Have you had your aircraft mounted on a stand (non-metallic) which places your aircraft at least 2 to 3 feet off the ground . Try this with no other changes and see what happens. I have found placing the aircraft on the ground not only reduces the range, but more important produces a very unreliable and inconsistent range check. So mount it up 2 to 3 feet off the ground and do the range check again.

You also mentioned you have a JR 8301 Tx with JR 9ch FM Rx! I have found the only way to know for sure if you are getting a safe flyable range is to do the Fully extended transmitter antenna range check. There are so many different transmitter designs you can't compare apples to apples unless you do the full antenna check, besides that's the way you are going to fly it!! The distances are going to be greater so you will need a cell phone for you and your buddy. The perfect distance is 4 to 5 tenths of a mile! ( a cell phone or walkie talkie will not effect your radio) If you can get those distances you are OK. I have seen a Futaba 8UF PCM system go out as far as 8 tenths a mile!! Over 1/2 a mile is great to exceptional. Less than 3.5 tenths a mile or 1848 feet, and you've got something wrong! In an inert aircraft (No ECU, lighting systems,smoke pumps, etc., etc. ) if your range is less than 3.5 (1848 feet) tenths a mile means your receiver or transmitter is very weak!! They need realignment!!
Lee H. DeMary
AMA 36099