I've got a spektrum DX3R Pro tx and several cars with Spektrum receivers in them. Last weekend, I drove my T4.1 and my TC6 both om the road in front of my house.. They both lose signal at the same certain points on each end of the road.. Less than 100 ft away. I have to walk within 10 ft of the car to regain signal in either car. I installed longer antenna tubes, and cut body holes allowing them to extend up outside the body. I also replaced the batteries in my tx.. Nothing seems to help. Any ideas? I had pretty much ruled out interference, being that the system is 2.4 ghz. I am under the impression that it's nearly impossible to get any glitching with these new systems. Any help is appreciated guys.

I noticed you said out in the street. How many trees with over hanging limbs and how many power lines over head? Even with the spektrum my truck did some funky stuff in the street but fine on the track.

make sure none of the recievers have dirt or debris in them.. take them out,open the cases up, dust out the dirt off of the board and out of the case, and try them again.. a small amount of dirt does funny things to them.

I had this problem with a futaba 2.4ghz radio system and a orion vortex esc and motor. The solution after the whole time was to just go ahead and buy the little Spektrum $4.99 voltage protector cap. You plug it into your receiver and wolahh fixed. I know you won't believe it's that easy but it took me over 6 months of losing signal the way you are and going back and fourth to a hobby shop untill i found one of these voltage protectors. When i used it I've never ever encountered another problem. Worked for me and im sure your problem sounds the same as mine so it should work for yours.

I hope this has helped you to be able to fix your cars but it's not much to ensure they run everytime

For some reason Spektrum DSM radios are susceptible to interference.. At the track a bunch of us with Airtronics M11s with Spektrum modules would get hits from what we narrowed down to those Chinese FlySky / whatever branded 2.4ghz radios.. Every time one would show up.. We'd get hits..
Last year at Motorama a bunch of M11/Spektrum module radios would lose signal all together at this one section of the track for no apparent reason as well..
In terms of interference protection, the FHSS (Frequency hopping) systems are much better.. (Airtronics, Futaba, KO.. etc) I personally have just come to terms that Spektrum DSM will get interference every now and again