Newbie - Trying to simulate 3.5MHz Xmtr - LTSpice

[Talion]

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 33ľ
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 2.5ľh
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 0.01ľ
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 0.01ľ
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 100ľ
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 100ľ
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 0.01ľ
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 ------

 

[Mike Engelhardt]

Talion,

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:

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 100ľ
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 100ľ
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 0.01ľ
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 .01ľ
TEXT 510 258 Left 0 !.tran 10m startup
TEXT -136 80 Left 0 ;3.58007MHz
TEXT 504 304 Left 0 !.options method=trap