I finally got round the drilling the front panel today. All went reasonably well as I used a printed template but the four buttons that control PPLL functions sort of slipped a little and are not central to the VFO LCD. It is rumoured that a few expletives were heard around that time.
There were also some layout issues behind the front panel as space is very limited. All looks OK now and it is time to wire the PPLL VFO.
I have made up a splitter for the PPLL VFO RF output to feed to RX mixer and TX driver. Both toroids are wound on FT37-43 as detailed in “Experimental Methods in RF Design” pages 3.36 and 3.35. There is also a 2:1 step down transformer to match the 50 ohm output of the DDS VFO to the 25 ohm input to the splitter. Bench tests show that the arrangement works well, is very broadband and has enough loss to avoid adding an attenuator in the RX side!
The TX LPF board is complete, tested and working. It needed some slight adjustment to the turns on some toroids to push the drop off frequency high enough to avoid attenuation on the higher bands on the 40/30 and 20/17 sections.
The TX driver stage with pin diode attenuator is also complete and housed in a tinplate box on the lid of the RX demod and audio board which is in a diecast box.
(Click on an image to enlarge, navigate using < < or >> then click the image to close.)
