After some research on the Internet. I concluded this.
MFJ-1026 Noise Canceller modification Plan
1. Reduce Low frequency attenuation (increase gain at 1.8 MHz)
- Change C8, C16 (680pF) with 1.6nF for Better high pass filtering
- Change C18 (680pF) with 1.6nF for better pass through
- May Change L3, L4, L5, L6 (5.6 uH) with 10 uH ==> No need to change (Just Increase Cap to decrease attenuation at 1.8 Mhz)
2. Better IM Dynamic range
- Remove Diodes D6, D9, D10, D11
3. Better Gain
- Add 4:1 transformer to the output of Q4 (C1)
4. Better control of Phase range (Swap inputs)
- ADD DPDT SW & Coax to swap the inputs of Q8 and Q5
- Q8 -> SW -> R20; Q5 -> SW -> R9
5. Getting Better phase range and control
- Change C13 (120pF) with (47pF => 68pF) - Increased range for high band position
- Change C12 (470pF) with 680pF - Better phase control for low band position
6. Protect Aux Antenna FET from high power operation
- Install an AUX antenna input grounding Relay.
- Connect Relay (+) to (C2-Q1 junction pad) and Relay (-) to (R5-Q2 junction pad), -Install a diode
- Install a protection diode
- Need a 12V relay for isolation and a Diode for protection (NA1S TQ2-12V, Single side stable)
