Removing spurs
Raj VU2ZAP has confirmed that surface mount components can be used in the LPF after the 45MHz filter.
He used SMD Yellow shielded inductors 331nH x 2 + 51pf to ground.
Summary of recommended fixes to address unintended spectrum products
- Replace K1, K2 and K3 with Axicom 12v relays (low current models are fine) to remove harmonics to acceptable levels in most rigs on most bands.
- Install a 45MHz filter across TP13 (v3 board). Ashhar Farhan VU2ESE inserts a 0.3µH inductor in series with a 10 pf capacitor across TP13 on the v4 board. This is on the output of the 45 MHz IF amp going to the front end of the mixer. The inductor comprises 8 turns on a T30-6 toroid (to give 0.3µH or 300nH). Or use Raj’s alternative as above.
- Consider also changing out L5 and L7 with shielded surface mount inductors (yellow type). See this article.