Good guide to radio and aerial wiring?

[danny_galaga]

I have yet to wire up my radio, headphone jacks and aerial. Actually I don't even have an aerial 😄

 

Looking at whether I need shielded wiring on ALL wires into the radio, and would they all need to be grounded? Is it a matter of 'this wire is a must to be grounded, but the more the merrier '?

 

I've wired most of my panel. I've used shielded wire to the ignition switches. The shielding is grounded to the negative bus bar which is on the instrument panel.

[danny_galaga]

Will answer my own question, at least partly 😄

 

First of all, my own radio operation manual has some advice.

 

Also

 

This looks like a good read:

 

http://www.sullivanuv.com/wp-content/uploads/2014/06/Aircraft-Wiring-Best-Practices.pdf

[rgmwa]

The Aeroelectric Connection by Bob Nuckolls is another well regarded reference for homebuilt aircraft.

[kgwilson]

I had to replace all of my radio wiring because I initially didn't used shielded cable. I used single core shielded cable for all wiring. If the frame is metal you must make sure there are no earths anywhere except back at the radio and a main earth bus that goes directly to the battery. For the aerial the cable is also shielded with BNC connectors either end or the cable may be part of the aerial & with a BNC connector at the radio end when the cable is cut to length. If the aerial you install is not tuned then cut it to an optimum length for the middle of the Aviation frequency band. If the aircraft skin is metal you won't have a ground plane issue. If it is fabric or plastic then making a good ground plane and positioning becomes important for good reception & transmission. This should all be in the wiring best practices book. 

[danny_galaga]

Thanks guys. What is the 'wiring best practices book'!

 

For an aerial, I've read about these recently 

 

http://www.advancedaircraft.com/

 

At least one of the Bushcat guys uses one and is happy with it. No ground plane. Will copy his installation.

 

[Kyle Communications]

All your mic and heaset wiring needs to be shielded. DO NOT earth the shields at both ends only the aircraft end. Your headset sockets must not be grounded to the aircraft frame keep them totally isolated. All earths should be bought back to the one place for all your avionics. I use a earthing brass bar..basically a Neutral link like used in your house. You bring the negative from the battery to that link then onto the engine. Earth loops cause all the issues usually

 

[kgwilson]

3 hours ago, danny_galaga said:

Thanks guys. What is the 'wiring best practices book'!

 

 

 

The one you put a link to in your earlier post

[danny_galaga]

5 hours ago, Kyle Communications said:

All your mic and heaset wiring needs to be shielded. DO NOT earth the shields at both ends only the aircraft end. Your headset sockets must not be grounded to the aircraft frame keep them totally isolated. All earths should be bought back to the one place for all your avionics. I use a earthing brass bar..basically a Neutral link like used in your house. You bring the negative from the battery to that link then onto the engine. Earth loops cause all the issues usually

 

Oh yes. I'm on top of the negative return aspect. I misspoke earlier, I said I had shielded the ignition switches. I meant radio switch

[Kyle Communications]

Good to see you using at least one deustch connector

 

I use deutsch for everything except my CAN bus stuff

 

[danny_galaga]

Kitplanes website has some articles too, worth having a search there:

 

https://www.kitplanes.com/antenna-wiring/

[Blueadventures]

What are you doing for a ground plane?

[sfGnome]

We don’t want ground planes. We want air planes… 😝

[Blueadventures]

55 minutes ago, sfGnome said:

We don’t want ground planes. We want air planes… 😝

All builds are ground planes until fist flight🙃😁😉

[danny_galaga]

Mine has been a ground plane for nearly four years. 

I am using a dipole antenna 

[danny_galaga]

So this is probably such a dumb question you may not get what I'm asking- with your shielded wiring (head, mic etc), you piggy tail a wire on the shielding and hook it to the negative bus bar. Do you do the same with the aerial coax cable?

[kgwilson]

Terminate all the shields (earth) back to the radio earth at the radio and a single earth wire from there to the earth bus. The radio aerial is connected via a BNC connector at the radio which includes the earth shield. Do not earth the shields anywhere else on the aircraft or you will get earth loop hum or worse. If you use a tuned whip aerial the coax earth will be connected to the ground plane. In a metal aircraft that is the skin. Check wiring diagrams if you are using a dipole ground plane.

[danny_galaga]

Thanks. For some reason I couldn't see that the shielding was connected electrically to anything. But after your post, I found an old coax cable that happened to have BNC on both ends and proved to myself with a ohmmeter that the outer of the BNC is connected to the shielding and thus the earth is through that connector, no external connections required 🙂

 

Like I say, so obvious people would find it hard to tell what I'm asking 😂