The R29
Here is a neat little Regenerative Receiver that showed its stuff tonight when the going got messy - it beat my R390A on a set of weak ones under really tough 80M conditions. I was in a CW QSO
Mike WU2D
That is a cool-looking project, and I've always understood that the re-gen sets are exceptionally "quiet."
So how does it compare on AM ?
I started putting an SP600 through such a comparison, and have found it beats the R390A for audio quality.
That's no big surprise, since the Hammarlund uses LC circuitry rather than a mechanical filter to establish selectivity. The mechanical filter passband looks kinda like a square wave, and it induces a "ringing" effect that shapes the audio sort of like listening through a paper towel cardboard.
The SP600 sounds much more like the R390, which also uses LC rather than mechanical filtering.
Example of the SP600. 18Mb *wav file, uncompressed, no EQ.
Aircheck Recording