Originally Posted by Jim Cate
Bill, thanks for that report. It supports my gut feeling that the specs are VERY conservative. Something that I have questioned before: the battery life is purported to be X years, but the required replacement period is X/2... how come?
The only question that comes to mind about your test is wondering if removing the antenna
meant that the transmitter did not actually come up to full working power. The SWR seen by the output stage of the xmtr would be very high, and in some circuits, this causes the output to be ramped down. True in my ham rig and in my AIS
... no idea about the EPIRB
I agree that the findings are interesting, but I, too, wonder how representative they are...
RE: Battery shelf life ratings: From what I've gleaned- without finding anything specific yet- it appears the manufactures may establish battery shelf life on worse case storage environment
[55°C/131°F in the case of the unit tested.]
RE: Was it transmitting without an antenna
? I pondered that as well. I may make an inquiry of the manufacturer but given the age of the unit, any response may not be representative of newer units.
I proceeded with the reasoning that EPIRBs are essentially designed to perform once. Given the 5 watts max transmit power [for 406MHz], I'm guessing they wouldn't bother with signal attenuation logic [hence the remove antenna and wrap in foil instructions...] because, considering the circumstances when one would be activated, any transmission
is better than no transmission
... [But I am only guessing; something I don't like to do...]
This is my gut feeling from years of being a link in various liability chains; I wouldn't want to have to defend my product by describing why it was designed to self-preserve instead of perform at all costs... But I am back to guessing...
If I had had access to a small portable AM or FM radio
, I would have put it in the oven
and listened for transmission 'clicks.' [I understand any station on AM; 99.5 on FM...] But without an antenna, that might not be definitive either... I was guessing again- sponsored by the foil recommendation- that some signal might escape. [Or perhaps the manufacturer was mitigating liability (CYA) with an erroneous foil suggestion...]
Anyway, with this [potentially flawed] logic I proceeded to light up my oven
with a xenon strobe for 4 1/2 days...
Thanks for the feedback. I will add this to the addenda in the original blog post in coming days...
May we never have to test these things for real...