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I have tried a slightly different solution for the spur. A screened 80nH tunable coil (like Coilcraft's) in parallel with a 150pf just across C22 and ground. These values should resonate at 45mhz and have a reasonable Q (greater than 2) to attenuate 90Mhz. However the CW power output dropped to just 5W (more than 3db loss then) on 40m so I have removed it. On SSB the power seemed less effected, why?

Il 12/nov/2018 09:01, "Ashhar Farhan" <farhanbox@...> ha scritto:

i have further simplified the fixes:

1. change the resistors R26 and R46 to 220 ohms (from 470 ohms). this increases the darlington pair's standing current and decreases the Harmonic distortions.

2. the 90 MHz trap was difficult to tune unless you had a spectrum analyzer. Instead, we can use a Low Pass Filter instead. A 'T', rather than a Pi was used. This helps better in isolation or RX/TX path.?

3. The LPF consists of an L-C-L of 300nh, 47pf, 300nh.?

4. With the relays that are now used for ubitx,? the harmonics at 3.5, 7 and 10 are in under -45 dbc. we don't need the axicom relays.

I am attaching a hand-drawn circuit to explain this better.

- f