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