Antenna Doubler - Comments/review Requested

[BillL]

I have reviewed all posts on doublers and this is what will be used for a Comant bent whip mounted behind the spar on the outboard cell.



Here is the location of the (to be) finished doubler.



Hopefully a better view of the doubler in position. Note that the rivets along the bottom of the spar flange, and on right along the outer skin would be drilled and common rivets used to secure two sides of the doubler.


This is the best shot of the doubler alone. The two slots are to clear fluting on the side skins on the floor. The joggles go the right direction although it does not appear so.

I have looked at AC43-13 but don't see where guidelines for rivets in the flat area are stated - some help there would be appreciated.

How does this look, too much? Problems/issues? It just appeared easier to joggle and use existing rivet locations for appearance and better structure. The part will be alodined prior to riveting.

Constructive comments invited.

[Mel]

That should work fine assuming you have checked clearance between the connector/cable and the aileron pushrod in all possible control positions.

[Paul K]

Like Mel said! I screwed up and had to buy two very expensive 90 degree connectors. Stein has em!

[BillL]

Mel, Paul

No holes drilled yet, so I will double check the clearance. I did not precisely check this installation detail. I always thought the backup was a 90 deg BNC.

Thanks for the comments!!

[az_gila]

Originally Posted by Paul K

Like Mel said! I screwed up and had to buy two very expensive 90 degree connectors. Stein has em!

Try here...

http://www.mouser.com/catalog/catalogusd/646/1410.pdf

[Ron RV8]

For what it's worth, here's a shot of how I did it in the -8.

Antenna / aileron pushrod clearance was close, but worked out ok with a few tie wraps...

[SteinAir]

Originally Posted by az_gila

Try here...

http://www.mouser.com/catalog/catalogusd/646/1410.pdf

Every time Gil does this I have to go back and explain those aren't the same connectors...don't think you're buying a $50 connector for $9....they aren't remotely the same unit. There is a reason that us, ACS, and other reputable shops don't use those cheaper 90 degree versions. While we certainly could stock and offer those cheap ones (and I agree the good ones are ridiculously expensive), people would get upset pretty quickly when they find out how poor they actually are in comparison to the expensive ones. Again, this is one of those "looks good on paper" things that certain folks are experts at, but this is again where practicality and reality trumps theory. There are times to be "frugal" during the build of these planes, but this stuff is not one of them!

That said and back to the topic at hand, Bill's modification appears to be something I don't see any problems with other than what MEL mentioned...just ensuring the cable doesn't rub on the pushrod. RG-400 has a fairly reasonable and tight bend radius and a few zip ties, cable clamps, or other strain relief type of mounts should help it from having any interference issues. I might take an alodine pen and coat edges/holes, but other than that I have seen many installations in similar areas without much difficulty. As Bill knows, just keep the other antennas clear of that one by a couple/few feet and you'll be golden.

Just my 2 cents as usual.

Cheers,
Stein

[flightlogic]

Does a transponder antenna (stubby whip) need a doubler?

[az_gila]

Originally Posted by SteinAir

Every time Gil does this I have to go back and explain those aren't the same connectors...don't think you're buying a $50 connector for $9....they aren't remotely the same unit. There is a reason that us, ACS, and other reputable shops don't use those cheaper 90 degree versions. While we certainly could stock and offer those cheap ones (and I agree the good ones are ridiculously expensive), people would get upset pretty quickly when they find out how poor they actually are in comparison to the expensive ones. Again, this is one of those "looks good on paper" things that certain folks are experts at, but this is again where practicality and reality trumps theory. There are times to be "frugal" during the build of these planes, but this stuff is not one of them!
.......
Just my 2 cents as usual.

Cheers,
Stein

Stein,

I am still not sure why you don't like these connectors.

They are cheaper because they are easier to make - no 50 ohm right angle Teflon internal transmission line. The trade off is for the one crimp of the internal pin to be replaced by a soldered joint. Just think about the added complexity of the innards and their assembly compared to a straight BNC plug. The one I listed does not have this internal complexity - see drawing link at end. I'm really not saying they are same as the $50 connectors, I can just see why they are easier to make and therefore cheaper, for the cost of a 50% crimp solution vs. a 100% crimp solution.

I can see why you, and avionics shops, would prefer a fully crimped solution in a production environment, but soldering the center conductor and the time it takes to set up a soldering iron is usually not a big deal for a homebuilder...

The actual method of assembly is pretty close to the right angle connectors on the back of avionics trays, and not too many years ago almost all of the co-ax connectors had a soldered center pin.

http://www.amphenolconnex.com/downlo...er_drawing.pdf

[bruceh]

Just remember with that forward position of the doubler against the spar carry through bulkhead, you might have issues getting the wing bolts in place. You need to be able to tap those close tolerance bolts in there. I put my antenna doubler farther back in that area and it was still a bit tight getting the wing bolts pushed into place.