Electrickery

This forum has been developed to discuss maintenance topics in Canada.

Moderators: ahramin, sky's the limit, sepia, Sulako, North Shore

Message
Author
photofly
Top Poster
Top Poster
Posts: 6368
Joined: Tue Jan 18, 2011 4:47 pm
Location: Part of the "me, me, me" crowd, and loving every second of it.

Re: Electrickery

#101 Post by photofly » Wed Feb 10, 2016 7:00 pm

NeverBlue wrote:Noisy DC does not have AC components to it.
That is the dumbest thing I've read this month.
---------- ADS -----------
  
“This isn’t flying, it’s falling. With style.”

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#102 Post by NeverBlue » Wed Feb 10, 2016 7:34 pm

These AC signals are usually unintentional and can be reduced by having and AC coupling to the ground reference (which is what DC filters do),
Do you not know how an alternator is made?...or what power supply filter is?

Yes...noisy DC has AC riding upon it...it doesn't make the whole thing AC unless the current flows in the opposite direction...it's really very simple.

AC flows in BOTH DIRECTIONS.
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 6368
Joined: Tue Jan 18, 2011 4:47 pm
Location: Part of the "me, me, me" crowd, and loving every second of it.

Re: Electrickery

#103 Post by photofly » Wed Feb 10, 2016 7:44 pm

any time-varying signal is composed of a (possibly zero) DC component, and AC. You don't have to reverse the direction of current to have AC. The AC components can and will radiate.

This is basic basic high-school electronic theory....
---------- ADS -----------
  
“This isn’t flying, it’s falling. With style.”

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#104 Post by NeverBlue » Wed Feb 10, 2016 7:58 pm

You need to have AC to have any kind of EM propagation.

...and you also need a charge to move to have an EM wave to propagate...like a transmission line maybe? Which is capacitive?...holds a charge?...has two (2) conductors?...coax maybe?...antenna systems possibly?

Naaaaaaahhhhhhhh.........


You see a single conductor will pass a charge perfectly into space if it's length is a function of the frequency's wavelength and "it's not connected at one end".

A single conductor will also pick up just about every EM frequency around...but that won't change by moving a conductor in a Cessna 150 and following all standard industry practices as any AME would do, enough to cause any NEW problem.

But a single conductor carrying DC...noisy or not...loaded at both ends...will not propagate EM waves.
---------- ADS -----------
  
Last edited by NeverBlue on Wed Feb 10, 2016 8:16 pm, edited 1 time in total.

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#105 Post by NeverBlue » Wed Feb 10, 2016 8:08 pm

ALTERNATING CURRENT: current flows in both directions

DIRECT CURRENT (PULSATING INCLUDED): current flows in a single direction.

In order to create EM waves you need true AC...it's what moves the charge... and creates the 90 degree difference in the E & H elements....in layman's terms...
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 6368
Joined: Tue Jan 18, 2011 4:47 pm
Location: Part of the "me, me, me" crowd, and loving every second of it.

Re: Electrickery

#106 Post by photofly » Wed Feb 10, 2016 8:16 pm

NeverBlue wrote:ALTERNATING CURRENT: current flows in both directions

DIRECT CURRENT (PULSATING INCLUDED): current flows in a single direction.

In order to create EM waves you need true AC...it's what moves the charge... and creates the 90 degree difference in the E & H elements....in layman's terms...
Simply wrong.

Please study Maxwell's equations and note the time derivatives.
---------- ADS -----------
  
Last edited by photofly on Wed Feb 10, 2016 8:21 pm, edited 1 time in total.
“This isn’t flying, it’s falling. With style.”

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#107 Post by NeverBlue » Wed Feb 10, 2016 8:18 pm

Correct me then
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 6368
Joined: Tue Jan 18, 2011 4:47 pm
Location: Part of the "me, me, me" crowd, and loving every second of it.

Re: Electrickery

#108 Post by photofly » Wed Feb 10, 2016 8:24 pm

Just google "radiation from a time varying current".
---------- ADS -----------
  
“This isn’t flying, it’s falling. With style.”

User avatar
PilotDAR
Rank 10
Rank 10
Posts: 2556
Joined: Sun Sep 30, 2012 6:46 pm
Location: Near CNJ4 Orillia, Ontario

Re: Electrickery

#109 Post by PilotDAR » Wed Feb 10, 2016 9:38 pm

It's odd that you accuse PilotDAR of not being able to determine if a mod is major or not. Although DARs are a good source to help make the assessment, the decision remains in the maintenance realm. That's why all of regulations regarding this decision is in 571. DARs work mainly in the realm of 505 and 521 and of course the deign standards in 523/525/527/529/551. A DAR can certainly offer an opinion but the decision is the AME's.
A point which I had planned to make, but happily CID correctly made first.
Correct me then
Starting now? Better late than never I guess.
You claim to be a DAR...
I am a DAR. And I'm pretty sure I'm not the only DAR in this thread.

DARs provide a service to industry, which begins when a maintainer/owner/operator determines that they require approved data for a major mod or repair, which they need to do, and the data is unavailable. And sometimes, we can draw upon our skills and experience to help a project along, saving time and money for the owner. Or, the owner can apply, and wait for TC Engineers to undertake the project - but it may be a long wait!
---------- ADS -----------
  

Posthumane
Rank 7
Rank 7
Posts: 506
Joined: Sat May 09, 2009 6:16 pm

Re: Electrickery

#110 Post by Posthumane » Wed Feb 10, 2016 11:58 pm

Neverblue, why don't you come down to my lab some time, I'll be perfectly happy to show you how a small AC signal overlaid on a much larger DC signal will radiate just as well as if the DC weren't there. We can even make it loaded on both ends of the conductor (we usually call this a loop antenna, btw). We can set up a spectrum analyser with a receive antenna some distance away and see the propagation in real real time (or a high speed scope if you prefer to see it in the time domain, since we have a 10 GS/s sampling scope here now). Or if you want to set up your own experiment, take any capacitors and other filtering elements off of a set of ignition points and see if this switched DC current produces any emissions.

But all of that is moot, because you can still have electromagnetic interference when no radio frequency radiation is present. DC coupling through electrostatic and magnetostatic fields, as well as through conduction, is still a form of EMI which needs to be dealt with.

To answer your question, yes I know how an alternator is made. I also know how the currents produced in the alternator are rectified to a (roughly) direct current, how their filtered, what factors affect the load and line regulation of the system, what role intermodulation plays and how components have to be selected to minimize its effects... why do you ask?
---------- ADS -----------
  
"People who say it cannot be done should not interrupt those who are doing it." -George Bernard Shaw

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#111 Post by NeverBlue » Thu Feb 11, 2016 5:01 am

Just google "radiation from a time varying current".

are you seriously telling me that that's what I have in my feed-line??????


Holy COW! :roll:

are you saying my feed line is a di-pole???????????

you obviously don't know what a load is or a proper installation of a feed line from a generator to a bus.
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 6368
Joined: Tue Jan 18, 2011 4:47 pm
Location: Part of the "me, me, me" crowd, and loving every second of it.

Re: Electrickery

#112 Post by photofly » Thu Feb 11, 2016 5:05 am

Neverblue as Vizzini:
http://youtu.be/U_eZmEiyTo0
---------- ADS -----------
  
Last edited by photofly on Thu Feb 11, 2016 5:06 am, edited 2 times in total.
“This isn’t flying, it’s falling. With style.”

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#113 Post by NeverBlue » Thu Feb 11, 2016 5:05 am

I'll be perfectly happy to show you how a small AC signal overlaid on a much larger DC signal will radiate just as well as if the DC weren't there.

OH MY lord...


I'm a radio technician....I know what noise is...I know what superimposition is

DC will not radiate as RF......DUHHHHHHH!
---------- ADS -----------
  

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#114 Post by NeverBlue » Thu Feb 11, 2016 5:12 am

what factors affect the load and line regulation of the system, what role intermodulation plays and how components have to be selected to minimize its effects... why do you ask?
...because apparently some here believe that hooking a brand new load up to it with out any data (hand-held GPS installation) doesn't affect anything at all...


but thanks for pointing that out as well...
---------- ADS -----------
  

CID
Rank 11
Rank 11
Posts: 3544
Joined: Sun Jun 19, 2005 6:43 am
Location: Canada

Re: Electrickery

#115 Post by CID » Thu Feb 11, 2016 6:50 am

I'm sorry but a single conductor carrying DC current ( noisy or not) does not radiate EM waves.
This is so fundamentally wrong that I don't think Neverblue will ever see the light. He/she simply refuses to do the research and surprisingly (apparently) has a great deal of experience in the field while never coming to understand the science behind this phenomena.

"Noise" in a DC feed is caused by a few things but regardless of the source, the current generally remains DC albeit intermittent or pulsating. To say there is an AC component in a noisy DC line isn't quite accurate however the EM produced in a DC feed is certainly alternating. So it remains pulsating DC until it's coupled capacitively or induced.

This is the principal used in an ignition coil. The primary is simply excited with pulsating DC and the rapidly changing magnetic field induces a voltage into the secondary creating a large voltage for the spark plugs.

A DC feed from a generator does have generator/alternator noise on it that is often in the RF realm and can radiate. It also causes minor changes in the current to the loads and that changing current creates a corresponding changing magnetic field which absolutely causes EM waves.

Larger EM waves are caused by large loads being switched. Consider a electric hydraulic pump or a flap motor. The current from the generator increases instantaneously to that higher current with a corresponding increase in the magnetic field strength. This is the very definition of EM wave generation.

Add up all the loads as they switch, lighting loads with large inrush currents, de-ice boots with a relatively large inductive component, an HF that has a continuously varying current draw as you transmit and modulate.....and you have a very complex DC feed current that is constantly changing. The current never goes negative so it's still DC but the changing current and corresponding changing magnetic field absolutely causes EM wave emissions across a fairly wide bandwidth.

I suggest you try your own little experiment. Take a coil and connect it to your oscilloscope probe. Now while monitoring the scope, place the coil near your alternator feed on your car. Turn the headlights on and off. Turn on your stereo on high volume. Turn on your turn signal. What do you see? Some sort of sorcery? Or indication of EM waves being emitted from your alternator feed?
In order to create EM waves you need true AC...it's what moves the charge... and creates the 90 degree difference in the E & H elements....in layman's terms...
Nope. You need changing current regardless of the direction. It can all be in the same direction but if it's changing, you well have an EM wave. It's not dependant on the direction, it's dependent on changing the strength of magnetic fields.
---------- ADS -----------
  

User avatar
Troubleshot
Rank (9)
Rank (9)
Posts: 1291
Joined: Sat May 27, 2006 12:00 pm

Re: Electrickery

#116 Post by Troubleshot » Thu Feb 11, 2016 8:43 am

Hmmm...just like the "Checking Tach" thread....5 pages of every poster telling Neverblue he is wrong. Every thread turns in a multi-page shit-show he is in. EVERY THREAD. If they guy could except he is not an expert on every subject and maybe try and learn something it wouldn't turn out this way EVERY THREAD he is in. As soon as someone tells him he's wrong, its over.

I guess I'll take some joy in watching this clown being fed his lunch every post.

have fun with the Maintenance troll boys and girls!
---------- ADS -----------
  

Posthumane
Rank 7
Rank 7
Posts: 506
Joined: Sat May 09, 2009 6:16 pm

Re: Electrickery

#117 Post by Posthumane » Thu Feb 11, 2016 9:11 am

NeverBlue wrote: You see a single conductor will pass a charge perfectly into space if it's length is a function of the frequency's wavelength and "it's not connected at one end".

But a single conductor carrying DC...noisy or not...loaded at both ends...will not propagate EM waves.
NeverBlue wrote:are you saying my feed line is a di-pole???????????
I think the concept of a noisy, time varying DC not being pure DC and therefore having the potential to radiate has already been beat to death (with a very good explanation by CID, photofly, etc.), so I'll just touch on the the other mistake in the above post.

The fact that you think only a tuned di-pole is capable of radiating is hopefully just a memory lapse and not a lapse in training for all avionics techs, as it would be a shame to think that people who work on radios for a living aren't aware of the myriad of effective antenna designs.

A conductor connected at both ends, when fed with a time varying signal, can act as a balanced antenna depending on its configuration. One example that I've already mentioned is the loop antenna - either a resonant loop whose circumference is about a wavelength, or a small loop (magnetic loop) whose circumference is much smaller than a wavelength. In fact a resonant loop is basically just a differently shaped folded dipole, which itself is a dipole with the ends connected to each other by an additional wire. Another example is the Beverage antenna, which is not a tuned length antenna and can be anywhere from half to multiple wavelengths long (it can be a single conducted terminated to ground, or two parallel conductors with an end terminator). A rhombic antenna is yet another example. Single conductor antennas which are open at the end also do not have to be a tuned length, such as the random wire antenna, and if they don't even have to be a wire (such as a patch antenna).


Troubleshot - one good thing that comes from these types of threads is they act as a good information repository for other readers. Neverblue plays the role of the grossly exaggerated antagonist often seen in infomercials and public service announcements. :)
---------- ADS -----------
  
"People who say it cannot be done should not interrupt those who are doing it." -George Bernard Shaw

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#118 Post by NeverBlue » Thu Feb 11, 2016 10:04 am


I suggest you try your own little experiment. Take a coil and connect it to your oscilloscope probe. Now while monitoring the scope, place the coil near your alternator feed on your car. Turn the headlights on and off. Turn on your stereo on high volume. Turn on your turn signal. What do you see? Some sort of sorcery? Or indication of EM waves being emitted from your alternator feed?
Dude...you're picking up a purely magnetic field...turning it into a potential difference across your coil and looking at it with an oscilloscope...

That's not an EM wave you're looking at it's a electric signal made from a magnetic one....way different.

All you're looking at is a change in the magnetic field...not propagating EMI...not at all...

You need a transmission line to emit...not a single conductor...there must be an electric charge movement...impedance is crucial.

...and here's one for you CID:
Pull that coil away a few inches...what do you see? ...it's disappeared!...must be magic...
---------- ADS -----------
  

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#119 Post by NeverBlue » Thu Feb 11, 2016 10:35 am

Better yet...why don't you hook up a radio service analyzer to the feed line and listen to the EMI...oh wait...EMI is there all the time...whether I hook it up or not...

Wait...when I pull my squelch all I hear is EMI!!!!!!!!!......OH NOOOOOOoooooooooooo.
---------- ADS -----------
  

User avatar
PilotDAR
Rank 10
Rank 10
Posts: 2556
Joined: Sun Sep 30, 2012 6:46 pm
Location: Near CNJ4 Orillia, Ontario

Re: Electrickery

#120 Post by PilotDAR » Thu Feb 11, 2016 10:37 am

one good thing that comes from these types of threads is they act as a good information repository for other readers. Neverblue plays the role of the grossly exaggerated antagonist often seen in infomercials and public service announcements. :)
Very true! Thanks Posthumane!

I have learned a lot in this thread, and I quite appreciate the efforts of the well informed posters here. As I said earlier in this thread, we, the Canadian aviation industry are relatively small, but enjoy great freedom and credibility, pulling together as a team, to be a unified group toward solution is super! What a shame, that in this case, the solution required was presenting immense amounts of [very useful] information to demonstrate the reality of a situation denied by one poorly informed poster.

Thank you to those who took the time to post informatively.

Neverblue, as I said, you work in your world, I'll work in mine, it's a big country. I believe that your clients must suffer needless extra effort in the execution of their work, if done with the "Neverblue has it all figured out already" approach you so absolutely assert. You've argued here about Major/minor, out of your league, and elsewhere you argued about tachometers, again, without being conversant with the facts, or practical realities. By the way, on the tachometer thread, you argued a wrong approach against the group, which included a poster who actually participated in the CARAC decision making process, which developed the standard presented in 625 Appendix C (8). Why dig your heels into being more wrong, why not embrace the great knowledge collectively available here?!?

In this thread I have read information which exceeds my knowledge of certain aspects of EMI - and then I shut up about that, and just kept reading! Free learning for me - yippie! CID, Posthumane, and Photofly, in particular gave me good things to think about. Happily, this helps me fulfill one of the terms stated in my delegation manual:
Continue to increase my knowledge in the technical disciplines delegated to me, and with the airworthiness requirements, policies, and procedures;
---------- ADS -----------
  

User avatar
PilotDAR
Rank 10
Rank 10
Posts: 2556
Joined: Sun Sep 30, 2012 6:46 pm
Location: Near CNJ4 Orillia, Ontario

Re: Electrickery

#121 Post by PilotDAR » Thu Feb 11, 2016 10:49 am

That's not an EM wave you're looking at it's a electric signal made from a magnetic one....way different.

All you're looking at is a change in the magnetic field...not propagating EMI...not at all...

You need a transmission line to emit...not a single conductor...there must be an electric charge movement...impedance is crucial.
Okay... I'll play:

When I witness an EMI test, it includes the magnetic compass, and remote compass, if installed. A witnessed compass swing - required by TC, as an element of the EMI test = no successful compass swing, EMI compliance not demonstrated.

If the magnetic field in the aircraft, as the compass indicates it changes, because of a change to the aircraft electrical system, the electrical system change has caused and EMI affect, which requires resolution. I don't really care how the EMI affect was introduced (wave, propagated, transmission line or single conductor) it was detected, and is therefore present.

But, if I'm witnessing the test, it's probably already a major mod approval.

If an AME, or other aviation technical person, is witnessing the same test, they are already applying 571, Appendix A, and looking for an answer to:
(10) affect instruments, or indicators that are installed as part of a system required by the approved type design?
If EMI was detected (including an affect on a magnetic compass) (10) has to be answered "yes", and the design change just became "major". The modifier is going to require approved data (probably and STC) for it.
---------- ADS -----------
  

CID
Rank 11
Rank 11
Posts: 3544
Joined: Sun Jun 19, 2005 6:43 am
Location: Canada

Re: Electrickery

#122 Post by CID » Thu Feb 11, 2016 11:11 am

All you're looking at is a change in the magnetic field...not propagating EMI...not at all...
James Maxwell would be really surprised as he and Heinrich Hertz proved that changing currents in wire do in fact produce electromagnetic waves.
Pull that coil away a few inches...what do you see? ...it's disappeared!...must be magic...
Not magic at all. The intensity of the field is proportional to the inverse square of the distance to the source. Thank Gauss for that.
You need a transmission line to emit...not a single conductor...there must be an electric charge movement...impedance is crucial.
Wow. Just WOW.
---------- ADS -----------
  

DonutHole
Rank 7
Rank 7
Posts: 682
Joined: Thu Sep 13, 2012 7:36 pm

Re: Electrickery

#123 Post by DonutHole » Thu Feb 11, 2016 11:36 am

Lol. A GPS installation if for vfr use only is vied as a minor alteration by the faa, and as a minor modification by transport Canada. The policy letter says so explicit, as does the advisory circular it defers to.

Within the polixy letter it tells you exactly which specified data to use, it's clear as day.

Moving the generator to bus conductor in any certified aircraft is a major modification.

Pretty simple.
---------- ADS -----------
  

NeverBlue
Rank 8
Rank 8
Posts: 907
Joined: Mon Feb 04, 2008 12:53 pm

Re: Electrickery

#124 Post by NeverBlue » Thu Feb 11, 2016 11:57 am

changing currents in wire do in fact produce electromagnetic waves.
Actually no...the changing fields create EM waves...E fields exist between conductors...not around them...charges do...

You clearly do not understand the difference between E fields...H fields and propagating RF fields.
---------- ADS -----------
  

CID
Rank 11
Rank 11
Posts: 3544
Joined: Sun Jun 19, 2005 6:43 am
Location: Canada

Re: Electrickery

#125 Post by CID » Thu Feb 11, 2016 12:14 pm

Within the polixy letter it tells you exactly which specified data to use, it's clear as day.
By definition, modifications that are not classified as "major" require "acceptable" data. "Specified" or "approved" data is required for "major" modifications. Furthermore, it's not as simple as you state. When you install the antenna for example, that portion can become "major" in a hurry. Not usually a big deal though because for non-pressurized puddle jumpers you can use AC 43.13 as "specified" data to install antennas that are classified as "major" modifications.

Neverblue, read up on Maxwell, Faraday and Hertz. You will quickly realize the correct relationship between magnetic fields and electrical fields. Trying to explain it to you is like pissing in the wind.
---------- ADS -----------
  

Post Reply

Return to “Maintenance”