On Thu, 2 Sep 2010, Gordon Cooper wrote: > I guess that I do not have much to contribute on this > thread but to me it is very interesting reading. Gary has my sympathy, > his problem is duplicated here. Much of my repeater work relates to a > low power portable repeater on 141 MHz. We live near a medium sized > mountain range which has plenty of deer and wild pigs. Hunters go > looking for them and perhaps get lost, or fall and break a leg. Also, > there are recreational trampers who just get lost . Several times a > year we have to go find, and rescue them. The last time was two days > ago at 6.30 am. For once, it was not raining! > > Our repeater runs 5 watts output, needs to run three or four days off > a gelcell, and most importantly has to fit into a backpack to be > carried to a convenient hilltop. Fortunately, the split is 3 MHz so > that the duplexer is of a reasonable size.
You need lower power output and a further split and a big battery. Even running a repeater at five watts with commercial handhelds out in the field (each of which have a battery that will make it for eight hours), you're going to need somewhere around a 33Ah battery, which weighs 25 lbs. > The problem is getting reasonable coverage. Sure the search areas > are fairly small but usually encompass several ridges and deep > valleys. We use vertical polarisation with a 5/8 whip on the repeater > and the search teams have flexible dipoles that fit into their > backpacks. Sharp ridges and steep slopes contribute to coverage > problems. Would circular polarization help?? I think not. Remember, a quarter-wave has significant energy in the pattern from about five degrees to eighty-five degrees; if you're dealing with valleys, this may be a better choice for an antenna. -- Kris Kirby, KE4AHR Disinformation Analyst
