i consider this subject of extreme importance, hence i bring it here for all to know.
i asked master David T ( http://www.deltang.co.uk/) his opinion. this is what he said:
" Hi. I've done some flight tests with aerial orientations and I've been asked to comment on the 90' thing. Signal strengths are greatest out of and into the sides of aerials. So the Tx aerial should be 'side on' to the model. Personally I find horizonal easiest.
The Rx aerials receive strongest signals when they are 'side on' to the incoming signal. So orientate and place them where that is most likely. If you have two or more you can maximise coverage by using different positions in the model and different angles relative to each other. The model keeps changing orientation in flight so I guess this is where the 90' idea comes from.
Signal strength reduces over distance so if you fly gliders very high you probably want the Rx aerials horizontal to the ground at the bottom of the model to get most exposure to signals.
I believe signals reflecting off the ground cause problems for radios at low alititude. Coming in to land at low altitude towards you from a long way off is probably quite challenging for radios. If your Tx aerial is horizontal then at least one Rx aerial probably should be too. Having that aerial behind a big lipo or engine won't help!
So as already mentioned, there is no perfect layout. The objective is simple though. You want Tx and Rx aerials parallel as much as possible and this is more important in the difficult scenarios I've mentioned.
Regards, David".
(just in case: when he says 90' he means 90 degrees)

i asked master Lucien Miller from innov8tive what are these. he said:
They are all BEC circuits. The BEC and UBEC are both generic terms referring to a Battery Eliminator circuit. This is any device that will set the battery voltage down to 5 or 6 volts to run the Receiver and Servos. Typically, a BEC is a linear type circuit used on speed controllers designed to be used on 2, 3 or 4 Li-Po cells. The term SBEC means Switching BEC. This type uses a switching type voltage regulator instead of a linear type regulator. The switching regulator is much more efficient, and can be used with higher cell counts, some as much as 12 Li-po cells. Standard BEC circuits take the excess voltage and convert it into heat. Switching type BEC circuits chop the incoming voltage up into little pieces and only take as much energy as they need to create the output voltage required. By doing it this way, there is no wasted energy, and the circuits can be up to 95% efficient in converting voltage from one level to another.
good to know, isn't it?
i am also learning that sbecs are available-and needed-from 40 amps up.

there is another (and cheaper) way to get telemetry (maybe this is the cheapest), by using this system:
https://www.hobbyking.com/hobbyking/s...dproduct=10343
it includes the sender that goes into the plane, and the receiver, that is bolted to the radio.
in this case, the sender (transmitter) that is installed in the plane weighs 16 grams, that has to be added to the plane's receiver weight, in comparison with the other system that i mention in my blog (in which the receiver has telemetry included so it also sends data to the radio, and you don't need the additional transmitter in the plane).
but for planes that are medium to large size this is not much of a handicap, and there are some savings with this.
(the price for all is $49.99 to this day, +sh) or you can use a flexible antenna (lighter, easier to install) that is 4.95 + sh
and for more planes, an aditional transmitter ($29.99 + $6.95 sh) https://www.hobbyking.com/hobbyking/s...mp_Amp_V2.html https://www.hobbyking.com/hobbyking/s...dProduct=10896 is 4.95 + sh
am learning that is very convenient to add a temp/amp sensor ($19.79) https://www.hobbyking.com/hobbyking/s...dProduct=11251
so altogether we need: basic system: 49.99; flex ant: 4.95; plus amp sensor: 19.79=$74.73
there is a thread that analizes all with great detail: https://www.rcgroups.com/forums/show....php?t=1267361

this is my view of sailplanes:
recently i have been flying 2 meters (some 80 inches) electric powered sailplanes and have reached the conclusion that they are in need for telemetry, as there are no signs of when the pack is going to be exhausted and the plane will crash-or get lost.
with electric powered planes, when the motor slows down, that means 'land as soon as possible', but with a sailplane there are no warnings.
still, i was reluctant to invest some $450-or more-until i learned from a friend another way:
getting a 9x tx from hk, and the other components from aloft hobbies, the total initial investment is $153.78, and after that, all that i need per plane is $34.01.
details are as follows:
9x tr: 53.95 https://www.hobbyking.com/hobbyking/s...idProduct=8992
sh 23.59
http://www.google.ca/search?q=aloft+...OMnd0QGZ9YDwBA
FrSky DJT - JR Transmitter Telemetry Module DJT $22.76
FrSky FLD-02 - LCD Display FLD-02 $20.47
FrSky D8R-II Plus - 8 Channel Receiver w/ telemetry D8R-II plus $25.71
Battery Voltage Sensor FBVS-01 $2.55
s h 5.75

total (tx and parts):153.78

after this investment, all that i will need for each plane that follows will be:
8 ch rx 25.71
volt sensor 2.55
s h 5.75
total 34.01
that is it: 34.01 per plane!

(the tx is from hk, the rest from aloft hobbies)

folks: i see that both terms are sometimes misused.

from wiki:
Decalage angle:
difference in angle of the chord line of the wing and the chord line of the horizontal stabilizer.

incidence:
Angle of incidence is a measure of the angle at which the wing or horizontal tail of an airplane is installed on the fuselage, measured relative to the axis of the fuselage.

just in case...