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Sanwa 'DB Laser' 7H and 7P

Written for 'RCMW'.

Medium-tech? - Items common to both systems - 7P system - 7H system - Conclusions


In an age when radio control equipment for models is diverging into a choice between the fairly cheap basic four channel outfit or the 'high-tech' multi-channel, computerised, set with all the 'whistles and bells' this new Sanwa equipment offers an attractive compromise. Its only, directly comparable, competitors are the JR 'Apex' and the Futaba 'Gold' series.

Two versions of the 'DB Laser' system are available to cater for helicopters (7H) or fixed wing models (7P). They are both 7 channel outfits and utilise identical airborne packs, the differences lying in the transmitters.

Items common to both systems

The transmitter case is built around an aluminium extrusion which forms the front panel and top and bottom faces. End panels and the case rear are plastic mouldings with the latter incorporating a plug-in RF module and a removable 500 mAH battery pack enclosed in its own robust moulding.

Apart from the usual two stick units - both mode 1 and mode 2 versions are available - the front panel incorporates a digital clock/stopwatch, a sliding on/off switch and a hinged tinted transparent cover which encloses the reversing switches, end point adjustments, etc.

A recessed portion at the top edge of the front panel houses an RF meter, two warning lights and dual rate switches for the aileron and elevator channels. The top panel has a robust metal handle, a plastic aerial socket and various switches which vary between the two versions. Further trim controls, which also vary on the two types, are fitted to the side panels.

The previously mentioned warning lights fulfil a dual function. When the transmitter is switched on they both illuminate. If one, or both, of the rate switches is in the 'on' position the appropriate light will flash to give warning of the fact. There is no direct connection between the clock and the rest of the transmitter and a separate battery is used which fits into a recess behind the main transmitter battery. Time is shown in the 24 hour mode and the setting buttons double as start/stop and reset buttons when the stopwatch is selected. Having started the stopwatch it continues to run if the clock is then selected.

A very compact receiver, with plug-in crystal, has integral sockets for the servo and battery plugs as is normal with most sets these days. In order to save space the seventh channel socket is incorporated into the battery plug and a special 'Y' lead adapter is supplied for those who wish to use this channel. On the 7H system this channel is normally used to turn the gyro on and off, while on the 7P it is operated by a trim arm on the left hand side of the transmitter case.

A 500 mAH 'flatpack' battery is supplied together with a switch harness which utilises a very small switch. The dual charger has a mains lead for the fitting of a mains plug rather than the more usual type which has integral pins and requires some form of adapter. It can be used to charge either battery separately as well as simultaneously.

Four SM-631 servos are supplied complete with spare arms, fixing screws, rubber grommets and those often neglected items, eyelets. All plugs and sockets are three pin types with the pins crimped on to the wires and are of very similar size to all other equipment of Japanese origin. With care, they are probably more or less interchangeable with most of the other types - but don't quote me on that!

Other items supplied include a miniature screwdriver, a plain orange frequency pennant (no numbers! - some people do still use 27.095MHz don't they?), a battery for the clock/stopwatch and a very nicely laid out set of instructions.

All seven channels have reversing switches and there is separate end point adjustment for each extreme of the aileron, elevator and rudder channels. The throttle has a 'high' point adjustment, with the low point being set by the trim lever.

7P system

The main features of this system are the inclusion of a 'snap roll' pushbutton and a Flap/elevator mixer. An 'inhibit' switch is fitted to the snap roll button to prevent accidental operation, which would be traumatic since it drives aileron, elevator and rudder servos to their extreme positions! A switch adjacent to the pushbutton selects 'up' or 'down' snap rolls (inside or outside). A choice of left or right roll is also available via the inhibit switch which is a three position type.

Flap/elevator mixing is very comprehensive and allows the elevator trim to be changed when the flaps are lowered and also lets the flaps be connected to the elevator for additional manoeuvrability.

Operation of the flaps is achieved by means of a three position switch (where would the modern R/C world be without the three position switch?) which selects no flap at all or two presettable amounts of flap deflection. In the first position, the flaps are connected to the elevator by a variable amount - if no mixing is required, simply set it to zero. In the other two positions, an amount of compensating elevator trim can be applied. Note that there is only one adjustment for this which assumes that the trim change caused by lowering the flaps is completely linear throughout the range. A flap trim adjustment allows fine tuning of the flap position.

7H system

The heart of any helicopter radio lies in the various combinations of pitch and throttle coupling which are controlled by the throttle stick. On some modern systems these combination are many and varied and are probably way beyond the comprehension of all but the serious competition flyer. In the 'DB Laser' system these are commendably simple. A three position switch labelled 'On 1/Off/On 2' gives the full pitch range when in the 'off' position or selects two different pitch end point settings in the 'on 1' or 'on 2' positions. The 'on 1' position freezes the throttle in a preset position and serves as a throttle hold switch. There is also an 'idle up' switch which, when switched to the 'on' position, allows the idle speed to be raised to any point between idle and a little over half throttle.

A collective pitch/tail rotor mixer is included, with the usual adjustments for tail compensation when ascending (rev. mix up) or descending (rev. mix down). On most equipment the changeover between these two adjustments occurs at half throttle, but the 'DB Laser' has a 'hovering memory' switch which allows this position to be set to the hover point. It is merely necessary to hover the model and put the 'hovering memory' switch into the 'on' position. When this switch is in the 'off' position it also switches off the tail mixer.

An additional switch on the recessed top of the front panel can be used in two ways. It can be used to turn a gyro on and off or set in such a way that the gyro is turned off when a preset amount of rudder deflection is used. Different amounts can be set for left and right deflection.

Pitch trim is set by a knob at the top of the left hand side panel, while a similar control in the right hand panel sets the 'hovering throttle' trim. For those unfamiliar with this control, it is effective only on the centre portion of the throttle travel. The writer has mixed feelings about the type of overall pitch trim used on this - and other - sets, since it changes the end point settings. A 'hovering pitch' trim, similar to the throttle would be much more useful. Both of these knobs, incidentally, have a large range of movement which allows easy setting and are labelled to show the direction of operation - unlike most competing equipment.


A very well thought out set of equipment, in either of its versions, which offers all that would be required by any but the most dedicated contest flyer and at a very reasonable price.

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