[Elecraft] OT: wall wart for RX-only PS?

[Jim Brown]

On Sun, 6 Dec 2009 14:21:47 -0800 (PST), Mel Farrer wrote:

>Most of the wall warts are just rectified AC.  Very little if any 
>filtering. 

We have a lot of power interruptions up here in the Santa Cruz 
mountains, thanks to storms, falling trees, and wild fires. Rather 
than buy a lot of commercial units, I have put together a bunch of 
little home-brew back-up power supplies for most of this gear. I 
simply find suitable batteries at swap-meets and use a wall wart as 
a float charger, with a parallel feed to the equipment. To avoid 
overcharging the battery, I carefully match the "normal" charging 
current so that current into the battery falls into the "trickle" 
range (5% -10% of the 10 hour discharge rate). This tends to work 
quite well. When power drops, our internet router, AC powered 
phones, Ethernet switch, etc. all continue to work just fine, even 
through relatively long outages. Likewise, my 12-14v ham gear runs 
on a couple of big Costco deep cycle batteries that are charged from 
a little 10A supply. Again, charging current is kept below that 
which could degrade the batteries. They won't run a big amp, but 
they do fine to keep K3s and a VHF rig running.  

73,

Jim K9YC