The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • SMA Attenuators vs. Broadcast FM vs. NooElec SDR

    Four SMA attenuators arrived from halfway around the planet:

    SMA Attenuators
    SMA Attenuators

    The top line has ATTENUATOR wrapped around the body. They’re rated for 2 W = +33 dBm, suitable for antennas and SDR and suchlike, not real radios or even HTs.

    That assortment provides 39 dB of attenuation in 3 dB steps:

    • 3 6 9
    • 10 13 16 19
    • 20 23 26 29
    • 30 33 36 39

    Sweeping them on the spectrum analyzer shows they’re doing what they claim, to within the resolution of the analyzer, and remain flat through 1.5 GHz, where my cheap N-to-SMA adapter cables roll off by 3 dB. Stacking them produces 38 dB of attenuation, which is certainly the small difference of large values and fine for my simple needs.

    Conversely, a quick test with a NooElec SDR shows plenty of hocus-pocus betwixt antenna and display: the RF doesn’t attenuate nearly the way you’d (well, I’d) expect.

    Direct from the antenna, with AGC off and 50 dB of RF gain:

    WPDH Spectrum - 0 dB atten
    WPDH Spectrum – 0 dB atten

    3 dB attenuator:

    WPDH Spectrum - 3 dB atten
    WPDH Spectrum – 3 dB atten

    6 dB attenuator:

    WPDH Spectrum - 6 dB atten
    WPDH Spectrum – 6 dB atten

    10 dB attenuator:

    WPDH Spectrum - 10 dB atten
    WPDH Spectrum – 10 dB atten

    20 dB attenuator:

    WPDH Spectrum - 20 dB atten
    WPDH Spectrum – 20 dB atten

    Ain’t nothin’ simple…