Increased preamble to 32 for <sf9 and left at 16 for sf9 and above

src/helpers/radiolib/CustomLR1110Wrapper.h

@@ -19,7 +19,7 @@ public:
 
   void onSendFinished() override {
     RadioLibWrapper::onSendFinished();
-    _radio->setPreambleLength(16); // overcomes weird issues with small and big pkts
+    _radio->setPreambleLength(LORA_SF <= 8 ? 32 : 16); // overcomes weird issues with small and big pkts
   }
 
   float getLastRSSI() const override { return ((CustomLR1110 *)_radio)->getRSSI(); }

src/helpers/radiolib/RadioLibWrappers.cpp

@@ -26,6 +26,7 @@ void setFlag(void) {
 
 void RadioLibWrapper::begin() {
   _radio->setPacketReceivedAction(setFlag);  // this is also SentComplete interrupt
+  _radio->setPreambleLength(LORA_SF <= 8 ? 32 : 16); // longer preamble for lower SF improves reliability
   state = STATE_IDLE;
 
   if (_board->getStartupReason() == BD_STARTUP_RX_PACKET) {  // received a LoRa packet (while in deep sleep)