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G8MNY  > TECH     26.01.17 12:08l 61 Lines 2607 Bytes #999 (0) @ WW
BID : 32740_GB7CIP
Read: GUEST
Subj: Spectrum Harmonic Demo circuit
Path: IW8PGT<IZ3LSV<IK6ZDE<F1OYP<LU4ECL<GB7CIP
Sent: 170126/1050Z @:GB7CIP.#32.GBR.EURO #:32740 [Caterham Surrey GBR]
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  
                                               |    |
          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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