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G8MNY > TECH 15.08.09 23:03l 75 Lines 3514 Bytes #999 (0) @ WW
BID : 34586_GB7CIP
Read: GUEST
Subj: SSB Demo circuit
Path: IZ3LSV<IK2XDE<DB0RES<WA7V<CX2SA<GB7CIP
Sent: 090815/2045Z @:GB7CIP.#32.GBR.EU #:34586 [Caterham] $:34586_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Dec 04)
(8 Bit ASCII Graphics use code page 437 or 850)
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 & 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) & 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 ÄÄÄÄÄÄÄÄÁÄÄÄÄ 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 & the Spectrum display
with 100kHz AF as this gave clear sideband signals (& distortion products in
course) & it was easy to select either upper of low sideband with ñ100kHz off
set of the RF signal generator.
See also my tech bul on "Spectrum Harmonic Demo circuit".
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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