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RV-10 Coax Length?

ppilotmike

ppilotmike

Well Known Member
I'd like to determine how much coax to order and have given thought to getting a spool if the lengths add up to a significant amount:

1) Can someone give me a good length for coax going out to the wing tip in a 10 (Archer antenna), allowing a little extra for waste?
2) Also, would you recommend purchasing/installing heated pitot and/or AP servos before closing up the wing bottom skins (mast already in)? I'd like to wait as long as possible, but don't want to paint myself into a corner.
3) Is RG-400 coax really so much better than the RG-58? My coax will be in a conduit so I'm not too worried about wear, but there will also be lighting wires in there with the coax (LEDs)...

Thanks for the help guys.
 
I can't answer your first question as I don't have wingtip antennae. However, I have two COMM, transponder, marker beacon (why not? It's built into the avionics), and NAV whiskers in the back. Get a spool; the wingtip is not your only COAX. Oh, and my Lightspeed Ignition also uses COAX...

The other two questions call for opinion. For me, it made sense to put in the pitot and servos as I built. I don't recall anyone having trouble changing out pitot masts. As for the servos; they are pretty standard but, in my case, I had made my brand decision early anyway.

For the last question, RG-400 is better but only as good as the connections you make. It's not any harder to make good connections than RG-58, so my general answer is go with the RG-400. 'Better' implies a lot of factors and so a full engineering analysis might return a different answer but I don't have the time to start a discussion that will only see a lot of arguing over technical details. Life is too short. Most avionics recommend RG-400 for their equipment; why not follow the recommendations?
 
Thanks Patrick...

... for your reply, and especially for your take on the RG 400 vs 58 coax. I'm hoping to make the call on AP and pitot at OSH this year, but it seems like so many waited until far into their builds, which leads me to belive they had their bottom skins on when they installed those components.
 
No need on the AP before closing out the skins

No need to install the servos before closing out the skins. Really the servo just bolts right in. I installed mine, then had to remove it to be able to buck the rivets on the bottom skin, then put it back in, then found I really needed to remove it for paint as I did not want any water on it while prepping for paint.

AP servo can be right at the end.

Depending on the HEATED pitot tube, some require a controller mounted near the tube. If so it would be easier to mount it (or at least put some nutplates for mounting) before closing the bottom skin.

Don't know the length of RG-400 I used, but I know it was a lot more than I had originally estimated. I know I re-ordered it 2 times, with the second order being as much as I originally ordered.
 
1. Measure the lengths yourself. There are too many variables in how you or someone else routes the coax. You will be surprised at how many feet you use within the cockpit, going up, down, back, forward, etc. Leave a two foot service loop at the wing tip so you can remove the tip, rotate it up onto the wing.
2. I put that part of the pitot mast which is riveted on prior to, or at the same time, as the wing skin. Everything else I did later. I was afraid I'd snag and damage the pitot taking the wing out and in of the craddle. I put autopilot (Trio) on after the wing was on the plane.
3. For GHz (DME, transponder, GPS) you really want RG400. RG58 will work okay for nav/com. But now you need to stock two different cables, different BNCs, etc. Problem with RG58 is time - at bends there is a tendancy for the inner conductor to slowly migrate thru the dielectric. Since it bends more easily there is a greater chance that you will over bend it. Besides, the 400 just looks nicer! Unless you are on a very tight budget I'd use 400 everywhere (which is what I did, and I was watching the budget).
 
Pitot

Make SURE you put the pitot tube doubler in before you close up the bottom. This was the case with the greta mount that I used.

If you are using the Safe Air1 mast, this might not be the case...
 
Saf-Air Mast

I installed the Saf-Air mast, which doesn't (according to instructions) require the skin doubler, although it seems like the Gretz install is quite a bit beefier.
 
Typically I'm right about where Rick is in my recommendations...I tell folks 75' to start (gives you a few feet for mistakes and routing) and 100' if you add ADSB, or other "stuff". I also am obviously a proponent of using RG-400 all the way around.

Just my 2 cents as usual!

Cheers,
Stein
 
while i am way way way off on this. any reason not to use LMR240, SFX500, LDF4, or FSJ4? I have several thousand feet of this stuff so If i can use it, great if not no biggie.
 
SteinAir said:
Typically I'm right about where Rick is in my recommendations...I tell folks 75' to start (gives you a few feet for mistakes and routing) and 100' if you add ADSB, or other "stuff". I also am obviously a proponent of using RG-400 all the way around.

Just my 2 cents as usual!

Cheers,
Stein
Click to expand...

Dang it, Stein! It's like you're always watchin!...:D I'll be placing an order for a spool soon. Since I don't have any connectors or wire yet, do you have any recommendations on other spools I should order (that will be used a lot). I have a heat shrink printer and yellow heat shrink which I will be using to label everything. My thinking is that I'd like colored wires (not all white) and I'd like to try bundles and/or twisted pairs/triples when able. I've looked at your master kit, but don't know whether I'll go with a Vertical Power system or not, so it might not make sense.
 
daviid said:
while i am way way way off on this. any reason not to use LMR240, SFX500, LDF4, or FSJ4? I have several thousand feet of this stuff so If i can use it, great if not no biggie.
Click to expand...

While some of the above cables you mention would likely "technically" be acceptable on paper (I'm sure Gil could link to dozens of spec's), I'd strongly advise against using most of them for a whole host of reasons. Firstly, a couple of them are around 1/2" in diameter with solid center conductors or solid outer shields with poor insulators (definitely not conducive to routing multiple runs throughout something like an RV). Second, if and when you do modifications or maintenance finding connectors and tooling at various places would be difficult, whereas if you stick with the common cables you can get parts at pretty much any avionics shop.

Realize that this is the part of your airplane that will carry your navigation signals, GPS signals, radio signals, transponder signals, ADSB Weather/traffic signals, etc... and at most you'll spend perhaps $300 by using the right cable verses the wrong cable. There are good places to try and save money - this is probably not the best place to try and do so.

Lastly, most of the mfgr's secify one of the more common cables for install, so if you use something wonky like 1/2" diameter coax cable, you'll likely see poor support from any avionics folks at all, ranging from the shops to the mfgrs.

Just my 2 cents as usual!

Cheers,
Stein
 
Stein's $.02 is worth more than my $2 any day. Oh, listen to what dat man say!

And I agree, I'm working through a 100' roll of RG-400 for my entire airframe. Fingers crossed, it should be enough.
 
Stein Order

Patrick,

Since Stein didn't answer my questions yet, do you have any recommendations on what to order with my spool of coax (perhaps connections, coax cutter)? I'm looking to order wire too, but really don't know yet what I need. I've heard people order all white spools of perhaps 18 and 20, but what about shielded vs. unshielded, twisted pairs, etc? Do you find you use a lot of any particular wire types?
 
Mike,
It is hard to give a general answer since a lot depends on specifics.
I would plan on buying or borrowing proper crimp tools for coax and d-sub pins.
Wire is pretty cheap, order some extra.
Some things (landing lights, strobe power) will need #14. Get a copy of one of the wire size charts (gauge vs current vs length) that are floating around.
Make your own twisted pairs by chucking them up in an electric drill.
You need to look at specific equipment. For example, Garmin and PS will generally require you to purchase a wiring harness from a dealer, so you do not have to duplicate that. But if you are installing a different brand intercom, you'll need two twisted wires plus shield for each mike jack; three twisted wires plus shield for each stereo headphone jack (two plus shield if mono).
EFIS units usually come with the wires needed for remote connections to magnetometers, etc., but not to other avionics (I suggest signal wires be 22, not 24; 24 is too small to handle!). Look at any autopilot servos, see what wires they need. I bought Steins pre-bundled wires for this; better to have too many than not enough!
 
ppilotmike said:
Patrick,

Since Stein didn't answer my questions yet, do you have any recommendations on what to order with my spool of coax (perhaps connections, coax cutter)? I'm looking to order wire too, but really don't know yet what I need. I've heard people order all white spools of perhaps 18 and 20, but what about shielded vs. unshielded, twisted pairs, etc? Do you find you use a lot of any particular wire types?
Click to expand...

Hi Mike,

Sorry about that, I didn't read your post carefully enough...

In regards to wire, it's very difficult to get an accurate number because it really can depend on the equipment you choose (which lights, which antennas, multiple landing lights, heated pitot, extended tanks, equipment in the panel, IFR/VFR, stick grips, cabin lights, etc..). That said, at a minimum I think everyone could pretty easily start with:

100' AWG 18Red and AWG18Black.
100' AWG 16 Red and AWG16Black.
50' AWG14Red and AWG14Black.
100' AWG18White
50' AWG16White
50' AWG14White.
100' AWG20Black
100' AWG20Red
50' AWG20White

Regarding the rest of the stuff, you will use a LOT of AWG22 in the panel, and a lot of twisted shielded triple wire for the headset/mic jacks, but again those will vary greatly depending on what you choose, where you put things, and whether you purchase harnesses prefabricated or no. The above should give you a pretty good supply of general airframe wire to start with. You'll likely run out of some and have extras of others, but that is a nice stock to have around your shop. The above package I think works out to right around $250.

Hope that helps!

Cheers,
Stein
 
Thanks Guys!

Looks like I've got some planning to do, but I knew that was coming..:rolleyes: Before I got going, I figured I'd check for any of those "oh definitely get a spool of this and bundle of that" type of hints from those of you that have gone before.
Oh well, time to start up Excel and build a wiring plan! :eek: :D
 
ppilotmike said:
... for your reply, and especially for your take on the RG 400 vs 58 coax. I'm hoping to make the call on AP and pitot at OSH this year, but it seems like so many waited until far into their builds, which leads me to belive they had their bottom skins on when they installed those components.
Click to expand...
I'll be the contrarian. RG-58 has worked fine in certified aircraft for more than 50 yrs. There are reasons the RG400 is needed for transponder, GPS that operate in the 1000 MHz vicinity, but is overkill for 108-135 Mhz range your VHF equipment operates in. Why spend over $3 a foot for RG-400 when RG-58 does a fine job at $.060 a ft? For wing tip antennas or tail mounted antennas that adds up to $100 hamburger in a hurry.
 
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