SSB Carrier Supression

[xanadunow]

the speed

1.. 2.. msec.. nah.. this seems "to fast" - the antivox should "judge" the "envelope/noise" of the voice comming out of the speaker - as it is. I do know a woman that can speak so fast that it would break the "rule" .. but 30msec.. or even more, will do me.. - to let the antivox enough time to give the vox (mic) the permission to speak(or not) within the "breaks" between the words received and activate the tx.

xanadunow

 

[xanadunow]

the phase again

I have stated that earlier too, but I have been contradicted and could not find a "live" example to prove it quickly enough.

You feed a part of the signal from your receiver's output back to the mic stages - but in opposite phase to the speaker's signal - and, the need for the antivox dissapears.. except, mic stages have to be "clever" enough to cover for the different volume of your listening habits..

Why don't we just use the headphones

The antivox - does hold it's value..

 

[xanadunow]

Even if your feedback does come from the slider of the "volume control" it will never account for the size of the speaker, it's laudness and the distance from it to the mic.. Just - to many variables and you would not know how to scale the feedback to match the real time response.

 

[Nigel Goodwin]

You feed a part of the signal from your receiver's output back to the mic stages - but in opposite phase to the speaker's signal - and, the need for the antivox dissapears.. except, mic stages have to be "clever" enough to cover for the different volume of your listening habits..

That's what anti-VOX is, it just prevents the speaker output affecting the mike input - you're making it far more complicated than it is

 

[xanadunow]

It will just not know where the speaker is.. is it on the shelf abowe, at the back of the room or under the table.

 

[Nigel Goodwin]

It will just not know where the speaker is.. is it on the shelf abowe, at the back of the room or under the table.

It doesn't matter a great deal - you simply adjust the level accordingly.

 

[xanadunow]

Thank you

I do not use it much at all; PTT is my choice Nigel, but the internal aspects have become very much more clear to me because of this thread.. and - I do thank you all for that.

Regards,
xanadunow

 

[audioguru]

An ordinary PA system breaks into acoustical feedback howling regardless of the phase of the wires on the speaker because the phasing is different at each frequency.

Speakerphones have the mic and speaker very close together so reflections in a room won't affect phasing but they don't use simple reversed phase to cancel the amount of speaker sound picked up by the mic. Because the phasing is different at each frequency.

 

[Space Varmint]

Just got a 59 from Skyler County,IL

 

[Nigel Goodwin]

An ordinary PA system breaks into acoustical feedback howling regardless of the phase of the wires on the speaker because the phasing is different at each frequency.

Speakerphones have the mic and speaker very close together so reflections in a room won't affect phasing but they don't use simple reversed phase to cancel the amount of speaker sound picked up by the mic. Because the phasing is different at each frequency.

You're still not getting the point AG - you don't have microphone and speaker working at the same time, it's purely simplex - so because there's no wanted input to the mike, it's simple to cancel enough of the speaker signal out to prevent the VOX triggering. Then a required voice input is plenty to trigger the VOX.

 

[Space Varmint]

SHew! I'm beat. I just reworked the 80 watt linear. It's working great! That's how I got that 59. I can just grumble in the mike and I see the frequency pop up on the freq counter through the air. It's clean from no to low to full signal. One thing I had to do that surprized me, was to raise the base impedance slightly. I rewound the filter coils and inductor on the input It's biased with an LM317. It's sweet.

 

[Nigel Goodwin]

How about posting a photo of the inside of this infamous device?.

 

[Space Varmint]

How about posting a photo of the inside of this infamous device?.

Hey that's not a bad idea. I was catching up on some rest. I think I'm gonna take a PLL I built recently and convert it to 11MHz For the up converter VFO. I think that 80 watter is pulling it off frequency.

 

[Space Varmint]

Yep that's what I'm gonna do. I'm really gonna do it alright. I got VXO in the modulator section and I'll put PLL on the VFO and should be good to go.

 

[xanadunow]

More on AntiVox while SV is looking for the camera on his mobile phone..

The AntiVox, you have described Nigel is most certainly the way and the solution in the rigs that I do remember.. This is exacly the way they operate; the opposite phase to the mic comming via wire, to the phase comming through air from the speaker to the mic and the adjustable level to trim, and - importantly the Vox being the "governor", i.e. if you insist to "talk" - the transmitter does comes on..

Enclosed is a different approach and I have been confused by not remembering the "ropes".

In the Vox/Antivox solution (as per your description) - you are the person who makes the decision to make the transmitter to come ON. Quite right.

======

Altrnative approach:

In the enclosed "solution" you do not have that choice, you either force it by pressing the PTT or you wait for the AntiVox to allow you to transmitt. The Antivox becomes the "governer" of the Vox.

There is an AC pickup from your Rx-audio being delivered to an OpAmp acting as full wave rectifier outputting DC levels only. Subsequently, the R1-C1 and C1-R2 circuits - do controll the rising and decaying slope and - resulting "envelope" of the RX'ed signal.

The distinction between a valid received transmission and noise is done using the comparator taking as it's 2nd input the DC level from a pot set just above the noise floor of the RX'ed audio(adjustable).

The rest is just pure "logic"

The OR gate does accept the Antivox decission or it is overriden by the PTT and - the NAND gate ensures that any side tone will disable the operation of the Antivox while you are already in the transmit mode listening just to the sidetone, meaning - your Tx is already On.

The "output" from the OR gate energises the digital "relay" and disconnects both mic and the keyer from the possibility to transmitt when the valid RX signal is pressent.

This idea was brought in the effort to provide a fast "break-in" especially in the CW mode and the Vox can employ exactly the same "slope detection/shaping technique" to ensure a true hands free operation (unless your hand is keying in the CW mode ofcourse).

=====

I do wish it was/is mine

The attached picture, represents only the logical flow of the signal and is not the exact diagram. In particular - the shaping of the receiving envelopes can probably be done better using an op amp; the R1, C1, R2 are only informative here to show paths for the capacitor C1 to charge and to discharge.

The main difference is, that the AntiVox controlls the operation and not the Vox.

Except for the "PTT override", the Vox controlls only when to quit the TX mode and the AntiVox gives the the Vox permission - when to begin it.

Being fast, it allows to break in between words/sentences (on SSB) and letters (on CW).

Regards,
xanadunow

PS. Sorry for the quality, it was all done in a hurry. The OR gate should really be the AND gate and the contact from the PTT override should really be shown as NC too .. do I need to redraw it? (engaging the PTT should prevent the gate from operating and deactivate the relay)

This idea is old and this is why I do not recall the original author.
Yes, the time delays of your TRX to go from one mode to another are longer and all you can do is to give it the "best shot"

 

[Space Varmint]

An ordinary PA system breaks into acoustical feedback howling regardless of the phase of the wires on the speaker because the phasing is different at each frequency.

Speakerphones have the mic and speaker very close together so reflections in a room won't affect phasing but they don't use simple reversed phase to cancel the amount of speaker sound picked up by the mic. Because the phasing is different at each frequency.

Hey man, I did go back and re-do the audio a little. I noticed when I spoke loudly I was getting a whistle. I think thats what that guy meant when he said my frequency jumped around. I noticed some clipping and I broadened the frequencies. It sounds allot better best I can tell listening to myself. Another thing was I had to increase the resistance to the oscillator from the balanced modulator. Even though it's VXO, it is a weak lock and was fulling the frequency with a heavy load.

 

[Mikebits]

You need a buffer or amp between the LO and mixer as someone else has already mentioned.

Should be like LO----Amp ---LPF---attn pad---mixer. The pad helps match Z. All your ports should have same Z, whatever it may be.
The LPF helps keep unwanted crap out of your mixer, mainly your second harmonic which will be quite large.

 

[Space Varmint]

You need a buffer or amp between the LO and mixer as someone else has already mentioned.

Should be like LO----Amp ---LPF---attn pad---mixer. The pad helps match Z. All your ports should have same Z, whatever it may be.
The LPF helps keep unwanted crap out of your mixer, mainly your second harmonic which will be quite large.

Oh, hey Mike. Didn't think anyone was up. You know I read an article where it specifically said, "Do not use a buffer" right there. I still get plenty of signal through, but I think I now know the true source of the problem because it still does it when I hook up the 80 watt amp. It's rf getting into it. Could be through the power or any number of sources as this was kinda of a quick throw together.

Do you think the filters would help this, or it may just be shielding problems?

I bet it's coming in on the power buss. I got everything including power running through RG-174U cable. Might be a little rf porous. Might try a filter right at the feed point.

And where would it be getting into it?

I think the rf is getting right on to the VXO.

 

[Mikebits]

Oh, hey Mike. Didn't think anyone was up. You know I read an article where it specifically said, "Do not use a buffer" right there.

Who ever wrote that article is sadly mistaken.

And like I have been saying put a seperate regulator for your LO.

You want a clean setup then do this;
Vcc----->Vreg---->Lo---Amp--->LPF---->Attn---->Mixer

And I am up late working homework. Have a 4 week intersession class. The 4 week class is the same as a normal semester class of 16 weeks. So no time to sleep. I stop by here when I need a break.

 

[Space Varmint]

Who ever wrote that article is sadly mistaken.

And like I have been saying put a seperate regulator for your LO.

You want a clean setup then do this;
Vcc----->Vreg---->Lo---Amp--->LPF---->Attn---->Mixer

And I am up late working homework. Have a 4 week intersession class. The 4 week class is the same as a normal semester class of 16 weeks. So no time to sleep. I stop by here when I need a break.

\
Mike, we always but heads. Granted that's great design but I have a symptom hear. What I want is to isolate it and resolve it. Take a look at this link: N1NKM's PSK31 ELMER page

Note that I do not have this problem until I hook up the 80 watt amplifier.