CB Radio power supply?

[L. Fiar]

Thanks,
Now i'm confused. Anyway, I have just picked up the cb I
intend to use with this power supply, but I need to get
a mike and aerial for it. On the back of the cb is
stamped 13.2 volt. I think I will definitely go with
what Stan recommends above and use two diodes in parallel
to drop down to about 13.2 volt.

The sets were often marked as 13.2 volts, but would usually take
from about 11.2 to 15.2 volts.
You may get a slight problem with the supply being switched mode,
such as some noise from it blocking out weaker signals. It may
not happen, but it can with those supplies.

This cb was made in 1981 I do not want to push my luck.

Many of those made back then were well made, although some were made to a
price (just put them on any channel, and hear all 40 at once). Modern UK
sets all have better filters in them, as the law was changed to force the
manufacturers to design the receivers better.
The microphone will need to be wired correctly for the specific radio.
Assuming it is one of the legal ones (marked "CB 27/81" on the front), what
make and model is it?

Another issue, is licensing... CB is supposed to become licence free later
this year, although nothing definite has been put out. For more info, there
is a CB newsgroup:
uk.rec.radio.cb
For more CB related info, including microphone wiring for UK CBs:
http://www.citizensband.radiouk.com/

 

[L. Fiar]

This is a commtron cb40f.

Hi.

This sounds like one of the old Maxon designs, used in many of the Midland
and Colt CBs in the UK back in the early 1980s. Although there were slight
variations of the Maxon circuits, the ICs in it would most likely be:
KIA7205 audio amp - Max 18v.
MC3357 NBFM IF system - run from a regulator.
LM324 op amp - Max 32v, but run from a regulator.
LC 7137 PLL - run from a regulator.
MC7808 regulator - Max 35v.
The output transistor will be a 2SC2078 - Max 75v (Vce).

As someone has mentioned, a car electrical system voltage will go up and
down, so the radios are designed to take those voltage ranges.
If you are still unsure, find a standard regulated supply made for running
automotive type equipment. They can be found quite cheap now, maybe a pound
or two on a car boot or flea market.
You may find CB rather quiet now, depending upon your area, but someone on
there may be selling a CB power supply.

 

[Mike Berger]

It's a matter of chemistry. A Lead-acid wet cell delivers 2.2 v.,
and there are 6 of them in an automotive "12 v." battery.

 

[Allodoxaphobia]

It's a matter of chemistry. A Lead-acid wet cell delivers 2.2 v.,
and there are 6 of them in an automotive "12 v." battery.

And, as a matter of mathematics,

6 x 2.2 = 13.2 ,

for various values of 2.2.

Jonesy

 

[Dbowey]

Jonsey posted:

<< On 7 Jun 2004 15:21:58 -0700, Mike Berger hath writ:

It's a matter of chemistry. A Lead-acid wet cell delivers 2.2 v.,
and there are 6 of them in an automotive "12 v." battery.

And, as a matter of mathematics,

6 x 2.2 = 13.2 ,

for various values of 2.2.
Actually, a lead-acid cell voltage, on float, is 2.17V. It would only be 2.2V
on charge. That's for most any value of 2.17.

Don

 

[Howard Eisenhauer]

Jonsey posted:

<< On 7 Jun 2004 15:21:58 -0700, Mike Berger hath writ:

And, as a matter of mathematics,

6 x 2.2 = 13.2 ,

for various values of 2.2.

Actually, a lead-acid cell voltage, on float, is 2.17V. It would only be 2.2V
on charge. That's for most any value of 2.17.

Don

Actually, it depends on the cell's chemistry- lead-calcum,
lead-antimony etc. By rights the float should also be adjusted for
cell temperature.

The batteries I maintain at work are speced for 2.23 V @ 22C. The
equalize voltage is closer to 2.28. Most of the installations I look
after do monitor the cell temp & adjust the float accordingly.

Howard.

 

[Dbowey]

Howard posted:

<<

Jonsey posted:

<< On 7 Jun 2004 15:21:58 -0700, Mike Berger hath writ:

And, as a matter of mathematics,

6 x 2.2 = 13.2 ,

for various values of 2.2.

Actually, a lead-acid cell voltage, on float, is 2.17V. It would only be 2.2V
on charge. That's for most any value of 2.17.

Don

Actually, it depends on the cell's chemistry- lead-calcum,
lead-antimony etc. By rights the float should also be adjusted for
cell temperature.

The batteries I maintain at work are speced for 2.23 V @ 22C. The
equalize voltage is closer to 2.28. Most of the installations I look
after do monitor the cell temp & adjust the float accordingly.In an early part of my time with a telco, I was responsible for a dozen or more
offices, each having battery strings of 24, 52, 130 and/or 250 Volts. All the
lead-acid batteries were floated at 2.17 Volts per cell, and the temperature
was never a consideration for the FLOAT volts per cell. Temperature, while
always recorded, was not a concern except when the cells were being subjected
to their routine over-charge.

Don

 

[Howard Eisenhauer]

Howard posted:

<<


Actually, it depends on the cell's chemistry- lead-calcum,
lead-antimony etc. By rights the float should also be adjusted for
cell temperature.

The batteries I maintain at work are speced for 2.23 V @ 22C. The
equalize voltage is closer to 2.28. Most of the installations I look
after do monitor the cell temp & adjust the float accordingly.
In an early part of my time with a telco, I was responsible for a dozen or more
offices, each having battery strings of 24, 52, 130 and/or 250 Volts. All the
lead-acid batteries were floated at 2.17 Volts per cell, and the temperature
was never a consideration for the FLOAT volts per cell. Temperature, while
always recorded, was not a concern except when the cells were being subjected
to their routine over-charge.

Don

Don, again it depends on the cell's chemistry. I've been responsible
for either commisioning or maintaining more 24 & 48 V battery plants
than I can remember, literally in the hundreds. I was involved one
time in replacing a string of wet cells where we had to change the
float voltage because one set was lead/calcium, the other was
lead/antimony. I've seen plants (a long time ago) that float @ 2.17
as you have you, I've seen a lot more that float @ 2.23. These are
mostly GNB Absolyte 11P, some C&D Liberty plants & a few strings of
C&D & Exide wet cells.

As for adjusting the float according to cell temp, this is something
that has become "a cause" in the last 10 years or so. Some people
say it's BS, others swear by it. In an office environment where the
temperature is relativly constant & close to the temp speced for the
nominal float V it's not normally a big deal, however not all
batteries get installed in a controlled environment.. Unfortunatly I
can't find an on-line referance but if you can find a copy of a GNB
Absolyte maintenance manual you'll see that they, at least, put a lot
of stock in the idea.

Recording the cell temp is always good. A few months back I was
contracted to do load tests on some ~10-~12 year old strings that had
NOT been maintained according to the manufacturer's standards. When
one cell shot up over 40 C & started making snapping noises right at
the start you can bet your A$$ I stopped that test & recorded the
reason why .

FYI- The hot tickie these days for battery maintenance is a unit built
by a company called Midtronics. This thing will actually (they claim)
measure a cells internal resistance. Again, some caim its BS, some
swear by it. I've used them a few times, you certainly can see the
differance between a cell that will hang in there on load & one that
will drop to critical V well before the rest.


Howard.