Review of the Silvertone Mark22, reprinted courtesy of Airborne Magazine.

In his literature introducing the Mark 22 R/C system Bob Young of Silvertone Electronics states quite emphatically that he set out to design a completely unique system that in no way duplicates the work of the overseas manufactures, preferring instead to fill the gaps in local requirements left by the mass produced imports.

And in this he has succeeded admirably. He has created a classic basic eight channel system combining the best of old and new technology. At first sight the transmitter case strikes one as a tad old fashioned, being a welded seam, powder-coated aluminium unit. However to the hand it feels solid yet light and obviously built to last a lifetime. The metal case provides an excellent ground plane and the radiation levels are high with no apparent weak spots in the transmitted polar pattern.

The simple uncluttered face is easy to clean and belies the power of the internals. The powder coated finish is tough and scratch resistant. The quick release back is removed via a single nut and once removed reveals an interior that immediately dispels any doubt about the modern hi-tech nature of the beast.

Upon removal of the back, one is immersed in the reek of high quality engineering. It oozes from every nook and cranny in the incredibly neat interior. Here is a unit that is built more like a precision electronic test set than a model R/C transmitter.

From the obviously quality surface mount PCBs to the gold plated connectors through to the heavy duty aluminium mounting brackets designed to act as heat sinks for the output transistor, here is engineering excellence. The transmitter can be run until the batteries go flat on the hottest day and with the antenna collapsed, with no danger of the output FET blowing due to overheating. The expanded scale voltmeter on the front panel is interesting in that as long as the needle is on the scale it is safe to fly. Once the meter reads zero then there is a safety margin of fifteen minutes before the batteries reach an unsafe level. There is no abrupt cutoff point but the range will start to deteriorate at this point.

All this is of course absolutely unique in a model R/C system, just as the man said. However it does not end there. The transmitter consists of two main modules. The RF module and the encoder module. The RF module swarms with novel features such as reduced third order intermodulation levels for enhanced field safety. When combined with the Frequency interlock socket built into the TX case to prevent accidental shoot downs due to transmitters being inadvertently left on, this makes the Mark 22 TX one of the safest transmitters on the market. Add to this the radical new field programmable AM-FM feature to provide the maximum flexibility to the user. Thus it is now possible to mate a clever transmitter to older AM systems. This transmitter can be matched to most older PPM receivers and the 29MHz module means that one can avoid the crowds on any field.

For the R/C experimenter it is possible to replace the existing encoder with one of your own design, very easily and simply via the ten pin plug on the RF module. There is even a program option for CW (carrier wave) and a simple test point for PA current. The module is available on 27, 29, 36 and 40MHz. Band change (27 - 40MHz) is by module replacement and frequency change is via plug-in crystals within any band. There is also a facility for direct connection from the encoder to the decoder to provide a hard wired system. Alternatively it is possible to replace the RF link with an IR or optic fibre link if required. All this is made possible by the modular nature of the system.

For service personnel this is a very civilised system. The unit is designed so that any competent electronic technician can handle it with ease. All circuits and servicing instructions have been published in Silicon Chip Magazine and are freely available from them or from Silvertone.

The encoder is on a single PCB and may be removed for service very quickly by removal of four screws. All interwiring connections are via gold plated connectors and service is via module replacement for quick service turn-around.

The encoder is again absolutely unique featuring a solid state, discrete encoder devoid of the now customary computer. It is here that the Mark 22 TX shows it's soft underbelly. No computer means no model memory and that can be a serious shortcoming to some modellers.

If you want to change from very different kinds of models such as "V" tail gliders to helicopters then this is not the transmitter for you. However for the modeller who flies basically similar models then the host of unique features more than makes up for the lack of model memory.

For those modellers who do not want to get lost in computer manuals with all their complexity and confusing language, and yearn for a smart transmitter that bridges the gap between the simple to operate old basic transmitter and the clever transmitter, then this transmitter bears close examination.

Programming is simplicity in itself being very visual in nature. The encoder consists of eight identical sub-units designed around the most simple to use programming elements of all time, the three pin plug and potentiometer. Every sub-unit in the Mark 22 TX is fitted with an identical three pin plug. Here is the secret of the absolute uniqueness and power of the Mark 22 transmitter. Once one channel is mastered and this is not difficult, all eight channels are mastered.

There are eight, channel sub-units with servo reversing, gain control (ATV), and dual rate, four mixing sub-units, two inverting (reversing) and two non-inverting and two toggle switch sub-units again with servo reversing and gain control. The gain control on the toggle modules may be used to extend a suitable standard servo to 180^o rotation. (See Fig 1)

Fig 1

In addition there are two expansion ports, one to accept plug-in configuration modules and the other to accept an expansion module allowing the number of channels to be expanded to sixteen or twenty-four. These units are optional extras. The only configuration modules available currently are the F3B module which it is powerful enough to convert the transmitter to a fully configured F3B transmitter with CROW, CAR, coupled elevator/flaps etc. This module is powerful enough to handle most complex mixing situations.

The mini module is designed to double as a simple pseudo model memory module. It is possible to replace one module with another module set up for another model. Using the mini module makes it possible to change from say a conventional model with coupled flaps/elevator to a "V" tail glider. Other modules are planned for the future.

All front panel controls are fitted with an identical three pin socket and here is another novel feature of the Mark 22. Instead of a front panel bristling with switches that may never be used, the standard Mark 22 has only four switches. These may be programmed to suit the pilot merely by plugging each switch onto the appropriate three pin plug. Thus any switch may be programmed as a Dual rate switch, retract switch or mix IN/OUT switch. In this manner four switches do the work of many and the function is located exactly where the operator needs it. Extra switches may be fitted if required. Because of the absolute flexibility it is not possible to label any control on the front panel. Any switch or knob can be any control the pilot desires.

There are two knobs which are provided for the proportional auxiliary channels plus the usual twin two axis control sticks. The control sticks are fitted with adjustable length levers. A novel feature are the trims located on the outside of the sticks, making them very accessible in flight.

Because all control knobs, switches and levers are fitted with identical plugs channel allocation is simply a matter of deciding which of the eight channels to plug each control into. Any channel may be a proportional or switched channel. Servo reversing is simply a matter of rotating the control socket 180^o.

Due to the non-computer nature of the encoder, certain features such as exponential are not available. However all of the basic functions are available with ATV serving as a pseudo end point control and allowing adjustment between 30% - 130% normal servo travel.

Mixing is available from any channel to any channel with up to four free mixers available on the main encoder PCB.

Dual control is available as an option and again the unique Silvertone dual control system provides features not found on the imports. Mixed modes are permitted and the instructor may be on the master or slave transmitter.

The receiver is again unique featuring a small twin deck layout with several novel features. There are two basic modules to the receiver, the receiver deck and the decoder deck. The receiver deck is available in two styles, AM or FM with both styles available on 27, 29, 36 or 40MHz. 36MHz AM is not recommended for club work whilst two transmitters are permitted to operate 450/460kHz apart. All receiver decks are fitted with a plug-in crystal.

The decoder module is a basic eight channel unit and features an expansion port to allow the addition of a 16 or 24 channel expansion module. BEC is fitted allowing operation on higher battery voltages. All three decks plug together in a very clever arrangement and the PCBs clip into a neat aluminium case. Here again is engineering excellence made possible only by the new CAD-CAM techniques now available.

The standard eight channel receiver is however only a two deck unit in a case measuring 42 x 35 x 30mm and all up weight is 39gm. The 24 channel case measures 42 x 35 x 40mm and weighs all up 48gm. Very robust and featuring gold plated servo connectors (to match JR, Futaba, Hitech servos) set into the usual high quality PCB the eight channel receiver is a very reliable unit that will suit almost any PPM transmitter. If you have an old transmitter you would like to put back into service then one of these receivers is an ideal replacement for your old U/S receiver.

So has Bob Young achieved what he set out to do? In my mind he has. The Mark 22 system is absolutely unique in almost every respect. There is to my knowledge nothing comparable on the world market. That is not to say that it is outstandingly better, merely different. It has it strengths and its weaknesses but for those looking for something unusual that offers features not found in any other system then this one bears close examination.

As an electronic service engineer to my mind the servicing aspects of the Mark 22 are streets ahead of all other systems. Here is a system that is one of the most simple to service that I have yet encountered. A very important point in today's market where labour costs usually outweigh the parts cost by a wide margin. The other consideration is naturally that of replacement ensuring that no secondary fault of an intermittent nature may still be lurking within the "repaired" PCB assembly.