I have a mini circuits DC-22MHz filter. Would it be possible to slightly adjust range up by 2MHz with extra components?
Short answer: not really. Mini-Circuits “DC–22 MHz” parts are fixed, 50 Ω-matched, sealed networks (usually elliptic/Chebyshev LC). To move the cutoff up by ~2 MHz you’d need to reduce the effective shunt C / series L inside the network, which you can’t do from the outside. Any external “tweak” (a little series L, shunt C, or an L-match) will mostly just:
- wreck the return loss and create peaking/ripple near the edge,
- unpredictably shift the shape (on one unit it might help, on another it won’t),
- and degrade the stopband above ~30–40 MHz.
What you can try, if you’re desperate (and accept the trade-offs):
- See if you can live with it as-is. Many Mini-Circuits LPFs have their 3 dB point ≈ the model number, but the slope is gentle—at 24 MHz you might only be a couple dB down. Verify with a VNA: measure S21/S11 and decide if the extra loss is acceptable.
- Add a tiny “peaking” equalizer ahead of the filter (e.g., a very small series inductor—tens of nH—plus a resistive pad of 3–6 dB to keep things well-behaved). This can flatten the top end a bit, but you’ll pay with worse match and worse rejection. It’s trial-and-error and unit-specific—fine for a bench lash-up, not for a dependable instrument.
Best practice:
- Swap the filter for a higher-cutoff model (e.g., a 24–25 MHz or 30 MHz LPF) and, if needed, add a modest follow-on notch (parallel RLC to ground via a tee) at any specific out-of-band you care about.
- Or design a new 7th/9th-order Chebyshev/elliptic LPF for 24–25 MHz with 50 Ω terminations; you’ll get the exact edge you want and predictable behaviour.