Sunday, December 6, 2015

Double Side Band (DSB) Generation III

I have now built the Si5351 clock generator, attenuators, and Arduino Uno in one metal box and the NE612 mixer in another. This shielding was required because the clock generator was so powerful it was getting into the measurement receiver by radiating it! Here are the tin boxes I used:







Here they are open:







The below image is a screen shot from the 817 Commander tool that has a scanner function which plots the s-meter values over the scanned frequencies. I was feeding the balanced modulator with the carrier and a 4 kHz audio tone. You can see the two side bands and the center carrier. The carrier is in fact below the side bands as I expected. Using my FT-817 as the measurement receiver and using the s-meter measurement method, I was able to confirm the suppressed carrier.
Based on the FT-817 S-meter calibration data I found  HERE this is ~ 27 db below the side bands and probably at least 30 db since the s-meter on the 817 is not linear. Next step is the RF amplifier stages to bring the level up to a couple of watts.




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