I will assume you had the transmitter antenna fully collapsed or removed. I'm not familiar with the 9x transmitter configuration does the antenna come off or just collapse completely. Either way 150 foot range is very poor. I'll also assume the other transmitters antennas were fully extended. From the information you've given us it sounds like you've got a transmitter module & receiver that need a serious tuning & alignment.

With proper receiver / transmitter tuning you should be able to have other transmitter antennas 1 foot or closer to your receiver antenna and be able to get at least 10 - 15 feet away (NO antenna on your transmitter) before failsafe occurs. I call that test a swamp test... your swamping your receiver with full power R/F at close range. This check is a good way to know quickly if your receiver is tuned and aligned properly for sideband rejection. In fact this test will quickly cull out bad receiver / transmitter over all tuning & alignment.

A 1 to 10 ratio is the minimum that I consider acceptable. The very best receiver / transmitter combo's that I have seen you can walk out just about 30 feet with your receiver antenna wrapped around the interfering transmitters fully extended antenna. I tried this swamp test with a 2.4 gig Spectrum radio and found the R/F link is unaffected during the swamp test.

I'll bet your receiver will not pass the swamp test at all. Your failsafe distance is 1/2 of what it should be. Send your radio back to the Service center and tell them not to send it back until it will pass a swamp test and have at least a 250 foot range check. Actually the best way to do the range check is to have your transmitters antenna adjusted to 7 inches extended. At that antenna length tell the Service Center to tune it up well enough to get at least 570 feet of range.

NOTE: Quality control these days is really getting poor.... I would not trust any brand of new radio until it passes several tests. Vibration, temp, swamp, and of course a good range check.
Lee H. DeMary
AMA 36099