction cups, or be used bicycle or motorcycle mobile, or in city driving on a window clip mount. Adding a ground plane or counterpoise to a 1/2 wave produces about 2 db of gain. A telescoping half-wave boosts the readable simplex range of a typical 5 watt, 2-meter HT from about a mile with a rubber duck to 3 miles or more, depending upon terrain. Adding a tiger tail improves receive and extends simplex range up to about 5 miles.

    Telescoping antennas are more fragile and work best when stationary or in the open, avoiding side impacts or rough handling. Avoid prolonged mobile use of telescoping antennas on mobile window clips at highway speed, because excessive flexing loosens 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 antenna.

    Flexible antennas are safer when working in close quarters around people and are more durable when walking through dense vegetation for wildfire suppression or search and rescue operations. They a better choice for dual-banders because most telescoping antennas are single-band. Most common dual-band flexibles approximate a 1/4 wave on 2 meters and a 5/8 wave on 70 cm, are optimized for one band and may resonate poorly on the other. Some antennas do perform better than others, 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 a telescoping half-wave, flexible dual-band quarter wave; or half-wave, dual-band-mobile magnetic mount, which will work without a ground plane, offer the best "bang for the buck." Whatever HT gain antenna you get should be able to handle 25W so that it can also serve as an emergency mobile antenna or be used with a brick amp. In our group experience the Comet CH-72 and SBB-1 dual-band flexibles, rated for 50w, work well. Adapters enable either to be used on an HT, attached to a mag mount or pulled into a tree with an attached tiger tail and coax leading from a mobile or brick amp.

    A mag-mount works best on a car, but an improvised ground plane can almost always be found around the home or office, such as a metal filing cabinet, metal trash can, cookie sheet, rain gutter, refrigerator, window air conditioning unit, balcony railing or any other large metal object. On bikes, motorcycles, Humvees or ambulances with fiberglass caps use a half-wave mobile antenna which doesn't require a ground plane.

    BATTERY POWER BASICS

    The most common operator error working public service events is failure to carry enough batteries to last all day. Always carry two fully charged NiCd packs AND an extra AA battery case, so that you can keep operating if you can't recharge your nicads. Cycle and recharge dry nicad packs every two to three weeks. Write the recharge date on a strip of tape on each pack. In cold weather it is important to keep NiCd packs warm by keeping them in an inside coat pocket and not exposed on your belt.

    Adapter cords enabling you to take power from an auto cigarette lighter plug or a gel cell battery are needed for extended operation. Cigarette lighter plug cords are often unreliable because the sockets are often contaminated and not the best conductors and they very in size so that the plug may vibrate loose,. As an alternate power source you should still have one, because they are ubiquitous and in a pitch much better than nothing.

    Auxiliary power cords to power your HT and small brick amp from an external gel call battery should follow the 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 set is $0.99 from Radio Shack, Part No. 274-222, rated at 8A, which is adequate to power small brick amps up to 35w output. Tech America carries the genuine Molex parts in bulk, which are rated at 11 amps and suitable for bricks or mobiles up to 50w.

    Wiring is simple. The end of the two-conductor Molex plug in cross section resembles a little 2-story house with peaked roof. Remember proper polarity by the word associations "red roof" and "black basement," or "pointy positive" and "flat black." Crimp wires 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 12-14V, 250mah-500mah wall transformer and for normal charging use a time and current to equal 120% of the battery's capacity. You can rig two sets of cords directly to your car battery to power an HT and your brick amplifier without using the cigarette lighter plug. This works well for commuters who use an HT in the car and take it with them after they park. Splice AGC type fuse holders onto both leads, as close to the battery as possible. Use 2 amp fuses for the HT and 10 amps for brick amps up to 40w. Use different wire gages such as AWG16 for the HT and AWG12 for the brick amp, so that the two different cords are readily distinguishable by sight and feel.

    HAND HELD DUTY CYCLE LIMITS

    If compact HTs are subjected to frequent 5w transmissions of several minutes, they overheat and the final power transistors may fail prematurely. Kenwood and Yaesu state that their HTs are rated for 20% duty cycle at 5w PEP, or 30 seconds transmit to 2 minutes of standby. This is not common for today's Hts. When I first got my license, I burned up three sets of "finals" during the year warranty period, powering an HTX-202 from an auto cigarette lighter plug.

    After the warranty ran out, I replaced it with a Kenwood TH-22A and within a few months repeated the same result. Kenwood's Virginia Beach service center politely admonished me that I was "exceeding the recommended duty cycle" for a hand held and should buy a mobile. I followed their recommendation, sought other HTs for ARES /RACES /Skywarn and now pass that advice along.

    Of the popular 2-meter HT's, only Standard doesn't restrict duty cycle and warrants their amateur hand helds equal to their commercial, aviation, marine and public safety band portables. Unless your HT is a Standard, old Icom "brick" or "pre-tiny" Yaesu, use low or medium power most of the time to save your finals and limit your full power 5w use to short transmissions.

    ADVICE ON BRICK AMPLIFIERS

    If you have 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 emergency simplex operation. An ideal amp for HT owners to upgrade portable ARES or RACES equipment at modest cost should weigh under a 1=BD pounds, be capable of 10 to 15w output when driven by an HT at =BD to 1w, or 20 to 40w output when driven by the same HT at its normal 2 or 3w output from a standard NiCd 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 best, because a preamp brings in intermod on FM. Small brick amps we have found satisfactory for ARES are use the Diawa 2035, Mirage B-23, B-34, dual-band BD-45 and Rf Concepts Mini 144. There are larger amps producing 100+ watts output when driven by an HT, but their size, 5+lb. weight and 20+ amp power requirements lend them more to contesting than to "backpack" portable ARES or SAR use. Be wary of, "no-name" amps at hamfests or in discount catalogs. Many are not aligned for the U.S. 2-meter band, lack protection for over voltage, overdrive or high VSWR or have inadequate heat sink so they overheat and simply quit. Seek a quality amp with ample heat sink, of a known brand which stands behind the product, rather than the smallest "box" at the lowest price.

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