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A Dead Easy 50 mhz Preamp by VK3CJS
6M Preamp - Page 3
Just hitch the thing between the antenna and your 50 mhz Rx and apply power. Turn the Gain pot to maximum (+ 12v) and tune around with the other for maximum noise. Then start winding out the slug(s) on the IF transformer(s) for max noise. You may have to take the slugs right out.... that's OK. Just where you leave the gain setting depends on the sensitivity of your set and your locality with respect to strong signals. I live in the quite countryside, so mine is set near max.
My image problem is completely cured.... the pream tuning is quite sharp. Signal to noise is light years better than crappy old CB front end by itself.
In the end I installed a simple resistive pad between the preamp and the Rx to tame excess gain. About 10db attenuation in my case.
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Here is the preamp in all it's glory, strapped down on one end of the PA with a cable-tie (never mind the expense).
You can see the pots hanging by their tags and the attenuator resistors hanging in space. One day I'll get around to tidying it all up.
But why stop there? I got carried away and added a Jackson Planetary Drive to the VXO. Now I can tune 'em in after a night
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on the red wine. The circular dial is the end sawn from an empty solder spool, marked with a fine-liner.
The box has the obligatory S-meter (wow!.. now I can give signal reports) and an MCW audio oscillator with break-in and delay. It is tons easier to plug one of these in than to unbalance the balanced moduator for CW. The little black disk is for sidetone. It is one of those tiny piezoelectric squawky things from a computer motherboard.
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Does it all work, I hear you cry..... you bet it does!
Happy fiddling guys..........
73 de Chris VK3CJS
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