S-Band signal source

I finally got around to building an S-Band signal source for use in the future with my S-Band downconverter. I basically followed the design of Bertrand VE2ZAZ that he describes in detail on his website.

The 40MHz oscillator (type XO40.00/14-TTL) came from Viewcom Electronics, the aluminium box from Jabdog and most of the other components from Maplin. The SMA socket and antenna took a bit more searching. Eventually, I sourced the panel-mount SMA socket from Cybermarket and I bought some short patch leads on eBay from "cryptiensis2004"; these have a short length of semi-rigid coaxial cable ready terminated in an SMA plug.

Unlike Bertrand, I soldered the oscillator directly to the SMA socket, so I kept the patch leads for making the dipole antenna. I also added an LED power indicator.

I have found the output signal within 250Hz of the nominal 40MHz fundamental frequency. When I have time, I will check for harmonics up to UHF with my FT-847. 2.4GHz testing will have to wait until I have the downconverter working.

Ugly VFO test results

I have run a couple of quick tests on the ugly VFO. It covers 6.62MHz to 6.73MHz, somewhat wider and lower than its 7.0MHz to 7.1MHz design range. But since this was just a test piece, I had not bothered to include any trimmer capacitors to adjust this.

Stability was a bit variable. In two 15 minute tests, I got drift of 40Hz and 350Hz respectively. I am glad there is a bit of drift; when I add the "huff and puff" stabiliser, it should be clear whether or not it improves things.