[jdeas]

Proper Coax for Nav/comm

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]

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]

I have them in my RV9A

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]

rg-142

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]

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]

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]

Limited com range in wingtip

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]

Belly Com

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]

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]

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.

 

[az_gila]

Minor difference

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.

RG-142 is only 0.25 db better at 100 MHz over RG-58 for a 25 ft. length, and hence 0.1 db for the 10 ft. length that Mel used. These numbers are essentially negligible in the RF world...

... but I prefer the RG-58 that has a stranded core... RG 58 C/U is one... just check the specs. on-line.

Older avionics manuals specify RG-58, but the newer ones usually specify RG 400, which has a Tefzel outer jacket, as opposed to the PVC jacket of RG-58.. just send more $$$.... Now preferred by the FAA, but not mandatory for our experimentals.

gil in Tucson

 

[Ironflight]

Put me down as another vote for RG-58 XX....not that the 400 isn't good stuff, but I already had lots of 58 (and the appropriate connectors) laying about, and as Larry said - the runs are so short that it makes almost no difference....

Now, if I'd had 400 lying about, I am sure I would have used that!

Paul

 

[jdeas]

Thanks all

Like many others, I have a bunch of RG-58 and their connectors about my shop. Given the cost of some of the more unique connectors I'm sticking with RG-58, Archer nav and a belly com.

Thanks everyone.

 

[gmcjetpilot]

Good enough

Jim Weir of Kitplane had a recent article about RG-58 and other so called better coax like RG-400. He came up with the same conclusion after crunching the numbers, RG-58 is still an excellent and very suitable product now and for some time to come, both cost wise and performance wise.

RG-400 may last 120 years, verses RG-58's only 80 years, but I'm sure I will not care in 80 years. Hummm will I have my medical when I am 120 years old? May be I better go with RG-400.

 

[az_gila]

Fire rating...

Jim Weir of Kitplane had a recent article about RG-58 and other so called better coax like RG-400. He came up with the same conclusion after crunching the numbers, RG-58 is still an excellent and very suitable product now and for some time to come, both cost wise and performance wise.

RG-400 may last 120 years, verses RG-58's only 80 years, but I'm sure I will not care in 80 years. Hummm will I have my medical when I am 120 years old? May be I better go with RG-400.

Gorge... I believe the move by the FAA to the RG-400 is for the Tefzel outer jacket.

The PVC jacket of the RG-58 gives off bad stuff in a fire... which might be a problem in big planes, but I don't think we have enough coax cable in our RVs to be a real problem....

Some of our other wires are PVC jacket anyway... the strobe cables (I think) and the multi signal cable to the trim motors come to mind....

Electrically, it's a wash.... and "better" depends on your criteria....

gil in Tucson

 

[gmcjetpilot]

Darn you are sharp gil

Gorge... I believe the move by the FAA to the RG-400 is for the Tefzel outer jacket. gil in Tucson

gil darn it you are sharp, hoped you would not notice. Yep that is true, but if your coax is on fire, you are in deep deep doo-doo. My runs are so short and so close to my body, if there's a fire in the cockpit, under the panel, I'm in trouble and already overwhelmed by other fume. Hope I have my parachute on that day (which is one reason why I've got a chute, a massive fire).

But good point the tefzel is better than PVC for toxic fumes, very true. Good on you.