Why?

[Captain Kilowatt]

Ok, then if your on SSB can you understand someone on AM?

Sure if you adjust the clarifier properly. My first amateur radio was a Heathkit DX-60 that only transmitter AM and CW. I had MANY contacts by tuning my transmitter to EXACTLY the frequency of the other station I was listening to on SSB and when I called him he had no idea I was on AM until I told him. Best contact I had doing that was with 12 watts of carrier on 20m into an indoor dipole in the attic of a two story home from Nova Scotia to Novosibirsk Russia. The guy thought it was great I was able to do that.

 

[sunbulls]

Sure if you adjust the clarifier properly. My first amateur radio was a Heathkit DX-60 that only transmitter AM and CW. I had MANY contacts by tuning my transmitter to EXACTLY the frequency of the other station I was listening to on SSB and when I called him he had no idea I was on AM until I told him. Best contact I had doing that was with 12 watts of carrier on 20m into an indoor dipole in the attic of a two story home from Nova Scotia to Novosibirsk Russia. The guy thought it was great I was able to do that.

Back in the mid 60’s with my DX 60, I worked mostly other AM stations, mainly on 40, but every once in awhile a SSB station that assumed I was on the same mode would answer my CQ. Barry Goldwater was one such contact. With such a prominent mixture of both modes during that time, AM stations would usually use a BFO or a SSB receiver to be certain nobody was being left out. Having a BFO or a SSB receiver was also useful for zero beating stations. Mixed modes got along well for the most part . It wasn’t until much later when bitter territorial battles started to take place.

 

[Captain Kilowatt]

Back in the mid 60’s with my DX 60, I worked mostly other AM stations, mainly on 40, but every once in awhile a SSB station that assumed I was on the same mode would answer my CQ. Barry Goldwater was one such contact. With such a prominent mixture of both modes during that time, AM stations would usually use a BFO or a SSB receiver to be certain nobody was being left out. Having a BFO or a SSB receiver was also useful for zero beating stations. Mixed modes got along well for the most part . It wasn’t until much later when bitter territorial battles started to take place.

Cross mode contacts were very popular when SSB first came into being. I used a Kenwood R-1000 receiver with my DX-60. Still have both.

 

[Shadetree Mechanic]

Here is a section from the Galaxy 99v user manual. It basically says that a USB signal can't be heard correctly in LSB mode and vice versa. Is this correct?


"An SSB signal may be received only when the listening receiver is functioning in the same mode. In other words, an upper sideband signals (USB) may be made intelligible only if the receive is functioning in the USB position. If a lower sideband (LSB) signal is heard when the receiver is in the USB mode, no amount of tuning will make the signal intelligible. The reason for this may be understood if you consider that when modulation is applied to the transmitter’s microphone in the USB mode, the transmitter’s output frequency is increased whereas in the LSB mode, the transmitter’s output frequency is decreased. The result in listening to the receiver is that when the mode switch is in the proper position (either USB or LSB), a true reproduction of single tone of modulation will result, and if the tone is increased in frequency (such as a low-pitched whistle a high-pitched whistle) you will hear the increase in the output tone of the receiver. If the incorrect mode is selected, an increase in tone of a whistle applied to the transmitter will cause a decrease in the resultant tone from the receiver. Thus when a voice is used in place of a whistle or tone, in the proper listening mode the voice will be received correctly whereas in the incorrect mode, the voice will be translated backwards and cannot be made intelligible by the voice lock control. When listening to an AM transmission, a correct sideband is heard in either mode since both upper and lower sidebands are received"

 

[543_Dallas]

Here is a section from the Galaxy 99v user manual. It basically says that a USB signal can't be heard correctly in LSB mode and vice versa. Is this correct?


"An SSB signal may be received only when the listening receiver is functioning in the same mode. In other words, an upper sideband signals (USB) may be made intelligible only if the receive is functioning in the USB position. If a lower sideband (LSB) signal is heard when the receiver is in the USB mode, no amount of tuning will make the signal intelligible. The reason for this may be understood if you consider that when modulation is applied to the transmitter’s microphone in the USB mode, the transmitter’s output frequency is increased whereas in the LSB mode, the transmitter’s output frequency is decreased. The result in listening to the receiver is that when the mode switch is in the proper position (either USB or LSB), a true reproduction of single tone of modulation will result, and if the tone is increased in frequency (such as a low-pitched whistle a high-pitched whistle) you will hear the increase in the output tone of the receiver. If the incorrect mode is selected, an increase in tone of a whistle applied to the transmitter will cause a decrease in the resultant tone from the receiver. Thus when a voice is used in place of a whistle or tone, in the proper listening mode the voice will be received correctly whereas in the incorrect mode, the voice will be translated backwards and cannot be made intelligible by the voice lock control. When listening to an AM transmission, a correct sideband is heard in either mode since both upper and lower sidebands are received"

That is correct. Listening to usb on lsb or vice versa is just a garbled up mess. If someone were using 38 lsb you would have to listen on 27.382 usb to have their signal in your passband, but it wouldn't be intelligible.

 

[Handy Andy]

@Shadetree Mechanic - you raise a good point.

The mode you are using - play the part in how the signal gets "decoded".

USB and LSB are "mirrors" of each other.

But, using USB to decode LSB, even when you're able to tune into the exact frequency, the signal sounds garbled - because it's INVERTED - it's not going the "right way" for the receiver to track it.

Same thing happens when LSB tries to decode USB - again, the frequency is there, you can tune to it, but the signal is INVERTED - you hear "garbled" because you're in the wrong mode to decode it.

Think of it as a freeway, a highway - so to speak.

​

Upper Side band is ABOVE the Carrier frequency - going to the top of the graphic - in US, you're on the Right side traveling forward - towards the horizon - the carrier contains information (your white line) that tells you how to interpret your side of the road.

Lower side band is still on the highway, it's using the information in your Carrier - but is BELOW the carrier frequency - so think of it as information traveling on the highway, but to interpret it, you see it arriving towards you travelling the opposite direction towards and past you - so you see it and can decode it, but you have to understand it is in the oncoming lane..

You can pass information by changing your frequency - you can even go into the OPPOSITE lane if you wish by SHIFTING your frequency, but don't expect that traffic to understand your intent or even be able to process the signal your sending on this highway. - because it's not in the MODE of that lane.

• So whether your travelling forward, or going back home on this same highway
  • - just remember that the lane you're in, you see the traffic ahead of you in your lane as able to travel along with you...
• It's the opposite lane the Opposite MODE - is the trouble - it's not going to understand you or your intent - in being there in their lane in the wrong MODE

To understand the traffic you either follow their direction - or you can change YOUR direction to follow the other lane - but to process the other lane, you need to be travelling in the same direction - with it.

It's about as basic as I can make it to help understand that your carrier is the center line - your audio information travels above and below it, but if you use the wrong lane you can't process it.

 

[Slowmover]

Someone somewhere ditched “a bad radio” over it.

 

[r carl]

So how does AM understand both lanes?

 

[Handy Andy]

Thru the carrier.

You adjust the AM carrier - you determine the Mode.

As you stay in your lane travelling, you will have traffic in the lane with you. The Am carrier - much like the IF side - that BFO carrier, travels and is part of your highway you use.

The Traffic in your lane - is on the same side of the carrier - your highway. So you approach or it approaches you at a much slower speed,

• So if you think of it as traffic, the same lane traffic, you're all able to "decode" each other.
• The opposite lane, the traffic coming at you, is too fast to be decoded easily. - it's not travelling in the same direction - the MODE is different.

It's why I show this graphic,...


Your carrier is your ZERO beat,

Look carefully at the graphic to show the "speed" or audio portion of the spectrum, you hear close to the carrier - Bass tones, then tone shifts up in frequency, into the treble range as a factor of DEVIATION in frequency from the carrier being the "Zero" starting point.

LSB and USB are mirrors, and are a mutual effect of CARRIER mixing in with Audio - you get signal above and below - but are the effort, the results - of summing, addition and subtraction at the same time - you are experiencing the differences the audio being applied to the carrier, does to the AM signal.

You still have carrier, but there is signal, above and below that carrier.

• The Carrier isn't changing - it's AM - NOT FM. You get audio thru DEVIATION in FM.
• IN a way, you are experiencing DEVIATION using SSB - but you decode ENVELOPE
• Carrier - which is just it, the only "steady" information for AM or even CW

What is present - above and below - in audio range of pass band the radio uses to process or filter your Mic audio - is your audio information.​

 

[543_Dallas]

Good stuff Andy.

SDR dongles are cheap...beer money cheap. The sdrplay really nice for the price. Using an SDR really helped me wrap my brain around this.

 

[Mustang 131]

Why not

 

[Slowmover]

Why not

Dude, that’s soooo 1969.

 

[Handy Andy]

Dude, that’s soooo 1969.

And "Facebook", was a real Book, - of FACES...

Color Optional...
​

 

[guitar_199]

Thanks for that info on AM vs SSB HA!
Just last night I had Lou Franklin's book starting the chapter on SSB circuits. I've always "kind of" understood it but walking through the description of SSB generation in the radio really helped cement it.

Then, along comes your description above..... hand in hand .... it helps!

Thanks!

 

[guitar_199]

AM demodulation does not have the "same problem to solve".

When the radio is in AM mode the modulated signal is just passed through and tuned/sharpened through the IF strip. When you reach the demodulator "the part we are after" is not the high frequency of the carrier... it is the "wiggly shape" that the modulating audio gave it! The "outer shape" if you will.

So first, the RF is run through a diode to get rid of either the positive half or the negative half. It does not matter which... the modulation curve is the same on both. Then it is "filtered" or "smoothed" to remove the high frequency carrier signal (usually done with a component called a capacitor.... it stores up electrical charge... in a WAY removing it at the high frequency!).

What is left at the end of this process.... IS the audio signal you are trying to capture. So, in the simplest sense... from there... they feed it into audio circuits to amplify it...and then send it to a speaker.... job done.

Here is a video that may help....

So how does AM understand both lanes?