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A question.... again.... to up my education......
- Thread starter guitar_199
- Start date
I understand what you're saying though. I run more than 100% modulation so the bird does swing. It's 1950s transmitter that makes real AM.
The original swing kit was published in QTH magazine. I believe it was October 1956. It allowed more audio to be put on the carrier without the negative peaks hitting baseline and potentially destroying a modulation transformer. I use a variation of that with my tube transmitters and it works well. They called it "ultra modulation."
So there you have it. Ham radio had swing kits first.
I am sure CK will correct me but most AM broadcast transmitters have a fixed carrier and modulate to 80%, its the carrier that drives the signal not the modulation. What 11-meter ops are doing is more like double sideband which is effectively AM without the carrier.
Ahh, now were getting to the good part...
Making what was symmetrical, and linear, - now asymmetrical and non-linear...Swing or not, - non-linear amplification is what many would call "swing".
FM is a type of "Swing" - on better defined as "deviation"
AM, carrier - being "Steady" - is a requirement for the "modulation of the envelope".- but not really for sending, only for receiving (Detection) - else SSB would not even exist.
So when deviation is not excessive, or non-linear - you have symmetry.
Same can be applied to the equal halves of a AM envelope - even fully modulated, still averages out to be Carrier + Audio Power in it's sidebands. But only when it's modulated - in other words, action has to take place to form the envelope - so modulation is that action to generate it. So when no audio is applied, you have just carrier.
Yes, you can get carrier and audio to be just as steady due to symmetry. It's a part of what Class D is, you are borrowing from carrier to provide envelope.
The FM side of things is similar, only you waste more BANDWIDTH using greater levels of Deviation than carrier to envelope.
Making what was symmetrical, and linear, - now asymmetrical and non-linear...Swing or not, - non-linear amplification is what many would call "swing".
FM is a type of "Swing" - on better defined as "deviation"
AM, carrier - being "Steady" - is a requirement for the "modulation of the envelope".- but not really for sending, only for receiving (Detection) - else SSB would not even exist.
So when deviation is not excessive, or non-linear - you have symmetry.
Same can be applied to the equal halves of a AM envelope - even fully modulated, still averages out to be Carrier + Audio Power in it's sidebands. But only when it's modulated - in other words, action has to take place to form the envelope - so modulation is that action to generate it. So when no audio is applied, you have just carrier.
Yes, you can get carrier and audio to be just as steady due to symmetry. It's a part of what Class D is, you are borrowing from carrier to provide envelope.
The FM side of things is similar, only you waste more BANDWIDTH using greater levels of Deviation than carrier to envelope.
Eng-u-land swings like a pendulum do. Bobbies on bicycles two by two. Westminster Abby the tower of Big Ben. The rosy red cheeks of the little children.
73
73
It is not possible to modulate the amplitude and not have the amplitude change. That's like saying that when the frequency is modulated, the frequency doesn't change. If there is no "swing" on an AM signal when viewed on a scope or peak meter, then your modulation would be 0% with respect to the carrier. When talking on AM, the amplitude is modulated at an audio rate, making the signal appear to swing with your voice.
I talk to a couple of guys in broadcast and they will tell you more audio on the carrier is good for amateur work. 125% positive peaks is a good number.
The guys that work AM with a factory Johnson transmitter (or similar) with a d104 sound great when they are s9+20. When band conditions are poor they are hard to copy.
There's not much benefit to reducing a carrier just for the sake of more swing but a high level modulated transmitter is tuned at carrier power and then modulation is applied. More audio equals more pep power. It truly does make you louder.
It can be desirable to lower the carrier when the modulator doesn't have enough power to fully modulate the carrier. You never want to over modulate in the negative direction but hitting 95 to 98% is important.
K4KYV did a test with a synchronous receiver and found that another station running the same pep power was easier to copy running less carrier and the same peak envelope power. Maybe not "real" AM but interesting.
https://forums.qrz.com/index.php?threads/double-sideband-reduced-carrier.592016/
Here's a way to look at it...
Swing - thought of a motion - you're adding power, into the Audio Sidebands.
But, if a "Steady state", that a typical AM only radio has, the DC isn't going up or down, the Audio being applied to it is...
The DC bias gives up energy in way for form a frequency component that the Carrier in it's frequency, will be offset by.
We know of two ways of doing that in nearly every CB out there...
Reactance Modulation being the process of converting a DC into a signal with an AC (in this case Audio) component at the same time. We generate a Phase (type of FM) signal but pass it thru a diode to prevent phase or deviation - only envelope audio - the carrier adds or subtracts the power accordingly.
AM Regulation - converting DC into an Audio Signal with a DC component - a BIAS - using a form of regulation that forms the audio and DC signal with a level of symmetry - hence the use of Regulation - to acts as a guide or a means to offset the swing to maintain constant regulation control over the Bias and Audio - you get the Carrier and Audio Envelope together without a Phase component.
Both borrow power from the DC realm to add or impose audio signal.
PEP meters, See this as an increase, in BANDWIDTH - they rectify the detected signal and weight accordingly to show gain above the carrier power - a simpler additional power that is modulated - added to carrier and detected from carrier. How strongly this envelope is generated, demonstrates the "swing" as Peak Envelope Power.
Then why wouldn't FM show this same effect? Because of the Relative change in FREQUENCY at an Audio rate of change - you're carrier isn't changing - just shifting in frequency as a sum of difference in Carrier To Audio Frequency being applied they're mixing together - The audio adds and subtracts from the carrier - shifting the frequency.
IF we didn't use the Diode in the Modulator - nearly all CB's would be FM or Phase modulated using the Transformer method. The diodes prevents the "shift" as a negative going Audio and DC component - the energy is kept going forward - as a shift in frequency - the carrier then sees this audio component It too then mixes with and arrives to the same result of summing the Audio and Carrier - together, but the DC bias present - then keeps Carrier as Carrier - Audio then mixes in and using the add and subtract mixing - the envelope is made.
This is what gets interesting - the transformer method is lossy compared to AM Regulation - but provides a voltage component the TX strip can use to offset the losses in current - you don't get that in the DC realm, OR can AM regulators provide it - it's the DC loss as a voltage and current drop - a power hit against the system. So the additional power from the Audio then changes the reactive - inductive side - into a vector that shifts in relation to the DC power - a phase shift. You may lose current (DC component inclusive), but gain the Voltage component for the Audio to use as a level of energy forced on the carrier's frequency to shift the carrier using that energy.
Swing - thought of a motion - you're adding power, into the Audio Sidebands.
But, if a "Steady state", that a typical AM only radio has, the DC isn't going up or down, the Audio being applied to it is...
The DC bias gives up energy in way for form a frequency component that the Carrier in it's frequency, will be offset by.
We know of two ways of doing that in nearly every CB out there...
Reactance Modulation being the process of converting a DC into a signal with an AC (in this case Audio) component at the same time. We generate a Phase (type of FM) signal but pass it thru a diode to prevent phase or deviation - only envelope audio - the carrier adds or subtracts the power accordingly.
AM Regulation - converting DC into an Audio Signal with a DC component - a BIAS - using a form of regulation that forms the audio and DC signal with a level of symmetry - hence the use of Regulation - to acts as a guide or a means to offset the swing to maintain constant regulation control over the Bias and Audio - you get the Carrier and Audio Envelope together without a Phase component.
Both borrow power from the DC realm to add or impose audio signal.
PEP meters, See this as an increase, in BANDWIDTH - they rectify the detected signal and weight accordingly to show gain above the carrier power - a simpler additional power that is modulated - added to carrier and detected from carrier. How strongly this envelope is generated, demonstrates the "swing" as Peak Envelope Power.
Then why wouldn't FM show this same effect? Because of the Relative change in FREQUENCY at an Audio rate of change - you're carrier isn't changing - just shifting in frequency as a sum of difference in Carrier To Audio Frequency being applied they're mixing together - The audio adds and subtracts from the carrier - shifting the frequency.
IF we didn't use the Diode in the Modulator - nearly all CB's would be FM or Phase modulated using the Transformer method. The diodes prevents the "shift" as a negative going Audio and DC component - the energy is kept going forward - as a shift in frequency - the carrier then sees this audio component It too then mixes with and arrives to the same result of summing the Audio and Carrier - together, but the DC bias present - then keeps Carrier as Carrier - Audio then mixes in and using the add and subtract mixing - the envelope is made.
This is what gets interesting - the transformer method is lossy compared to AM Regulation - but provides a voltage component the TX strip can use to offset the losses in current - you don't get that in the DC realm, OR can AM regulators provide it - it's the DC loss as a voltage and current drop - a power hit against the system. So the additional power from the Audio then changes the reactive - inductive side - into a vector that shifts in relation to the DC power - a phase shift. You may lose current (DC component inclusive), but gain the Voltage component for the Audio to use as a level of energy forced on the carrier's frequency to shift the carrier using that energy.