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Old May 19, 2010, 09:36 PM
First to go over 106K feet
Crist Rigotti's Avatar
USA, IA, North Liberty
Joined Mar 2008
2,480 Posts
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Spektrum DX7 Booster Mods For Long Range

Here is what I did to my DX7 to boost the output to acheive 5 3/4 miles (30,563 feet, 9.3km) and still have control on my FPV Skywalker. I am using an full range AR7000 dual receiver. I'm using a SunSky Fox 800mw video transmitter at 1280 MHz.

I saw this mod on DIY Drones here:
http://diydrones.com/profiles/blog/s...age=1#comments

I ordered a 500mw booster from DIY Drones here:
http://store.diydrones.com/product_p/wi-amp-24-500.htm
Please note they don't carry the 500mw boosters but carry the 1000mw booster now. 1000mw would mean even more distance!

Note: I am using the 1W booster now. (8/4/2010)

I wanted to use the antenna that came with the booster on the transmitter so I ordered a 4" (101.5mm) U.FL to RP-SMA coax to go from the transmitter module to the top of the transmitter case here:
http://cgi.ebay.com.au/ws/eBayISAPI....m=120481141256
The antenna screws directly on the RP-SMA connector on the coax.

I also needed a 6V UBEC which I got from Hobby City here:
http://www.hobbycity.com/hobbycity/s...SBEC_for_Lipo_

I needed a 6db attenuator which could be bought here. Do a search on eBay for 6db attenuator.
Note: I'm using a 4db attenuator now. (8/4/2010)

I used a SunSky Fox 800mw 1280 MHz video system which I bought here:
http://www.sunsky-online.com/view/13...ransmitter.htm

I made an inverted vee antenna for the video system described here:
http://www.rcgroups.com/forums/showthread.php?t=1159968

This is an example of what I did to my DX7. If you decide to do this mod proceed at your own risk!

1) I removed the battery cover and then removed the battery.
2) I opened up the transmitter by removing the 6 screws from the back.
3) I carefully popped off the existing U.FL connector from the transmitter module.
4) I removed the 4 screws that hold the RF board to the transmitter.
5) I carefully swung it out of the way.
6) I removed the screw from the bottom of the existing antenna.
7) I removed the metal clip and pulled the antenna from the top of the case.
8) I then cut off the finned part of the existing plastic antenna mount flush with the top of the case.
9) I cut a circle of 1/8 (3.17mm) 5 ply Birch plywood and drilled 1/4 (6.35mm) hole through the center. This is the mount for the RP-SMA antenna connector.
10) Using the lock washer and nut provided I attached the connector to the plywood plate. I made sure this was tight!
11) I then used JB Weld epoxy to glue the plate to the TOP of the case threading the coax down through the hole in the case. I then filled the underneath area with JB Weld to be sure it was strong. CAUTION: I found out that you cannot get any JB Weld on the underside PERIMETER of the transmitter case. This will prevent the cases from "nesting" when putting the back of the transmitter case back on.
12) I wanted the booster to turn on/off with the transmitter switch. I used my mulitmeter and found battery voltage that was switched on/off with the switch. I soldered on some 26 awg servo lead wire to the spots that were switched. Red was + and brown was - .
13) I ran this wire along the existing bundle of wires to the back of the transmitter and out through the battery connector hole. I used some very small ty-raps to secure the wires together.
14) Then I attached a JST connector to the wires.
15) I reassembled the transmitter board using the 4 screws.
16) Then I attached the U.FL connector on the transmitter. I was very careful doing this.
17) I closed up the transmitter by replacing the 6 screws.
18) I used a small piece of 3M Multi-Task tape to secure the wires to the corner of the battery box.
19) I sanded a chamfer into the battery box cover to allow the cover to go on with the wires hanging out the back.
20) I removed 2 screws from the antenna side of the booster and using 2 3mm screws, washers, and MS25281-R3 clamps I attached the booster to the carrying handle. The handle is 3/16 (4.76mm) in diameter for reference.
21) Using velcro, I attached the 6V UBEC to the back of the booster.
22) I wired the input of the UBEC to the JST connector.
23) I cutoff the power plug from the ac adapter and wired to the 6V output of the UBEC.
24) I then attached a 6db attenuator to the input side of the booster.
25) I made up a short length of RG316 coax and crimped on a 90 degree RP-SMA plug for the antenna connector on top of the transmitter and crimped on a 90 degree SMA plug that goes to the attenuator.
26) I then routed the coax from the top of the transmitter to to attenuator.
27) I then double checked my work, and checked my voltages.
28) I then screwed on the antenna to the top of the booster and I was ready to go.

http://www.youtube.com/watch?v=EXvu0ac8Ps8

Pictures to follow in the next post.
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Last edited by Crist Rigotti; Dec 07, 2010 at 06:00 PM. Reason: Added notes on distance, 1W booster, and 4db attenuator.
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Old May 19, 2010, 09:36 PM
First to go over 106K feet
Crist Rigotti's Avatar
USA, IA, North Liberty
Joined Mar 2008
2,480 Posts
Here are the pictures:
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Last edited by Crist Rigotti; Mar 03, 2011 at 10:55 PM.
Old May 19, 2010, 09:37 PM
I AP'd myself again......
aviatordave's Avatar
Yawn....Iowa
Joined Mar 2005
2,500 Posts
waiting patiently.......looking forward to seeing it in real life when we fly.
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Old May 19, 2010, 09:37 PM
First to go over 106K feet
Crist Rigotti's Avatar
USA, IA, North Liberty
Joined Mar 2008
2,480 Posts
Didn't need this space reserved.
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Last edited by Crist Rigotti; May 19, 2010 at 11:14 PM.
Old May 19, 2010, 10:21 PM
crd
Always thinkering
crd's Avatar
United States, FL
Joined Nov 2006
1,235 Posts
Damn nice mod, Just Kidding, suscribed
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Old May 20, 2010, 12:41 PM
Registered User
Joined Sep 2006
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What was your range before the mod?
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Old May 20, 2010, 12:50 PM
My other plane is the TARDIS
jbpilot's Avatar
Philly 'burbs.
Joined Feb 2009
320 Posts
Wow...

I'm going to have to think about this one. You're using a lot of the same equipment I'm using. (I'm using a 400mW vRx about to switch to the same 800mW vRx you have)

JB
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Old May 20, 2010, 02:36 PM
First to go over 106K feet
Crist Rigotti's Avatar
USA, IA, North Liberty
Joined Mar 2008
2,480 Posts
Quote:
Originally Posted by rcboosted View Post
What was your range before the mod?

If I remember right it was around 3500 feet.
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Old May 20, 2010, 02:51 PM
The Fixer
Martin Y's Avatar
Canada, ON, Milton
Joined Jan 2009
3,780 Posts
Chris
If you use a patch antenna, your distance will be nuts. I did that mod to my DX6i last year but I use a 500mw booster. Havent tested it (too scared in loosing it) but now I have my autopilot working now I can. With a 9db patch just on the dx6, I did a ground test to just over 5.5kms.

Martin
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Old May 20, 2010, 04:11 PM
Registered User
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Quote:
Originally Posted by Martin Y View Post
Chris
If you use a patch antenna, your distance will be nuts. I did that mod to my DX6i last year but I use a 500mw booster. Havent tested it (too scared in loosing it) but now I have my autopilot working now I can. With a 9db patch just on the dx6, I did a ground test to just over 5.5kms.

Martin
Martin,

I'm not understanding what you did. In your thread, http://www.rcgroups.com/forums/showthread.php?t=1087634 you said you modified your RX. But the wifi attenna is for your TX. Also, what is that patch attenna attached to?
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Old May 20, 2010, 04:17 PM
The Fixer
Martin Y's Avatar
Canada, ON, Milton
Joined Jan 2009
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Quote:
Originally Posted by rcboosted View Post
Martin,

I'm not understanding what you did. In your thread, http://www.rcgroups.com/forums/showthread.php?t=1087634 you said you modified your RX. But the wifi attenna is for your TX. Also, what is that patch attenna attached to?
I take off the wifi and screw on the patch in it's place, If I want longer range.
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Old May 20, 2010, 04:43 PM
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Ah, I didn't know you can use patch antenna to transmit as well, not just receive.
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Old May 20, 2010, 07:12 PM
The Fixer
Martin Y's Avatar
Canada, ON, Milton
Joined Jan 2009
3,780 Posts
Quote:
Originally Posted by rcboosted View Post
Ah, I didn't know you can use patch antenna to transmit as well, not just receive.
Any antenna that receives also can used to transmit.
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Old May 20, 2010, 07:24 PM
I AP'd myself again......
aviatordave's Avatar
Yawn....Iowa
Joined Mar 2005
2,500 Posts
Christ -

How old is your AR7000? I got mine right when Spektrum came out. Are the newer rx's more robust?
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Old May 20, 2010, 07:42 PM
Registered User
United States, CA, Galt
Joined Mar 2009
54 Posts
i did the same mod for my dX6, when i put a 6db between the DX6 and the transmitter, the small green "TX" light went off fairly quickly, with a 3 db it lasted a little longer, now I'm running it without any attenuator, works great! and the 6 db 2 watt attenuator on the output gets warm. i was also concerned that the attenuator may also limit the dx6's ability to find a clean channel.
I'm thinking the dx7 must have more power output.
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