diff --git a/main/packets.h b/main/packets.h
index f027309..9c9190c 100644
--- a/main/packets.h
+++ b/main/packets.h
@@ -19,6 +19,7 @@ typedef struct __attribute__((packed))
     uint32_t packetIndex;
     uint8_t packetType;
     uint32_t missionTimer;
+    uint32_t CRCCheck;
 } DownBoundPacket;
 
 typedef struct __attribute__((packed))
@@ -90,6 +91,8 @@ typedef struct __attribute__((packed))
     int16_t currentServoB;
     int16_t targetServoB;
 
+    uint8_t telemetryIndex;
+
 } TelemetryPacket;
 
 typedef struct __attribute__((packed))
@@ -97,6 +100,7 @@ typedef struct __attribute__((packed))
     char syncPhrase[10];
     uint32_t packetIndex;
     uint8_t packetType;
+    uint32_t CRCCheck;
 } UplinkPacket;
 
 typedef struct __attribute__((packed))
diff --git a/main/radio.c b/main/radio.c
index 329d270..db5d751 100644
--- a/main/radio.c
+++ b/main/radio.c
@@ -27,6 +27,10 @@ void send_ack(uint32_t packetIndex, uint32_t crc)
     uplinkHeader.packetIndex = uplinkPacketIndex++;
     uplinkHeader.packetType = UplinkPacketType_ACK;
 
+    uint32_t crcCheck = esp_rom_crc32_le(0, (uint8_t *)&ack, sizeof(ack));
+
+    uplinkHeader.CRCCheck = crcCheck;
+
     uint8_t txBuf[256] = {0};
     int offset = 0;
 
@@ -146,6 +150,8 @@ void printTelemetryPacket(const TelemetryPacket *packet)
     ESP_LOGI(TAG, "  Servos:");
     ESP_LOGI(TAG, "    Servo A: Current = %d, Target = %d", packet->currentServoA, packet->targetServoA);
     ESP_LOGI(TAG, "    Servo B: Current = %d, Target = %d", packet->currentServoB, packet->targetServoB);
+    ESP_LOGI(TAG, "  TelemetryIndex: %d", packet->telemetryIndex);
+
 }
 
 void handle_downlink_packet(uint8_t *buf, uint8_t rxLen)
@@ -171,6 +177,13 @@ void handle_downlink_packet(uint8_t *buf, uint8_t rxLen)
     uint8_t *payload = buf + sizeof(DownBoundPacket);
     uint32_t payloadSize = rxLen - sizeof(DownBoundPacket);
 
+    uint32_t crcCheck = esp_rom_crc32_le(0, payload, payloadSize);
+
+    if (crcCheck != down.CRCCheck) {
+        ESP_LOGE(TAG, "Received BAD CRC for packet %d, crc is %ld, should be %ld", down.packetIndex, crcCheck, down.CRCCheck);
+        return;
+    }
+
     switch (down.packetType)
     {
     case DownlinkPacketType_Telemetry:
@@ -227,7 +240,7 @@ void lora_comms_task(void *pvParameters)
         }
     }
 
-    uint8_t spreadingFactor = 6;
+    uint8_t spreadingFactor = 7;
     uint8_t bandwidth = SX126X_LORA_BW_250_0;
     uint8_t codingRate = SX126X_LORA_CR_4_8;
     uint16_t preambleLength = 8;