[KYHAM] KEN Training for Sept. 16: Getting the Most from Your Hand-Held, Part 3

[Ron Dodson]

Getting the Most from Your Hand-Held Transceiver (Last of a
3 Part Series)
�1998-2002 Virginia RACES, Inc. Nonprofit reproduction
permitted with source attribution By Ed Harris, KE4SKY,
Virginia RACES State Training Officer 

BATTERY POWER BASICS

A common error of new  RACES / CERT operators is failure to
plan to carry enough battery power.  Always carry at least
one spare charged NiCd pack and AA battery case, which
enables you to keep operating when the power goes off, if
you can't recharge your NiCd pack. 

Cycle and recharge dry NiCd packs monthly.  Write the
recharge date on a strip of tape on each pack.  In cold
weather keep NiCd packs warm by keeping them in an inside
coat pocket and not exposed on your belt.

An adapter cord to power your transceiver from an auto
cigarette lighter plug or a gel cell battery is needed for
extended operation.  Cigarette lighter cords are often
unreliable because auto sockets aren't the best conductors,
due to contamination and size variations, which cause the
plug to vibrate loose.  As an alternate power source, you
should still have one, because they are ubiquitous and in a
pinch, much better than nothing!   

Portable power packs such as Quantum are excellent, but
expensive.  We encourage our operators to make their own
using 12-volt gel cell batteries obtained from local
hospitals.  Sealed lead-acid (SLA) batteries are used to
power emergency lighting, alarm systems, medical instruments
and computer backup power supplies.  They are replaced on a
fixed schedule, usually before they are worn out. Because
SLA batteries require disposal as hazardous waste unless
recycled or reused, a hospital donation to your RACES or
CERT communications unit reduces their disposal cost. 
Contact your local hospital and explain how SLA batteries
they discard can support auxiliary emergency communications
in your community. 
  
Donated SLA batteries must be inspected, recharged and
load-tested.  Any 12V batteries with an open circuit voltage
(Voc ) of 12.8V or more are tested immediately and
distributed for reissue, if OK.  Batteries with Voc <12.8V
are connected in parallel across a regulated 13.8V power
supply.   Those which are not accepting charge after 4 hours
are discarded.  Total charge time and current should not
exceed 140% of battery capacity.  Gel cells should never be
recharged at over 14V due to gassing.   
Reject batteries if their internal resistance exceeds an
ohm, as determined by voltage drop divided by the current
load in amps.  Good batteries suitable for re-issue should
not drop below 11.7V under a test load approximating AC,
their amp-hour capacity, for 30 secs. or AC/5" for one
minute. 

A simple test load for small gel cells up to 20ah is a 50w,
12V-marine/RV bulb or automotive droplight. This equals
about 3.8A, approximating a mobile radio on low power 5w
transmit or a portable 2-meter hand held, plus a laptop PC
and packet TNC.  Using two bulbs and Y adapter simulates a
mobile or brick amp at 25w RF output.  This is a good test
load for batteries to 30amp-hours.  In a good battery
voltage drop stabilizes quickly, does not fall below 11.5V
under load and recovers quickly when the test load is
removed.   

STANDARD POWER CORD CONNECTORS

Auxiliary power cords for low current devices up to 8A
should use twin lead, red-black AWG14 or AWG16 with Molex
Series 1545, 2-pin polarized connectors and .093
pins.  Female pins are assembled into the male plug,
(attached to the power source) and the male pins into the
female receptacle, (connects to the rig). 

The plug, receptacle and pin set is rated for 8A continuous
duty and costs $0.99 from Radio Shack, Part No. 274-222. 
Wiring is simple.  The end of the two-conductor Molex plug
in cross section resembles a 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.
Reinforce the wires behind the plug and receptacle with heat
shrink or tape.  On the battery leads attach crimp female
tab terminals to fit the male tabs on the battery.   Solder
tabs to battery terminals and tape over them to prevent
accidental shorting in handling.

It is recommended that you rig two sets of cords directly to
your car battery to power your portable or mobile radio, and
laptop computer, if you will send data via packet radio to
your EOC.  Splice type fuse holders onto both leads, as
close to the battery as possible. 

If all you have is a portable transceiver, the above
information will help to ensure that you can provide an
adequate signal for reliable emergency communications. 
Doing so is vitally necessary to 
enable your volunteer disaster unit to complete its mission
efficiently and safely.  More training materials for amateur
radio operators to learn essential core skills in emergency
communications are featured on the Virginia  RACES Training
page located at:

http://www.racesva.org/Training/training.html