How does amplification on Nooelec SAWBird H1 vary with voltage on power supply input?
Short answer: the SAWbird H1’s gain is essentially fixed by its RF amplifier bias network and SAW filter — within the manufacturer’s recommended supply window (≈3.3–5.5 V) you should see the rated gain (~+40 dB at 1420 MHz) with only small changes. The vendor does not publish a detailed gain-vs-VCC curve, so any precise numbers beyond the datasheet specs require measurement.
Details and practical points
- Recommended supply: 3.3–5.5 V DC (bias-tee, USB or header). The datasheet lists 3.3 V minimum and ~5 V typical. Running it inside that range is what Nooelec guarantees.
- Nominal gain & noise: the module is specified at roughly +40 dB gain (around 1.420 GHz) with an ultra-low noise figure — that is the figure you should expect when powered in the recommended range.
- Below the minimum voltage: if VCC drops under the recommended minimum (≈3.3 V) the amplifier biasing will be off and gain will fall — possibly rapidly — and noise performance will degrade.
- Above the recommended voltage: the unit may tolerate higher voltages for short periods (Nooelec notes overvoltage protection and that units “should still work” up to higher voltages), but long-term operation above 5.5 V is not recommended (may reduce lifetime or void warranty).
- RF input level matters separately: the amplifier’s linearity (compression, intermodulation) depends on RF input power, not supply voltage. The datasheet shows an input-power guidance (Pin ≤ 0 dBm typical) — very strong signals will compress the gain regardless of VCC.
If you want a precise gain-vs-VCC curve (recommended)
- Feed a stable, calibrated CW or swept signal at 1420 MHz (use a signal generator).
- Measure output power on a spectrum analyzer (or an SDR with a calibrated attenuator and known reference).
- Record gain = Pout − Pin while stepping VCC across the range (e.g. 2.5 V → 6.0 V in 0.1–0.5 V steps).
- Watch for current draw changes or abnormal heating (signs of overvoltage stress).