Canard Aviation Forum  

Go Back   Canard Aviation Forum > Talk All About Canard Aviation > Great Threads that can help plane builders, lurkers and fliers
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

 
 
Thread Tools Display Modes
  #1  
Old 05-08-2004, 05:52 PM
John Slade's Avatar
John Slade John Slade is offline
Flying TurboRotaryCozyIV
 
Join Date: Apr 2004
Location: KRUT
Posts: 5,224
Default Removing oxidation from wires

I'm tracing my antenna wires and I'm finding that ALL the connections are corroded. I didnt want to trail around 30 feet of cable when I built the winglets, so I put connectors in the lines just as they headed down the wings. Big mistake - both connectors came out when I pulled the cables.
The second connector is at the wing root inside the spar. I took the left wing off this morning Both connectors are showing signs of oxidization. Welcome to Florida

OK. Enough of this BNC stuff. I bought the fancy $50 crimper thing and what do I get? Crappy connections that let humidity in. I really need a working radio. I don't plan on taking the wings off ever again, so I think I'll run continuous cable from the winglet to the panel. I have one connection to get right on each side. How hard can that be? The 6 inch stub of cable coming out of the winglet has black oxidization all the way up the shield under the insulation. I plan to solder the center cores together, shrink wrap with RTV, then pull the shields together, solder them, and shrink wrap with RTV again.

What's a good way to get the black copper oxidization off and ensure a good permanent connection of the shields? I was thinking I could dip it something - mild acid? what?

Note to others - You WILL have you're antenna tested before you put the wings on for the last time. This isnt an instruction or recommendation. It's a simple statement of fact. I'm about to put my wings on for the last time, so I know it's true.

PS - Mike, I think we need to open up the electrical section like we did the firewall aft.
  #2  
Old 05-08-2004, 09:39 PM
Clutch Cargo's Avatar
Clutch Cargo Clutch Cargo is offline
w/ Spinner and Paddlefoot
 
Join Date: May 2004
Location: Cape Coral, FL
Posts: 634
Default corroded thread...

Hi John, my job in WPB got put off until Monday, otherwise I could have stopped by to offer some meager advice:
I never reuse old connectors if I can replace them. When I replace them, I use 2 pieces of heat shrink tubing about 3 times as long as the connector when connected. I put the connection together then I squirt some silicon dielectric grease in some shrink tubing, center it on the connection, and heat it up from the outside ends first, (this forces the grease into the unseen, but "oxidizable" cavities of the connector) then I heat the middle until most of the grease oozes out. Then I have the second piece waiting further up the cable (if there's room, if not I use the heat shrink tape) heat shrink it around the original piece. If it needs repaired you just cut it off and add more heat shrink tubing and grease.
If I can't replace them, I use silver jewelry cleaner. After it drys somewhat I use electric motor cleaner spray (the ozone safe kind ) to neutralize the remaining acid. Then I give it the above treatment.
You can also use butyl tape. It's bulky and sticky but it lasts for years. You wrap a layer around the entire connection and then wrap a layer of electric tape over that.
RF connectors are lossy (about 1 DB) anyway. A bad crimp, a little corrosion, a slice in the dielectric and your power to the antenna suffers. Some newer radios incorporate circuitry that monitor the final rectifier and cut down the power output when the SWR goes too high to save the "finals" from getting fried. I would think they would come up with a better 50 ohm rf connector than the BNC, but it's served well for years (in dry climates I think) and all the new technology in rf transmission was kicked to the side in favor of more efficient means (fiber/light) as it was just getting interesting. Cellular/wireless technology skipped into sub microwave which uses tiny connectors which carry far less power than VHF cables.
So I would advise keeping some extra BNCs handy and be careful when you're stripping. The silicone dielectric grease is readily found at your local auto parts store (used for spark plug wire terminal protection).

One more thing we do in Florida. If you leave a coax cable end exposed for any length of time, the moisture can corrode way down the cable (osmosis). Dip the end in some of that stuff that you dip tools in to coat the handles or use some regular silicone sealant to seal the end off. When your ready to put a connector on it, just lop the end off...etc.

See you later!
  #3  
Old 05-08-2004, 10:21 PM
StRaNgEdAyS's Avatar
StRaNgEdAyS StRaNgEdAyS is offline
Member
 
Join Date: May 2004
Location: New South Wales Australia
Posts: 503
Default

Elecrtical connections can be espescially troublesome in coastal environments. CC's solution using the dielectric grease an heatshrink is an excellent one.
As for removing the corrosion on your existing wires, because it exists at both ends, I really think you would benefit from replacing the wires completely. This is really a simple procedure, just attach the new wire to the end of the old one and pull it through. In corrosion friendly environments, it's best not to allow any moisture to encroach into the join at all, the best way to do this is to use solder connectors instead of crimp ones. It's a little more tricky, but the results are a much better connection, and a more durable one.
Then whack on some heatshrink and grease a-la previous reply and you have an excellent all weather joint!
  #4  
Old 05-08-2004, 10:48 PM
Dust's Avatar
Dust Dust is offline
89% done 96% to go
 
Join Date: Apr 2004
Location: Troy, Michigan
Posts: 7,072
Default

Great idea strange, only the other side is under glass and solderred in place to the copper foil antenna
__________________
Canardcommunity.com

Enjoy the build,njut av byggandet, godere il costruire, nyd bygningen, geniesse den Bau, apolafse tin kataskevi, disfrute la construcción, curta a construção, Pidä hauskaa rakentamisen parissa, bouw lekker,uživaj grade?inaslajdaites postroikoi, geniet die bou
dust

maker of wood, fiberglass, foam dust, metal bits and one day a Cozy will pop out and swiftly whisk me from meeting old friends and family to adventures throughout the world
  #5  
Old 05-08-2004, 11:50 PM
Clutch Cargo's Avatar
Clutch Cargo Clutch Cargo is offline
w/ Spinner and Paddlefoot
 
Join Date: May 2004
Location: Cape Coral, FL
Posts: 634
Default Corrosion, connections etc.

I am hoping this will be a continuation of the corrosion thread on the other section...
(plus it wouldn't let me post a reply)
"Strange" mentioned soldering direct which is the EIA approved way for all non-RF type connections and is safe and waterproof. However to insure the proper impedence to the antenna, the properties of the dielectric have to remain the same (50 ohm) BNC SO and other connectors do lose some power but they keep the 50 ohm impedence. It is difficult to keep the dielectric (insulation between inner conductor and braided shield) properties once they have been severed. The problem is that it's more a question SWR and impedence than signal "leaking" through the braided shield. Most solder jobs are "close enough" and the only trade off is effective radiated power is lower than what it could have been without the splice. Idealy, there would be no splice, coil the extra up and dip the end. If you have to splice, make it semi-permanent (you can solder some connectors - use a good flux) and weatherproof it. They do sell weatherproof connectors. Newark has TNC connectors that will handle the power Here they are.. They are meant for harsh areas with vibration etc. and are good for splices. I think they are about -1 db @ 120 mhz (average) No offense but you never know how lossy a soldered coax connection is..
Have Dust building the fun with all.

Striking it's dyslexia again!

I mean: Have fun building with all the dust.

Or the other way works too.
  #6  
Old 05-09-2004, 12:17 AM
John Slade's Avatar
John Slade John Slade is offline
Flying TurboRotaryCozyIV
 
Join Date: Apr 2004
Location: KRUT
Posts: 5,224
Default

Kevin,
I have no idea what you just said.
  #7  
Old 05-09-2004, 01:18 PM
Clutch Cargo's Avatar
Clutch Cargo Clutch Cargo is offline
w/ Spinner and Paddlefoot
 
Join Date: May 2004
Location: Cape Coral, FL
Posts: 634
Lightbulb explanation...

I'll try to explain this a little better..

1. It's not a good idea to try to splice coaxial cables by soldering them together.
Why? Since it carries a "tuned" RF wave, the splice can alter the impedence of the cable. At best it will lose a little power when transmitting, worse case, it could fry the radio's final rectifier(s).

2. If you cannot replace the entire run (recommended) then use a connector with known RF electrical characteristics and make it semi-permanent by soldering it and/or using the method described by the last post.

3. There are weatherproof and vibration resistant connectors you can use to splice which are small and easy to work with.

My experience with RF connections comes from my stint as a Cellular Tower and Antenna installer back in the late 80's and early 90's where I learned first hand the importantance of a good connection in the face of extreme weather conditions 24/7 with very little power at sub-microwave radio frequencies (900 MHZ)

In our case, a radio can recieve with a mis-matched antenna and even transmit to another radio close by. But because the power is lessened by a mismatched cable or antenna, it may only transmit a few hundred feet, if that.

If you want, I can explain the formula and you can figure out how much power you should have at the antenna (ERP = effective radiated power) or I can stop by tomorrow and confuse you further in person.
  #8  
Old 05-09-2004, 02:10 PM
John Slade's Avatar
John Slade John Slade is offline
Flying TurboRotaryCozyIV
 
Join Date: Apr 2004
Location: KRUT
Posts: 5,224
Default

Quote:
or I can stop by tomorrow and confuse you further in person
Yes, please stop by - but don't explain it - just bring the fancy measuring gizmo and FIX the @#@$ing thing for me .

Call and let me know when you'll be there.
  #9  
Old 05-09-2004, 02:39 PM
mplafleur's Avatar
mplafleur mplafleur is offline
Finally at Chapter 4!
 
Join Date: Apr 2004
Location: Lathrup Village, MI (Metro Detroit)
Posts: 1,332
Default

Can't have one run, or you will never be able to detach the wing.

I was thinking of using N connectors instead of BNC or SO-239 (the worst).
__________________
Michael LaFleur
Big EZ Retract
And no trees were harmed or killed in the creating and sending of this message. However, a large number of electrons were terribly inconvenienced...
http://banners.wunderground.com/weat...tions/57516.gi
 

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 11:53 AM.


Powered by vBulletin® Version 3.6.7
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.