AFAIK, an Automatic Noise Limiter is just a diode that shunts off
spikes (zener diode?). Can anyone help shed any light on my quest to
homebrew one? (Like what they might use, or where it might go).

I couldn't find any examples of one or schematics of one, so I'm at a
loss.

On a sunny day (18 Aug 2006 16:51:43 -0700) it happened "SparkySKO"
wrote in
om:

AFAIK, an Automatic Noise Limiter is just a diode that shunts off
spikes (zener diode?). Can anyone help shed any light on my quest to
homebrew one? (Like what they might use, or where it might go).

I couldn't find any examples of one or schematics of one, so I'm at a
loss.


One type of ANL in analog TV used a capacitance diode.
Anytime a big spike occurred, it de-tuned the circuit (38MHz IF).
This was Philips design IIRC, possibly patented.

If you wanted to go more 'advanced' you could delay the signal
with an analog delay line for a few micro seconds, trigger some
circuit on the spike, and then mute the delayed the signal _before_
the spike starts for some time...

Could be done digital too(when will CB go digital to 300 channels
in the same band? oh well...)

If you want to use the varicap system all you need is a varicap, capacitor,
resistor bias likely.

SparkySKO wrote:
AFAIK, an Automatic Noise Limiter is just a diode that shunts off
spikes (zener diode?). Can anyone help shed any light on my quest to
homebrew one? (Like what they might use, or where it might go).

I couldn't find any examples of one or schematics of one, so I'm at a
loss.

Are we talking RF or audio ANL?

telstar-electronics.com

Are we talking RF or audio ANL?

telstar-electronics.com

I imagine it's an RF ANL. Something inside the radio rather than
something on the speaker side.

On a sunny day (Wed, 23 Aug 2006 05:02:48 +0100) it happened "Peter"
wrote in 44f4a7c0.0@entanet:

"SparkySKO" wrote...

AFAIK, an Automatic Noise Limiter is just a diode that shunts off
spikes (zener diode?).

Not quite, shunting spikes is more like the work of the noise blanker (NB).
The ANL cuts off the background hiss. This can simply be a diode, biased just below
cut-off, which will only conduct when the level takes it above cut-off.

Can anyone help shed any light on my quest to
homebrew one? (Like what they might use, or where it might go).

I couldn't find any examples of one or schematics of one, so I'm at a
loss.

Is this what you are looking for...

President Adams (PC346)... Diode D12.
Cobra 148GTL (not the DX)... Diode D23.
In the above circuits, the ANL appears to be ON unless disabled by the
switch. This is done by placing a capacitor across the diode, allowing
all audio to pass through.

Cobra 148GTL-DK MK1 (PC879)... Diode D35.
Cobra 148GTL-DX MK2 (PB-010)... Diode D28.
President Jackson (PB-042)... D22.
Presiden Grant (PC-999)... D28.
In the above circuits, the ANL is ON unless disabled by the switch. This
is done by DC shorting the diode, allowing all audio to pass through.


Cybernet chassis PTBM059... Diode D26.
Cybernet chassis PTBM121... Diode D26.
Cybernet chassis PTBM125... Diode D39.
Cybernet chassis PTBM133... Diode D37.
Cybernet chassis PCMA001... Diode D39.
In the above circuits, the ANL is OFF unless enabled by the switch. When
off, a pair of resistors allow signal to bypass the diode. To switch the ANL
on, a capacitor shunts the bypass signal to ground... leaving only that
passing through the diode.

Emperor Shogun... Diode D114.
A quick look at the circuit suggests that the diode is normally biased just
below cut-off, with the ANL being switched off by biasing the diode fully on.

I also have a Maxon type diagram, which I believe is something like a Commtron CXX (AM / FM).
Standard type AM PCB (LC7120) with added FM board and crystal board for High and UK channels.
This looks like a built in ANL, D106, with nothing to switch it off.


IF you don't have any of the above diagrams and you want the ANL diagrams, I can
Email them to you. Please don't use "reply to", as the Email address in my
header is despammed and never used.
You can contact me through the contact form on the CB Website below.


Regards,
Peter.
http://www.citizensband.radiouk.com/

There is actually an other way to reduce noise in the transmister-
receiver chain.
This is to use an expander in the transmitter, and a compander in the receiver.
One could use a Philips NE570 chip (if you could still find one) in the audio
on each side, but you can also use the NE570 as expander only in a receiver
(like your diode, the noise will be less amplified then the signal).

As all this requires electronics, and may pose problms for some, but you can do
it with a PC an Linux too, using the sox program:

Compander:
sox example.wav example_companded.wav compand 0.003,.013.5 -80,-40,-60,-30,-40,-20,0,0 1

Expander:
sox example.wav example.expanded.wav compand 0.003,.013.5 -40,-80,-30,-60,-20,-40,0,0 1

With 2 soundcards you can put the CB audio out into one soundcard input, use
that PCM as input for sox, and have sox write to the other soundcard for output.
http://panteltje.com/panteltje/cb/

There is a small delay... but you can use it in the transmit side too, add echo and other
effects etc..

Digital signal processing.

Here is the future.

On a sunny day (Wed, 30 Aug 2006 11:32:04 GMT) it happened Jan Panteltje
wrote in :

This is to use an expander in the transmitter, and a compander in the receiver.

Should of course be: compander in transmitter, expander in receiver.
You reduce dynamic range so it matches that of the radio channel.

"Jan Panteltje" wrote...

There is actually an other way to reduce noise in the transmister-
receiver chain.
This is to use an expander in the transmitter, and a compander in the receiver.


"Jan Panteltje" then wrote...

Should of course be: compander in transmitter, expander in receiver.
You reduce dynamic range so it matches that of the radio channel.

I was just about to correct that one.

A better system involves splitting the high and low frequencies first. As the unwanted noise
is at the high frequency end, only high frequencies are compressed and expanded. You can split
into more bands, but I think the OP wants simple starter ideas.

One could use a Philips NE570 chip (if you could still find one)

Got one sat here in stock.


As all this requires electronics, and may pose problms for some, but you can
do it with a PC an Linux too, using the sox program:

One could also use pre-emphasis and de-emphasis, which is very simple. Maybe
the OP should start with the ANL and, if he is game for more, go on to try some of
the other ideas.


There is a small delay... but you can use it in the transmit side too, add echo and other
effects etc..


What is it What with is what CB is it and with it echo with CB and echo CB and echo CB and echo
and echo echo?


Regards,

Peter.
http://www.citizensband.radiouk.com/

On a sunny day (Thu, 31 Aug 2006 04:07:05 +0100) it happened "Peter"
wrote in 44f65e01.0@entanet:

One could also use pre-emphasis and de-emphasis, which is very simple. Maybe
the OP should start with the ANL and, if he is game for more, go on to try some of
the other ideas.

Yes

There is a small delay... but you can use it in the transmit side too, add echo and other
effects etc..


What is it What with is what CB is it and with it echo with CB and echo CB and echo CB and echo
and echo echo?

LOL
:-)