Ability to hear any range of (audio) frequencies between 20Hz and 20kHz is very much an individual matter of a human and is rarely attributed to a particular "hobby" as implied in the message by uncle above. If anything - the age, the listening habits and perhaps, the occupation (namely the protective gear for the ears) - are the major factors in the deterioration of frequency boundries we can hear as individuals during the span of our life.
But it is well outside this particular thread, we were talking about SSB here.
It would seem to me that L1 and C15 would shunt out your xtal by presenting a very low impedance. What value inductance have you figured for L1? I am guessing your oscillator is just using L2 and the Cap, but heck if you say it works who am I to argue?
Pondering about the power consumption was the leading factor to discovery that in the AM modulation - 50% of the transmitter's power is consumed by the "carrier" frequency and 25% for the "side-band" each. There are two of them, the upper (USB) and the lower (LSB).
It was also discovered, that for legible reception we do not need a carrier (50% of power saving) and out of the two - only one side band is required (another 25% of power saving). It meant, that the whole whooping 100% of transmitter's power can be dedicated to transmit the only thing required for a legible reception of the voice - a ONE Singe Side Band (hence the SSB). USB or LSB - to be more exact.
"I was getting ready to put in an MC1496 chip, but think I will back down. Most all of the spec sheets show a split power source."
I used it with a single 12v supply.
I got the circuit from either an ARRL Handbook or an issue of Ham Radio of the 1970s. Just maybe the 60s.
I am eager to learn.. please follow up with more information Jim..
xanadunow
OK Lets try a quick and dirty explanation first.
To 100% modulate a 100watt carrier, you need 50watts of audio, (assuming high level plate and screen modulation for us old thermionic types).
So we have a total of 150 watts, 100w carrier and 50w in the sidebands. The sidebands are identical so there is 25w in each sideband.
25/150 = 1/6
A bit more sophisticated explanation.
Looking with an oscilloscope, an un-modulated carrier has a peak voltage V.
When modulated to 100%, the maximum peak voltage is 2V and the minimum peak voltage is 0.
The peak voltage varies from 0 to 2V at the modulation rate.
This variation is due to the voltages of the two sidebands adding to and subtracting from the carrier.
The sidebands are identical in amplitude so the voltage of each sideband is V/2.
If the voltage is halved the power must be divided by 4.
So each sideband has 1/4 the power of the carrier.
If the carrier power is 100W the power in each sideband is 25W, to tal power =100 + 25 + 25 = 150W
25/150 = 1/6
OK XanaDoesKnowNow?
JimB
I am very happy now JimB. You have added the audio power to the RF power. It is not such a bad idea, but it is not the way I was tought.
He's only describing one particular method of producing AM, high level modulation using an audio power amplifier and a transformer.
For the point of this discussion it's confusing things a lot
An alternative method (and the modern radio amateur way) is to do it with a linear amplifier like SSB does, using the same modulator and everything else. You switch the modulator to NOT cancel the carrier, and the filtering NOT to remove the other sideband, and you have a perfectly fine AM modulation that goes through the linear amplifer stages just as SSB does. This is the method which you should compare to SSB, and is what you already understood.
The datasheet for the MC1496 shows most of the circuits with a dual polarity supply because both inputs are biased at 0V. The Balanced Modulator circuit shows a single supply and resistors biasing both inputs positive a few volts.
Well, I just don't understand the chip well enough. I ended up with about 6 data sheets and app notes. What a bunch of _____. The ony thing I need is some suppressed carrier and I want it ballanced. The fact that you don't even need a balanced modulator to produce SSB and can be done with a filter alone, is enough for me to realize what I don't get from the balanced mod. I can make up for in the filter. In fact I think I'm gonna follow up this filter with a partial ladder network. I think that could be a big part of where the residual carrier was coming from.
The balanced modulator cancels the carrier. I don't think a filter will remove enough of the carrier without also removing some of the wanted sideband.
The filter selects the wanted sideband and attenuates the unwanted sideband.
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