What if any is potential benefit for adding filtering and amplification at antenna in meteor scatter detection arrangement at 143.050 MHz?

Short answer: yes—put a low-noise preamp at the antenna and (usually) a filter right after it. You’ll lower the system noise figure by multiple dB and make weak pings at 143.050 MHz (e.g., GRAVES) much easier to detect. Numbers below.

What changes, quantitatively

Let’s compare a typical setup at 143 MHz. Assumptions (all very common with SDRs):

• Receiver noise figure (NF): 5 dB
• Feedline loss from mast to shack: 2 dB
• LNA at the antenna: NF = 0.6 dB, Gain = 20 dB
• Optional band-filter insertion loss: 2 dB

Using Friis’ formula:

A) No LNA (coax → receiver):
Overall NF = coax loss × receiver NF = 2 dB loss × 5 dB NF ⇒ ≈ 7.0 dB

B) LNA at the antenna, then coax, then receiver:
Overall NF ≈ 0.75 dB
→ ~6.3 dB improvement vs. no LNA (that’s roughly a factor of 4 in noise power).

C) Add a 2 dB filter before the LNA:
Overall NF ≈ 2.75 dB
→ Still far better than no LNA, but you “spend” ~2 dB by filtering before the LNA.

D) Put that same 2 dB filter after the LNA:
Overall NF ≈ 0.86 dB
→ Almost as good as case B, but with the interference protection of the filter.

Takeaway:

• The single biggest win is a low-NF LNA mounted at the antenna.
• If you need a filter, put it after the LNA whenever possible to avoid burning precious SNR.
• Only put a filter ahead of the LNA if you’re fighting very strong out-of-band signals that would drive the LNA or SDR into compression.

Why it helps for meteor scatter

• Meteor echoes are often near the noise floor; cutting the system NF from ~7 dB to ~0.8–1 dB yields ~6 dB SNR headroom, turning marginal, short “pings” into clearly detectable events.
• A post-LNA band-pass (or FM/airband notches) prevents desense and spurs from strong 88–108 MHz FM, 118–137 MHz airband, and other VHF services without penalizing NF much.

Practical picks (what to aim for)

• LNA: NF ≤ 1 dB (0.5–0.8 dB if you can), Gain 15–25 dB, high IP3 (≥ +15 dBm) so it won’t fold under strong locals. Weatherproof, mast-mounted, with ESD/lightning protection and a bias-T.
• Filters:
  • Best: a narrow 143.05 MHz band-pass (helical/cavity).
  • Or: a wide VHF pass plus deep FM/airband notches.
  • Keep insertion loss low; if it’s >1–2 dB, place it after the LNA.
• Feedline: good coax (e.g., LMR-400/Ultraflex) to keep loss low, though the LNA largely “cancels” downstream loss for NF purposes.
• Gain staging: Total front-end gain (LNA + any post-LNA filter loss) of ~15–25 dB is usually enough before the SDR; more can invite overload.

Rule-of-thumb improvements you can expect

• SNR on weak pings: +4–7 dB vs. an un-amplified, long-coax setup.
• Dynamic range / clean spectra: markedly better with post-LNA filtering (desense and intermod products drop dramatically).