BNC Connection Help

szicree · #1 09-25-2005, 02:03 PM

Well, after much research I decided to mount my Comant bent whip on the centerline about six inches ahead of the spar. Everything looks terrific except for one small problem. The connector is directly underneath the bottom tip of the control stick. Once I get the little 90 degree adapter on there, the clearance between stick and connector is about 3/4 inch. I just don't like the idea of such a non-movable object protruding so close to the bottom of the stick. One option is to relocate the stick and fill the holes (not my first choice). The other is to figure out some sort of low profile wat to attach the antenna cable. I can easily put a small stud on the antenna doubler and connect the sheild with a crimp-on ring terminal, the problem is in finding a way to connect the center conductor. What I'd like best is a way to have a stud coming straight out of the antenna. I'm hoping somebody has a great idea because I really don't want to move my antenna.

Steve Zicree
RV4

Ironflight · #2 09-25-2005, 04:13 PM

Steve,

Do a web search on BNC connectors, and you'll find a lot of varieties out there. Unfortunately, I had a similar clearance issue with the back of my Garmin 430, and ended up having to make what I needed (but I have some clever technicians at my disposal) from several different connectors. A good, cheap, low-profile right angle connector is what the world needs! I tried to buy the one that you get with the ICOM radio, and they were happy to sell me one - for about a hundred bucks! Airway robbery.....

My experience with direct connections like a ring lug for ground, and then putting the center conductor on the antenna with another ring lug (ala cheap, bent whip antennas) has been very bad - you get more RF energy bouncing around inside the plane than you end up radiating.

Wish I could be of more help - just lettign you know my experiences.

Paul Dye

sf3543 · #3 09-25-2005, 04:37 PM

This site could provide an idea for you.

http://home.comcast.net/~jwdanie/Finish15/finish15.html

SteinAir · #4 09-25-2005, 10:00 PM

Steve,

Don't bother with relocating the antenna or using that 90 degree adapter/coupler.

We along with other part suppliers stock and sell a right angle crimp BNC connector that is also made by Amp, but they are not cheap (downright outrageous). They crimp together just like regular BNC's, and don't protrude any higher than your regular BNC, but let the coax exit at a 90 degree angle.

I'm sorry, but I think the above method just plain looks kludgy to me.

We routinely use these right angle BNC's for exactly the installation you describe, and I personally did it that way on my RV6 with the bent whip under the seats.

Contact me off list if you have any questions.

Cheers,
Stein.

mark manda · #5 09-25-2005, 10:33 PM

would adding a spacer on the fuse between the body help give you a bit more room?

szicree · #6 09-25-2005, 11:16 PM

Stein: How outrageous? It's okay, I can take it.

Mark: Dang! That is so brilliant and so simple I'm embarassed I didn't think of it myself.

I'm thinking that a combination of both will get that thing right down against the skin if I want. I feel so happy that I don't have to fill those holes.

Steve Zicree

mark manda · #7 09-25-2005, 11:39 PM

I was dealing with a tight fit when I wanted my Com. antennae dead center on the fuse awhile back.

I can't find my pict of my spacer plate. mark

szicree · #8 09-26-2005, 12:09 AM

Mark,

How thick was the spacer and did it look ugly?

Steve

mark manda · #9 09-26-2005, 01:03 PM

thought I posted two hrs ago. I'll try again.

I was thinking of my Garmin 330 antennae but same idea.

I barely cleared with my Com. 90 deg. connector also but no spacer. Sorry about the big picts.

az_gila · #10 09-27-2005, 07:59 AM

The spacer is probably not a good idea. The antenna is sized for the correct frequency at 1/4 wavelength (about 3 inches in this case) and needs a metallic ground plane to work correctly.

The spacer has increased the effective length of the antenna by a measurable percentage.

Yes.... I know "it works", but it doesn't work as efficiently as originally designed, or as required in any TSO (I believe the transponder system is one that does have to meet TSO specs. even in our homebuilts)

gil in Tucson