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AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
On Mon, 2 Jul 2007 23:03:36 -0700, "Ron Baker, Pluralitas!"
wrote: "John Smith I" wrote in message ... Radium wrote: snip Suppose you have a 1 MHz sine wave whose amplitude is multiplied by a 0.1 MHz sine wave. What would it look like on an oscilloscope? --- LTSPICE circuit list: Version 4 SHEET 1 1672 1576 WIRE 32 880 -256 880 WIRE 192 880 32 880 WIRE 528 912 336 912 WIRE 192 944 -112 944 WIRE -256 992 -256 880 WIRE -112 992 -112 944 WIRE -256 1120 -256 1072 WIRE -112 1120 -112 1072 WIRE -112 1120 -256 1120 WIRE -256 1168 -256 1120 FLAG -256 1168 0 FLAG 32 880 in SYMBOL SPECIALFUNCTIONS\\MODULATE 192 880 R0 WINDOW 0 37 -55 Left 0 WINDOW 3 55 119 Center 0 SYMATTR InstName A1 SYMATTR Value mark=1e6 space=1e6 SYMBOL voltage -256 976 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 10 SYMBOL voltage -112 976 R0 WINDOW 3 24 160 Left 0 WINDOW 123 24 132 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(.5 .5 1e5) SYMATTR Value2 AC 1 TEXT -96 1240 Left 0 !.tran 5e-5 TEXT -96 1208 Left 0 !.params w0=2*pi*1K Q=5 --- What would it look like on a spectrum analyzer? --- | | | | | | --------+--------------------+-------+------+---- 100kHz 0.9MHz 1MHz 1.1MHz --- Then suppose you have a 1.1 MHz sine wave added to a 0.9 MHz sine wave. What would that look like on an oscilloscope? --- LTSPICE circuit list: Version 4 SHEET 1 880 680 WIRE 240 64 176 64 WIRE 432 64 320 64 WIRE 352 144 224 144 WIRE 352 160 352 144 WIRE 16 176 -208 176 WIRE 160 176 96 176 WIRE 176 176 176 64 WIRE 176 176 160 176 WIRE 320 176 176 176 WIRE 432 192 432 64 WIRE 432 192 384 192 WIRE 320 208 288 208 WIRE 288 256 288 208 WIRE 16 288 -48 288 WIRE 160 288 160 176 WIRE 160 288 96 288 WIRE 224 320 224 144 WIRE 352 320 352 224 WIRE -208 336 -208 176 WIRE -48 336 -48 288 WIRE -208 448 -208 416 WIRE -48 448 -48 416 WIRE -48 448 -208 448 WIRE 224 448 224 400 WIRE 224 448 -48 448 WIRE 352 448 352 400 WIRE 352 448 224 448 WIRE -208 496 -208 448 FLAG -208 496 0 FLAG 288 256 0 SYMBOL voltage -208 320 R0 WINDOW 0 -42 5 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 .1 1.1e6) SYMBOL res 112 160 R90 WINDOW 0 -33 56 VBottom 0 WINDOW 3 -31 61 VTop 0 SYMATTR InstName R1 SYMATTR Value 1000 SYMBOL voltage -48 320 R0 WINDOW 0 -39 4 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 .1 .9e6) SYMBOL res 112 272 R90 WINDOW 0 -38 56 VBottom 0 WINDOW 3 -31 59 VTop 0 SYMATTR InstName R2 SYMATTR Value 1000 SYMBOL res 336 48 R90 WINDOW 0 -36 59 VBottom 0 WINDOW 3 -36 61 VTop 0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL voltage 352 416 R180 WINDOW 0 14 106 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 12 SYMBOL voltage 224 304 R0 WINDOW 0 -44 4 Left 0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V4 SYMATTR Value 12 SYMBOL Opamps\\UniversalOpamp 352 192 R0 SYMATTR InstName U2 TEXT -252 520 Left 0 !.tran 3e-5 Tricky!!! It looks like AM but it isn't, it's just the phases sliding past each other slowly and algebraically adding which creates the illusion. --- What would that look like on a spectrum analyzer? --- | | | | -----------------------------+--------------+---- 0.9MHz 1.1MHz -- JF |
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