Is there anyone manufacturer a quality range extension add on or stand alone.

Hello and good day. Thank you for reaching out and for the inquiry regarding the Range Extender or Signal Antenna Range Booster Amplifier. I hope that you will get the best information from our valued DJI co pilots who uses the said 3rd party accessories. Just a friendly reminder that DJI does not recommend you to your 3rd party accessories on your DJI Drones  or modify your DJI product. These 3rd party accessories might affect the said DJI drone when in use. Actually, there is a possibility that these 3rd party accessories will be able work. However, since it's not yet optimized and tested by DJI we cannot guaranteed the stability of the said 3rd party accessory if it will work all the time with no issues and might void the warranty of the said DJI product. Thank you.

I've had some luck with this one, while it doesn't necessarily "extend" the range, it does help keep a better signal when the signal is weak due to overcrowding or objects in the way.

Plus, it's dirt cheap!
RCGEEK Foldable Extender
https://www.amazon.com/RCGEEK-Extender-Foldable-Compatible-Controller/dp/B0757LZ9J8/

First if all, a cool thing. A bald eagle showed up to check out my drone yesterday. Didn't seem scared at all, circled close a few times, then kept going before I could get the camera on him. Only about 240 ft high

I'm brand new w a used Phantom 3 Standard. I'm loosing connection as close as 300 ft. distance. Sometimes it reconnects, sometimes it goes into Return to Home. On top of a hill, nothing in between, way above trees. I've looked everthing over. Firmware is up to date, gps calibrated. Quarter mile away from metal fence and power lines. Any advice?