12V DC mobile power supply (battery pack)

[Andrew Kesterson]

I have been looking on google and can't find anything on this subject.

I want to take a mobile CB radio, designed to run off of a 12 volt
power line in an automotive vehicle, and convert it to run on 9V, C, or D
cell batteries so I can put it in a backpack and take it with me when I go
on long hikes away from home and the like, and talk back to a base station
in the house.

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the current
(if too high), or using an amplifier to raise it?

I have some basic electronics books on these subjects (basic, basic
digital, and basic communications electronics books from radio shack), but
I wanted to get some input before I went and tried to do something and
blew up my radio.

Would this be possible using the methods I described? Would I need other
methods? Or would I just need to give it up and try something else?

(Also, does anyone know where I might find information about changing the
frequencies the radio runs on? If I could find a way to make it run on the
same frequencies as some smaller GMRS radios I have, that'd be awesome...
but from what I understand it would probably require changing the entire
guts of the radio... so if that's not feasible don't worry too much about
it.

Thanks alot in advance

 

[Form@C]

On Sun, 18 Apr 2004 13:48:26 -0500, Andrew Kesterson wrote:

I have been looking on google and can't find anything on this subject.

I want to take a mobile CB radio, designed to run off of a 12 volt power
line in an automotive vehicle, and convert it to run on 9V, C, or D cell
batteries so I can put it in a backpack and take it with me when I go on
long hikes away from home and the like, and talk back to a base station in
the house.

If you really must.... ;-)

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the current
(if too high), or using an amplifier to raise it?

You can use NiCd or NiMH cells wired in series to give the required
voltage. Both of these are 1.2v per cell, so a 12v supply would need 10
cells. The portable CB radios tend to use the AA size, but Cs or even Ds
are ok if you don't mind the extra weight and cost! Whatever you
do, *please* fit a little fuse adjacent to the battery pack - especially
if using NiMH cells as these can easily give enough current on a short
circuit to be dangerous.

Don't attempt to modify the internals of the CB at all. Just provide 12v.
You could also use a sealed lead-acid battery of course.

You will probably have a high/low power switch on the CB. Use low power
whenever possible. It will lengthen your talk time appreciably. It is also
rather unwise to use high power when you are using a little rubber aerial
a few inches from your head!

I have some basic electronics books on these subjects (basic, basic
digital, and basic communications electronics books from radio shack),
but I wanted to get some input before I went and tried to do something
and blew up my radio.

Would this be possible using the methods I described? Would I need other
methods? Or would I just need to give it up and try something else?

(Also, does anyone know where I might find information about changing
the frequencies the radio runs on? If I could find a way to make it run
on the same frequencies as some smaller GMRS radios I have, that'd be
awesome... but from what I understand it would probably require changing
the entire guts of the radio... so if that's not feasible don't worry
too much about it.

No - two reasons. First, its illegal. Second, it needs careful setting up
with specialised test gear just to move the frequency a little. They just
won't go into the GMRS band - and wouldn't communicate with them even
they did! If the range of a GMRS is sufficient you would be better using
one of those anyway.



Follow-ups set to alt.electronics

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux...
Nascom & Gemini info at http://www.nascom.info

 

[Vidor Wolf]

"Andrew Kesterson" <andrew@aklabs.net> wrote in message
newsan.2004.04.18.18.48.25.860367@aklabs.net...

I have been looking on google and can't find anything on this subject.

I want to take a mobile CB radio, designed to run off of a 12 volt
power line in an automotive vehicle, and convert it to run on 9V, C, or D
cell batteries so I can put it in a backpack and take it with me when I go
on long hikes away from home and the like, and talk back to a base station
in the house.

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the current
(if too high), or using an amplifier to raise it?

I have some basic electronics books on these subjects (basic, basic
digital, and basic communications electronics books from radio shack), but
I wanted to get some input before I went and tried to do something and
blew up my radio.

Would this be possible using the methods I described? Would I need other
methods? Or would I just need to give it up and try something else?

(Also, does anyone know where I might find information about changing the
frequencies the radio runs on? If I could find a way to make it run on the
same frequencies as some smaller GMRS radios I have, that'd be awesome...
but from what I understand it would probably require changing the entire
guts of the radio... so if that's not feasible don't worry too much about
it.

Thanks alot in advance
About 20 years ago, I was doing the same thing with UK CB radios.

If I remember correctly, I was modding the tiny (and crappy) Maxon 21E with
10 x AA NiCads in a holder on its back..
Gave around 13 Volts and lasted quite well.
I used and external telescopic aerial with either a center or base loaded
coil (depended on what was available).
I think Midland also made a similar commercial set to this.
You could also try a small 12Volt Gel Cell.
Cheers.
Mark.

 

[js_530]

"Andrew Kesterson" <andrew@aklabs.net> wrote in message news:<pan.2004.04.18.18.48.25.860367@aklabs.net>...

I have been looking on google and can't find anything on this subject.

I want to take a mobile CB radio, designed to run off of a 12 volt
power line in an automotive vehicle, and convert it to run on 9V, C, or D
cell batteries so I can put it in a backpack and take it with me when I go
on long hikes away from home and the like, and talk back to a base station
in the house.

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the current
(if too high), or using an amplifier to raise it?

You could not get a voltage higher than what you have from the
batteries, so the amplifier cannot be used. You need 12 volts or
higher from the batteries, because there's probally a good reason the
radio runs on 12 volts. If you had a voltage higher than 12 volts,
you could use a 12 volt regulator, but not resistors. The radio is
non-linear, and changes resistance based on whether or not it's being
used, so a regulator is needed. You might want to see how much
current the radio draws, and buy a 12 volt regulator higher than your
maximum current rating. If you are using a source slightly higher
than 12 volts, than you need a minimum voltage dropoff rating on the
regulator of the difference between the battery voltage and 12 volts.

I have some basic electronics books on these subjects (basic, basic
digital, and basic communications electronics books from radio shack), but
I wanted to get some input before I went and tried to do something and
blew up my radio.

Would this be possible using the methods I described? Would I need other
methods? Or would I just need to give it up and try something else?

(Also, does anyone know where I might find information about changing the
frequencies the radio runs on? If I could find a way to make it run on the
same frequencies as some smaller GMRS radios I have, that'd be awesome...
but from what I understand it would probably require changing the entire
guts of the radio... so if that's not feasible don't worry too much about
it.
I believe this is possible, and inexpensive, but I'm not sure how you

would do this. You would have to desolder either a crystal or a
capacitor, then solder on another one. Both componants are under a
dollar.
> Thanks alot in advance

 

[Seth Koster]

"Andrew Kesterson" <andrew@aklabs.net> wrote in message news:<pan.2004.04.18.18.48.25.860367@aklabs.net>...

I have been looking on google and can't find anything on this subject.

I want to take a mobile CB radio, designed to run off of a 12 volt
power line in an automotive vehicle, and convert it to run on 9V, C, or D
cell batteries so I can put it in a backpack and take it with me when I go
on long hikes away from home and the like, and talk back to a base station
in the house.

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the current
(if too high), or using an amplifier to raise it?

8 1.5V batteries will give you 12V (C or D), the circuit will draw
the amperage it needs (probably more than you want, considering
battery life). You might consider buying one of those handy talky
type radios which are designed to run on batteries.

I have some basic electronics books on these subjects (basic, basic
digital, and basic communications electronics books from radio shack), but
I wanted to get some input before I went and tried to do something and
blew up my radio.

Would this be possible using the methods I described? Would I need other
methods? Or would I just need to give it up and try something else?

(Also, does anyone know where I might find information about changing the
frequencies the radio runs on? If I could find a way to make it run on the
same frequencies as some smaller GMRS radios I have, that'd be awesome...
but from what I understand it would probably require changing the entire
guts of the radio... so if that's not feasible don't worry too much about
it.

Sure its possible, its also illegal and harder than just getting a
ham radio license and then getting a lot more range by applying good
antenna designs to a good ham band radio.

 

[SB]

IS it illegal?? Both FRS and CB bands are open....no license required!

It's the transmit power that's the regulated portion of each (<5W for CB and
not sure for FRS).

If he's thinking of FRS then dump the CB idea....traffic seems to be getting
less and less all the time (just the odd trucker looking for a good place to
chow!).



"Form@C" <mick@mixtel.co.uk> wrote in message
newsan.2004.04.18.20.29.29.936064@mixtel.co.uk...

On Sun, 18 Apr 2004 13:48:26 -0500, Andrew Kesterson wrote:

I have been looking on google and can't find anything on this subject.

I want to take a mobile CB radio, designed to run off of a 12 volt power
line in an automotive vehicle, and convert it to run on 9V, C, or D cell
batteries so I can put it in a backpack and take it with me when I go on
long hikes away from home and the like, and talk back to a base station
in
the house.


If you really must.... ;-)

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the
current
(if too high), or using an amplifier to raise it?


You can use NiCd or NiMH cells wired in series to give the required
voltage. Both of these are 1.2v per cell, so a 12v supply would need 10
cells. The portable CB radios tend to use the AA size, but Cs or even Ds
are ok if you don't mind the extra weight and cost! Whatever you
do, *please* fit a little fuse adjacent to the battery pack - especially
if using NiMH cells as these can easily give enough current on a short
circuit to be dangerous.

Don't attempt to modify the internals of the CB at all. Just provide 12v.
You could also use a sealed lead-acid battery of course.

You will probably have a high/low power switch on the CB. Use low power
whenever possible. It will lengthen your talk time appreciably. It is also
rather unwise to use high power when you are using a little rubber aerial
a few inches from your head!

I have some basic electronics books on these subjects (basic, basic
digital, and basic communications electronics books from radio shack),
but I wanted to get some input before I went and tried to do something
and blew up my radio.

Would this be possible using the methods I described? Would I need other
methods? Or would I just need to give it up and try something else?

(Also, does anyone know where I might find information about changing
the frequencies the radio runs on? If I could find a way to make it run
on the same frequencies as some smaller GMRS radios I have, that'd be
awesome... but from what I understand it would probably require changing
the entire guts of the radio... so if that's not feasible don't worry
too much about it.


No - two reasons. First, its illegal. Second, it needs careful setting up
with specialised test gear just to move the frequency a little. They just
won't go into the GMRS band - and wouldn't communicate with them even
they did! If the range of a GMRS is sufficient you would be better using
one of those anyway.



Follow-ups set to alt.electronics

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux...
Nascom & Gemini info at http://www.nascom.info

 

[Form@C]

On Tue, 20 Apr 2004 00:23:34 +0000, SB wrote:

IS it illegal?? Both FRS and CB bands are open....no license required!

It's the transmit power that's the regulated portion of each (<5W for CB
and not sure for FRS).

Yep, the restrictions are on the radiated power, frequency band and
modulation modes. OK, so may be *possible* to change any or all of these
but you arn't going to do it and keep the equipment legal unless you can
set it up correctly. You arn't going to do that without the proper test
equipment! It is one thing to change a crystal but something else
to *prove* that the new one or the coil tweaks needed to make it work
arn't introducing harmonic signals all over the band. Whether it is
economically feasible to make the mods is something else...

I haven't looked at the radio regs for a long time, but at one time I
think it atually *was* illegal to make modifications to a CB rig. They
were type-tested and certified - carrying the CB/27 symbol. Any mods meant
that the certification was automatically lost, making them illegal. There
are probably still clauses like this as well as those limiting the type of
aerial that can be connected (restricting the erp).

If he's thinking of FRS then dump the CB idea....traffic seems to be
getting less and less all the time (just the odd trucker looking for a
good place to chow!).

Dunno. I gave up on CB many years ago - before I took my RAE. Sounds like
the OP only wants a radio link back to base so it probably doesn't matter
which he uses providing he can get enough range.

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux...
Nascom & Gemini info at http://www.nascom.info

 

[SB]

Well, you don't often hear about guys being pulled over at CB checkpoints!
It's one of those things that isn't enforced until it HAS to be. So
basically, if mods made to a radio DON'T interfere with someone then I doubt
you'll hear otherwise.

There's plenty of Ham radio guys that build their own radio that don't have
to get it certified....however, those bands are all based on etiquette.

As far as poor mods....well, I wouldn't call it a mod if nobody else can
hear you cuz your mod is killing your signal (bad quality/etc.).

I have an old airband radio (ex SAR guy gave it to me) and he had it
"opened" up.
This didn't let me transmit on any extra bands, but it did let me listen to
a lot more...basically turned it in to a scanner....

At work, we're expecting some issues with US wireless LANs interfereing with
our transmitters. The Canadian made LAN equipment has provisions to keep
out of our band, but being so close to the US allows easy importing of
equipment that will drop on us in the band. We're lucky at the moment that
we're out in the boonies but will have issues in our suburban equipment.
We've made our complaints and the FCC/Industry Canada are checking
things....but if nobody complains it's not a big deal.



"Form@C" <mickREMOVE-THIS@mixtel.co.uk> wrote in message
newsan.2004.04.20.17.49.27.519325@mixtel.co.uk...

On Tue, 20 Apr 2004 00:23:34 +0000, SB wrote:

IS it illegal?? Both FRS and CB bands are open....no license required!

It's the transmit power that's the regulated portion of each (<5W for CB
and not sure for FRS).


Yep, the restrictions are on the radiated power, frequency band and
modulation modes. OK, so may be *possible* to change any or all of these
but you arn't going to do it and keep the equipment legal unless you can
set it up correctly. You arn't going to do that without the proper test
equipment! It is one thing to change a crystal but something else
to *prove* that the new one or the coil tweaks needed to make it work
arn't introducing harmonic signals all over the band. Whether it is
economically feasible to make the mods is something else...

I haven't looked at the radio regs for a long time, but at one time I
think it atually *was* illegal to make modifications to a CB rig. They
were type-tested and certified - carrying the CB/27 symbol. Any mods meant
that the certification was automatically lost, making them illegal. There
are probably still clauses like this as well as those limiting the type of
aerial that can be connected (restricting the erp).

If he's thinking of FRS then dump the CB idea....traffic seems to be
getting less and less all the time (just the odd trucker looking for a
good place to chow!).


Dunno. I gave up on CB many years ago - before I took my RAE. Sounds like
the OP only wants a radio link back to base so it probably doesn't matter
which he uses providing he can get enough range.

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux...
Nascom & Gemini info at http://www.nascom.info

 

[Form@C]

On Tue, 20 Apr 2004 22:08:50 +0000, SB wrote:

Well, you don't often hear about guys being pulled over at CB checkpoints!
It's one of those things that isn't enforced until it HAS to be. So
basically, if mods made to a radio DON'T interfere with someone then I
doubt you'll hear otherwise.

....probably 'cos you have either got it set right or are running such low
power that no-one can hear you.

There's plenty of Ham radio guys that build their own radio that don't
have to get it certified....however, those bands are all based on
etiquette.

They are also based on learning how to set the gear up, and what to test
for. It isn't all that easy to build a transmitter that is legal. Even the
amateurs get into a lot of trouble if they don't set their gear up
properly! Many years ago we used to get away with all sorts of lash-up
valve transmitters, but with increasing demands on bandwidth - and a lot
of commercial people that begrudge the amateurs *any* space at all - it
has become far more important to keep the transmitters as "clean" as
possible.

As far as poor mods....well, I wouldn't call it a mod if nobody
else can
hear you cuz your mod is killing your signal (bad quality/etc.).

LOL! - not a very effective mod either...
I once did a mod on an old CB rig to move it into the 28MHz band. It
worked, but as I was never able to check it properly for transmitted
harmonics, it has spent almost all it's modded life disconnected! It
wasn't helped that my licence didn't cover 28MHz at the time anyway... ;-)

I have an old airband radio (ex SAR guy gave it to me) and he had it
"opened" up.
This didn't let me transmit on any extra bands, but it did let me listen
to a lot more...basically turned it in to a scanner....

That should be ok. The receiver section doesn't cause problems (in most
cases - before someone mentions TRFs!)

At work, we're expecting some issues with US wireless LANs interfereing
with our transmitters. The Canadian made LAN equipment has provisions
to keep out of our band, but being so close to the US allows easy
importing of equipment that will drop on us in the band. We're lucky at
the moment that we're out in the boonies but will have issues in our
suburban equipment. We've made our complaints and the FCC/Industry
Canada are checking things....but if nobody complains it's not a big
deal.

Looks like you could be having some fun there... I bet there will be some
complaints of corrupted or insecure data before long.

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux...
Nascom & Gemini info at http://www.nascom.info

 

[Leif Neland]

js_530 wrote:

"Andrew Kesterson" <andrew@aklabs.net> wrote in message
news:<pan.2004.04.18.18.48.25.860367@aklabs.net>...
I have been looking on google and can't find anything on this
subject.

I want to take a mobile CB radio, designed to run off of a 12 volt
power line in an automotive vehicle, and convert it to run on 9V, C,
or D cell batteries so I can put it in a backpack and take it with
me when I go on long hikes away from home and the like, and talk
back to a base station in the house.

Would it be as simple as connecting a bunch of batteries together in
circuit and using a resistor (or series of resistors) to lower the
current (if too high), or using an amplifier to raise it?

You could not get a voltage higher than what you have from the
batteries, so the amplifier cannot be used. You need 12 volts or
higher from the batteries, because there's probally a good reason the
radio runs on 12 volts. If you had a voltage higher than 12 volts,
you could use a 12 volt regulator, but not resistors. The radio is
non-linear, and changes resistance based on whether or not it's being
used, so a regulator is needed. You might want to see how much
current the radio draws, and buy a 12 volt regulator higher than your
maximum current rating. If you are using a source slightly higher
than 12 volts, than you need a minimum voltage dropoff rating on the
regulator of the difference between the battery voltage and 12 volts.
´

"12V" in a car ís at least 13.6V, and the CB will probably survive 15 v or
so at least.

Leif