Jimmie D wrote:
No it works quite well, but it is not something you would want to show off
and I dont ever infer anything. If I didecide to keep one it will be built a
lot better than this one of better componets but even this thrown together
piece of junk clipper will work a hell of a lot better than your compressor.

Temper, temper. I merely thought that when you said it sounded like you
turned on a big amp... that you were referring to how most people
overdrive their amp... and sound distorted. I guess that's not what you
meant. Don't be so sensitive... you're getting just like Frank.

www.telstar-electronics.com

"james" wrote in message
...
On Sat, 13 Jan 2007 22:13:25 -0500, "Jimmie D"
wrote:

+++
+++"james" wrote in message
om...
+++ On Sat, 13 Jan 2007 17:43:52 -0500, "Jimmie D"
+++ wrote:
+++
++++++
++++++"Jimmie D" wrote in message
. net...
++++++
++++++ "Telstar Electronics" wrote in
message
++++++ ups.com...
++++++ Jimmie D wrote:
++++++One thing did get me thinking. I
++++++ have a nice scope to look at the output of my TX and to lookat
the
++++++ output of
++++++ the processor , for me its a piece of cake to setup. How can
you do
+++this
++++++ without test equipment?
++++++
++++++ Absolutely, I have a nice Tektronix scope I use...
++++++
++++++ Don't miss seeing the new CB Radio Speech Processor Prototype
at
++++++ http://www.telstar-electronics.com/d...s/WhatsNew.htm
++++++
++++++ But how does most of the people who buy them do it?
++++++
++++++Even a good quality limiter/compressor is just anotheer splatter
box if
+++its
++++++not set up right.
++++++
+++ ************
+++
+++ The theory behind a compressor amp is to provide a more constant
power
+++ signal to the modulator. There have been many schemes in the past 70
+++ yrs or so to do that. Even to the point of what was once called Super
+++ Modulation.
+++
+++ A properly setup with compression will not have excessive compression
+++ and also not use the compression stage as the major gain stage. Where
+++ most compression schemes come into dislike is when the person using
it
+++ feels he needs to get far more gain from the circuit than is really
+++ necessary and so much compression that you can hear a roach fart 20
+++ feet away.
+++
+++ The idea behind audio compression and other audio/rf processing
+++ schemes is to increase signal to noise ratios. When using AM and the
+++ carrier is already 30 dB above the ambient atmospheric noise then any
+++ processing is typically useless. The gain in signal to noise ratio is
+++ not worth the effort or even the cost of adding such a circuit. Audio
+++ compression is totally useless on FM unless you want a constant
+++ deviated signal. For what ever reason that one would want this is
+++ beyond all logic.
+++
+++ Even when the AM signal is marginal to the atmospheric noise, audio
+++ compression alone yields between 1 and 2 dB improvement in the
+++ received signal to noise ratio. On AM, when you are at 6 to 8 dB
+++ signal to noise ratio, improving one to two dB is generally worthless
+++ improvement.
+++
+++ james
+++
+++
+++Clippers are much more useful. Ususally you can clip off the top 8 or 9
db
+++without substantial effecting intelligebility of the voice. This does
make
+++for a louder signal without overmoduation. Compression works best when
used
+++with an expander on the rx end. But how often are you going to see
that..
+++
**********

The goal of both compression and clipping of the audio signal is
reduce the peak to average power of the human voice. Typical Human
voice peak to average power range is about 3:1.

Clipping can be as high as 30 dB as long as there is sufficient
filtering after the clipping stage to restore the audio bandwidth to
its original bandwidth. Otherwise you have splatter or increased
modualted bandwidth.

Compression is somewhat more effective in reducing the peak to averge
power in the voice. It can be implemented with better results. A major
drawback to compression over clipping is increased cost with a more
complex circuit and more difficult adjustments. All to often in CB
work the compression stage also doubles up to be mic amp and a large
gain stage at the very low level stages of the audio stream. I
personally don't like this as it requires to many adjustments for one
stage. Audio compression is better done, in my opinion, in or near the
final stage, high level, of the audio stream. This too is not without
its drawbacks either.

Oh my! Don't bring up high level modulation to Brian or he'll soon be trying
to install one of his hacks in an old tube type transmitter! We don't want
to get him killed!

Yo Mamma wrote:
Oh my! Don't bring up high level modulation to Brian or he'll soon be trying
to install one of his hacks in an old tube type transmitter! We don't want
to get him killed!

A college freshman who knows it all, and is ready to take on the
world... LOL

www.telstar-electronics.com

On 14 Jan 2007 17:19:38 -0800, "Telstar Electronics"
wrote:

+++james wrote:
+++ Then again I would expect a tech to not totally understand the subtle
+++ differences between AM and SSB.
+++
+++You fit this description well...
+++
+++www.telstar-electronics.com
********

You are entitled to your opinion. However small it may be.


james

On Sun, 14 Jan 2007 22:28:56 -0500, "Jimmie D"
wrote:

+++From my experience compression is more to allow consistent modulation when a
+++change in voice, such as the difference when I talk on the radio and my wife
+++talks. IF she tries without readjusting the mike gain she may not be heard.
+++
+++Clipping really removes audio not needed for effective modulation and
+++amplifies that that contains the most intelligence. This often shows up on
+++the rx S meter as less than an S unit change over an unclipped signal but
+++sounds like 10db or more increase.I dont have a clipper except for this
+++peice of junk I threw together the other day but when I did have one the
+++reaction was usually" wow how big is that amp you just turned on."
+++
+++On SSB average power out of a 100 wat tx on voice may be only 12 watts
+++average add a clipper and you can increase that to 80
+++
+++My preference is a clipper with some AGC action to keep the average output
+++level faily constant.
*************

Again I reiterate that both audio clipping and audio compression
attempt to to the same thing, that is to reduce the peak to average
power in an audio signal.

Compression techniques are basically a variable gain stage in which
the gain is contrtolled by the input signal power. Therefore as teh
input is low the gain is high. As power increases the gain reduces.
This raises the average audio power while maintianing the peak power.
Compression suffers from attack time and decay time issues. Set the
decay to slow and the gain does not return to higher levels fast
enough to amplity lower power signals. Set the decay time to fast then
the compressor becomes ineffective. The attack time issues are even
more critical in their adjustments.

A clipper works by removing the power above a certain threshold. That
power does not just go into oblivion. Instead the power goes into
harmonics of the audio frequencies that make up the power signal.
Therefore with clipping the peak to average is reduced by moving the
power in the peaks of the audio power signal into the harmonics of
that signal. There filtering will attenuate the harmonics to restore
the original bandwidth. You need sufficient filtering with clipping
somewhere in the amplifier chain before that audio power signal
reaches the modulated stage.

The major issue of audio processing to decrease the peak to avergae
power is not to do so much that you over stress the average
characteristics of the modulated stage and any subsequent amplifier
stage. Also do not confuse PEP (Peak Envelope Power) with Peak to
average. They are two different identities.

A clipper with some form of agc is eesentially a clipper/compressor
combination. Another best unto itself.

james

On Tue, 16 Jan 2007 18:21:55 GMT, james wrote
in :

snip
A clipper with some form of agc is eesentially a clipper/compressor
combination. Another best unto itself.


Which brings us right back to what I had suggested very early in this
discussion: Take Brian's hack-job and follow it with an RF-type
clipper. The two could probably be combined but I suspect alignment
would be a whore.

"james" wrote in message
...
On 14 Jan 2007 17:19:38 -0800, "Telstar Electronics"
wrote:

+++james wrote:
+++ Then again I would expect a tech to not totally understand the subtle
+++ differences between AM and SSB.
+++
+++You fit this description well...
+++
+++www.telstar-electronics.com
********

You are entitled to your opinion. However small it may be.


james


Be careful, he'll "LOL" you to death!



Posted Via Usenet.com Premium Usenet Newsgroup Services
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On Tue, 16 Jan 2007 21:33:06 -0500, wrote in
:

On Tue, 16 Jan 2007 18:22:27 -0600, "U-Know-Who"
wrote:


"james" wrote in message
. ..
On 14 Jan 2007 17:19:38 -0800, "Telstar Electronics"
wrote:

+++james wrote:
+++ Then again I would expect a tech to not totally understand the subtle
+++ differences between AM and SSB.
+++
+++You fit this description well...
+++
+++www.telstar-electronics.com
********

You are entitled to your opinion. However small it may be.


james


Be careful, he'll "LOL" you to death!


That's because he watches too much TV. He thinks life is a sitcom so
he needs to add a "virtual laugh-track" to his posts.

"Frank Gilliland" wrote in message
...
On Tue, 16 Jan 2007 18:21:55 GMT, james wrote
in :

snip
A clipper with some form of agc is eesentially a clipper/compressor
combination. Another best unto itself.


Which brings us right back to what I had suggested very early in this
discussion: Take Brian's hack-job and follow it with an RF-type
clipper. The two could probably be combined but I suspect alignment
would be a whore.



Well the idea is good but the method of doing it is a little overdone if you
use Brians compressor.

On Wed, 17 Jan 2007 00:45:51 -0500, "Jimmie D"
wrote in
:


"Frank Gilliland" wrote in message
.. .
On Tue, 16 Jan 2007 18:21:55 GMT, james wrote
in :

snip
A clipper with some form of agc is eesentially a clipper/compressor
combination. Another best unto itself.


Which brings us right back to what I had suggested very early in this
discussion: Take Brian's hack-job and follow it with an RF-type
clipper. The two could probably be combined but I suspect alignment
would be a whore.



Well the idea is good but the method of doing it is a little overdone if you
use Brians compressor.


True. And I try to avoid using ASIC's whenever possible.