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#61
January 13th 07, 11:39 PM
posted to rec.radio.cb
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What makes it tick?
"james" wrote in message ... On 12 Jan 2007 16:33:42 -0800, "Telstar Electronics" wrote: +++james wrote: +++ You are correct in that they are two different modes. They are +++ amplitude modulated signals and are derived from the same general +++ equation. Look in any Communications Text book used in Electrical +++ Engineering school. +++ +++Like I said... they are very different. +++ +++Don't miss seeing the new CB Radio Speech Processor Prototype at +++http://www.telstar-electronics.com/d...s/WhatsNew.htm ********* No they aren't. They are more similar than different. SSB is an AM signal that has the carrier supressed and the opposite sideband filtered out. Then again I would expect a tech to not totally understand the subtle differences between AM and SSB. james SSB is AM with part of the spectrum reuced. Its still AM. |
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#62
January 13th 07, 11:43 PM
posted to rec.radio.cb
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What makes it tick?
"Jimmie D" wrote in message ... "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. |
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#63
January 14th 07, 03:23 AM
posted to rec.radio.cb
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What makes it tick?
On Sat, 13 Jan 2007 17:39:49 -0500, "Jimmie D"
wrote: +++ +++"james" wrote in message m... +++ On 12 Jan 2007 16:33:42 -0800, "Telstar Electronics" +++ wrote: +++ ++++++james wrote: ++++++ You are correct in that they are two different modes. They are ++++++ amplitude modulated signals and are derived from the same general ++++++ equation. Look in any Communications Text book used in Electrical ++++++ Engineering school. ++++++ ++++++Like I said... they are very different. ++++++ ++++++Don't miss seeing the new CB Radio Speech Processor Prototype at ++++++http://www.telstar-electronics.com/d...s/WhatsNew.htm +++ ********* +++ +++ No they aren't. They are more similar than different. SSB is an AM +++ signal that has the carrier supressed and the opposite sideband +++ filtered out. +++ +++ Then again I would expect a tech to not totally understand the subtle +++ differences between AM and SSB. +++ +++ james +++ +++SSB is AM with part of the spectrum reuced. Its still AM. +++ ************** I believe I stated that earlier. Oh well. james |
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#64
January 14th 07, 03:42 AM
posted to rec.radio.cb
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What makes it tick?
On Sat, 13 Jan 2007 17:43:52 -0500, "Jimmie D"
wrote: +++ +++"Jimmie D" wrote in message . .. +++ +++ "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 |
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#65
January 14th 07, 04:13 AM
posted to rec.radio.cb
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What makes it tick?
"james" wrote in message ... On Sat, 13 Jan 2007 17:43:52 -0500, "Jimmie D" wrote: +++ +++"Jimmie D" wrote in message .. . +++ +++ "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.. |
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#66
January 14th 07, 10:45 PM
posted to rec.radio.cb
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What makes it tick?
On Sat, 13 Jan 2007 22:13:25 -0500, "Jimmie D"
wrote: +++ +++"james" wrote in message m... +++ On Sat, 13 Jan 2007 17:43:52 -0500, "Jimmie D" +++ wrote: +++ ++++++ ++++++"Jimmie D" wrote in message et... ++++++ ++++++ "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. Neither circuit requires the receiver to have any special ciruitry to enhance intelligibility. james |
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#67
January 15th 07, 02:19 AM
posted to rec.radio.cb
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What makes it tick?
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 |
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#68
January 15th 07, 04:28 AM
posted to rec.radio.cb
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What makes it tick?
"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. More like 30 to 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. My experience has been that 9 or 10 db is enough clipping. I cant imagine 30 db of clipping 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. 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. Neither circuit requires the receiver to have any special ciruitry to enhance intelligibility. james |
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#69
January 15th 07, 01:22 PM
posted to rec.radio.cb
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What makes it tick?
Jimmie D wrote:
.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." So I guess the inference here is that the audio output is grossly distorted? www.telstar-electronics.com |
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#70
January 15th 07, 03:20 PM
posted to rec.radio.cb
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What makes it tick?
"Telstar Electronics" wrote in message ups.com... Jimmie D wrote: .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." So I guess the inference here is that the audio output is grossly distorted? 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. www.telstar-electronics.com |
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