Proper Coax for Nav/comm and VOR

jdeas · #1 05-16-2007, 11:57 AM

I am planning to install the Archer VOR and Com antennas in my wing tips. Not having the radios, I do not know the proper coax cable to run in the wings.
Can anyone suggest the proper coax or the impedence? Also any comments on how well these antennas work in the RV7 wingtips?

So far I have been given RG-58U and RG-174 as options.

Thanks

elippse · #2 05-16-2007, 01:08 PM

If you want the very best, get Andrew FSJ1-50 50 Ohm cable. You can get it from Talley, who is a distributor for Andrew, at $1.49 / ft. They also have the $10 BNC connectors. LA - 1 800 949 7099; SF - 1 800 2323 4949

kentb · #3 05-16-2007, 02:08 PM

Nav on the left along with 40" of unshielded coax for the marker beacon. Com on the right. One bent whip belly for my second com radio.

I am happy with the nav to both radios (SL30 and GNS430), but the com side the belly antenna can pickup almost twice as far away. I have not found this to be a problem, if I am a ways off I will just use the better antenna and when I get closer and want to pickup awos or the field freq. I just switch over to the wing tip antenna.

Kent

fmarino1976 · #4 05-16-2007, 02:49 PM

I wouldn't use RG-58, It has too much attenuation. For COMS and Navs RG-142 works really well. (That's what we use here at a major helicopter completion center) If you need something a little more flexible you could use RG-400 that is about the same as 142 but the center conductor is stranded instead of a solid conductor. In my opinion the FSJ1-50 cable is really good but way overkill.
The most important thing on antenna installations is the bonding to the airframe.

My 2 cents.

jdeas · #5 05-16-2007, 02:50 PM

Quote:

Originally Posted by kentb

but the com side the belly antenna can pickup almost twice as far away.

Kent,
Thanks for the feedback on the range. Has anyone else had this problem? I'm not married to internal antennas if this is the expected loss over a belly mounted unit.

ptrotter · #6 05-16-2007, 03:22 PM

The problem with wingtip comm antennas is that the comm requires a vertically polarized antenna and wingtip is not thick enough to do it properly, so a vertically polarized antenna in the wingtip is a compromise at best. The nav antenna works well because it is a horizontally polarized antenna. Also, if the station you are trying to reach is on the side away from the antenna, the metal of the plane can block some of the signal. I am putting in a nav antenna in the wingtip and my comm antennas on the belly.

jdeas · #7 05-16-2007, 04:02 PM

I noticed that Archer also has an internal com for the tail. That would take care of the H/V thing but it appears to be too large for the RV7 tail fiberglass. Guess I'm going with the belly for com and wingtip for nav.

hevansrv7a · #8 05-16-2007, 04:36 PM

Quote:

Originally Posted by jdeas

I noticed that Archer also has an internal com for the tail. That would take care of the H/V thing but it appears to be too large for the RV7 tail fiberglass. Guess I'm going with the belly for com and wingtip for nav.

I fought this battle and lost. You will be happy with the belly bent antenna for the com. The Archer works great for Nav. My radio is an SL-30.

Mel · #9 05-16-2007, 05:16 PM

For the runs used in the RV, good quality RG-58 works just fine. I've used it in many RVs and mine has been flying for 14 years with no problems at all.

n5lp · #10 05-16-2007, 05:26 PM

Quote:

Originally Posted by Mel

For the runs used in the RV, good quality RG-58 works just fine. I've used it in many RVs and mine has been flying for 14 years with no problems at all.

That is the key. Attenuation specs are normally given for a 100 feet. 10 feet of just about any coax at VHF isn't going to have much loss.