A few weeks ago I finished the build of the 80m/40m PA. A quick test of the RX with a short wire aerial into Rocky software (including the best part of a day messing with soundcards before I got a dual soundcard system to work) revealed a lot of interesting whistles, but no signals. Not having a transceiver to generate a signal, and running out of time, a few weeks have passed while I've been away a bit on business.
Thinking about how to test further I decided to build a one transistor LC oscillator to generate a test signal. I found a BC109 in the junk box and wound a small transformer on an FT137-43 core (8 turns in collector circuit and 2 turns for feedback to the base). After getting the feedback phase right and dropping the gain with a suitable emitter RC network I got vaguely sine wave oscillation but with only stray capacitance it ran at under 6MHz. I soldered in about 100p of capacitor across the collector turns and got it to run at about 3.5MHz, giving me a harmonic around 7MHz. My AOR scanner gave me a nice signal around this frequency and a fun time playing it as a "Theremin" as waving hands near it scanned it across the 7MHz band. Reverting to the Softrock I now got a good spectrum display as the oscillator zoomed around the band, so I guessed that the receiver was actually okay. The correct display seemed to require the I and Q selection of Rocky to be reversed from what I expected. Still not sure why.
A quick test of TX into a dummy load and detected on my scanner showed that TX seemed to be working. I had been dreading this, expecting smoke, but all seemed in order.
Transplanting the Softrock from the workbench to the shack bench I connected my roof antenna and - amazing - lots of stations across the 40m band. The spectrum display and DSP detection was amazing to play with, quite an eye-opener.
More about some weird issues with mutliple images and testing the TX further in the next update...
