[aprssig] Portable Ops from 12v via 115 VAC

Robert Bruninga bruninga at usna.edu
Wed Dec 29 11:11:08 EST 2004

>YES, for *transfering* the power, over a long distance, 
>the higher voltage is better...

For example, each of these can deliver 12.6v at 20 amps:
from a 13.8V car battery(+engine) system:

A) 500' of #18 lamp type zip cord at 115VAC w/inverter
B) 25'  of #10 

Not only do you get 20 times further, but  the 115 VAC zip cord 
and the regulated 13.8 VDC supply will deliver the 20 amps 
at the original 13.8 V without the "brown-out" of the DC
system under load.

Yes, you need 24 amps from the Engine to get the
20 amps at the load, but the ability to go 20 times
further away is worth it when needed.

Oh, and 300' of lamp cord takes up only about as much
space under your seat as a 25' conventional "extension cord".
The difference is the conventional extension cord is 70% 
plastic for physical protection and is considered "safe"
even in the hands of idiots.  Lamp cord in this app should not be
used except under controlled conditions or far away from idiots.

That's why I'd put a 3 amp fuse in it to make sure some idiot
does not try to use it for a space heater or a chain saw or


----- Original Message ----- 
From: "Robert Bruninga"
Subject: [aprssig] Portable Ops from 12v via 115 VAC

> For long distance portable operation from the car's 12v
> system, dont overlook using lots of small wire and an
> 110 inverter.
> Run an efficient inverter at the car to 110 then run
> your portable station on  AC using modern switching
> supplies.
> Even if your 12v rig draws 20 amps peak, this should
> only be about 2 amps over the AC cord and even if the
> drop over 300 feet of zip cord goes down to 90 volts, almost
> all switching power supplies these days can still work
> and deliver their rated output at the load.
> Bob

>>>> wa7nwp at jnos.org 12/29/04 2:37:58 AM >>>

>> Bill, are you suggesting this actually WORKS?
>> I have a 300 watt inverter (500 surge), and it
>> Draws OVER 30 AMPS.  No car alternator will put
>> Out enough current to keep up with the drain at idle.
>> Are you willing to put a brick on your gas pedal and
>> Idle at 3,000 RPM to get enough current?

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