R:190719/0943Z 5823@GB7YEW.#79.GBR.EURO LinBPQ6.0.18
R:190719/0943Z @:GB7CIP.#32.GBR.EURO #:12857 [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....

┌────────┐
50Ω│SPECTRUM│ ┌───────┐
Bypass ┌─┤ADAPTOR ├─┤ X-Y │
┌──────┐ ┌──────┐ ┌──────────┐ │ │0-90MHz ├─┤DISPLAY│
│RF SIG│ │DIODE │ o┘ ┌──────┐ │ │ └────────┘ └───────┘
│ 6MHz ├──┤PROBE ├──o─>o──┤ VIDEO│ └o │┌─────────┐
│ 1V │ │INSERT│ │ WALL ├──o<─o───┴┤ SCOPE │
└──────┘ └──────┘ │FILTER│ T│WAVEFOREM│
└──────┘ └─────────┘

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 50Ω 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 ┤ │ f2 0 ┤ │ Cleaner
-10 ┤ │ | f4 -10 ┤ │ Spectrum
-20 ┤ │ │ f3 | f6 -20 ┤ │
-30 ┤ │ │ │ │ f5 | f7 f8 -30 ┤ │
-40 ┤ │ │ │ │ | │ . | -40 ┤ │
-50 ┤ │ │ │ │ │ │ │ │ -50 ┤ │ f2
-60 ┴───┴───┴───┴───┴───┴───┴───┴───┴─>F -60 ┴────┴────┴──────────>F
6 12 18 24 30 36 42 48MHz 6 12MHz


SCOPE DISPLAYS

/''\ /''\ /'`\ /'`\
| | | | | | | |
RF _▌ ▐______▌ ▐____ ▌ ▐ ▌ ▐
▐ ▌ ▐ ▌
| |
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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