SSB Carrier Supression

[Mikebits]

the conceivable way to do it is to cut out the mic input when there is presence of the audio input from the speaker, flat5 is right - I was sure I did forget something.

How do you distinguish audio from a speaker as opposed to audio from the mouth?

 

[Nigel Goodwin]

How do you distinguish audio from a speaker as opposed to audio from the mouth?

Basically you feed the direct audio signal from the speaker amplifier to the audio preamp, in anti-phase, this cancels the speaker audio from the mike.

 

[Mikebits]

Basically you feed the direct audio signal from the speaker amplifier to the audio preamp, in anti-phase, this cancels the speaker audio from the mike.

This requires sophistication of something like a DSP, which I said earlier.

 

[Nigel Goodwin]

This requires sophistication of something like a DSP, which I said earlier.

No, it can be very simple, and work perfectly well for HAM use.

However, I would never consider using VOX anyway

 

[Space Varmint]

This requires sophistication of something like a DSP, which I said earlier.

How about a tranformer?

 

[xanadunow]

How do you distinguish audio from a speaker as opposed to audio from the mouth?

The output amp for the audio (speaker) does have definable volume even before it is adjusted with the volume pot.

It is then, only a matter of defining the minimum amplitude before the antivox kicks-in and monitoring the max amplitude to detect periods of silence to cut out or not your VOX/mic

 

[Mikebits]

No, it can be very simple, and work perfectly well for HAM use.

However, I would never consider using VOX anyway

I see it working in principle, but something in the back of my mind tells me otherwise.
For example, something received at RX A while sender speaks at TX A, TX A will be cutout.

Get what I was meaning? Hard to explain.

 

[xanadunow]

VOX monitors your mic input, ANTIVOX monitores you speaker output (before the volume control) and cuts out the VOX if/when required.

 

[xanadunow]

when you transmit, you do not receive.. and if you wnted to hear yourself in the speaker, a simple "yes" - I am transmitting, or "no" - I am receivng will decide if the ANTI-VOX will cut in, or not.

 

[Mikebits]

Consider this. RX gets a signal in. ~~~ TX at the same time sends ~-~-

Now how is this VOX circuit going to differentiate between the two? Only with complex DSP is this going to happen.

 

[Mikebits]

when you transmit, you do not receive.. and if you wnted to hear yourself in the speaker, a simple "yes" - I am transmitting, or "no" - I am receivng will decide if the ANTI-VOX will cut in, or not.

Your missing my point. With VOX the speaker has no idea when the far end will send. So at the same time, far end and near end want to send. The first one to speak will cause the slower one to get cancelled out by the vox. For full duplex, the best way is two frequencies.

 

[xanadunow]

Mike

For the purpose of transmitting, you have GND'ed .. errm.. you have made your receiver DEAD .. and you have also provided logical information to your ANTIVOX that you are in the transmit mode.. and this is all info needed.

 

[Mikebits]

For the purpose of transmitting, you have GND'ed .. errm.. you have made your receiver DEAD .. and you have also provided logical information to your ANTIVOX that you are in the transmit mode.. and this is all info needed.

Okay, I buy that. Damn, now I am speechless

 

[xanadunow]

when you're receiving - you also provide the "logical" information to your anti-vox.. so it is never confused - what to do

 

[Mikebits]

Well maybe not completly speechless. Your concept works fine for transmitt, but not for receive. Now we are back to the original argument. Sound comes in over RX speaker, how does vox know it is not you trying to transmitt?

 

[xanadunow]

It's OK.. I do know this feeling too

 

[Mikebits]

Talk about a circular argument...

 

[Mikebits]

What do you think of my new avatar? Kinda distinguished don't ya think?

 

[xanadunow]

OK.. again then.. for simplicity: the receiver does see only the product of the detector - pure audio that will arrive at the volue control of the speaker or headphones.. your receiver will never "hear" your mic. So, you have a distinction between two very independant circuits.. one of them is looking at your mic(vox).. the other is looking at your speaker (antivox). There is also the yes/no answer whether you are in the receive or in the transmit mode, what other information would you need?

 

[xanadunow]

Kinda like that pic but this thing has a sharp beak and my wonderfull cat I wanted to put as my avatar could be "harmed".. so you have spoiled it .. (not for long)