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G8MNY > TECH 10.11.25 16:48l 77 Lines 3613 Bytes #6 (0) @ WW
BID : 44691_GB7CIP
Subj: SSB Demo circuit
Path: JH4XSY<N3HYM<CX2SA<GB7CIP
Sent: 251110/0741Z @:GB7CIP.#32.GBR.EURO #:44691 [Caterham Surrey GBR]
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....
ﾚﾄﾄﾄ>SCOPE AFﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ
ｳ ﾚﾄ>SCOPE DSB & AMﾄﾄﾄﾄﾄﾄﾄﾄﾄｿY1 ｳY2
ｳ D1 ｳ ﾚﾄﾄﾄﾄﾄﾄﾄﾄｿ ﾚﾄﾄﾄﾄﾄﾄﾄｿ
ｳ ﾚﾄﾄｴ<ﾃﾄﾄﾂﾄﾄﾄﾄﾄ>oﾄﾁﾄ68�ﾄo<ﾄﾄﾄｴSPECTRUMﾃﾄ>X ｳ SCOPE ｳ
ﾚﾄﾄﾄﾄﾄﾄｿ u1 ｳ ｳ |) oｿ ﾚo ｳANALYSERﾃﾄ>Y ｳDISPLAYｳ
ｳAF OSCﾃﾄｴﾃﾄﾂﾄﾄﾁﾄﾄ4k7ﾄﾄﾂﾄﾄｴ T1 |)ﾄﾄｿ _ｳ_ _ｳ_ ｳ ADAPTORｳ ﾀﾄﾄﾄﾄﾄﾄﾄﾙ
ｳ0 - 2Vｳ 4k7 === ｳ |) ｳ ﾚ---------ｿ ｳ 1-90MHzｳ
ｳ100kHzｳ ｳ 1nｳ ﾀﾄﾄｴ>ﾃﾄﾄﾙ ｳ ﾀ---------ﾙ ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾙ
ﾀﾄﾄﾄﾄﾄﾄﾙ 0-5V ﾚﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄｿ D2 ｳ ｳ ｳ
DC ｳRF SIG GENｳ ﾃﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾁﾄﾄ
ｳ 21.4MHz ｳ _ｳ_ 21.4 MHz
ｳ �100kHz ｳ /// XTAL FILTER
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ
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
resolution) & it is totally unmatched, but works well with only a 68� to
equalise the loss for filter bypass (DSB) mode.
SPECTRUM DISPLAYS
CARRIER ｳ AM ｳ DSB ｳ ｳ SSB ｳ
Y ｳ ｳ ｳ ｳ ｳ ｳ (upper or)ｳ
ｳ ｳ ｳ ｳ ｳ ｳ (lower) ｳ
ﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄ ﾄﾁﾄﾁﾄﾁﾄﾁﾄﾁﾄﾁﾄﾁﾄ ﾄﾁﾄﾁﾄﾁﾄﾁﾄﾁﾄﾁﾄﾁﾄ ﾄﾄﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄ X
| | Mixer|/ \ Carrier
Over Mod Distortion Nul
Products
SCOPE DISPLAYS
/'\ /'\ /'\ /'\ /'\ /'\
AF------------- AF | | | AF | | | AF | | |
Y1 \./ \./ \./ \./ \./ \./
_ _ _ _ _ _
RFｰｰｰｰｰｰｰｰｰｰｰｰｰ RF/' `\._./' `\._ RF/ \./ \./ \./ \ RFｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰ
Y2ｰｰｰｰｰｰｰｰｰｰｰｰｰ \._./' '\._./' \_/'\_/'\_/'\_/ ｰｰｰｰｰｰｰｰｰｰｰｰｰｰｰ
|
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 & the Spectrum display
with 100kHz AF as this gave clear sideband signals (and distortion products in
cos) and it was easy to select either upper of low sideband with �100kHz off
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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