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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.

 

Review: FlyDream V3 2.4GHz (Part 2)

IT REALLY SHOULDN'T WORK AS WELL AS IT DOES

Dated: 22 Apr 2010

The construction of transmitter and receiver modules is quite good with no signs of bad soldering or "last minute" fixes to the layout.

The Transmitter Module

As I mentioned earlier, the Futaba module that was provided for review has switched to the inferior "straight out the back" antenna connection but apart from that there's not much to find fault with.

Fly Dream Futaba antenna issue

The transmitter module now has two buttons, one for binding and the other for activating the low-power range-test mode. Both the binding procedure and range-test work perfectly. Topmarks.

FlyDream 2.4GHz transmitter module PCB FlyDream 2.4GHz transmitter module PCB

Inside the module the electronics are nicely laid out and show good quality assembly.

A big plus for the FD transmitter module is that it uses a switching regulator to drop the 9.6V down to the much lower 3.3V actually used to power the semiconductor devices inside. This provides two benefits. It reduces the total current drawn by the module and also means it runs far cooler than those systems (like Corona) which use a linear regulator.

The plastic was a good fit in the Optic 6 and Eclipse 7 transmitters I tried the module in. Not too tight, not too loose. Some other manufacturers have had difficulties in acheiving this "good fit" so top marks to FlyDream.

But now to something very strange...

FlyDream spectral analysis FlyDream spectral analysis

FlyDream claim this is a FHSS system and indeed, it does hop around a bit but it spends the vast majority of its time occupying just three portions of the band (note the green "energy" peaks in the spectrum analysis above), despite the claims that it uses 20 different channels.

What's more, the FlyDream's output density is surprisingly low. What does that mean?

Well although the amplitude of the radio signal is pretty much standard, it doesn't transmit for a very high proportion of the time, unlike most other systems on the market.

FlyDream spectral analysis FrSky spectral analysis

You can see the much lower amount of energy the FlyDream puts into the band when comparing these spectrum analyzer screens.

Unless the transmitter module I received was faulty, there is clearly a huge difference in the amount of energy the two systems are pumping into the band.

What does this mean to the performance of the system?

Well you'll still get good range and control but this lower density may indicate that the FlyDream has a little less headroom than other systems, when it comes to coping with strong interference.

However, in my tests, it coped quite well with strong interference so it's clear that the system is still perfectly adequate, as borne out by my flight tests.

The Receivers

As previously mentioned, there are currently three receivers in the FlyDream range, even though the differences between the 6-channel and 8-channel are so small as to be hardly worth the effort of bothering with the 6-channel one.

FlyDream 2.4GHz receiver PCB FlyDream 2.4GHz receiver PCB

Under the thin shrink-wrap cover there are two circuit boards, one containing the 2.4GHz bits and the other containing the logic circuitry.

As with the transmitter module, the layout and soldering is of good quality.

However, there is a design choice that causes me a little concern with the 6 and 8-channel units.

These receivers have two wire-antennas that are connected to the circuit-board by the usual short coaxial cables. Unlike other similar-looking receivers however, this does not mean the FlyDream units have true antenna diversity. Far from it in fact.

FlyDream 2.4GHz lacks diversity

Closer examination indicates that these two antennas are simply brought to a common input on the receiver so are effectively just loosely connected in parallel.

From an RF design perspective, this is bad. In fact, it in some situations it's actually worse than having just a single antenna.

The problem with just wiring two antennas together like this is that they interfere with each other. A strong signal received by one antenna might actually be almost totally negated by an out-of-phase signal from the other. I tested this and found it easy to create a scenario where, by carefully spacing the two antennas half a wavelength apart and placing one behind the other in relation to the transmitter, I could cause the link-light to go out and control was lost.

Here's where the engineer in my starts to frown but the pragmatist is still smiling.

This is not a good way to implement an antenna but I know that so long as the two wires are *always* oriented at 90 degrees to each other, they should still work well enough to avoid any real problems in the air. Still, it would have been nice if the FlyDream receivers didn't promise more than they deliver in this area.

Other than this issue, the Fly Dream receivers seem to perform just fine. The swamping apparent on the older version has been fixed, they offer smooth servo movement, the same low reboot voltage as before and a fairly quick reboot time.

Page 3 (Summary)

Page 1 (First look)

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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.

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