Jan G0BBL offers interesting parts and kits through the website www.sdr-kits.net. She is one of them frequency synthesizer kit based on the si570 circuit controlled by Atmel. This bypasses the usual way of controlling the si570 circuit via USB.
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Features of the PA0KLT si570 frequency synthesizer
The PA0KLT wiring uses a rotary encoder for tuning, four control buttons and a two-line backlit LCD display. The control firmware allows the smallest tuning step of 1Hz, switching between VFO A, VFO B and 32 memories. It is also possible to configure frequency offset and frequency multiplier (suitable, e.g. for SDR, where the desired frequency is 4 times the one shown). The advantage is the BCD output with information about the set band, which can be used, for example, to switch bandpasses.
Production of the PA0KLT si570 kit
I received the kit in the mail about a week after ordering. The construction is a mix of classic and SMD parts. Blocking SMD capacitors are supplied in the number of 1-2 extra pieces, which has proven itself very well. The capacity value is also marked on the packaging tape with a colored marker. The board connection is double-sided, tinned and covered with a non-solderable mask outside the contact surfaces. The construction and revival procedure is in the manual, which is available on the website. I recommend following it.
Soldering si570
The biggest difficulties are with the soldering of the si570 circuit. The terminals are on the side in slots and as flats on the underside of the integrated circuit. Soldering on the bottom has worked for me, in the way that both the IO and printed circuit boards are first tinned, the IO is placed on the printed circuit, and the tin on the printed circuit is melted and fused with the tin on the IO with microsoldering. Depending on the si570 version, do not forget to connect the output to the printed circuit board.
Improvements
The supplied switches are not of the highest quality, they are sufficient for revival and testing. In my case, there was no problem with revival, all indicated values of voltages and currents agreed. I recommend adding a cooler to the stabilizer 7805, especially if the supply voltage is higher than 10V.
Summary
Although the connection is not difficult, it requires practice with soldering SMD components and basic measuring technique (A, V, I recommend a counter or an oscilloscope). An advanced designer can thus make the basic part of RF equipment (RX, TRX, RF generator, etc.) for a relatively favorable price.