Thanks for the replies Jamie and Jerry. I'll look at the links you provided. This is my friend's first radio construction project although he's built electronic circuits before. I thought modular construction would be instructive, debugging stage-by-stage (if necessary) and we can always upgrade modules when the whole thing is working. I have a couple of Si5351 breakout boards bought at a rally and doing nothing. Using them we wouldn't have to worry about drift, and a digital display will be easy too.
On 27 May 2017 at 15:23, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The BitX40 schematics up on are probably a good place to start, adjustments for 20m would be restricted to the BPF, the transit LPF, and the VFO. You need to decide if you are going with an analog VFO, I'd suggest using an Si5351 for both VFO and BFO as is done on the uBitx: ? In fact, not a bad idea to just go with the uBitx schematics, has a number of improvements over the Bitx. The SBL-1's should work fine, though it's possible that building up from torroids and diodes could work slighty better as they don't need to work at 500mhz. The 1n4148's should probably have more drive than they get on the Bitx. The Bat54 schottky diodes on the uBitx have lower drive requirements, same as the SBL-1's at 7dBm into 50 ohms. ?
On Fri, May 26, 2017 at 11:39 am, John wrote:
I see that there are variants of the BITX20 on the web so I wonder whether anyone can recommend a particular circuit to follow. I have a good supply of iron dust toroids, 2N3904s and 2N2222s. I have a few SBL1s recovered from old boards. Are these much better than rings of 1N4148s?
