Antenna setting resets after stream activation

[TobiasWooldridge]

Problem

The antenna setting configured via setAntenna() is reset to a default value after calling activateStream() on some configurations. This forces applications to re-apply the antenna setting after stream activation and verify it was applied correctly.

Observed Behavior

1. Call setAntenna(SOAPY_SDR_RX, 0, "Tuner 1 50 ohm")
2. Verify with getAntenna() - returns correct value
3. Call setupStream() and activateStream()
4. Call getAntenna() again - returns different value (e.g., "Tuner 2 Hi-Z")

Workaround

Applications must:

1. Query antenna after stream activation
2. Re-apply antenna if it changed
3. Verify again

Example workaround code:

# After activateStream()
actual_antenna = sdr.getAntenna(SOAPY_SDR_RX, 0)
if actual_antenna != requested_antenna:
    sdr.setAntenna(SOAPY_SDR_RX, 0, requested_antenna)
    # Verify it stuck
    final = sdr.getAntenna(SOAPY_SDR_RX, 0)
    if final != requested_antenna:
        logger.warning(f"Antenna mismatch: wanted {requested_antenna}, got {final}")

Expected Behavior

Antenna setting should persist through stream activation, or the driver should automatically re-apply the configured antenna after internal resets.

Environment

• macOS (Apple Silicon)
• SDRplay RSPduo
• SoapySDRPlay3 driver

Suggested Fix

In the driver's activateStream() implementation, after any internal API calls that might reset state, re-apply the cached antenna setting:

int SoapySDRPlay::activateStream(...) {
    // ... existing activation code ...
    
    // Re-apply antenna setting if it was explicitly set
    if (_antennaConfigured[channel]) {
        // Re-apply the cached antenna value
        setAntenna(direction, channel, _configuredAntenna[channel]);
    }
    
    return 0;
}

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