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Ground/earth

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f.kyle(at)sympatico.ca
Guest

Posted: Mon Oct 27, 2014 12:17 pm Post subject: Ground/earth

In discussing various coax choices and installing different radio sets, it came to me to suggest to our lesser radio-concious fellows to make a suggestion which I hope will avoid some bad results otherwise.

There are grounds (earths) and other grounds.... When an electronic device is planned for installation, there may be two grounds involved - ne’er the two should meet. there will be a DC ground whence cometh the juice to power the beast. There is also a RADIO ground which is used to connect two parts of the radio. Sometimes these two are confused, or even badly described in the text. ALWAYS ensure you know exactly which is which; otherwise it’s likely that interference will show up later.

Ferg.

 [quote][b]

rampil

Joined: 04 May 2007
Posts: 870

Posted: Tue Oct 28, 2014 6:09 am Post subject: Re: Ground/earth

Hi Ferg!



Sorry, but there is no Ground but The Ground in a composite aircraft! 



That is to say, the negative side of the battery.  



From that it is simply a matter of practice in

minimizing the resistance back to that point. Noise is created when 

changing current flows move across a resistance, and those changes 

in current occur at high enough frequency to radiate to adjacent conductors.



Prevention of noise therefore seeks to minimize resistance to ground, 

and improve shielding.



Ira

_________________
Ira N224XS

peterz(at)zutrasoft.com
Guest

Posted: Tue Oct 28, 2014 7:03 am Post subject: Ground/earth

I defer to Ferg, and my Trig avionics installation manual which does indeed have grounding directions as per Ferg.

fwiw,



Cheers,

Pete

Ferg - you must be close to flying now?Â  Or is it a springtime launch?

On Tue, Oct 28, 2014 at 10:09 AM, rampil <ira.rampil(at)gmail.com (ira.rampil(at)gmail.com)> wrote:

[quote]--> Europa-List message posted by: "rampil" <ira.rampil(at)gmail.com (ira.rampil(at)gmail.com)>

 

 Hi Ferg!

 

 Sorry, but there is no Ground but The Ground in a composite aircraft!

 

 That is to say, the negative side of the battery.

 

 >From that it is simply a matter of practice in

 minimizing the resistance back to that point. Noise is created when

 changing current flows move across a resistance, and those changes

 in current occur at high enough frequency to radiate to adjacent conductors.

 

 Prevention of noise therefore seeks to minimize resistance to ground,

 and improve shielding.

 

 Ira

 

 --------

 Ira N224XS

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=432404#432404

 

 

 

 

 

 

 

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 pa-List" target="_blank">http://www.matronics.com/Navigator?Europa-List

 ===========

  FORUMS -

 _blank">http://forums.matronics.com

 ===========

 b Site -

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 target="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 [b]

rampil

Joined: 04 May 2007
Posts: 870

Posted: Tue Oct 28, 2014 3:18 pm Post subject: Re: Ground/earth

Sorry, but in the noble tradition of Bob Nuckolls, I feel compelled to squash

electronic mysticism.  Reducing impedance in ground paths is the prime

consideration. Short, fat and tight! No special distinct classes are required.

At least no voodoo is required below UHF.



I pulled the trig y91 install manual off their site. Look at the wiring diagram

on page 52. 



Observe: 

1)that all power and signal grounds are tied together and to aircraft ground.

Indeed, in the text, it says they only provide 5 ground pins yet 9 are 

required, so tie them all together (section 5.6.12 on p22)!



2) Next, direct your attention to the RF coax connector. Note that there is only

the center conductor shown. That is because the coax ground is tied directly

to the chassis/case ground. The signal grounds go to the same place as the 

chassis (section 5.6.11)!

_________________
Ira N224XS

steven.pitt2(at)ntlworld.
Guest

Posted: Wed Oct 29, 2014 8:02 am Post subject: Ground/earth

Ira/Ferg/Peter

Your input came at just the moment I am rewiring my radio and transponder 

equipment for mode S and 8.33khz and I was reviewing my ground/earth 

installation.

As a non aviation electrician I have always been confused by these concepts 

and the issue of earth loops so can I ask for clarification.

Shielded wire for the mikes and phones are shown as connected in the Trig 

diagrams so that suggests to me that connecting them all together and then 

running one wire back to the battery negative contact would be the way to 

go.

But then what about the ground strap to the engine block and the PTT wires 

which are shown as 'earthed'. How can you do that in a plastic aircraft.

Sorry if this is really basic and although I have been flying for 8 years in 

'DH I have always been uncertain that I had wired up the grounds correctly.

Regards

Steve

---

rowlandcarson(at)gmail.co
Guest

Posted: Wed Oct 29, 2014 9:05 am Post subject: Ground/earth

On 29 Oct 2014, at 16:01, Steven Pitt <steven.pitt2(at)ntlworld.com> wrote:



 	  Quote: 	
		   Ira/Ferg/Peter

 Your input came at just the moment I am rewiring my radio and transponder equipment for mode S and 8.33khz and I was reviewing my ground/earth installation.

 As a non aviation electrician I have always been confused by these concepts and the issue of earth loops so can I ask for clarification.

 Shielded wire for the mikes and phones are shown as connected in the Trig diagrams so that suggests to me that connecting them all together and then running one wire back to the battery negative contact would be the way to go.

 But then what about the ground strap to the engine block and the PTT wires which are shown as 'earthed'. How can you do that in a plastic aircraft.

 Sorry if this is really basic and although I have been flying for 8 years in 'DH I have always been uncertain that I had wired up the grounds correctly.


	


Steve - you can get good advice about this and many other aeroplane wiring issues from 'Lectric Bob. His website is at:



http://www.aeroelectric.com



Many years ago I purchased a paper copy of the AeroElectric Connection which helped me translate many of the principles I already knew as an electrical/electronic/audio engineer into practical guidelines for wiring my aircraft.



You can get the publication on paper or CD-ROM, or you can just wade into the Matronics AeroElectric list and start asking questions.



You can also see how I planned my own electrical installation at:



http://www.rowlandcarson.org.uk/aviation/europa_435/wirebook.php



There are many references in my diagrams to “common earth” either cockpit side or engine side. This is a couple of stout metal plates fastened together through the firewall, with many tabs on each side for 1/4” blade connectors, and a big terminal to connect to the battery negative.



B & C Speciality makes this item and you can see it at:



http://www.bandc.biz/grounding-supplies-battery-cables.aspx



In UK, Airworld stocks it:



http://shop.airworlduk.com/ground-bus-2448-position-300941-367-p.asp



Everything that requires to be “earthed” or “grounded” has a wire running all the way back to that block of tabs. On my main circuit diagram (based on the one in the Europa build manual) a line marked “ground return busbar” is shown. To match the physical reality, that should really be shown as a single point, but that would make the diagram very messy.



Hope this helps.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

| pictures: http://picasaweb.google.com/rowlandcarson

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Oct 29, 2014 5:55 pm Post subject: Re: Ground/earth

Hi Steve!



I also endorse Bob's treatise which you can download from his aeroelectric site.



Bob's "forest of tabs" is a convenient way to tie all of your panel 

grounds together with minimal resistance. The tab field can conveniently

be bolted to the bottom of your panel molding. You will probably need

above 50 tab points for all the panel grounds. From the ground tabs 

reserve two or three tabs for #8 or 10 ga wires to an amphenol

connector through the firewall. On the other side of the firewall a 1/4" bolt

is convenient to attach ring crimp connectors to the battery and to the

engine block.

_________________
Ira N224XS

f.kyle(at)sympatico.ca
Guest

Posted: Thu Oct 30, 2014 7:15 am Post subject: Ground/earth

Time: 07:10:25 AM PST US

Subject: Re: Ground/earth

From: "rampil" <ira.rampil(at)gmail.com (ira.rampil(at)gmail.com)>

Hi Ferg!

Sorry, but there is no Ground but The Ground in a composite aircraft! 

That is to say, the negative side of the battery. 

 	  Quote: 	
		  From that it is simply a matter of practice in

minimizing the resistance back to that point. Noise is created when changing current flows move across a resistance, and those changes in current occur at high enough frequency to radiate to adjacent conductors.

Prevention of noise therefore seeks to minimize resistance to ground, and improve shielding.      Ira

Ira,

            Quite right regarding the term “Ground” and its complications. SO I added the UK ‘earth’, trying to show that it’s not so simple when radios are added. Radiating to adjacent conductors is OK provided they aren’t part of a radio installation. The purpose of the coax is to shield such conductors from noise nearby. That can be accomplished only if the coax is ‘grounded’ to the radio’s prescribed point. Often, installations design a circuit to forestall noise coming from the aircraft ground and so direct coaxes to a radio ground, not the aircraft one. Old-style strobes can bang out mighty peaks - and added to the audio noise.

            What we need is another word for ground/earth and all I wanted to do was suggest strict attention to installation instructions.

Cheers, Ferg

 [quote][b]

graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Thu Oct 30, 2014 11:27 am Post subject: Re: Ground/earth

I dont like the sound of a 'forest of tabs under the panel" unless there are at least two, a quiet ground and a noisey ground and both going back to meet at the battery negative with as thick as you can. transponder, fuel pump, trim and anything else noisey such as giros away from audio/radio and things that just need a reference.

_________________
Graeme Bird
kit4 (Wagstaff) TBD
Kit3 G-CLXU (Gregory) mono 914 xs Woodcomp
Kit2 G-PATS - (kesterton) Mono Classic 912 warpdrive
Kit 1 G-UMPY - Mono Classic/XS 912S, Woodcomp G(@)gdbmk.co.uk

f.kyle(at)sympatico.ca
Guest

Posted: Fri Oct 31, 2014 7:02 am Post subject: ground/earth

I obviously opened a can of worms with this topic. My only intent was to draw attention to strict instructions when installing radio equipment - not just VHF transceivers but any device sensitive to small signals.

I have no quarrel with fellow builders but the last correspondent mentioned “noisy grounds” and “quiet grounds”. The ‘forest of tabs’ I found to be an excellent organiser of various aircraft ground return paths - and have used it since the day I saw it. This can be a ‘noisy’ ground because it is subject to all the noise (strobes, large on/off selections and even received radio signals) - that’s because they are meant to be DC sources.

Ah, but the ‘quiet’ ground probably sits somewhere on the radio set. It is designed to absorb the noise created and then subject it to circuitry before unleashing it on the aircraft ground. If the coax is to be grounded ( and thus be free of interference) it goes to the quiet ground first.

All I wanted to say was - be sure to follow the radio installation instructions to the letter. The fault lies with the use of “ground or earth” for both points. We need another term for radio ground - maybe “quiet” works?

Cheers, Ferg

P.S: I heartily endorse Bob Nuckolls’ (AeroElectric) advice - I invited him to conduct a well-attended lecture at our hangar

 

 [quote][b]

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