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e9999 · 04-27-08, 03:09 PM

no doubt there can be electronic issues due to voltage drop, noise etc. But saying that you're likely to start a fire because of using the lighter plug is a bit of a stretch for a 50W radio, IMHO...

over and out on this issue...

added later on: OK, never mind that last one, I'll add one more thing. I did go and check the voltage drop on mine since this is an interesting issue and George knows his stuff. At highest power (antenna inside the truck not sure what difference that makes), I measured 12.7V at the fuse downstream of the lighter plug when the battery terminals were about 14.3V or so (engine running). That's about 1.6V drop at 10+ A (I did try to measure the current but my meter tops off at 10A and it was OL). More than I expected. Maybe the cheap plug? So, indeed, with the engine off, it could well give you only 11V (WAG). Now the 7800 specs say 13.8V +/- 15%, so that implies 11.7V min. Not sure if that's a real lower limit. But indeed the supply may well be too low with engine not running. No biggie, I can run the radio directly off my jumper battery if the engine is out, but still good to know. Now, of course, there would be a drop with direct connection to the battery as well, but that should be much lower. 12 ga is something like 0.02 ohms for 10 ft.
Still not too worried about fire, though...

04-27-08, 03:09 PM	#17
e9999 You want to do what...? Join Date: Sep 2003 Location: PRK Posts: 10,206	no doubt there can be electronic issues due to voltage drop, noise etc. But saying that you're likely to start a fire because of using the lighter plug is a bit of a stretch for a 50W radio, IMHO... over and out on this issue... added later on: OK, never mind that last one, I'll add one more thing. I did go and check the voltage drop on mine since this is an interesting issue and George knows his stuff. At highest power (antenna inside the truck not sure what difference that makes), I measured 12.7V at the fuse downstream of the lighter plug when the battery terminals were about 14.3V or so (engine running). That's about 1.6V drop at 10+ A (I did try to measure the current but my meter tops off at 10A and it was OL). More than I expected. Maybe the cheap plug? So, indeed, with the engine off, it could well give you only 11V (WAG). Now the 7800 specs say 13.8V +/- 15%, so that implies 11.7V min. Not sure if that's a real lower limit. But indeed the supply may well be too low with engine not running. No biggie, I can run the radio directly off my jumper battery if the engine is out, but still good to know. Now, of course, there would be a drop with direct connection to the battery as well, but that should be much lower. 12 ga is something like 0.02 ohms for 10 ft. Still not too worried about fire, though... __________________ '97: 88K, 3xlock, Custom HD roo bar for sale, 285 MT/Rs on steelies, Hanna sliders, 851+1.5"/863/N73/N74E/SD24, ARB bull with M12, Kaymar with duals, Kaymar rack, Slee TC skid, 2m/440, more stuff, loose nut behind the wheel!) '03: 99K, the better half's... DD souped up DR650 Last edited by e9999; 04-27-08 at 09:37 PM.