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Newbie - Trying to simulate 3.5MHz Xmtr - LTSpice

Greetings,

I have never used a schematic capture program before and I am just getting back into electronics after many years, so I'm a bit rusty. Please bear with me.

I am trying to simulate a low-power transmitter in the 3.5 MHz range in LTSpice. I would like to look at a plot of the emissions at ANT to see what my frequency output looks Like. Effectively, a frequency spectrum plot. I understand I should use an FFT plot after running a transient simulation, but I seem to be having no luck.

I'm at a loss as to whether my schematic is faulty, I don't understand how to properly use LTSpice or both. In particular, I wonder if I have configured the crystal properly (a colorburst crystal) and whether I need a 50 Ohm load instead of the ANT output?

Any insight would be appreciated, and I thank you in advance.

My LTSpice circuit follows:

----- snip 3.5MHZ xmtr.asc -----

Version 4 SHEET 1 892 680 WIRE 96 144 48 144 WIRE -16 144 -16 208 WIRE -80 272 -80 288 WIRE -80 288 -16 288 WIRE -80 208 -16 208 WIRE -16 288 -16 336 WIRE 48 224 48 144 WIRE 48 144 -16 144 WIRE 48 304 48 400 WIRE 48 400 336 400 WIRE 112 240 112 224 WIRE 112 224 160 224 WIRE 160 192 160 224 WIRE 160 224 192 224 WIRE 192 288 192 320 WIRE 192 320 112 320 WIRE 112 320 112 336 WIRE 48 144 48 32 WIRE 112 32 144 32 WIRE 160 96 208 96 WIRE 432 400 464 400 WIRE 464 400 464 416 WIRE 256 128 256 96 WIRE 256 96 336 96 WIRE 432 96 464 96 WIRE 336 128 336 96 WIRE 336 96 368 96 WIRE 336 208 336 400 WIRE 336 400 368 400 WIRE 336 400 336 448 WIRE 256 192 256 336 WIRE 288 448 336 448 WIRE 208 448 160 448 WIRE 160 448 160 464 WIRE 208 32 208 96 WIRE 208 96 256 96 WIRE 464 96 464 16 WIRE 464 16 560 16 FLAG -16 336 0 FLAG 112 336 0 FLAG 464 416 0 FLAG 256 336 0 FLAG 160 464 0 FLAG 560 16 ANT IOPIN 560 16 Out SYMBOL polcap -96 208 R0 WINDOW 3 24 64 Left 0 SYMATTR Value 33µ SYMATTR InstName C1 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 mfg="Nichicon" pn="UPR1A330MAH" type="Al electrolytic" ppPkg=1 SYMBOL res -32 192 R0 SYMATTR InstName R1 SYMATTR Value 5.6k SYMBOL res 32 208 R0 SYMATTR InstName R2 SYMATTR Value 15k SYMBOL res 96 224 R0 SYMATTR InstName R3 SYMATTR Value 470 SYMBOL npn 96 96 R0 SYMATTR InstName Q1 SYMATTR Value 2N2222 SYMBOL Misc\\\\xtal 112 16 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C3 SYMATTR Value 3.56169600e-014 SYMATTR SpiceLine Rser=3.56169600e-014 Lser=0.0555779237 Cpar=8.90424001e-012 SYMBOL ind 320 112 R0 SYMATTR InstName L1 SYMATTR Value 2.5µh SYMATTR SpiceLine Ipk=1 SYMBOL voltage 304 448 R90 WINDOW 0 -32 56 VBottom 0 WINDOW 3 32 56 VTop 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL polcap 144 48 R270 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C4 SYMATTR Value 0.01µ SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1 SYMBOL polcap 176 224 R0 WINDOW 3 24 64 Left 0 SYMATTR Value 0.01µ SYMATTR InstName C2 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1 SYMBOL polcap 240 128 R0 WINDOW 3 24 64 Left 0 SYMATTR Value 100µ SYMATTR InstName C5 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1 SYMBOL polcap 368 112 R270 WINDOW 3 24 64 Left 0 SYMATTR Value 100µ SYMATTR InstName C6 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1 SYMBOL polcap 368 416 R270 WINDOW 3 24 64 Left 0 SYMATTR Value 0.01µ SYMATTR InstName C7 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1 TEXT -98 514 Left 0 !.tran 0 10m 0 startup TEXT -128 464 Left 0 !.option plotwinsize=0

------ snip end of file ------

Reply to
Talion
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Talion,

I made some adjustments to the circuit. Now it oscillates. It takes several milliseconds for the oscillation level to become stable. When you do the FFT, you'll want to limit the "Time range to include" to exclude the startup time.

--Mike

--- osc.asc --- Version 4 SHEET 1 892 680 WIRE 96 144 -160 144 WIRE -336 240 -336 288 WIRE -256 256 -256 288 WIRE -160 224 -160 144 WIRE -160 144 -256 144 WIRE -160 304 -160 400 WIRE -160 400 336 400 WIRE 160 240 160 224 WIRE 160 192 160 224 WIRE 256 304 256 336 WIRE 160 320 160 336 WIRE -32 16 48 16 WIRE 160 96 208 96 WIRE 432 400 464 400 WIRE 208 96 336 96 WIRE 432 96 560 96 WIRE 336 160 336 96 WIRE 336 96 368 96 WIRE 336 240 336 400 WIRE 336 400 368 400 WIRE 336 400 336 464 WIRE 272 464 336 464 WIRE 192 464 160 464 WIRE -256 144 -256 176 WIRE -336 288 -256 288 WIRE -256 288 -256 320 WIRE -336 176 -336 144 WIRE -336 144 -256 144 WIRE -160 144 -160 16 WIRE -160 16 -96 16 WIRE 256 336 160 336 WIRE 160 336 160 352 WIRE 160 224 256 224 WIRE 256 224 256 240 WIRE 48 112 48 96 WIRE 48 32 48 16 WIRE 48 16 112 16 WIRE 176 16 208 16 WIRE 208 16 208 96 FLAG -256 320 0 FLAG 160 352 0 FLAG 464 400 0 FLAG 160 464 0 FLAG 560 96 ANT IOPIN 560 96 Out FLAG 48 112 0 SYMBOL res -272 160 R0 SYMATTR InstName R1 SYMATTR Value 15K SYMBOL res -176 208 R0 SYMATTR InstName R2 SYMATTR Value 45K SYMBOL res 144 224 R0 SYMATTR InstName R3 SYMATTR Value 470 SYMBOL npn 96 96 R0 SYMATTR InstName Q1 SYMATTR Value 2N2222 SYMBOL Misc\\\\xtal -32 0 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C3 SYMATTR Value .03561696p SYMATTR SpiceLine Rser=0 Lser=55.5779237m Cpar=8.90424p SYMBOL ind 320 144 R0 SYMATTR InstName L1 SYMATTR Value 100µ SYMBOL voltage 288 464 R90 WINDOW 0 -32 56 VBottom 0 WINDOW 3 32 56 VTop 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL polcap 368 112 R270 WINDOW 3 24 64 Left 0 SYMATTR Value 100µ SYMATTR InstName C6 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine Rser=2.3 SYMBOL polcap 368 416 R270 WINDOW 3 24 64 Left 0 SYMATTR Value 0.01µ SYMATTR InstName C7 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1 SYMBOL cap 176 0 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C4 SYMATTR Value 200p SYMBOL cap 32 32 R0 SYMATTR InstName C5 SYMATTR Value 100p SYMBOL cap -352 176 R0 SYMATTR InstName C1 SYMATTR Value 25p SYMBOL cap 240 240 R0 SYMATTR InstName C2 SYMATTR Value .01µ TEXT 510 258 Left 0 !.tran 10m startup TEXT -136 80 Left 0 ;3.58007MHz TEXT 504 304 Left 0 !.options method=trap

Reply to
Mike Engelhardt

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