Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?

wrote:

Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?

Computer power supplys are designed to produce a heck of a lot of power
at the processor's voltage, which is 2.5, 1.8, 1.2 or some other
absurdly low figure, and not much at 12V.

Check the surplus places for power supplies: Marlin P Jones and All
Electronics are two good ones in the US.

http://www.mpja.com/
http://www.allelectronics.com/

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

wrote in message
oups.com...
Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?

You may want to think through what you want longer term. There are a number
of projects around to convert a computer power supply to 12 volts. Might be
a bit of a push for a 50 watt radio, I'm not sure. Google for "St. Louis
Switcher" or similar.

Supplies are pretty simple, so building one from scratch isn't impossible,
but the transformers can be hard to come by.

A cheap commercial supply will give you days of good use. Seriously, there
is a lot of pure junk out there, some of it not so cheap. Many of them are
very noisy and can put hum on your transmitted signal or make it hard to
hear. Some will work for a short while before dying.

Before you make the investment think about your future needs. A good supply
can run well over $100 but can last you for decades. Are you going to get
on HF and thus need more amps? Are you going to get interested in meteor
scatter and need an amplifier for still more amps? Don't go buying a 10 amp
supply only to discover that you need another 10 and then another 10. If
you decide to go for a good supply go ahead and get 30 or 50 amps worth so
your future needs are covered.

Many folks use a marine battery and a trickle charger. This not only gives
them plenty of power for the shack, but it keeps them on the air when the
lights go out. You need to take care about ventilation and battery leakage,
but I don't know anyone who has done this and ever thought about going to a
commercial supply. I'm pretty happy with my Astron, but when the lights go
out, I'm limited to my HT.

...

Here is the cheep and ham way of getting a psu. Try and get your hands on a
BIG 12v charger ( a used of the kind used on service stations) 60 -70 amp.
This is the base for your psu. The rest you can find on the drawing.
http://www.qsl.net/yo5ofh/projects/power_supply.gif

Geir

wrote in message
oups.com...
Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?

wrote in message
oups.com...
Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?


I prefer linear power supplies for this size of radio, such as the Astron
RS-12A. Plentiful at hamfest, surplus and eBay.

IF you find an Astron that is broken and is offered to you for free (GRAB
IT) .. its like being handed money !
Astrons are easy to repair (unless transformer failed - very rare), skip the
Pyramids (many models have under rated heat sinks or electrolytic
capacitors)

Web sites for linear power supply repair and home built designs:

http://www.kbt-dc-supplies.com/index.php

http://www.seits.org/features/pwrsup.htm

gb

"gb" wrote in message
...
wrote in message
oups.com...
Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?


I prefer linear power supplies for this size of radio, such as the Astron
RS-12A. Plentiful at hamfest, surplus and eBay.

IF you find an Astron that is broken and is offered to you for free (GRAB
IT) .. its like being handed money !
Astrons are easy to repair (unless transformer failed - very rare), skip
the
Pyramids (many models have under rated heat sinks or electrolytic
capacitors)

Of course then there are the Pyramids that can function 24 hours a day 7
days a week from the day you buy it. Mine has been on (except for the
occasional blackout) for over 6 years.

At this apt I turned it on when I moved in and haven't touched it since.

"john graesser" wrote in message
...

"gb" wrote in message
...
wrote in message
oups.com...
Is there a best place to find or make a cheap power supply for a 50
watt mobile radio to use as a base station? Are computer power supply's
good?


I prefer linear power supplies for this size of radio, such as the Astron
RS-12A. Plentiful at hamfest, surplus and eBay.

IF you find an Astron that is broken and is offered to you for free (GRAB
IT) .. its like being handed money !
Astrons are easy to repair (unless transformer failed - very rare), skip
the
Pyramids (many models have under rated heat sinks or electrolytic
capacitors)

Of course then there are the Pyramids that can function 24 hours a day 7
days a week from the day you buy it. Mine has been on (except for the
occasional blackout) for over 6 years.

At this apt I turned it on when I moved in and haven't touched it since.

John -

I have heard that recent Pyramid linear models have addressed these design
issues.
(I have no "hands-on" personal experience to verify these design changes by
Pyramid).
Unfortunately, the used models I see at the hamfests are the earlier models
that I have repair experience with and had these design problems. Possibly
someone will eventually have a web based differentiation guide for these
Pyramid models.

gb

" Many folks use a marine battery and a trickle charger. This not only
gives
them plenty of power for the shack, but it keeps them on the air when the
lights go out. You need to take care about ventilation and battery
leakage,
but I don't know anyone who has done this and ever thought about going to
a
commercial supply. I'm pretty happy with my Astron, but when the lights
go
out, I'm limited to my HT.
==================================
A marine battery is fine ,simple and reliable . However if 'trickle charger
' is really a trickle charger ,when operating on FM (with full carrier) the
voltage when battery was fully charged might drop from say 13.8 to 12.8 V
,with battery still being 80 % charged. This means the power input and hence
RF ouput will probably be less than the transceiver's rated power
..............although that probably won't matter much signal wise.
If the transceiver is multimode and when operated on SSB ,the average
current on transmit will be lower resulting in an average output voltage
much closer to 13.8 Volt., even when using a trickle charger.


Frank GM0CSZ / KN6WH

"Highland Ham" wrote in message
...

A marine battery is fine ,simple and reliable . However if 'trickle
charger
' is really a trickle charger ,when operating on FM (with full carrier)
the
voltage when battery was fully charged might drop from say 13.8 to 12.8 V
,with battery still being 80 % charged. This means the power input and
hence
RF ouput will probably be less than the transceiver's rated power

You make a good point, Frank. A couple of years ago I bought a relatively
cheap battery charger (for the car, not for the radio), and was surprised at
what microprocessors have done to these things. Float charging, which is
basically what you want, is available from these things pretty commonly now,
as well as a myriad of other features. I guess the engineers put a $2 PIC
into one of these things and now they got to make excuses to use it. They
can't charge a lot less than the next guy so they need to out-feature them.
Anyway, the modern automotive battery charger has all nature of features.
It has become another of these devices with an impenetrable manual!

...