[Mobile-Portable] Wire Size

[Jim Miller]

>     My question is: How much bigger should I go?  I am thinking about
> 8-gauge.  Will this be adequate?  (The length is approximately 15-feet.)

Take your pick.
The DC resistance of #12 wire is 1.7 ohms per 1000 ft.  The voltage drop in
15 ft at 20 amps will be .51 volts.
The DC resistance of #10 wire is 1.1 ohms per 1000 ft.  The voltage drop in
15 ft at 20 amps will be .33 volts.
The DC resistance of #8 wire is .61 ohms per 1000 ft.  The voltage drop in
15 ft at 20 amps will be .18 volts.

>     Final question: Does anybody have any experience with these new (to
me)
> DC power supplies.  They are said to maintain a reliable 13.6-Volt output
> regardless of the input voltage (within reason).  In principle, they seem
> like a good idea, especially when running the HF rig for prolonged periods
> with the engine turned off.

Whether you are talking about running from the car battery to an inverter
and then to a switching power supply (wasted power) or through a DC to DC
converter, they should work fine BUT you will need to have a meter or an
alarm to warn you when your battery gets too low to start your vehicle.
This type of setup will allow you to operate much longer on your battery
than without it (which is what it sounds like you want).  The safe way to
not leave yourself stranded somewhere would be to have a separate battery to
run this off of that can be switch connected to your vehicle battery for
recharging.  You may also want to install a simple current limiter in the
recharge line to restrict the current during recharge.

>     Another question: What is considered state of the art, now, for an
> in-line fuse holder?

I have individual fuse holders that are quite large and heavy plastic that
are sealed from the weather by rubber gaskets when the two halves are
screwed together over the fuse and the ones I bought came with pigtail wires
on each side.  No internal degradation can occur.  I found them at a
hamfest.  I have no other information on a source but they are the thing to
use.

Hope this helps,
73, de Jim KG0KP