Thanks Paul and Kris for your suggestions.
While 29 MHZ could well be better, we do not have that option. These
are non-amateur operations although the base station and repeater are
owned and operated by local amateurs. We do have a few amateurs
scattered amongst the search teams too - but most of them are trampers,
deerstalkers & Police using frequencies allocated for emergency work..
We have used 440 MHZ occasionally for linking with our own group but
it falls down badly in the dense bush particularly when leaves & trees
are wet.
So 141 MHz it is, with 5 and 3 MHZ available for longer hops -
although rigging aerials for these is not easy in the bush.
The repeater includes a 28 AH battery - making about half the weight and
we allow for connecting an external battery (something else to carry in
by backpack or chopper) if the search goes over 4 days. The whole
business of power consumption is helped by a semi-sleep mode, in the
absence of traffic, the repeater shuts down everything not needed for
listening. It takes 2-300 milliseconds to fire up again so our users
are told to delay briefly between pushing the mike button and opening
their mouths.
You mentioned 8 hours time for the portables, yep that is about right
so they carry spare batteries - particularly if they are camping out
overnight and/or have an automatic tracking GPS running off the same
battery.
I will do more experimenting with aerials thanks.
Gordon ZL1KL
