In article ,
Cecil Moore wrote:

Estimate the number of hours out of that 12 hours
that you would be transmitting. Multiply that by
the current consumption during transmit. Multiply
the rest of the hours by the current consumption
during receive. Add them together to get an
estimate of the necessary ampere*hour rating
for the gel cell. Be sure to take into account
the minimum operating voltage required by the
hand-held.

.... but do consider the possible benefits of using a lower-voltage
battery. A lot of popular 2-meter HTs will develop a watt or so of
output power on 6 volts, and a couple of watts on 8 volts. You only
need 10-12 volts into the radio if you absolutely insist on getting
the full 5 watts out.

Such an HT, fed from a 6-volt SLA battery, and equipped with a
full-length "spaghetti noodle" whip antenna and a rat-tail wire
counterpoise, would probably outperform the same radio fed from 12
volts but using only the standard lossy "rubber duck" antenna... and
it would do so on both receive and transmit. The battery would weight
only about half as much... or, conversely, would allow for twice the
amp-hour capacity at the same battery weight.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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