I posted this on RC Groups last week. It illustrates some of your concerns:
Here's the thread so you can see the replies:
Here's my original post:
I haven't seen any of this info posted, so I ran my own experiment today:
I wanted to find out what the relative ranges of the AR6000, AR6100 and AR7000 were -- especially when used INSIDE a carbon sailplane fuselage.
Here's the equipment I used:
Spektrum DX7 TX
JR 4 cell Nicad pack
Hitec HS 85 MG servo
Cappuccino 2.6M Carbon fuselage:
I mounted the servo with a highly visible long "servo arm" made from yellow corplast so I could see it easily as I paced off the distance. The servo wire was fished through a wing root hole so I could leave the servo mounted outside the fuse for the tests that were "out" vs "in" concerning the fuselage.
The 3 receivers were bound to 3 different models in the TX, and I taped them to the box "test stand" as shown. They're off the ground about 1 foot which is typical for a Gas/glo fuel installation when doing range checks. This may differ from the "typical" sailplane range check, but all RX's were at the same height for the checks.
When determining the acceptable range, the TX "bind" button was pressed and held in during the entire range check. To verify control integrity, I oriented the TX antenna in various positions when testing "good" vs "no good", and always declared "good" when ALL TX antenna orientations were acceptable. I found that 2 paces was often the repeatable resolution in distance to re-acqure a control integrity condition once lost (ie: "no good", step 2 paces closer, declare "good", then back up 2 paces again to verify "no good").
Here are my results:
...............Outside Fuselage.......Inside Fuselage
AR7000..........80 paces................26 paces
AR6000..........55 paces................19 paces
AR6100..........30 paces................12 paces
Note the AR6000 displays a superior range check than the AR6100 in all cases. My guess this is due to the longer antenna wires of the AR6000.
You can see there =IS= a drastic attenuation due to the carbon fuselage. I consider the Cappuccino to be a typical carbon layup. The moral of the story is to be sure to range check your own installation. The accepted wisdom seems to be "30 paces is acceptable" and that is almost within spec for the AR7000 inside a carbon fuselage. It would be nice if the folks at Spektrum offered a remote antenna option on a new sailplane receiver. I didn't see this offered on the new AR9000.
I hypothesize that one may poke 2 holes in a carbon fuse to route the (longer) AR6000 antennae outside the fuselage, and obtain a superior range check than a fully enclosed AR7000. I did not verify this (yet). I consider the AR7000 antenna too short to attempt this.
Does anyone know if it would be possible to lengthen the antennae of ANY of these receivers to acquire better range -- especially for sailplane use?