SSB Carrier Supression

[Space Varmint]

A volume control will not stop over-modulation. You need an audio limiter circuit like radio stations have.

Hey, where did you hear that? That makes allot of sense.

 

[Leftyretro]

Hey, where did you hear that? That makes allot of sense.

Typically ALC is used in the ham world. Keeps the finals from 'flat-toping'. Especially common when running a external linear with a transciever, gives feedback from the amp to the low level transciever circuit that the output is getting too hot and to please cool it a bit.

Lefty

 

[flat5]

Yeah I thought of ALC too but it is not audio derived and is only for the final. An audio limiter (most often a compressor, really) works at the input of a transmitter...at the mic. Look for circuits used in cheap cassette recorders or rip one out. There might be an IC designed for just this. Sorry to state the obvious but I like to post now and then

 

[audioguru]

Many years ago a JFET was used in an audio limiter circuit.
The audio was rectified and turned on the JFET that was used as an attenuator.

Signetics developed "compandor" ICs before Philips bought Signetics. Philips is called NXP nowadays.
There are (were?) 4 stereo compandor ICs. Each channel can be a compressor or an expander circuit.

 

[Space Varmint]

Many years ago a JFET was used in an audio limiter circuit.
The audio was rectified and turned on the JFET that was used as an attenuator.

Signetics developed "compandor" ICs before Philips bought Signetics. Philips is called NXP nowadays.
There are (were?) 4 stereo compandor ICs. Each channel can be a compressor or an expander circuit.

Man, I never seen one like that before. It looks pretty simple kinda. When I get back to the audio, I might try that out. Works pretty good hey?

Now is this just one chip? Or is the differential amp looking thing separate? If so, what is it?

 

[audioguru]

The circuit I posted is one channel of the stereo compressor/expander IC.
To the IC you add a few resistors and capacitors.

 

[Space Varmint]

Is it a Motorola? I've seen some Motorola companders

 

[audioguru]

Signetics invented the NE570 compander IC. Then Philips bought Signetics and Philips (now called NXP Semi) makes it. Motorola became ON Semi who also makes it.

 

[Space Varmint]

Signetics invented the NE570 compander IC. Then Philips bought Signetics and Philips (now called NXP Semi) makes it. Motorola became ON Semi who also makes it.

Oh yeah, I remember Signetics. They used to make the DTMF chips.

I hooked up my P-P amp and yeah, it bumped up the drive, It's still pulling harder on one side. I'm getting about 10 watts of clean power but think I will get more if I can ballance it. I'm using 2N2222's and I droped the emitter resistors down for a second and blew both transistors. I think what happened was I touched the resistor across one RE first and it pulled real hard and blew then the other pulled everything and it blew. I dropped the REs back to 100 ohms but they still run kinda warm. I need some little heat sinks for them.

 

[audioguru]

Why don't you post the schematic of your P-P amp and we will help you fix it.
I can simulate it to show how much distortion it has.

 

[Space Varmint]

Why don't you post the schematic of your P-P amp and we will help you fix it.
I can simulate it to show how much distortion it has.

I posted it on other thread. Well it didn't have part values. It may be doing the job. I think it is. It looks like I'm getting feedback when I increase the power output. Wouldn't you know

 

[Nigel Goodwin]

Bit late, but I happened to come across this today



That's how you connect one aerial to full duplex transmit and receive (600KHz apart).

 

[audioguru]

Why did you copy the lousy P-P amplifier from the Philips 1955 handbook?
What is it for? A modulator?
Why two transformers?
Why any transformers instead of a pair of complementary emitter-followers like in an audio amplifier IC?

I think it causes a lot of distortion without the 100 ohm resistors but I cannot simulate it because it is too old.

 

[Nigel Goodwin]

Why did you copy the lousy P-P amplifier from the Philips 1955 handbook?
What is it for? A modulator?
Why two transformers?
Why any transformers instead of a pair of complementary emitter-followers like in an audio amplifier IC?

I think it causes a lot of distortion without the 100 ohm resistors but I cannot simulate it because it is too old.

I think you've missed the point AG, it's supposed to be an RF power amplifer, not an audio one.

 

[audioguru]

I think you've missed the point AG, it's supposed to be an RF power amplifer, not an audio one.

When he said the P-P amplifier "bumped up the drive" I thought it is the transmitter's modulator.
A pair of little 2N2222 transistors do not produce much power.

 

[Nigel Goodwin]

When he said the P-P amplifier "bumped up the drive" I thought it is the transmitter's modulator.
A pair of little 2N2222 transistors do not produce much power.

I was presuming it was some bizarre driver stage?.

 

[Space Varmint]

Why did you copy the lousy P-P amplifier from the Philips 1955 handbook?
What is it for? A modulator?
Why two transformers?
Why any transformers instead of a pair of complementary emitter-followers like in an audio amplifier IC?

I think it causes a lot of distortion without the 100 ohm resistors but I cannot simulate it because it is too old.

I didn't copy anything. That's just a typical P-p Amp. I didn't think you would be able to check it. It's doing pretty good. I'm doing a finger check...lol. They are both are pretty warm. With big emitter resistors I don't think you need to be too concerned with matching the transistors.

 

[Space Varmint]

I was presuming it was some bizarre driver stage?.

No, well you got to figure. It's a home brew. So I wanted one big hairy ass filter on this board along with some drive. Since I'm putting the board in a cat food can, I only got room for one amplifier stage. So in order to get as much drive as possible, I went with a P-P amp.

 

[Space Varmint]

Bit late, but I happened to come across this today



That's how you connect one aerial to full duplex transmit and receive (600KHz apart).

LOL...that's OK. I think we are all interested. So one antenna. Don't they use a diplexer? Guess I will find out.

 

[Space Varmint]

Back to original topic.

Where is my freaking brain?

I was not satisfied with the amount of carrier suppression. I really had to shout into the mic to see the carrier come through the crystal filter. Coming out of the balanced modulator the signal appeared to be pretty hefty but I suffered a great deal of attenuation through the filter. All of the sudden it hit me like a ton of bricks! The balanced modulator is a mixer which has been discussed. A POST MIXER AMP! I need a post mixer amp! I put it in and damn! It is great! Now I got to go back through my mixer and all that garbage because the carrier is really slamming now, but the modulation is way over that.