Friday, September 23, 2011

ARRL Homebrew III Challenge Update: Cleaning up transmit spurs

TX spurious emissions test

front panel of 10m/6m SSB/CW ARRL homebrew challenge 3 challenge entry

I've spent the past two weeks working on mitigating spurious emissions from the transmitter at 6m.  The specification for 6m is to have the spurs at least 60 dB below carrier.  This radio may be unusual compared to other homebrew challenge 3 radio entries in that it has a 100 watt transmitter rather than the specified 25 watts.  For this reason there are multiple driver stages, some of which are driven into compression, amplifying and multiplying transmit mixer spurs.  Great care was taken in the strategic placement of filters to eliminate these to meet spec.

Now that the transmitter is clean i hope to have this radio on the air soon.  Stay tuned.....