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1) Principle
2) Lead & PPM-inverter
3) Connections
4) Futaba
5) Graupner
6) Conclusions
7) Examples

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4. FUTABA & ROBBE connections for the clever ones who did not yet buy a buddy box :

The person that send me an E-mail on the 25th of september 2008 with a solution
for connecting a Graupner to an EVO-12, please contact me again; your E-mail was accidently deleted by my anti-spam filter

Read the previous chapters before starting this one !!!

You better bought a radio where the buddy box is standard from factory...if you knew...

You where gullible once, don't show you would be cheated twice by buying a buddy box when it is not necessary...

Apparently Futaba and Graupner (and Robbe, before the joint-venture with Futaba) are the only brand not to equip systematically from factory all transmitters with a buddy box. Business is tough...

Following transmitters have not a buddy box standard from factory : F 14, F 16, FC 16 and FC 18 all types and Futaba Attack 4.

All these transmitters are build in +/- the same type of plastic box (except Attack 4).

4.1 FUTABA F 14 : I never saw this transmitter ; I received the info from Maarten Zanders, the basic drawing has been found on the website of FMS :

Flight Model Simulator

F14 as slave : use the Ground and the PPM OUT from the connector marked « Multi-op » (fig. 4-01)
ATTENTION : the contacts of this connector are totally different than for the F 16, FC 16 et FC 18 !
The Futaba F14 as slave with a MC15 as master does not work. Maarten tells me : "I think that the amplitude of the signal of the F14 is not big enough. Furthermore Graupner uses other pauses in the PPM-signal. A microcontroller would be necessary to connect these two transmitters."

F14 as master : It is possible to use the F14 as master when applying the modifications as marked in red and blue. Maarten writes : "The analog-digital printboard and the HF-printboard are connected to each other with a wire-bridges to transfer the PPM-signal. I unsoldered a bridge-wire and I fit a momentary switch in order to chose which PPM-signal shall be send to the HF-section : the original or the external. The Futaba Attack 4 as slave with the F14 as master works great."

4.2 Futaba Attack 4 :according Maarten Zanders : the light blue wire (right hand side)is the PPM-signal, the other is the ground (see picture below)

4.3 FUTABA F16 , FC16, and FC18 all types :


For the F 16, FC16 and the FC 18 all type, the male vertical connector of 4 contacts in line (2mm pitch) on the circuit board for connecting the buddy box is located at about the same place and is marked by the word "trainer". The cover of the transmitter being removed, the aerial pointed opposite your body and viewing inside your transmitter, you'll find from left to right the next connections (fig. 4-02).

It is easy to use two red BEC/ESC-connectors from a RC-shop (Futaba ref. F1410, Protech ref. PL 030). These connectors have a pitch of 2.5mm, theoretically they are not compatible. You have to fit them abeam in order to connect separately one connector to the Ground and the other to the IN or OUT. Another solution is to use a recycled connector with 2mm pitch from an old PC or CD-rom drive.

Futaba plugs his buddy box with a flat lead of 4 coloured wires from left to right :

YELLOW (= IN)    ORANGE (= OUT)    RED (= +9.6V)    BLACK = GROUND

I disadvise you to make a buddy box system with the DIN-sockets 6 contacts (fig. 3-01) for the following reasons :
a) it's more complicated to make than the system with jack-connectors 3.5 mm, and you'll need to make a printboard
b) with the male DIN-connector connected to the transmitter (from underneath the radio), not possible to put the transmitter down somewhere without the DIN-connector being in the way
c) the original Futaba lead with 2 DIN-connectors leads also the positive battery tension from end to end to provide power from the master to the slave transmitter, system which I firmly disagree with (see chap.1, para.1.2)
So if you really want a buddy box system with DIN-connectors, look here : www.chez.com/bugpat/ecolage.htm.

I propose you a much simpler system with a 3.5mm mono jack connector, the female connector being fitted in one of the many places provided for switches on those transmitters. For the male jack connectors, I advice you to use the 90°-type of jacks.
Disadvantage of the jack-connectors :
a) the lead slave jack-connector to DIN master-connector is not the same as the lead slave DIN-connector to jack master-connector
b) the positive battery tension is not available on the jack-connector, and is necessary if a signal inverter is to be fitted into the lead.
For those who do not know how to make a buddy lead jack 3.5mm to DIN 6 pins Futaba, see chapter 7 for some examples. But the major principle stays the same : ground to ground, OUT to IN (see chapter 2).

2. BUDDY BOX for FUTABA FC18V3.x or FC18V3.x Plus :

The FC18V3.x (contrary to the other radios F16-FC16 and FC18V1 et V2) has a software permitting to intervene at all times to correct the flight of the pupil without fully taking over the control. Therefore the buddy box is slightly different from the other. The momentary switch to transfer the control to the pupil is independent from the buddy box and must be connected to one of the extensions (1-9 or A-D) and must be assigned by programming into menu 37.
In fig. 4-03 you have 3 possibilities for a buddy box. The inductances (self) have a value of 10 µH (micro-Henri), but doesn't seem to be necessary (I played instructor during 2 years without these inductances). But if Futaba is fitting his buddy box with inductances (and sells them like being gold), there's perhaps a reason (anti-distortion). I finally soldered these inductances directly onto the female jack (to have a rested mind), protected by heat shrinking tube.

3. BUDDY BOX for FUTABA FC18V1, V2, V1Plus or V2 Plus, FC16 and F16 :

Here the momentary switch must be connected directly to the buddy box (see fig. 4-04).
Note for the F16 only : on the F16, the original wire-bridge between the IN and OUT on the buddy connector must be removed an be kept aside (is needed for the transmitter when the buddy box circuit is removed).


Robbe Terra Top and Terra Top FMSS/PCMS :

On the Robbe Terra Top radios the buddy box is (was) optional.

The male connector of 5 contacts in line (pitch 2.5 mm) on the printed circuit where the buddy box should be connected, is to be found on the left (Terra Top FM) or on the right (Terra Top FMSS/PCMS) of the aerial, view from aft with open cover. The cover of the transmitter being removed, the aerial pointed opposite your body and viewing inside your transmitter,

you'll find from left to right the next 5 connections (fig.4-05) :

+V Switched    not used    OUT    GROUND    IN

Just like on the F 16 you have to remove the white female plug with wired bridge. The system of buddy box is the same as for the F16 (see above). For the connections, use a servo connector and a female jack 3.5mm. If for the Terra Top FM you only need the OUT-signal and Ground, you will also find it on the female DIN-connector on the front of the transmitter, connections as described in figure 3-04.