[NLRS] The woes of 13.8 vdc

[Donn Baker]

At 13:26 12-07-03 EDT, W0ZQ@aol.com wrote:
>1.  Add a single cell in series.   A single cell lead acid is about 2.1 vdc 
***** There are single lead-acid cells available (Gates makes them -
they're the size of a 'D'-cell), but ones that will supply the current you
need are expensive, or dangerous for portable use (liquid electrolyte).
Not a good choice.

>2.  Go with a two battery system to provide18 vdc or 24 vdc and build a 
>regulator to regulate at 13.8 vdc.    The regulator would need to pass
around 
***** WASTES power.  My opinion is NO.

>3.   Go with a DC/DC converter of some type.
***** Relatively easy, actually.  Chris, N0UK, had one solution.  Another
is to use an LT1270A part in a "current-boosted boost" configuration.
Relatively easy, less than a dozen parts.  (LT1270A is 5-pin TO220.  About
$15 from Digi-key.  Magnetics will be about $10; everything else, maybe
$5.)  Linear Technologies AN-19 tells you everything you need to know to
build these.  I have a copy.  (Its l-o-n-g.)  I've built several of these
using smaller parts (less current) and they're easy.  The same part will
also get you +24v from +12.  (Unfortunately, -24v is much harder to get,
but possible.)

Another possibility is a "Battery Booster" I've seen on the Web.  Its claim
to fame is that it doesn't go from 12 to 13.8V... it adds (in this case)
1.8V to 12 to get 13.8.  I don't know anything about it other than what I
have seen on the web page (I don't know the URL... its at work.)  Try a
Google search on 'battery booster'.

As an aside, I'm building 12-13.8V DC/DC converters based on the LT1270A
for all the gear.  My i.f. rig requires somewhat less power, and I don't
need the "current-boosted boost"... just a "boost" configuration
(difference is in the switching coil, and a snubber circuit).  I also hope
the 13.8 on the 10GHz XVRTR will help stabilize the XTAL drift.

>
>4.   Bite the bullet and get a different IF rig that uses current more 
>appropriate for its output power and that has a higher tolerance DC
voltage input 
>range.
****** Bob, W0AUS's comment is appropriate.  FWIW, I agree with him.

73 Donn
WA2VOI/0