The LD-1D prototype is assembled, and I’m evaluating it. I did get “interrupted”, sort of, by a motorcycle oil change that should have taken about 30 minutes turning into 4 hours. More about that at the end of the post.
It’s a good thing I did order a prototype run of 4 PCBs. I immediately discovered a phasing error in the doubly-balanced QSD, which was easily fixed with red wire so testing can proceed, but I won’t be selling any of the prototypes. The error resulted in enhancement of even multiples of the LO, and rejection of odd multiples. That’s the exact opposite of what I intended, and it didn’t take long to find the error. After correcting it, I found that spurious responses in the AM band and below (and probably everywhere else) are greatly reduced. The AM-band response to the second harmonic of the LO seems to have been eliminated completely, which is better than I had hoped. However, sensitivity is not quite up to that of the LD-1C. I have an idea about that, and expect to correct it easily.
I will also double-check all the filter element values, and see whether the extension to 54 MHz really works.
Stay tuned, the LD-1D will be available soon.
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