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Fixing Rx antenna lead ?'s...

Old 05-09-2004, 10:39 PM
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baxternick
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Default Fixing Rx antenna lead ?'s...

Today when I wrecked my plane I broke the antenna in two about 3 inches outside the Rx in the plane. Is it safe to solder these back togeather, and shrikwrap it? Or is there a better way, or is it just trash now??? Any help would be appreciated....
Old 05-09-2004, 10:50 PM
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Default RE: Fixing Rx antenna lead ?'s...

It is best to replace the entire antenna.. It is not difficult. (but you do have to be careful...)

22 to 30 AWG wire, the original antenna length will work. You want the stranded type as the solid wire is not as flexible and will break faster. Cut the wire appx 1/4 inch long, as you tend to lose a little...

Carefully examine the circuit board for where it has and DOESN"T HAVE solder bridges. Making an unwanted bridge is MUCH worse than accidentally eliminating one... you can find the desired one that was eliminated... its hard to find the one you made, and it is likely t destroy the RX if you apply power with an unwanted solder bridge.

Open the RX and CAREFULLY desolder the original antenna from the circuit board.

Strip appx 1/16 inch insulation from the new antenna wire and "tin" the end. The insulation will melt back most times... trim off so you only have 1/16 un-insulated. (be sure its tinned up to the insulation!)

Now solder the new wire in place and route it through the original holes and so forth.

Double-check that the antenna is the correct length... +/- UNDER 1/8 inch is OK. (it takes a bit more than that to detune the antenna significantly.)

Make SURE you clean things up and don't have any undesired solder bridges.

Close the RX case back up.

Range check the RX.
Old 05-10-2004, 12:58 AM
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Default RE: Fixing Rx antenna lead ?'s...

I'm curious about why it is best to replace the antenna. I don't know of an RF reason why you can't solder the two lengths of wire followed by shrink tubing as long as the total original antenna length was maintained. Certainly replacing the antenna is is best aesthetically. BTW, I would also replace the entire antenna.
Old 05-10-2004, 01:28 PM
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Default RE: Fixing Rx antenna lead ?'s...

Resoldering the old antenna together will work fine, it will make a weak joint (subject to breakage due to stress or vibration later) as compared to an all new wire. Just reinforce it by putting a layer of heat shrink tubing over it and all will be fine. As long as the antenna length is 39 inches plus or minus an inch, the receiver will be as good as before. Antenna length is not that critical.
Old 05-10-2004, 02:10 PM
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Montague
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Default RE: Fixing Rx antenna lead ?'s...

I just solder antenna's back to gether all the time. It's a heck of a lot faster than taking the RX apart to get to the board, and I don't risk trashing the RX if I goof up.

In theory, a solder joint doesn't have the same properties as the origional wire, so in theory you might measure a slight differnece in a lab, but in the real world, I've never had a problem with a repaired antenna.
Old 05-10-2004, 07:37 PM
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Default RE: Fixing Rx antenna lead ?'s...

Soldering the antennae back is OK but you weaken it at that point and it can break again (not flexible)
It is better to replace the antennae
Old 05-10-2004, 08:13 PM
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Default RE: Fixing Rx antenna lead ?'s...

If you put a sufficient length of shrink tubing over where the break was, any strain will not be exerted on the solder joint. Obviously, there is a limit to the number of repairs that can be done this way with one antenna because as Geistware points out, the antenna will not flexible at the solder joint.
Old 05-10-2004, 08:29 PM
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Default RE: Fixing Rx antenna lead ?'s...

I'm not so much worried about the strength loss in the wire as the flexibility issue... and the effect of the heat on the wire's resistance to fatigue fracture.

New wire will withstand a LOT of bending. You solder it and the area of the wire that is not "filled" with solder but was heated becomes less resistant to bending (has been annealed) AND more subject to fatigue cracking. A few bend cycles... its broke again.

About 15 cents worth of wire (if you pay too much) and a couple of extra minutes (Gee 2 screws and the RX pops open.... that was hard...[&:]) vs the risk of antennae breakage. You decide how much risk you want.

My (not the greatest...) solder skills are more than adequate for replacing the entire wire by soldering on the RX board. And If I goof, the RX won't work so I'm not going to be able to fly at all with something that is flaky.
Old 05-11-2004, 11:39 AM
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Default RE: Fixing Rx antenna lead ?'s...

I guess it all depends how you assess risk. And that is going to vary depending upon people's soldering skills. Replacement of an antenna by someone who may not possess good soldering skills may indeed cause a cold solder joint or solder splash or loose piece of solder rolling around in the receiver that may cause intermittent operation. Any problems caused by a poor re-soldering of the antenna wire may not be manifest right away- in which case someone would fly the plane.

If you feel confident in your soldering ability, and can open the receiver case without causing any damage, then I think the best course is to replace the entire antenna. If you feel unsure of your soldering skills, then I would recommend repairing the antenna as was described in previous posts.

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