[K3PZN-List] AM and FM

Mon Feb 29 09:11:50 EST 2016

Ok so after more research AM is when your actually changing the signal strength but keeping the frequency the same and FM is keeping the amplitude the same which is the up and down but changing the frequency either closer or further apart. 
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 
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