Most linear supplis have about +20V before the "pass element",
transistors.

And if a transistor shorts C to E, then ~+20V will appear at the
+12V output. A good OVP/crowbar is a must have!

But if an otherwise good supply lacks an OVP I would add my own.
The first link I gave has a diagram for a very good, in fact better
then
any I have ever seen built iinto any PS. The Areotech diagram specs 1%
resisitors. I used 5% with no decrease in functionality. Given the
orignal
use was to be in aircraft, the slight performance edge offered by 1%
ressitors was well worth it, that is a "life critical" mission. While I
value
my radios, I am more then willking to settle for a little less absolute
performance. I built the first one with teh specified 1% resisitors,
I built another unit with 5% resisitors, and as far as I can measure,
they both trip in about ~50mS. That is 0.05S. Thats for a jump of
13.69V
to +20V.

I use 13.69V because that is the most commonly suggested voltage to
keep lead acid gell cells "float charged". I added a 120V AC relay to
lift,
open, the + output from the PS so during power failures, my radios
keep running.

And as a rule, the larger a supply, the cooler it runs, and cool
equates
to LONG life.

Terry

wrote in message
ups.com...
Most linear supplis have about +20V before the "pass element",
transistors.

And if a transistor shorts C to E, then ~+20V will appear at the
+12V output. A good OVP/crowbar is a must have!

But if an otherwise good supply lacks an OVP I would add my own.
The first link I gave has a diagram for a very good, in fact better
then
any I have ever seen built iinto any PS. The Areotech diagram specs 1%
resisitors. I used 5% with no decrease in functionality. Given the
orignal
use was to be in aircraft, the slight performance edge offered by 1%
ressitors was well worth it, that is a "life critical" mission. While I
value
my radios, I am more then willking to settle for a little less absolute
performance. I built the first one with teh specified 1% resisitors,
I built another unit with 5% resisitors, and as far as I can measure,
they both trip in about ~50mS. That is 0.05S. Thats for a jump of
13.69V
to +20V.

I use 13.69V because that is the most commonly suggested voltage to
keep lead acid gell cells "float charged". I added a 120V AC relay to
lift,
open, the + output from the PS so during power failures, my radios
keep running.

And as a rule, the larger a supply, the cooler it runs, and cool
equates
to LONG life.

Terry


Ok I see. I'm good with my hands, can build a computer with ease, have done
lots of soldering, but when it comes to mission critical items like a PSU
that could end the life of one of my radios or cause a fire, I don't trust
in myself enough to do it. But, I learn very quickly. If I were to be there
with you, and watch you do it once, I could repeat it.

Funny how all these wall worts we use for our radios have none of these
features or protection. Or even are regulated. But, it's very important to
know. Using a simple Radio Shack regulated PSU got rid of the hum that was
driving me batty on my HF-150.

BTW, linear = regulated correct?

Lucky

Wall warts can only deliver so many ma, or for big ones an amp or 2.
A real power supply can deliver well over it's rated current for a few
seconds.

Long enough to turn most radios into slag.

Go with one with a built in OVP/crowbar and try building an
out board one later. In a extened power outage you might find it
usefull to be able to draw power from you car or truck. At that
time you really want to have a OVP/crowbar between your radios
and vehical's electrical system.

Flexiblility is important.

You might want to contact the alarm companies in your area as many
of the better ones retire perfectly good gell cells from alarm systems
for insurance reasons. Having a burgler alarm fall during a powqer
outage because a 3 year old gell cell died is real bad for business.

I have several gell cells that are 10 years old and going strong.
After overcharging them, heat is the biggest killer, keep them cool,
under ~90F, and they will last for years. Here in central Kentucky
we often have nasty T-storms that knock the power out for several
hours. It is very nice to be able to listen to my radios after the
storm
moves out. It is true that I mainly listen to my scanners, but having
a SW is very nice also.

One winter's night 2 years ago the lights went out and stayed out for
about 5 hours. Perfect listening conditions. No nearby TV,s PCs etc.
Very RF quite. Made the extra effort for the gell cells worth while.

Terry

wrote in message
oups.com...
Wall warts can only deliver so many ma, or for big ones an amp or 2.
A real power supply can deliver well over it's rated current for a few
seconds.

Long enough to turn most radios into slag.

Go with one with a built in OVP/crowbar and try building an
out board one later. In a extened power outage you might find it
usefull to be able to draw power from you car or truck. At that
time you really want to have a OVP/crowbar between your radios
and vehical's electrical system.

Flexiblility is important.

You might want to contact the alarm companies in your area as many
of the better ones retire perfectly good gell cells from alarm systems
for insurance reasons. Having a burgler alarm fall during a powqer
outage because a 3 year old gell cell died is real bad for business.

I have several gell cells that are 10 years old and going strong.
After overcharging them, heat is the biggest killer, keep them cool,
under ~90F, and they will last for years. Here in central Kentucky
we often have nasty T-storms that knock the power out for several
hours. It is very nice to be able to listen to my radios after the
storm
moves out. It is true that I mainly listen to my scanners, but having
a SW is very nice also.

One winter's night 2 years ago the lights went out and stayed out for
about 5 hours. Perfect listening conditions. No nearby TV,s PCs etc.
Very RF quite. Made the extra effort for the gell cells worth while.

Terry


Wouldn't the gel cell need to be 12 to 13.8v though? I've heard you guys
talk about gel cells for outdoor radio use. They sound interesting. So you
just add the correct sized plug to the gel cell for your radios power input
jack and you're good to go?

Lucky

To charge a lead acid battery regardless if
if it is liquid, like your car battery, or has a
gelled electrolyt, requires a higher voltage then
the nominal rated voltage be applied.

Broadly speaking there afre three classes of lead
acid service.
Starting, cycle, and flaot.
The first is your typical engine atarting service.
Requires gobs of vurrent for short periods and loafs after that.
Cycle is like for golf carts, fork lifts, VHS camcorders, and in truth
the way I used to use a gell cell to power my SW for weekend
radio picnics.
Standby is for "emergency" loss of power applicaitns like emergency
lightst in public areas, PC UPS and the like.
And each service has different suggested charging voltages.
See:
http://www.osibatteries.com/pdf/Gel%...ies%202004.pdf
for one take on the correct charging voltages.

Cars charge batteries at up to 15V. A gell cell wll get hot and fail
very rapidly at that voltage. I have found 13.69V to be good voltage.
Some go as low as 13.5 or so. Much below that 13.5 and the battery
will not charge.

Half these for 6 volt batteries. I have a couple of 6V gell cells
designed
to power camcorders that I use with our DX398 for week end radio
picnics. One DX398 will operate for over a day on a single battery.
To get slighlty longer run time I could charge them at ~7V, but I prfer
for my batteries to live longer then run longer.

Everything is a trade off. Longer run time for fewer charge/discharge
cycles.

At home I would just operate everything from my 12 gell cells, I have
linear step down regulators to reduce the 12V to 9V and 6V as needed.
With each devcie protected by a OVP after the reduction regulator.

If I knew a power outage was going to last a "long time", I would power

our DX398s from the 6V gell cells. I scalvaged 4 PV (solar cells) from
some dead lawn night lights that produce ~150mA at 4V in bright
sunlight,
by making 2 parallel sets of 2 in series I get 8V at ~300mA. With a
simple shunt regulator I get 6.845V,more then enough to keep the gell
cell topped off and operate 2 DX398s at the same time.

I have a couple of older Arco ~12V PV arrays that produce 18V @.75A
in bright sunshine, so I could recharge my 12V gell cells and or
operate some equipment during daylight hours. Remnants from the cold
war when the great nuke out seamed likely.

Terry

wrote in message
ups.com...
To charge a lead acid battery regardless if
if it is liquid, like your car battery, or has a
gelled electrolyt, requires a higher voltage then
the nominal rated voltage be applied.

Broadly speaking there afre three classes of lead
acid service.
Starting, cycle, and flaot.
The first is your typical engine atarting service.
Requires gobs of vurrent for short periods and loafs after that.
Cycle is like for golf carts, fork lifts, VHS camcorders, and in truth
the way I used to use a gell cell to power my SW for weekend
radio picnics.
Standby is for "emergency" loss of power applicaitns like emergency
lightst in public areas, PC UPS and the like.
And each service has different suggested charging voltages.
See:
http://www.osibatteries.com/pdf/Gel%...ies%202004.pdf
for one take on the correct charging voltages.

Cars charge batteries at up to 15V. A gell cell wll get hot and fail
very rapidly at that voltage. I have found 13.69V to be good voltage.
Some go as low as 13.5 or so. Much below that 13.5 and the battery
will not charge.

Half these for 6 volt batteries. I have a couple of 6V gell cells
designed
to power camcorders that I use with our DX398 for week end radio
picnics. One DX398 will operate for over a day on a single battery.
To get slighlty longer run time I could charge them at ~7V, but I prfer
for my batteries to live longer then run longer.

Everything is a trade off. Longer run time for fewer charge/discharge
cycles.

At home I would just operate everything from my 12 gell cells, I have
linear step down regulators to reduce the 12V to 9V and 6V as needed.
With each devcie protected by a OVP after the reduction regulator.

If I knew a power outage was going to last a "long time", I would power

our DX398s from the 6V gell cells. I scalvaged 4 PV (solar cells) from
some dead lawn night lights that produce ~150mA at 4V in bright
sunlight,
by making 2 parallel sets of 2 in series I get 8V at ~300mA. With a
simple shunt regulator I get 6.845V,more then enough to keep the gell
cell topped off and operate 2 DX398s at the same time.

I have a couple of older Arco ~12V PV arrays that produce 18V @.75A
in bright sunshine, so I could recharge my 12V gell cells and or
operate some equipment during daylight hours. Remnants from the cold
war when the great nuke out seamed likely.

Terry


Thanks for the explanations Terry. I'm going to try one instead of taking 16
battries with me and HF-150. I charge up 16 2100 mAh in my "8 ata time"
charger.
Does 8 in 8 hours so it's not that bad. The first charger I had took like
14-15 hours!

I refuse to charge the batteries in the Lowe itself. I wil not take the
chance of accidents and I don't believe in the radio being in use all the
time for such a simple process. I know I'm being overprotective of the radio
but I think it's worth it.

Lucky