Off topic, but you can`t power an antenna without power to the
transmitter.

I`m looking for a d-c to d-c converter that takes 28 volts on the input
and supplies 12 volts on the output. Up to 8 amperes may regularly be
drawn from the supply. That`s about 100 watts.

I need it now. That`s why I`m imposing on this group. There is no more
knowledgeable group to ask that I know of. I don`t have time to build
anything, though I`ve built such inverters and converters.

A simple voltage divider or regulator is too lossy for high utilization.
I need lossless resistance.

Maybe there is an applicable aircraft converter that is surplus
somewhere, or maybe there is a stock automotive item as there are such
28-volt battery systems used in some big rigs. I`m in a hurry or I would
quietly do all the hunting myself and not bother anybody.

I would like rugged, reliable, efficient, replaceable, and cheap.

Thank you in advance for directions to the source of my d-c step-down
transformer.

Please excuse the misuse of this forum, but I believe it is my best
resource for most things technical and unusual.

Best regards, Richard Harrison, KB5WZI

Hi Richard,

I have just what you are looking for. I will send you an email

73
Gary K4FMX


On Mon, 8 Mar 2004 15:15:55 -0600 (CST),
(Richard Harrison) wrote:

Off topic, but you can`t power an antenna without power to the
transmitter.

I`m looking for a d-c to d-c converter that takes 28 volts on the input
and supplies 12 volts on the output. Up to 8 amperes may regularly be
drawn from the supply. That`s about 100 watts.

I need it now. That`s why I`m imposing on this group. There is no more
knowledgeable group to ask that I know of. I don`t have time to build
anything, though I`ve built such inverters and converters.

A simple voltage divider or regulator is too lossy for high utilization.
I need lossless resistance.

Maybe there is an applicable aircraft converter that is surplus
somewhere, or maybe there is a stock automotive item as there are such
28-volt battery systems used in some big rigs. I`m in a hurry or I would
quietly do all the hunting myself and not bother anybody.

I would like rugged, reliable, efficient, replaceable, and cheap.

Thank you in advance for directions to the source of my d-c step-down
transformer.

Please excuse the misuse of this forum, but I believe it is my best
resource for most things technical and unusual.

Best regards, Richard Harrison, KB5WZI

On Mon, 8 Mar 2004 15:15:55 -0600 (CST),
(Richard Harrison) wrote:

I`m looking for a d-c to d-c converter that takes 28 volts on the input
and supplies 12 volts on the output. Up to 8 amperes may regularly be
drawn from the supply. That`s about 100 watts.

Hi Richard,

Try Jameco at:
http://www.jameco.com/Jameco/Products/ProdDS/206041.pdf

73's
Richard Clark, KB7QHC

In article ,
Richard Harrison wrote:

Off topic, but you can`t power an antenna without power to the
transmitter.

I`m looking for a d-c to d-c converter that takes 28 volts on the input
and supplies 12 volts on the output. Up to 8 amperes may regularly be
drawn from the supply. That`s about 100 watts.

I need it now. That`s why I`m imposing on this group. There is no more
knowledgeable group to ask that I know of. I don`t have time to build
anything, though I`ve built such inverters and converters.

Check with Vicor (www.vicr.com). They make a whole range of DC-to-DC
converter modules.

Example: their V24B12C200B converter module takes 18-36 volts in, 12
volts out (programmable from 10% to 11% of this, so you could get 13.2
out), efficiency 85%, 200 watts output. Current limit is 17 amps
minimum, 19.2 amps typical.

They do have a 100-watt module, but I suspect you'd be running it
right at the ragged edge of its specs.

There are other manufacturers playing in this market space... Datel is
one.

A simple voltage divider or regulator is too lossy for high utilization.
I need lossless resistance.

You won't get 100% efficiency out of anything like this. 80-90% seems
to be achievable with commercial products.

I would like rugged, reliable, efficient, replaceable, and cheap.

I think you can get the first four if you look around.

The fifth is likely to be the hardest, if you want the first four.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Richard,

try looking at http://www.astroncorp.com

They have two different converters like you are looking for.

"Dave Platt" wrote in message
...
In article ,
Richard Harrison wrote:

Off topic, but you can`t power an antenna without power to the
transmitter.

I`m looking for a d-c to d-c converter that takes 28 volts on the input
and supplies 12 volts on the output. Up to 8 amperes may regularly be
drawn from the supply. That`s about 100 watts.

I need it now. That`s why I`m imposing on this group. There is no more
knowledgeable group to ask that I know of. I don`t have time to build
anything, though I`ve built such inverters and converters.

Check with Vicor (www.vicr.com). They make a whole range of DC-to-DC
converter modules.

Example: their V24B12C200B converter module takes 18-36 volts in, 12
volts out (programmable from 10% to 11% of this, so you could get 13.2
out), efficiency 85%, 200 watts output. Current limit is 17 amps
minimum, 19.2 amps typical.

I suspect, since 'up to 8 amperes may be drawn', that
he'll have a hard time meeting the '17 amps minimum'
spec...
__
Steve
KI5YG
..

In article om,
Stephen Cowell wrote:


Example: their V24B12C200B converter module takes 18-36 volts in, 12
volts out (programmable from 10% to 11% of this, so you could get 13.2
out), efficiency 85%, 200 watts output. Current limit is 17 amps
minimum, 19.2 amps typical.

I suspect, since 'up to 8 amperes may be drawn', that
he'll have a hard time meeting the '17 amps minimum'
spec...

Sorry, I was unclear. What the phraseology means is "The converter's
maximum current output is limited to a value which might, in some
cases, be as low as 17 amperes, but is typically around 19.2 amperes."

I didn't mean to imply that you _must_ draw 17 amperes from the
converter in order for it to work. There doesn't appear to be a
significant lower limit - load reguulation is given as 0.2% typical
"no load to full load, nominal input" as long as you haven't trimmed
the converter to a lower output voltage.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Sorry, I was unclear. What the phraseology means is "The converter's
maximum current output is limited to a value which might, in some
cases, be as low as 17 amperes, but is typically around 19.2 amperes."

I didn't mean to imply that you _must_ draw 17 amperes from the
converter in order for it to work. There doesn't appear to be a
significant lower limit - load reguulation is given as 0.2% typical
"no load to full load, nominal input" as long as you haven't trimmed
the converter to a lower output voltage.

--
Dave Platt AE6EO


Dave,

Even though you may have been unclear, REAL radio amateurs knew
exactly what you meant - ignore wise-ass comments from those trying to be
a bit more clever than others - it illustrates various weaknesses .....

Nick

"nick smith" wrote in message
...
Sorry, I was unclear. What the phraseology means is "The converter's
maximum current output is limited to a value which might, in some
cases, be as low as 17 amperes, but is typically around 19.2 amperes."

I didn't mean to imply that you _must_ draw 17 amperes from the
converter in order for it to work. There doesn't appear to be a
significant lower limit - load reguulation is given as 0.2% typical
"no load to full load, nominal input" as long as you haven't trimmed
the converter to a lower output voltage.

--
Dave Platt AE6EO


Dave,

Even though you may have been unclear, REAL radio amateurs knew
exactly what you meant - ignore wise-ass comments from those trying to be
a bit more clever than others - it illustrates various weaknesses .....

Hey Nick... chupe' mis huevos. It was *not* clear, and Dave
knew it, and copped to it.
__
Steve
KI5YG
..

Richard,

Assuming there is a common ground, and input and output are the same
polarity, what you want is called a buck converter. To roll your own,
National and TI make chips. To buy a whole unit you need to go to a non
hobby distributor's web site like Newark, Allied, Avnet, or Arrow. Some
manufacturers of these things are Astec, Condor, Cosell, Elpac, and
Lambda(expensive).

Tam/WB2TT
"Richard Harrison" wrote in message
...
Off topic, but you can`t power an antenna without power to the
transmitter.

I`m looking for a d-c to d-c converter that takes 28 volts on the input
and supplies 12 volts on the output. Up to 8 amperes may regularly be
drawn from the supply. That`s about 100 watts.

I need it now. That`s why I`m imposing on this group. There is no more
knowledgeable group to ask that I know of. I don`t have time to build
anything, though I`ve built such inverters and converters.

A simple voltage divider or regulator is too lossy for high utilization.
I need lossless resistance.

Maybe there is an applicable aircraft converter that is surplus
somewhere, or maybe there is a stock automotive item as there are such
28-volt battery systems used in some big rigs. I`m in a hurry or I would
quietly do all the hunting myself and not bother anybody.

I would like rugged, reliable, efficient, replaceable, and cheap.

Thank you in advance for directions to the source of my d-c step-down
transformer.

Please excuse the misuse of this forum, but I believe it is my best
resource for most things technical and unusual.

Best regards, Richard Harrison, KB5WZI