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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW

By G8MNY (New Apr 10)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

Being involved with ham training, I have been doing all the techical demos including AM & FM (Sigen), but I was ask to do a SIMPLE demo of ferrite rings ability to reduce QRM to & from leads.

┌────────┐ ┌─────────┐
│ 100MHz │ │ ANALYSER│
│ SCOPE │ │ ADAPTOR │
┌────────┐ │ Y1 Y2 ├───────────┤ 0-90MHz │
│ SQUARE │ └┬───────┘ └───────┬─┘
│ WAVE │ _____ T│ _____ Test _____ │
│ OSC ├(_____)─┴─(_____)──>──L──<──(_____)─┘
│ 1Hz- ├┘ 50Ω Coaxes │ /~\ │
│ 50MHz │ │ \_/ │
└────────┘ │ │
└───────────┘

The oscillator can first be used to demonstrate the square wave shape on the scope (Y1) & also on the spectrum analyser harmonics of a square wave (Y2).

0dB_│
││
││ S Q U A R E W A V E S P E C T R U M
-10dB_││
││ │
││ │ |
-20dB_││ │ │ │ │ |
││ │ │ │ │ │ │ | |
││ │ │ │ │ │ │ │ │ │ │ | |
-30dB_││ │ │ │ │ │ │ │ │ │ │ │ │ │ | |
││ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │
└┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴>Harmonics
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Then via a 1 turn ferrite ring.

0dB_│
│
││ SHORING OUT THE L WILL SHOW
-10dB_││ ITS EFECTIVNES ON A 50Ω SYSTEM
││
││ │
-20dB_││ │ │
││ │ │ │ │ │
││ │ │ │ │ │ │ │ │
-30dB_││ │ │ │ │ │ │ │ │ │ │ │ | |
││ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │
││ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │
-40dB └┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴>Harmonics
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Then via a 8 turns on the same ferrite ring.

0dB_│
│
│
-10dB_│
│ Any interwinding capacitance will
││ bring back the higher frequencys.
-20dB_││
││
││ │
-30dB_││ │
││ │
││ │ │
-40dB ││ │ │
││ │ │ │
└┴──┴──┴──┴──┴─────────────────────────────────>Harmonics
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

This works for large rings that you can put over mains leads, or even tiny cores to be wired in series with Mic signals etc.


See also my tech buls on "Clip on QRM Probe", "Reducing Electronic RF QRM" "Spectrum Harmonic 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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* Origin: HAMRADIO telnet lu9dce.dynu.com (21:5/101)