[K3PZN-List] AM and FM

Mon Feb 29 12:54:11 EST 2016

 Again, the carrier is unchanged during the modulation process.The reason we say the amplitude changes is because the firstway to visualize the waveform was with an oscilloscope. Thatshows the instantaneous vector voltage of the carrier and the 
two sidebands. If you looked using a spectrum analyzer, youwould see that the carrier is the same, just more energy added in theform of sidebands that are mixed with the carrier during modulation.During detection, the signal is sent through a non-linear mixer,(your diode) and the audio is recovered by mixing the carrier and 
sidebands together and what we recover are heterodynes of the 
sideband beating against the carrier. AM is created and detectedby a mixing process. AM sounds better if created in the outputstage, either collector or plate modulation. It can be createdat a lower lever and amplified, but sounds fuller if high level is used
rather then low level. Most new amateur radios use low level modulation,which is why the AM sounds weak compared to a CB or an old Globe King.

HTH

      From: Dave Garrett <blackberryfan at gmail.com>
 To: Carroll County Amateur Radio Club <k3pzn-list at mailman.qth.net> 
 Sent: Monday, February 29, 2016 10:29 AM
 Subject: Re: [K3PZN-List] AM and FM

Kyle,

This might help you: https://www.youtube.com/watch?v=uZa6C0VY8p0

73,
Dave N3ZPC

On Mon, Feb 29, 2016 at 9:21 AM, Scott, KB3JQQ via K3PZN-List <
k3pzn-list at mailman.qth.net> wrote:

> The strength of the carrier is unchanged when you modulate am. Only
> sidebands are added. In fm, the carrier deviates from the center frequency.
>
> It's very common for people to believe the carrier changes when am is
> produced.
>
> - Weird words are due to my iPhone correcting me wrongly! -
>
> > On Feb 29, 2016, at 09:09, Kyle Thornton <kyle.3599 at outlook.com> wrote:
> >
> > Ok I think the way I see it is AM when you modulate the sine way so it
> goes up and down more as voice or data is added to the carrier. FM I
> believe is essentially just adding vertical lines to the sine was to
> represent voice or data.
> > Kyle
> > 73 de KC3FMP
> >
> >> On Feb 29, 2016, at 8:11 AM, Curt Milton via K3PZN-List <
> k3pzn-list at mailman.qth.net> wrote:
> >>
> >> Let me help just a little.  When we think of modulation there are two
> different domains to 'see it.'
> >>
> >> First, the time domain.  An unmodulated RF signal is a clean sine
> wave.  For AM the modulation is input to change the amplitude keeping the
> frequency the same.  You can imagine FM does the opposite -- changing the
> frequency around while leaving the amplitude constant.  By time domain, the
> X-axis is time.
> >>
> >> Second it looking at the same with the X-axis being frequency.  An
> unmodulated signal is just a vertical line.  When a audio signal at say 1
> kHz is input, two more lines form 1 kHz below and above the carrier.  FM
> looks a bit more complex, as it creates sets of lines.  The result of both
> is that the 'bandwidth' increases based upon the modulation.
> >>
> >> AM and FM are just two fundamental ways to modulate a signal.  SSB is
> just a special form of AM.
> >>
> >> Keep up your reading -- and of course discuss your questions - and you
> will figure it out well enough.
> >>
> >> 73 curt
> >>
> >>
> >>  On Sunday, February 28, 2016 10:16 PM, Kyle Thornton <
> kyle.3599 at outlook.com> wrote:
> >>
> >>
> >> Ok so your get the same carrier but double the side bands hence more
> noise.
> >> Kyle
> >> 73
> >> KC3FMP
> >>
> >>> On Feb 28, 2016, at 10:15 PM, Kyle Thornton <kyle.3599 at outlook.com>
> wrote:
> >>>
> >>> Ok so I think I got that basically when you modulate an AM signal your
> actually creating a duplicate of the carrier and side bands so essentially
> the whole signal and then when you transmit your power is being amplified
> due to the way the signal is being modulated? I'll have to read that
> section again but it was really confusing to me. FM I think I got down good.
> >>> Kyle
> >>> 73
> >>> KC3FMP
> >>>
> >>>> On Feb 28, 2016, at 10:11 PM, Scott, KB3JQQ via K3PZN-List <
> k3pzn-list at mailman.qth.net> wrote:
> >>>>
> >>>> AM is a mixing process. You add 50% audio to your carrier andget the
> unchanged carrier and 2 mirror image sidebands with25% of the modulation
> power. Average, you get 150% more powerthen unmodulated but 400% more in
> peak power. That's why a 100watt radio only has 25 watts of AM. When you
> add 50% more voltageto a fixed resistance (your antenna) you get 50% more
> current,so it squares at full modulation since power is voltage X current.
> >>>>
> >>>>    From: Kyle Thornton <kyle.3599 at outlook.com>
> >>>> To: k3pzn-list at mailman.qth.net
> >>>> Sent: Sunday, February 28, 2016 10:04 PM
> >>>> Subject: [K3PZN-List] AM and FM
> >>>>
> >>>> Hi all,
> >>>> I was reading though the general class license book and came across
> how AM and FM work. I haven't been on the radio lately cause of work but I
> can't quite grasp how AM is modulated. I think I have FM down as when you
> modulate the signal you're modulating the frequency so you get clearer
> sound but less range. This is probably something that was gone over in the
> tech book but I don't remember it.
> >>>> Kyle
> >>>> 73
> >>>> KC3FMP
> >>>> ______________________________________________________________
> >>>>
> >>>> 73 de K3PZN Westminster, MD
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