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Old Mar 26, 2010, 07:35 PM
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Question
Receiver antenna wire yanked out, repair?

Is it worth the risk to re-solder the wire back to the board? It broke off right at the solder joint. Should I replace the receiver with a different one?
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Old Mar 26, 2010, 08:51 PM
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Denver, CO
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I resolder mine. Some receivers are not easy to solder on. I have one that did not go well. Didn't have a good iron with me, and no magnifier. Ended up with a solder bridge that took some work to remove. I use new wire, the old wire might be broken inside.
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Old Mar 26, 2010, 09:16 PM
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United States, TX, Fort Worth
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It's just wire. And just soldering. If you can handle those, replace the wire. 1 1/8" or 10cm, if I recall the conversion right. Use stranded 28ga or thereabouts. Solid is prone to fatigue fracture. The gauge doesn't bear upon performance, the length does.
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Old Mar 27, 2010, 12:58 AM
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depends on whether you have the short or long antenna.
the short antenna is easy, just a simple one point solder.

the long is a pita. in fact i've never been able to successfully repair one so i just replace it with a short solid wire(about 25mm)

the problem with the long is stripping the shielded antenna wire without wrecking the ground shield. i've never been able to not damage it.


you need a soldering iron with a small tip, the pcb is crowded.

you should also make some sort of support or strain relief for the wire
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Old Mar 27, 2010, 01:14 AM
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The gauge wire can change performance on some of the fancy receivers. If the wire is thin like on a JR Scanselect, put in as close of gauge as you can get.
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Old Mar 27, 2010, 02:57 AM
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Whatever you decide, put a blob of hot glue on the wire where it pops out the RX to prevent it snapping etc
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Old Mar 27, 2010, 08:33 AM
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I did manage to de-solder the original blob on the PCB with some de-solder braid, and I elected to reuse the original wire. I don't think the wire was damaged, because this happened while the heli was on the bench during a rebuild (should have been more careful). The receiver is a JR 790UL scan select (as predicted above) and the wire is pretty long. I didn't see a ground wire inside of this, so I just took off a bit of insulation and carefully re-soldered, it seemed to work. The hot glue idea is a very good one that I will use to provide an additional margin of protection.

With all the work I needed to do to rebuild the heli this time, I was NOT expecting to have to do THIS!
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Old Mar 27, 2010, 09:03 AM
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i assumed you were using a 2.4 ghz radio, other freq bands for rc have much longer antennas that are just a wire, with no grounded shield.
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Old Mar 27, 2010, 09:52 AM
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No, I'm still low-tech, lol! 72MHz for now.
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Old Mar 27, 2010, 11:01 AM
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No, I'm still low-tech, lol! 72MHz for now.
it's ok in the city? i would expect lots of radio noise. lots of wifi too
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Old Mar 27, 2010, 12:17 PM
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Well, so far it has been OK, BUT my last crash has me wondering. I was flying at the same field that I usually fly at, BUT it was later in the afternoon, and the adjacent playground was full of kids and probably their parents with lots of cell phones. As I was flying a high and wide circuit, I had some kind of glitch and the motor seemed to stop and the heli started to fall out of the sky. I managed to get the heli in an upright orientation and I think the motor started turning again but it was on the way down so I flipped the throttle hold and basically autoed it down - I was surprised I landed right side up, but it was so hard that the bottom of the motor was crusted in dirt because of the impact. Bent the outer frames, the struts, and some other stuff, but it was still relatively intact.

Anyway I was wondering since I usually fly early in the morning when there are not many or any people around, maybe the cell phone/blackberries etc had something to do with this?
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Old Mar 27, 2010, 12:32 PM
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it's ok in the city? i would expect lots of radio noise. lots of wifi too
wifi operates at 2.4 GHz like the new receivers, not 72 MHz.
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Old Mar 27, 2010, 12:39 PM
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usually something that interferes with the rx is on the channel freq, or below it and a harmonic gets to the rx.2.4ghz, 1900mhz, 900mhz, the last 2 phone freqs are above 72mhz by a considerable margin, and i don't think there are any subharmonics generated.it woudn't be wifi or the phones.

however, it is a BIG city and all sorts of bands are active and it might have been something else, or EMI. which is a good reason to go spread spectrum.

running a logger helps in figuring out what happened in a case like this, how's your power system, wire connection? i have had helis fall out of the sky from a power/wiring problem.bad things happen to a vibrating heli's wiring under the shrink wrap.

there are spectrum analyzers available if you're intent on figuring it out, some in a usb form factor and relatively inexpensive, see www.rcmodelreviews.com for details
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Old Mar 27, 2010, 04:48 PM
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Well, I went over a few things on the bench and noticed that my deans connector on the ESC was sensitive to slight movement, it wasn't making a "tight" connection as it used to. I resoldered a new deans on the ESC that is nice and tight now. I guess several hundred battery connections later and it wore out?
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Old Mar 28, 2010, 04:10 AM
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Well, I went over a few things on the bench and noticed that my deans connector on the ESC was sensitive to slight movement, it wasn't making a "tight" connection as it used to. I resoldered a new deans on the ESC that is nice and tight now. I guess several hundred battery connections later and it wore out?
i've come to really despise deans.when i use up my stash i'm switching to something else that has better mechanical support for the wires. there is basically nothing supporting the wire on the deans except the solder and shrink wrap
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