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G8MNY > TECH 01.05.20 16:17l 70 Lines 2944 Bytes #999 (0) @ WW
BID : 52957_GB7CIP
Read: GUEST
Subj: Spectrum Harmonic Demo circuit
Path: IW8PGT<IZ3LSV<I3XTY<I0OJJ<I0OJJ<GB7CIP
Sent: 200420/0808Z @:GB7CIP.#32.GBR.EURO #:52957 [Caterham Surrey GBR]
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated May 09)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Being involved with ham training, I have been doing all the technical demos
including AM & FM (Signal Generator) & this one for harmonics....
ÚÄÄÄÄÄÄÄÄ¿
50ê³SPECTRUM³ ÚÄÄÄÄÄÄÄ¿ ³ANALYSERÃÄ´ X-Y
³
Bypass ÚÄ´ADAPTOR ÃÄ´ X-Y ³
ÚÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄ¿ ³ ³0-90MHz ÃÄ´DISPLAY³
³RF SIG³ ³DIODE ³ oÙ ÚÄÄÄÄÄÄ¿ ³ ³ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÙ
³ 6MHz ÃÄÄ´PROBE ÃÄÄoÄ>oÄÄ´ VIDEO³ Ào ³ÚÄÄÄÄÄÄÄÄÄ¿
³ 1V ³ ³INSERT³ ³ WALL ÃÄÄo<ÄoÄÄÄÁ´ SCOPE ³
ÀÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÙ ³FILTER³ T³WAVEFOREM³
ÀÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÙ
I cheated with the use of a diode probe (series schotky diode for UHF) insert
to produce a poor signal when the sig gen is set to 1V output. This caused the
RF sine wave is bent enough to see the harmonics on 6MHz on a scope (>20MHz) &
the diode output is terminated into 50ê by the spectrum analyser.
The filter I had is an 8 section M derrived video LPF & is 40dB down @ 8MHz,
but only 2dB down @ 6MHz. But any suitable filter will show the benefits of a
LPF after a harmonic rich source.
SPECTRUM DISPLAYS
NO FILTER WITH FILTER
dB f1 Rich harmonic spectrum dB f1
0 ´ ³ f2 0 ´ ³ Cleaner
-10 ´ ³ | f4 -10 ´ ³ Spectrum
-20 ´ ³ ³ f3 | f6 -20 ´ ³
-30 ´ ³ ³ ³ ³ f5 | f7 f8 -30 ´ ³
-40 ´ ³ ³ ³ ³ | ³ . | -40 ´ ³
-50 ´ ³ ³ ³ ³ ³ ³ ³ ³ -50 ´ ³ f2
-60 ÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄÄÄÁÄ>F -60 ÁÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄ>F
6 12 18 24 30 36 42 48MHz 6 12MHz
SCOPE DISPLAYS
/''\ /''\ /'`\ /'`\
| | | | | | | |
RF _Ý Þ______Ý Þ____ Ý Þ Ý Þ
Þ Ý Þ Ý
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Distorted RF With Filter \../
See also my buls on "SSB Demo circuit", "Scope RF Trick", "Tuned Circuit Scope
Demo" & "Oscilloscopes".
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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