SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Mar 27, 2009, 01:05 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Mini-HowTo
Multiplex Evo Spektrum Conversion - Another Approach

Like many of you, I've wrestled with the dilemma of converting to 2.4 GHz or keeping my Multiplex Evo 12. While the advantages of 2.4 GHz are obvious, I love the Evo's clear and logical approach to programming, and I was loath to give it up.

Even though Multiplex has announced the pending release of their own 2.4 GHz system and XPS offers a 2.4 GHz module specifically for the Evo, I settled on Spektrum for my 2.4 gig standard. This was a weighty decision, since it involved the eventual conversion of nearly 30 aircraft and helis from 72 MHz to 2.4 GHz.

I read through the lengthy existing Evo/Spektrum conversion thread (http://www.rcgroups.com/forums/showthread.php?t=682256), but I was lukewarm about the resistor hack and some other aspects to this approach. Instead, I decided to do my conversion based on the Multiplex/Spektrum external adapter marketed from Power RC Electronics: (http://home.page.ch/pub/mmmoret@net2...x_Page585.htm). This adapter was reviewed by Model Aviation Electrics columnist Greg Gimlick, and we'd discussed the product at length.

Unlike Power Electonic's external adapter, I wanted my installation to be completely internal and as tidy and "OEM-like" as possible. But I also wanted to be able to switch back to 72 MHz whenever necessary. I discussed my objectives with the owner, and he enthusiastically supported the project, providing detailed photos and installation tips.

What follows is a photo essay showing how the project turned out.

Jim
Jim Ryan is offline Find More Posts by Jim Ryan
Last edited by Jim Ryan; Apr 24, 2009 at 05:31 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 27, 2009, 01:10 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here's the starting point for the project, the Royal Evo 12 with the 72 MHz synth and scanner modules installed. If you're sharp-eyed, you'll see the Spektrum connector - the red Multiplex connector at left, is already installed in this view.

Jim
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 01:12 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here's the Power RC Electronics adapter trimmed down to it's bare essentials - the shrink-wrapped circuit board with it's input and output leads.
Jim Ryan is offline Find More Posts by Jim Ryan
Last edited by Jim Ryan; Apr 24, 2009 at 05:32 AM.
Reply With Quote
Old Mar 27, 2009, 01:17 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Getting down to brass tacks: Here's the Futaba Spektrum module prepared for installation. The adapter is mounted to the circuit board and wired to the appropriate inputs. The plastic "feet" are 1/8" thick nylon bushings from the hardware store, CA'ed in place. I've also cut the required notch to clear the header block on the Evo's main circuit board.
Jim Ryan is offline Find More Posts by Jim Ryan
Last edited by Jim Ryan; Apr 24, 2009 at 05:32 AM.
Reply With Quote
Old Mar 27, 2009, 01:21 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
UPDATE: Mount the module to the motherboard with velcro or other technique. Newer versions of the Evo use a multilayer PCB, with internal traces, and these will be damaged if you drill into the board.
Jim Ryan is offline Find More Posts by Jim Ryan
Last edited by Jim Ryan; Jun 23, 2009 at 09:06 AM. Reason: Procedure correction.
Reply With Quote
Old Mar 27, 2009, 01:25 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here all four leads have been soldered to the pins of the trainer port. The leads are:
White: PPM signal.
Green: Positive.
Yellow: Negative.
Brown: PPM Jumper (I'll explain this in a minute).
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 01:27 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here's the Spektrum module attached to the Evo's drilled and tapped circuit board with two 4-40 nylon screws.

UPDATE: Do NOT mount the module with screws. Newer versions of this transmitter use a multilayer circuit board.
Jim Ryan is offline Find More Posts by Jim Ryan
Last edited by Jim Ryan; Jun 23, 2009 at 09:07 AM.
Reply With Quote
Old Mar 27, 2009, 01:41 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
For a number of reasons (mostly the right angle RP-SMA connector) it's not practical to internally route the Spektrum module's antenna, so I obtained a screw-mount 2.4 GHz antenna like that used on wireless routers. To mount this antenna in the stock antenna housing, I made this antenna base.

The antenna base is a 1.875" length of 3/8" OD brass tubing. The 1/4-36 nut from an RP-SMA connector was just slightly shaved down so that it would press fit into the brass tube, and it was soldered in place.

The plastic base is a 1/2" nylon bushing from the hardware store. This was counterbored to 3/8" and press fit over the brass tube. The assembly was then mounted in a lathe and the nylon was turned down to .472" diameter so that it would fit in the antenna housing. If adding this plastic spacer seems like too much work, you could just as easily wrap the brass tube with tape until you get the correct diameter.

The antenna leads were a real find. I ordered these from a supplier in China via eBay. They made the leads to my exact specs (IPX connector on one end, RP-SMA on the other, RG178 cable and exactly 12" long). The hex base on the RP-SMA connector had to be turned down so that it would fit inside the brass tube.

The rubber O-ring helps to make the antenna base fit tighter in the gimbal at the top of the transmitter.
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 01:49 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here's the completed installation. The red Multiplex servo plug connects the module to the Evo via the trainer port. Remember the brown wire? When the Multiplex connector is plugged together, a jumper shorts that wire to the yellow ground wire. This switches the radio to PPM mode.

This installation makes it very easy to convert the radio from 72 MHz to 2.4 GHz and back. Remove the stock module and antenna, stick the Spektrum module in place, route its antenna up through the housing, and plug the Multiplex connector together. It's that fast and easy.
Jim Ryan is offline Find More Posts by Jim Ryan
Last edited by Jim Ryan; Jun 23, 2009 at 09:08 AM.
Reply With Quote
Old Mar 27, 2009, 01:51 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here's a closeup of the antenna mounted on its base. This whole assembly slips inside the antenna housing and is pulled into place.
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 01:55 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Here's a closeup of the Spektrum module installed, the Multiplex connector, and the RG178 cable routed up through the antenna housing. Note the redundant strain relief that ties the cable to the upper module board. The tiny IPX connector is fragile and is not intended for repeated disassembly.
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 01:59 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
Finally, I carefully drilled a hole in the back cover of the transmitter to align with the bind button. The bind button extender is pressed onto the blue button using a tiny piece of shrink tubing for a friction fit. Or you can just glue it on. Either way, you don't want to worry about losing the button extension every time you open your radio.

The LED makes the button glow nicely, so I didn't bother with adding a viewing lens.
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 02:04 AM
Registered User
Jim Ryan's Avatar
Cincinnati, OH USA
Joined Oct 2000
1,961 Posts
And here at last is the finished product. I've very pleased with the way the installation turned out, and now I can keep using my favorite radio as we transition to 2.4 GHz.

The only idiosyncrasy that bothers me about this conversion is that because I'm installing a Futaba module in a Multiplex radio, the first three receiver outputs get mixed up. Whereas normally the first four channels are:
1. Throttle
2. Aileron
3. Elevator
4. Rudder

With this conversion, the first four channels are:
1. Elevator
2. Throttle
3. Aileron
4. Rudder

I'd like to be able to fix this, but all things considered, it's a small price to pay for updating this great radio.

Jim
Jim Ryan is offline Find More Posts by Jim Ryan
Reply With Quote
Old Mar 27, 2009, 08:39 AM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
3,097 Posts
Hi Jim -

Does your 2.4 antenna pivot with the ball? If so, how do you prevent the antenna from hitting the bottom of the ball when it pivots since it's now coming down through the antenna tube?
Ron Williams is offline Find More Posts by Ron Williams
Reply With Quote
Old Mar 27, 2009, 08:50 AM
Registered User
WimH's Avatar
Belgium, Flemish Region, Oosterzele
Joined Dec 2001
5,499 Posts
Quote:
Originally Posted by Jim Ryan

With this conversion, the first four channels are:
1. Elevator
2. Throttle
3. Aileron
4. Rudder

I'd like to be able to fix this, but all things considered, it's a small price to pay for updating this great radio.

Jim
That should be easy. You can assign anything to anything with the MPX Royal radios ( except the Royal Evo7, but that one can be upgraded (free) to Royal pro software and then it's possible too...)
WimH is offline Find More Posts by WimH
RCG Plus Member
Latest blog entry: That elusive thermal...
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
For Sale MULTIPLEX EVO 9 Tx with XPS 2.4GHz conversion SoaringFool Aircraft - General - Radio Equipment (FS/W) 3 Apr 13, 2009 10:28 PM
multiplex evo 9 or another? sledge29 Radios 9 Apr 19, 2005 09:54 AM
Multiplex EVO Tutorial Joedy Radios 586 Mar 21, 2005 08:17 AM