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G8MNY > TECH 27.08.26 22:42l 77 Lines 3620 Bytes #999 (0) @ WW
BID : 3263_GB7CIP
Read: GUEST DJ6UX
Subj: SSB Demo circuit
Path: DB0FHN<DB0RKB<OK0NAG<F3KT<VA2RIZ<WW6Q<W9GM<KC9UHI<PI8ZTM<CX2SA<ED1ZAC<
GB7CIP
Sent: 260825/0657Z @:GB7CIP.#32.GBR.EURO #:3263 [Caterham Surrey GBR] $:3263_GB
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....
ÚÄÄÄ>SCOPE AFÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ÚÄ>SCOPE DSB & AMÄÄÄÄÄÄÄÄÄ¿Y1 ³Y2
³ D1 ³ ÚÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄ¿
³ ÚÄÄ´<ÃÄÄÂÄÄÄÄÄ>oÄÁÄ68êÄo<ÄÄÄ´SPECTRUMÃÄ>X ³ SCOPE ³
ÚÄÄÄÄÄÄ¿ u1 ³ ³ |) o¿ Úo ³ANALYSERÃÄ>Y ³DISPLAY³
³AF OSCÃÄ´ÃÄÂÄÄÁÄÄ4k7ÄÄÂÄÄ´ T1 |)ÄÄ¿ _³_ _³_ ³ ADAPTOR³ ÀÄÄÄÄÄÄÄÙ
³0 - 2V³ 4k7 === ³ |) ³ Ú---------¿ ³ 1-90MHz³
³100kHz³ ³ 1n³ ÀÄÄ´>ÃÄÄÙ ³ À---------Ù ÀÄÄÄÄÄÄÄÄÙ
ÀÄÄÄÄÄÄÙ 0-5V ÚÄÄÄÄÄÁÄÄÄÄ¿ D2 ³ ³ ³
DC ³RF SIG GEN³ ÃÄÄÄÄÁÄÄÄÄÄÁÄÄ
³ 21.4MHz ³ _³_ 21.4 MHz
³ ñ100kHz ³ /// XTAL FILTER
ÀÄÄÄÄÄÄÄÄÄÄÙ
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) and it is totally unmatched, but works well with only a 68ê to
equalise the loss for filter bypass (DSB) mode.
SPECTRUM DISPLAYS
CARRIER ³ AM ³ DSB ³ ³ SSB ³
Y ³ ³ ³ ³ ³ ³ (upper or)³
³ ³ ³ ³ ³ ³ (lower) ³
ÄÄÄÄÄÄÁÄÄÄÄÄÄ ÄÁÄÁÄÁÄÁÄÁÄÁÄÁÄ ÄÁÄÁÄÁÄÁÄÁÄÁÄÁÄ ÄÄÄÄÄÄÄÄÁÄÄÄÄÄ X
| | Mixer|/ \ Carrier
Over Mod Distortion Nul
Products
SCOPE DISPLAYS
/'\ /'\ /'\ /'\ /'\ /'\
AF------------- AF | | | AF | | | AF | | |
Y1 \./ \./ \./ \./ \./ \./
_ _ _ _ _ _
RF°°°°°°°°°°°°° RF/' `\._./' `\._ RF/ \./ \./ \./ \ RF°°°°°°°°°°°°°°°
Y2°°°°°°°°°°°°° \._./' '\._./' \_/'\_/'\_/'\_/ °°°°°°°°°°°°°°°
|
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
course) and it was easy to select either upper of low sideband with ñ100kHz 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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