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Your Reviewer

My Credentials
So who's doing this reviewing then?

Well I've been building and flying or driving radio controlled models for over 40 years and during that time I like to think I've built up a reasonable amount of knowledge.

I'm also a qualified electronics engineer who has worked in radio frequency, analog, digital systems and software for more than three decades. In fact I designed and built my first RC set back in 1969.

For the past nine years I've also been involved in the design and manufacture of some rather sophisticated engine technology and UAV flight control systems.

So, chances are I've been there, done that and have a huge pile of tee shirts to prove it.

Right now I'm heavily into 3D flying and enjoy all aspects of the RC hobby. I may be old but I don't feel it.

In the Pipeline

Here's just a little bit of what's to come on this site...

RC explained: Demystifying terms such as PCM, PPM dual conversion, single conversion, full-range etc., this feature will explain it all.

Cheap Chinese Engines: Just how good are those cheap Chinese glow and gas engines that sell for half the price of their "brand-name" equivalent? I put several to the test.

Build your own radio gear?: Back in the old days, building your own RC gear was not uncommon and now the arrival of 2.4GHz has made it practical again.


How do RC Servos Work?


Pots and Amplifiers

Inside every servo is a tiny circuit board that contains a bunch of components.

It is the job of this circuit (which is called an amplifier) to convert the signal from the receiver into a signal that drives the servo's motor to position the output arm to the requested position.

Way-back, when proportional RC gear was first developed, there was only one kind of servo amplifier: the analog amp, but today we also have digital versions.

Standard/analog Servo Amplifiers

Modern receivers send a series of pulses to each servo. Those pulses vary in width from about 1 thousanth of a second (1mS) to two thousandths of a second (2mS) -- with the center-point being around 1.5mS.

These pulses are sent at a rate of about 50 per second and every time a pulse arrives in a standard/analog servo, the amplifier checks to see if the servo's output arm needs to be moved one way or the other.

If the amplifier decides that the servo arm does need moving because the transmitter stick has been moved then it sends a short burst of power to the motor in order to rotate the gears and (ultimately) the output.

For most applications, this works just fine but since the servo motor isn't being driven continuously (only for a moment every time a new pulse is sent from the receiver), the full torque potential and speed of the servo isn't fully realized.

Another issue with standard servos is that the torque tends to drop off quite dramatically as the difference between the requested position and actual position of the output arm gets smaller. In fact, when this diference is very small, the torque of the servo be insufficient to move the arm against a slightly binding linkage and the result will be a buzzing noise.

Digital Servo Amplifiers

Since the standard/analog servo amp was designed, electronics have moved on significantly and now manufacturers can put tiny computer chips called microcontrollers in servos.

These little computers can provide significantly improved speed, torque and accuracy.

They do this by allowing the servo's motor to be driven far more frequently than was the case before.

Instead of only driving the motor each time a pulse arrives from the receiver (a mere 50 times per second), they effectively remember the length of the pulse and then drive the motor almost continuously (or at a much higher frequency).

The result is that the motor produces more torque and can accelerate/stop more quickly.

Digital servos are often easily identified when running because of the different sound they make as a result of this increased motor-drive. Hitec digitals will "sing" at a high frequency and some others like Futaba and JR will "growl".

Which is best?

Clearly, because of their greater torque, accuracy and speed, digital servos are usually superior to standard servos but in many cases, such as sport models, that extra performance might not be worth the extra price.

Feedback Pots

So how does a servo know exactly where its output arm is so that it can command the motor to move it to the position commanded by the transmiter stick?

Well that's the job of the feedback potentiometer ("pot" for short).

The pot is just a tiny version of the volume control knob on older-type radios and TV sets. It's a variable resistor which can be used to create a voltage that changes as the servo's output arm moves.

That voltage can then be used by the servo amp to work out the exact position of the arm and decide whether it needs moving and if so, which way to drive the motor.

Good servos use high quality pots, cheap servos tend to use inferior ones and the quality of the feedback pot is very important to the accuracy and reliablity of a servo. When a pot becomes worn or dirty, the servo can jitter and become erratic in movement. Cheap pots may also be adversely affected by high-vibration environments.

Next Page: Brand wars

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The Blog

Updated: 20 Sep 2012
Here's a blog that will keep you informed just what's going on behind the scenes at RC Model Reviews and also tells you a little more about myself.

How compatible are 2.4GHz RC systems?

23 Mar 2010
How come there's no compatibility between different brands of transmitters and receivers? Why can't you use a cheap Chinese receiver with your Futaba FASST radio?

How to get a product reviewed here

4 Mar 2010
Since this has become a very frequently asked question, I've posted this simple guide to getting your product, or a product you're thinking of buying reviewed here at RCModelReviews

How servos work

Useful information on what's inside your servos and how they work.

The Good Oil

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Heads-Up: 2.4GHz RC systems tested

How well do five different 2.4GHz systems stack up when hit by interference? The answers are here, with more to come.

Review: Bushnell's $80 Speed Gun

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Review: TowerPro MG995 servo

These are possibly the world's worst servos, find out exactly why you should avoid these boat-anchors at any cost.

Review: SK90


It's cheap but can it really stack up against other glow engines in the .90 market? Find out in this review.

Review: iMax 9X 2.4GHz radio

How does this cheap 9-channel 2.4GHz radio system perform when compared to big-name systems that can cost two or three times as much? Have the Chinese finally developed a real contender with the iMax 9X?

2.4GHz Explained

Does all this 2.4GHz stuff have your head spinning? 2.4GHz

I've done my best to demystify the whole subject so if you feel like a bit of learning, this is the stuff for you!

Fix That Engine!

How can you tell when your engine needs new bearings? Who has the best prices and service on replacements? Just how do you change them? Get all that information and watch a great video tutorial anyone can follow.

Chinese Servos - How do they stack up?


The Chinese are now churning out a huge number of very reasonably priced no-name servos. But are they any good?

Baffled by batteries?

Batteries Nicad, NiMH, Li-Ion, LiPoly, LiFePO4, A123... the range of different battery types has never been greater. So how do they differ and what type should you be using?

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