[G0HZU_JMR]

I had a go at the HP8568B filter alignment with mixed results. Looking through the cal/adjustment manual, I'd overlooked that within the 21.4MHz IF, the analyser briefly mixes down to 3MHz and back up again to 21.4MHz to do the very narrowest crystal filters. The rest of the crystal filters and the LC filters are done up at 21.4MHz

There are crystal filters in various modules to adjust and some special RC jumper links are needed to bypass the crystals during the adjustment process.

I've aligned the 21.4MHz crystal filters and achieved good symmetry, but I now have the 3MHz crystal filters to do. Hopefully, I'll be able to centre the 10Hz and 30Hz RBW responses on the CRT display. These filters are already symmetrical so I hope this will be easy. I've also worked through the logamp and video processor adjustment section, and this has improved the display accuracy.

I'll have to revisit the 21.4MHz crystal LC filters after doing the 3MHz filters as I think it's best to do it all in the correct sequence. So, lots left to do.