Clean up the airband junk before it hits the receiver. Real FM suppression.
FlatTop is a compact, purpose-built airband bandpass filter for aviation enthusiasts who are tired of scanning aviation frequencies through junk.
This compact 118–136 MHz airband bandpass filter is engineered to keep the aviation band flat while hammering nearby FM junk that can overload real receivers. Available in Standard and hand-screened Premium versions, FlatTop gives SDRs, scanners, handheld radios, and monitoring stations a cleaner front end, lower in-band loss, and stronger real-world airband performance.
In tested assembled units, FlatTop delivered roughly 0.8–2.0 dB insertion loss across the passband, 34–43 dB attenuation at 108 MHz, and a repeatable deep notch near 105 MHz in the 49–54 dB range. The result is simple: more airband, less junk.
FlatTop is offered in two versions
FlatTop Standard
FlatTop Standard is the production version for users who want a serious airband front-end filter without paying for premium screening paperwork. It delivers the same core FlatTop design: broad 118–136 MHz coverage, low loss in-band, and strong built-in FM suppression in a compact package.
This is the right choice for most SDR users, scanner users, handheld aviation radio users, and fixed monitoring stations.
FlatTop Premium
FlatTop Premium is the premium hand-screened version for customers who want the performance plus proof. Premium units are individually measured and selected for tighter screened performance, with serialized verification, for buyers who want greater confidence in exactly what their unit delivered on the bench. This is the right choice for demanding users, avionics troubleshooters, serious monitoring installations, and anyone who simply wants the best FlatTop we can send.
Why FlatTop is Different
Many filters in this category are either too broad, too lossy, too generic, or too narrow to be practical across the whole airband. FlatTop was developed through repeated design, build, VNA measurement, retuning, and relayout to hit a harder target: broad enough to cover the whole civil COM band, low-loss enough to preserve wanted signal, and aggressive enough below the band to keep FM from wrecking the receiver. Even the shield can lid is part of the RF design, improving the finished filter’s FM-notch behavior.
FlatTop is Ideal for
- Airband SDRs
- Aviation scanners
- Handheld aviation radios
- Fixed airband monitoring stations
- RF troubleshooting and front-end cleanup
60-day Guarantee
FlatTop includes a 60-day no-questions guarantee. Try it in your real setup. If it does not improve your airband experience, send it back.
Quick Comparison
Standard - $79.95 - Radiant # RI-2026-4
Best value for most users
Broad airband coverage
Low-loss performance
Strong built-in FM suppression
Premium - upgraded version - $119.95 - Radiant # RI-2026-5
Hand-screened premium units
Measured verification
Tighter screened performance
Best choice for demanding installs and bench-minded buyers
Bottom line
FlatTop was built to do what too many “good enough” filters do not: pass the band you want and punish the band you don’t.
READ JAMES' BLOG ABOUT THE TECHNICAL DETAILS BEHIND THE FLATTOP.
