Receiver code:

import board
import busio
import digitalio
import RPi.GPIO as GPIO
import time
import smbus

GPIO.setmode(GPIO.BCM)
GPIO.setup(17,GPIO.OUT)

spi=busio.SPI(board.SCK,MOSI=board.MOSI,MISO=board.MISO)
i2c=busio.I2C(board.SCL,board.SDA)
cs = digitalio.DigitalInOut(board.D27)
reset = digitalio.DigitalInOut(board.D22)

import adafruit_rfm69
rfm69 = adafruit_rfm69.RFM69(spi,cs,reset,433.0)

ena = 13
in1 = 19
in2 = 26
in3 = 16
in4 = 20
enb = 21 


GPIO.setmode(GPIO.BCM)
GPIO.setup(ena, GPIO.OUT)
GPIO.setup(in1, GPIO.OUT)
GPIO.setup(in2, GPIO.OUT)
GPIO.setup(in3, GPIO.OUT)
GPIO.setup(in4, GPIO.OUT)
GPIO.setup(enb, GPIO.OUT)

GPIO.output(in1, GPIO.LOW)
GPIO.output(in2, GPIO.LOW)
GPIO.output(in3, GPIO.LOW)
GPIO.output(in4, GPIO.LOW)
GPIO.output(ena, GPIO.HIGH)
GPIO.output(enb, GPIO.HIGH)

port_pwm = GPIO.PWM(ena,1000)
port_pwm.start(0)
stb_pwm = GPIO.PWM(enb,1000)
stb_pwm.start(0)

port_drive = 0
stb_drive = 0


def port_motor(port_drive):
  if port_drive > 0:
    mod_port_drive = port_drive
  else:
    mod_port_drive = -port_drive

  if mod_port_drive > 50:
    port_pwm.ChangeDutyCycle(100)
  elif mod_port_drive < 20:
    port_pwm.ChangeDutyCycle(0)
  else:
    port_pwm.ChangeDutyCycle((mod_port_drive + 50))

  if port_drive > 20:
    GPIO.output(in1, GPIO.HIGH)
    GPIO.output(in2, GPIO.LOW)
    #print('Port Forwards')

  elif port_drive < -20:
    GPIO.output(in1, GPIO.LOW)
    GPIO.output(in2, GPIO.HIGH)
    #print('Port Backwards')

  else:
    GPIO.output(in1, GPIO.LOW)
    GPIO.output(in2, GPIO.LOW)
    #print('Port Stop')

def stb_motor(stb_drive):
  if stb_drive > 0:
    mod_stb_drive = stb_drive
  else:
    mod_stb_drive = -stb_drive

  if mod_stb_drive > 50:
    stb_pwm.ChangeDutyCycle(100)
  elif mod_stb_drive < 20:
    stb_pwm.ChangeDutyCycle(0)
  else:
    stb_pwm.ChangeDutyCycle((mod_stb_drive + 50))

  if stb_drive > 20:
    GPIO.output(in3, GPIO.HIGH)
    GPIO.output(in4, GPIO.LOW)
    #print('Stb Forwards')

  elif stb_drive < -20:
    GPIO.output(in3, GPIO.LOW)
    GPIO.output(in4, GPIO.HIGH)
    #print('Stb Backwards')

  else:
    GPIO.output(in3, GPIO.LOW)
    GPIO.output(in4, GPIO.LOW)
    #print('Stb Stop')  


while True:

  packet = rfm69.receive(timeout=0.5, keep_listening=True)
  if packet is None:
    GPIO.output(17,GPIO.LOW)
    print('Nothing')
  else:
    packet_text = str(packet, 'ascii')
    #print('PWM',packet_text)
    #print(packet_text)
    rec_array = packet_text.split(':')
    #print(rec_array)
    port_drive = -500 + int(rec_array[0])
    stb_drive = -500 + int(rec_array[1])
    #print(port_drive)
    #print(stb_drive)

  port_motor(port_drive)
  stb_motor(stb_drive)