[Elecraft] Mobile from 117 VAC

[Edward R Cole]

Ted, KN1CBR

It seems to me simpler to set up a source of 13.6 vdc to power your 
SUV "portable" station.  Running dc leads from the vehicle battery is 
simplest but you need to guard against discharging it so much that 
the vehicle will not start.  With engine running you will get about 
14.2vdc at the battery which will only help (but your gas mileage will suffer).

But using dedicated 12v deep-cycle battery for the radio will insure 
against starting issues.  Not sure if you plan to install radio in 
SUV or just have it to set up on say a picnic table or folding 
table.  If the latter, the battery can be situated close the radio 
and use the standard dc power leads of the radio equipment.  You can 
recharge the radio battery when driving or just running engine in CG 
by use of some No. 12ga wire from vehicle battery to the radio 
battery (good for up to 10A charging current if under 20-foot 
length).  Use a isolation diode if you don't want the radio battery 
involved in starting (which draws probably 200A from the vehicle 
battery).  Probably a 10A diode would suffice for charging the radio 
battery.  Wire up the system and measure current using multimeter to 
be sure before getting a diode.

This will not keep the radio battery from discharging when operating 
100w on HF because the radio is probably drawing 15A on peaks.  If 
recharging only when driving it will likely take close to an hour for 
full recharging (depends on the volt-amp rating of the radio 
battery).  I used a system like this when living in a remote cabin 
without power.  It look about 45 minutes running the truck to 
recharge the cabin battery (which was placed in the truck with wiring 
for this purpose).  I had a 100AH Marine Diehard (Sears) battery.

Diode will not keep from discharging the vehicle battery so have a 
way to disconnect the radio battery when operating (unless you plan 
to keep engine running).  Marine electronic shops stock things like 
dc disconnect switches and isolation diode units if you do not want 
to make your own.  Also several ham suppliers handle such items.

Last year I bought a new 4x4 pickup and installed ham radio equipment 
(KX3 + KXPA100, etc.):
http://www.kl7uw.com/Mobile.htm
Truck has two batteries (diesel) so I did nothing but run off one of 
the batteries (but I used No. 8awg).

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   dubususa at gmail.com