Unlike model aircraft flying where the transmitter and joy-sticks are held in front of the operator, with KAP you need to keep your hands, and the space in front of you, free to fly the kite. This means you need to be creative with the equipment. This page describes the ground equipment designed for RIG02 and re-used with subsequent RC control rigs RIG04, RIG05, RIG08, RIG09 :

Bum-Bag Servo Transmitter

The Servo control, or uplink:

This uses standard model aircraft remote control 35MHz technology. Whilst the receiver in the rig is completely standard the joystick control used for aircraft is not suitable for KAP for two main reasons:

• The joysticks get in the way of flying the kite, and

• Joysticks tend to self-center, and are trimmed for aircraft straight flight, for KAP if you tilt the rig you want it to stay tilted.

Like some other KAPers I got round these issues by building my own transmitter, and housing it in a bum-bag so I can wear it on my back. The bag as shown has three compartments. When worn on the waist the left most (with the aerial) is round my back, the right with the controls beside by left arm, and the central pocket contains the batteries. The flying lead you see is the power supply to the TV receiver - more later.

The transmitter was bought as a kit from Micron which allowed me to customise it to KAP use and make it fit in the bum-bag. The Micron transmitter comes as two circuit boards, but without any joysticks - just what the KAPer ordered!

Servo Transmitter: Coder Module

The picture on the right shows the Micron coder board as finally constructed. From left to right:

1. On the edge of the box are two rotary controls for PAN and TILT. Between them a red button for the shutter and above it a center biased toggle for the zoom. Between the button and toggle (you can't see it) is a power indicator which is green but turns red if the battery is low.
2. Next you can see a white line which is an aluminium sheet for mounting the above parts.
3. Next is the edge of a circuit board, with 9 multi-turn presets, these define the end-stops for the various controls. The circuit simply translates between the KAP specific controls and standard RC controls.
4. At the right, face-up, is the Micron coder circuit board to encode the channels.
5. Finally hidden by a piece of masking tape, bottom right, is a low battery indicator. This emits an annoying tone when the battery voltage drops dangerously low.

Note the cables (multicore) connecting the unit to the battery and the RF module. There are circuit diagrams and layouts for the above parts included in pages 2 and 3 of these details plans .

Servo Transmitter: RF Module

The picture on the left shows the Micron transmitter board. This module takes the coder board's output signal and turns it into a 35MHz signal for transmission. 

Again, looking left to right:

1. On the edge of the box is the aerial (top) and the power toggle switch. Note the metal baffle on the ON/OFF switch to prevent accidental activation. 
2. In the center, the Micron transmit board.
3. Extreme right, a switch mode PSU to generate 6V to supply the TV downlink receiver.

Note at the top of the picture a clamp on ferrite to prevent interference passing between the downlink TV receiver and the Servo Control Transmitter.

Casio TV400 - Downlink Viewer

The Video viewfinder, or downlink Version 1:

For video Downlink I use the 70cm Amateur Band. RIG02, RIG04, RIG05, & RIG08 transmit a 100mW signal on this band which can be received on a standard handheld TV at the very bottom of it's tuning range. In fact the standard receiver has been modified in three ways to make it easier to use:

1. The received signal is very close to the bottom of the TVs range, so just in case it doesn't lock onto the signal it has been modified internally to extend the range of it's receiver down in frequency very slightly.
2. Although the TV came with a hand strap, it has been modified to a proper lanyard. This allows the TV to be worn round the operators neck, and be visible by looking down.
3. These little TVs don't work in bright sunlight, so a plastic baffle was added to shield the display and make it more visible.

To save on batteries (these little TVs eat batteries!), the TV optionally uses the same batteries as the Servo Transmitter as discussed above.

The Video viewfinder, or downlink Version 2:

For video Downlink I moved to 2.4G commercial systems in 2008 with RIG09, transmitting 10mW. The move was triggered by a desire to build a completely new rig from scratch using off-the-shelf components. This also allowed me to experiment with different systems, and leave RIG08 intact. The positive side to 2.4G is smaller transmit aerials, and lighter transmitter, the negatives are less power and more bulky ground equipment consisting on the downlink receiver and separate viewer. 

Control of the Kite:

Whilst you can get someone else to fly the kite, or attach it to a fixed point on the ground, the above does allow you to have most of the space in front of you free for kite control, so you can walk about for the best shot, or get yourself out of trouble :-). There is a lot of personal preference here, but I use the following technique:

1. On arriving at the launch area I first make sure I have a ground attach point (stake or local feature) then I launch the kite and assess it's flight. The kite is then attached to the ground stake whilst I prepare the KAP equipment. This gives me time to fully assess the kites stability and performance in the prevailing wind. 
2. Once I'm wearing the Ground equipment and the Rig is attached to the kite line I test the system with the kite a few feet off the ground.
3. I then transfer the kite from the stake to my belt, and hang the hoop-spool of kite line from my belt also. I use climbing karabiners and slings for attachment, and a climbing figure-of-eight. to control the ascent of the kite (Guess what I used to do when I was young :-). To bring the kite in I use brute force, or if there's enough space in the launch area I walk it down.

James Gentles March 2008 HOME PAGE KAP HOME PAGE