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.
DIY: Build your own FPV backpack PCB
AN EASY TO BUILD AND USE AIRBORNE FPV SYSTEM
Dated: 20 September 2012
The RCModelReviews FPV backpack is a DIY project that produces a simple, reliable, high-performance onboard FPV transmitter/camera setup that will deliver about 2Kms (1.25 miles) of range using standard circularly-polarized antennas and as much as 5Kms (3 miles) of range with a simple helical antenna that will be the subject of a future project.
The circuit-board bill of materials
To build this backpack's circuit board you're going to need a number of items, here's a list of the basics. I had intended to provide links to suppliers of these parts but it's a nighmare because most of the various suppliers have country-specific websites and the rest will only sell some parts in 1000+ quantities.
For that reason, I'm working on making up some kitsets which will cost about US$25 for all the components listed below except the PC board itself.
- 1x PC board - you can etch your own or you'll be able to buy one soon from a quality PCB fabricator, I'll post the URL when they're done.
- 1x 5.8GHz 200mW 5.8GHz video module. These are available from several sources at varying prices. Check the total cost, including freight to your location, before you order. Here are a couple of sources:
- 1x 3.3V LM1117 voltage regulator in a SOT223 package.
- 1x 1N4001 - 1N4007 diode in the regular axial-lead package
- 2x ceramic 22uF 16V surface-mount capacitors in 1210 SMD package
- 2x 330mfd, 16V electrolytic capacitors (radial) with 3.5mm lead spacing and 8mm can diameter.
- 1x 3-element DIP switch SPST (optional).
- 1x 5V 3A SBEC/UBEC (cheap is good).
The heart of the system is the tiny 200mW 5.8GHz video sender modules which can be purchased online from a number of sources. The price of these modules varies from US$15 to US$20, depending on your source.
It is this module that converts the video and sound signals into a radio-frequency transmission that is received on the ground and used to send the video to your FPV glasses, visor or screen.
Although these modules claim to be 200mW, I'm not so sure they're actually that powerful but right now I don't have any equipment to confirm that suspicion (test gear for working with 5.8GHz signals is very expensive). Never the less, these modules work very well for the kind of short/medium-range FPV for which this system is designed.
These modules require 3.3V of power -- any more and the magic smoke will come out -- any less and the range will be considerably reduced. For that reason, the backpack has a 3.3V regulator on its circuit-board that ensures the modules are properly fed and watered (so to speak).
While this regulator could have been designed to accept the full 11.1V of a 3S lipo, that would have meant making it bigger, heavier and wasting more of your battery's power as heat. For that reason, a cheap 3-5A SBEC is used to drop the full battery voltage down to 5V before it goes into the 3V regulator on the backpack. A simple solution to an otherwise complex problem.
The circuit board also contains a diode that reduces the full voltage of a 3S lipo pack (12.6V) down to the 9V-12V that most cameras need to operate reliably. This diode, in conjunction with a capacitor, also operates as a charge-pump that can reduce noise on the camera power feed by a useful amount.
Of course no FPV system is complete without an antenna and the RCModelReviews FPV backpack uses the popular clover-leaf, circularly polarized antennas developed by a gentleman calling himself IBCrazy. These are super-cheap to make and work much better than the traditional black plastic-covered dipoles that ship with most commercial FPV systems.
And, of course, you'll need a camera. See the RCModelReviews YouTube channel for the reviews of several cameras and decide for yourself whether you'll be able to get away with a cheap "under $20" camera, or whether it's worth spending an extra $30 for the "top of the line" high-resolution CCD camera with "wide dynamic range".
Here are files related to this project:
- Schematic and board layout (Zipped EagleCad format)
- Component overlay (PDF)
- PCB pattern - bottom (PDF)
- PCB pattern - top (PDF)
- Schematic (PDF)
And here are links to the PCB build-videos:
Check back, I will be updating this page with more pictures and info shortly.
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.
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?
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
Useful information on what's inside your servos and how they work.
Important facts you should know about the oils that are used in our model engine fuels.
How well do five different 2.4GHz systems stack up when hit by interference? The answers are here, with more to come.
Yes it does work on model airplanes but there are some limitations involved with this bargain-basement radar speed gun.
These are possibly the world's worst servos, find out exactly why you should avoid these boat-anchors at any cost.
It's cheap but can it really stack up against other glow engines in the .90 market? Find out in this review.
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?
Does all this 2.4GHz stuff have your head spinning?
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!
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.
The Chinese are now churning out a huge number of very reasonably priced no-name servos. But are they any good?
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?