With all the banter about KX3's and amp's, on batteries for "Emergency" use.
Please remember, that battery makers specify the AH figure, for a typical C/20 rate, (1/20th the nominal AH current value.) Some may quote it at C/10, check the data sheets for the battery of interest, they will often have example of typical discharge voltage curves, for various discharge rates too. That can be *Very* enlightening! Without going into specifics, 20A from a 7AH battery may on the face of it give you some 20 minutes operating (7 / 20 * 60) but in practice you'd be lucky to get even near half that of actual "Practical Use" of your amp'. Probably no more than 5 mins TX time at most before it all starts to collapse. The charge/discharge efficiency of SLA (and most other batteries) falls like a stone with high discharge currents, also, also the voltage is lower at high currents as the battery nears "empty", but many high current loads (Amp's etc) don't work well (if at all) at those lower voltages, so in practice you get even less usable run time.. Try your intended battery with something else that is a similar load, while monitoring the voltage... For Lithium family cell's, they (should) have a monitor circuit that will simply cut off the load to prevent over discharge (and resulting thermal "instability") leaving you totally dead in the water as it were. As others have said, if you don't already have the needed techniques, opt for some narrow band mode (the built in PSK31 if your CW is not good enough?) to get a message out if needed via as resonant as you can get it antenna.. Even 3W of that can be reliably decoded many 100's of miles away, on the right frequencies. Don't forget the counterpoise if using a wire. However, farmers fences can make good grounds, also antennas at times! :) (Avoid "Electric" fences of course!!!) A repeated short distress message (SOS or PanPan Medico?) including an international grid reference, sent on one of the QRP frequencies, I suspect would possibly result in some action, but I wouldnt garrantee it on HAM bands sadly.. Remember too, what is said somewhere in all mobile phone handbooks that I have ever seen (that no one ever reads) "this device uses radio signals, that are by their nature unreliable, you should therefore not rely on this or other radio service for emergency call's." But what do most people cite for their ownership of a mobile 'phone? "Use in an emergency"! If you **NEED** such comm's, perhaps a satellite 'phone is more appropriate, and even they are not without issues. Or carry an EPIRB with you if you're hiking well away from anywhere. Activate one of them, even on land, and all heck will come your way in very short order!. Even a sat'phone and EPIRB are lighter and smaller to carry than a KX3, amp and battery... But best of all, tell people you trust more or less where you are going, and your planned route + intended return date/time, and whatever late tollerance figure you think, just in case of delays. Then, if you don't appear, or contact them from elsewhere by any means, they can call the cavelry out. Of course, if your plans change "on the fly" get a message back to them, to that effect... Enjoy the outdoors, but stay safe. If you have known medical issues (type one Diabeties for example) talk to your doctor before planning any extended trip out "into the sticks", just in case. Given the choice, I'd prefer to ensure I can cary/find enough water & food, also perhaps a simple bivoac shelter kit for any significant hike out, also any needed indiginous venom antidotes etc, than carrying any Ham Radio gear I think. Regards. Dave G0WBX. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
