Message 19930 in TECH.WW
From: G8MNY
Date: Wed, 01 Apr 26 10:04:00 Z
Newsgroups: TECH.WW
Subject: SSB Demo circuit
Message-ID: <56005_GB7CIP>
Path: N2NOV|N2MH|N2MH4|N3HYM|K5DAT|GB7CIP
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Dec 04)
(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 SSB generation
which my siggen can't do. As I only have a wide 50kHz bandwidth filters in my
spectrum analyser scope adapter and wanted to show the sidebands etc, normal
comms SSB is out, so I came with this set up....
I cheated with 100kHz for the Audio to solve the analyser display problem. I
initially built from junk on just 2 BNCs, but I soon boxed it up. Diodes D1 & 2
are any small silicon type, I did find proper mixer types better (more linear)
but could only handle low level, but my scope was happier with larger signals.
T1 is a medium sized ferrite bead 6mm dia with 2x 8 turns (bifil) wound on it
with the centre tap (opposite end of each wire) earthed.
The filter I had is a 7.5kHz wide one (narrower than the spectrum analyser
equalise the loss for filter bypass (DSB) mode.
SPECTRUM DISPLAYS
| | Mixer|/ \ Carrier
Over Mod Distortion Nul
Products
SCOPE DISPLAYS
/'\ /'\ /'\ /'\ /'\ /'\
AF------------- AF | | | AF | | | AF | | |
Y1 \./ \./ \./ \./ \./ \./
_ _ _ _ _ _
|
Crossover
Nuls
AM can be displayed by off setting the balance of the mixer with DC.
I found the Scope display worked best with 1-10kHz AF and the Spectrum display
with 100kHz AF as this gave clear sideband signals (and distortion products in
set of the RF signal generator.
See also my tech buls on "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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