By G8MNY (New May 10)
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This modification puts a crude, but very effective clipper into this base mic when used with & powered from a simple TS50 rig.

EXTRA COMPONENTS
2x Germanium/Schottky Diodes
1 10K small preset pot
1 470R Variable R

CIRCUIT
No preamp
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÂÄÄ<Rig 8V
mic Ä>o + Cut track o<ÄÄRig \³ 1K8
o 1K Ú------------o Mic T2 ÃÄÄ´
³ ÚÄÄÄÄÅÄÄÄ´ÃÄÄÄÄÂÄÄÄÂÄÄÄ¿ ³ +ÄÂÄ>o e/³ ³
³ 39K ³/ _³_ _³_ ³ ³ ³ oÄÄ´ _³_
À´ÃÄÁÄÄ´ T1 /_\ \_/ 10K<Ù ³+ _³_ /_\' 3.6V
³\e ³ ³ pot === /_\ ³
ÃÄÄÄÄ¿ ³ ³ ³ ³ ³ |<-remove
220R 470<¿ ³ ³ ³ ³ Batt ³
ÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÁÄÄÄÁÄÄÄÁÄÄ ÄÄÁÄÄÄÄÄÁÄÄÄÄÁÄÄ

The 3.6V zener diode in the regulated supply is removed by heating & lifting
up one end. This gives the preamp much more headroom to facilitate symmetrical clipping with the added diodes. The extra 470R mic gain preset is placed over the tiny 220R. The 2 diodes & are mounted over the preamp in/out switch connector socket.

The track is then cut to the "Preamp in" position switch & the output level 10k preset mounted over the preamp in/out switch.

BUTTON PCB
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄ¿
³C ³ ³: Ú' '³
³ T1 UP DOWN SWITCHES T2 1k8 ³ ³:_|ú ú³ |=cut track
³220 Zener³ Ú bk³: ³
³ ³ Ã rd³: ' '³
³ PTT LOCK ³ ³ ÀÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ Batt SWITCH PCB

Setting up is best done with a scope looking at the signal on the diodes, check that at normal close mic use the diodes clip the peaks off, adjust the 470R mic gain to suit. Then operate the PTT & adjust output pot (& Rig mic gain) to just give full power (normal ALC drive) on a loud clipped whistle (almost at zero).

This clipper only works when the mic level is just right, your voice level is important, so aim for 3x (10dB) clipping level. On air tests gave it a good clear audio report with clipped audio not too noticeable, but sounds quite a bit louder.

CONTROLS
Using the Mic Impedance switch, some modulation control is posssable.

PREAMP MIC Z RESULT
out 50k Lowest unclipped (For loud background situations)
out 500ê Normnal unclipped
in 500ê Slightly clipped
in 50k Heavily clipped (For weak signal/noisy band)

WHY CLIPPERS WORK

Peaky Ý Ü ^ Clipped _ _ Resultant /~\ /~\ ^ Mic / \ / \_/~\_ ALC Mic / \_/ \_/~\ after / \ / ALC Audio Þ ß v Audio ALC level \_/ v

When the worst of peaks are clipped off, the lower level can then drive the rig with a higher mean level (less ALC action). This results in slightly noticeable audio distortion, but a MUCH LOUDER SIGNAL. Under weak/poor conditions the low level distortion products are not detectable, but the louder signal is more easily read.

Audio harmonics generated will be transmitted if they get through the SSB filter outside that they are filtered enough in the rig to not be a problem.

This is all very subjective, so heavy clipping should only be used for "weak & poor contacts", not strong local ones where the distortion becomes wearing to listen too!


Why Don't U send an Interesting Bul?

73 De John, G8MNY @ GB7CIP


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