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MPPalmer(at)aol.com
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 Posted: Fri Jun 13, 2008 12:33 pm Post subject: Radiated or conducted |
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I've written about this before, so I'm going to keep this brief. (Search the archives for "radiated" and "conducted."
There are two ways EMI can get into your radios. Either by the power cord (conducted) or by antenna. (radiated.) I don't know about this PC you're using. If it's battery powered and you get interference, then your problem is radiated. It could be the CPU or the screen drivers. In any event, metal shielding is the usual solution. If you put your gizmo in an enclosed metal box (for testing) and the radio noise goes away, it's radiated.
If your PC is powered by the aircraft bus and the noise goes way when powered independently, by a separate battery, then the solution is beads, capacitors, etc. on the power lines. Usually it's easier to squelch conducted than radiated RFI.
Of course, it could be a mixture of both kinds of interference.
Mike Palmer <><
(obsolete MSEE)
**************
Vote for your city's best dining and nightlife. City's Best 2008.
(http://citysbest.aol.com?ncid=aolacg00050000000102) [quote][b]
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tomgoddard(at)ns.sympatic
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| Posted: Sat Jun 14, 2008 8:04 am Post subject: Radiated or conducted |
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Hi Mike,
You responded to an email of mine on this topic several months ago about comm RFI EMI getting into everything in our panel and you suggested to sort it out to put a dummy load on the comm pigtail and key up and see what happened... we did that and all the trouble went away except the Tru Trak AP still had a heading change. So we concluded that we have both Radiated and conducted RF troubles. We did VSWR testing on our old antennas and they weren't too bad but changed them anyway from the Glasair Aviation copper foil dipole to the Bob Archer 006 with a well made connection and a proper install. Recall Bob Archer does not advocate the use of a balun. The VSWR didn't improve much... about 2-2.5 The problem persisted. We also found 1 very leaky B&C connector and fixed it, we routed the comm coax from the center of the plane to the fuselage side wall. We tried the AAE dipole with the built in balun and it seemed better than the Archer 006. We had a nice long pc of RG 58 coax that
I was able to walk around the hangar with ranging 20-30 feet from the Glasair and keyed up and things were alot better at a distance and when we keyed up close to the plane the problems were worse but better than the Archer 006 with no balun.
Our grounding seems good with a few exceptions. All the avionics and all panel electrics... lights, pitot heat, strobes etc are brought out to one common ground 10g wire that then goes to the copper strip avionics ground under the panel and that strip is in turn grounded to the engine block via 4g wire. Recall from my email a few months back that the panel is profesionally built and that company set up the 10 ground for us to run to the av ground bus. The 2 batteries negitives are brought together on 2 g and then through the center console through the fire wall to the engine block near were the avionics ground bus attaches to the block. There is good ground continuity from the avionics ground bus back to the batteries with resistance in the 300 mohm range. The exceptions to the grounding are that the ray allan trim and flap indicators, the trim connection from the stick to the relays and then to the trim motor and the flap connection from the flap momentary DPDT to the flap
motor may all or partly be doubly grounded. These connections were all provided for by the panel maker and therefore the ground accounted for through the 10g avionics ground wire. We ran into trouble using his connections because the wiring for them wasn't big enough so I think they are powered and grounded separetly but still connected to some extent via the panel makers original wiring.
So we may have a ground loop somewhere. So my thought is to disconnect items from the avionics ground bus in an organised way and key up and see if things improve before we resort to chokes etc.
That's alot to ask you to read and think on but if you made it this far what do you think.
Tom
| Quote: |
From: MPPalmer(at)aol.com
Date: 2008/06/13 Fri PM 04:29:31 EDT
To: glasair-list(at)matronics.com
Subject: Radiated or conducted
I've written about this before, so I'm going to keep this brief. (Search the
archives for "radiated" and "conducted."
There are two ways EMI can get into your radios. Either by the power cord
(conducted) or by antenna. (radiated.) I don't know about this PC you're using.
If it's battery powered and you get interference, then your problem is
radiated. It could be the CPU or the screen drivers. In any event, metal shielding is
the usual solution. If you put your gizmo in an enclosed metal box (for
testing) and the radio noise goes away, it's radiated.
If your PC is powered by the aircraft bus and the noise goes way when powered
independently, by a separate battery, then the solution is beads, capacitors,
etc. on the power lines. Usually it's easier to squelch conducted than
radiated RFI.
Of course, it could be a mixture of both kinds of interference.
Mike Palmer <><
(obsolete MSEE)<BR><BR><BR>**************<BR>Vote for your city's best dining and nightlife.
City's Best 2008.<BR> (http://citysbest.aol.com?ncid=aolacg00050000000102)
|
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bobf(at)feldtman.com
Guest
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| Posted: Sat Jun 14, 2008 10:06 am Post subject: Radiated or conducted |
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did you try putting ferrite beads or toroids on the 12 input into your radios? What kinda of radios do you have. I have a GX-65 apollo and think it is very noise sensitive - (poor noise rejection)... and am fighting RFI from the spark plug wires on my LOM engine in my glastar. Some radios just have better noise rejection than others. on the transmitting side, some radios have much poorer harmonic radiation rejection as well - I think you have done a great job with the antennas figuring them out and doubt the ground is the problem. We'll see what experts say on the blog here. I always learn something.
bobf
On Sat, Jun 14, 2008 at 11:02 AM, <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)> wrote:
[quote] --> Glasair-List message posted by: <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)>
Hi Mike,
You responded to an email of mine on this topic several months ago about comm RFI EMI getting into everything in our panel and you suggested to sort it out to put a dummy load on the comm pigtail and key up and see what happened... we did that and all the trouble went away except the Tru Trak AP still had a heading change. So we concluded that we have both Radiated and conducted RF troubles. We did VSWR testing on our old antennas and they weren't too bad but changed them anyway from the Glasair Aviation copper foil dipole to the Bob Archer 006 with a well made connection and a proper install. Recall Bob Archer does not advocate the use of a balun. The VSWR didn't improve much... about 2-2.5 The problem persisted. We also found 1 very leaky B&C connector and fixed it, we routed the comm coax from the center of the plane to the fuselage side wall. We tried the AAE dipole with the built in balun and it seemed better than the Archer 006. We had a nice long pc of RG 58 coax that
I was able to walk around the hangar with ranging 20-30 feet from the Glasair and keyed up and things were alot better at a distance and when we keyed up close to the plane the problems were worse but better than the Archer 006 with no balun.
Our grounding seems good with a few exceptions. All the avionics and all panel electrics... lights, pitot heat, strobes etc are brought out to one common ground 10g wire that then goes to the copper strip avionics ground under the panel and that strip is in turn grounded to the engine block via 4g wire. Recall from my email a few months back that the panel is profesionally built and that company set up the 10 ground for us to run to the av ground bus. The 2 batteries negitives are brought together on 2 g and then through the center console through the fire wall to the engine block near were the avionics ground bus attaches to the block. There is good ground continuity from the avionics ground bus back to the batteries with resistance in the 300 mohm range. The exceptions to the grounding are that the ray allan trim and flap indicators, the trim connection from the stick to the relays and then to the trim motor and the flap connection from the flap momentary DPDT to the flap
motor may all or partly be doubly grounded. These connections were all provided for by the panel maker and therefore the ground accounted for through the 10g avionics ground wire. We ran into trouble using his connections because the wiring for them wasn't big enough so I think they are powered and grounded separetly but still connected to some extent via the panel makers original wiring.
So we may have a ground loop somewhere. So my thought is to disconnect items from the avionics ground bus in an organised way and key up and see if things improve before we resort to chokes etc.
That's alot to ask you to read and think on but if you made it this far what do you think.
Tom
>
> From: MPPalmer(at)aol.com (MPPalmer(at)aol.com)
> Date: 2008/06/13 Fri PM 04:29:31 EDT
> To: glasair-list(at)matronics.com (glasair-list(at)matronics.com)
> Subject: Radiated or conducted
>
> I've written about this before, so I'm going to keep this brief. (Search the
> archives for "radiated" and "conducted."
>
> There are two ways EMI can get into your radios. Either by the power cord
> (conducted) or by antenna. (radiated.) I don't know about this PC you're using.
> If it's battery powered and you get interference, then your problem is
> radiated. It could be the CPU or the screen drivers. In any event, metal shielding is
> the usual solution. If you put your gizmo in an enclosed metal box (for
> testing) and the radio noise goes away, it's radiated.
>
> If your PC is powered by the aircraft bus and the noise goes way when powered
> independently, by a separate battery, then the solution is beads, capacitors,
> etc. on the power lines. Usually it's easier to squelch conducted than
> radiated RFI.
>
> Of course, it could be a mixture of both kinds of interference.
>
> Mike Palmer <><
===========
> ist" target="_blank">http://www.matronics.com/Navigator?Glasair-List
===========
MS -
k">http://forums.matronics.com
===========
e -
-Matt Dralle, List Admin.
t="_blank">http://www.matronics.com/contribution
===========
[b]
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tomgoddard(at)ns.sympatic
Guest
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| Posted: Sun Jun 15, 2008 6:45 pm Post subject: Radiated or conducted |
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Our radios are GNS 430W and a Garmin SL40. I have not tried any ferrites yet. Can you suggest any? I have hear that MGL avionics sells good ones… have you heard of them?
Tom
From: owner-glasair-list-server(at)matronics.com [mailto:owner-glasair-list-server(at)matronics.com] On Behalf Of Robert Feldtman
Sent: June 14, 2008 3:04 PM
To: glasair-list(at)matronics.com
Subject: Re: Glasair-List: Radiated or conducted
did you try putting ferrite beads or toroids on the 12 input into your radios? What kinda of radios do you have. I have a GX-65 apollo and think it is very noise sensitive - (poor noise rejection)... and am fighting RFI from the spark plug wires on my LOM engine in my glastar. Some radios just have better noise rejection than others. on the transmitting side, some radios have much poorer harmonic radiation rejection as well - I think you have done a great job with the antennas figuring them out and doubt the ground is the problem. We'll see what experts say on the blog here. I always learn something.
bobf
On Sat, Jun 14, 2008 at 11:02 AM, <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)> wrote:
--> Glasair-List message posted by: <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)>
Hi Mike,
You responded to an email of mine on this topic several months ago about comm RFI EMI getting into everything in our panel and you suggested to sort it out to put a dummy load on the comm pigtail and key up and see what happened... we did that and all the trouble went away except the Tru Trak AP still had a heading change. So we concluded that we have both Radiated and conducted RF troubles. We did VSWR testing on our old antennas and they weren't too bad but changed them anyway from the Glasair Aviation copper foil dipole to the Bob Archer 006 with a well made connection and a proper install. Recall Bob Archer does not advocate the use of a balun. The VSWR didn't improve much... about 2-2.5 The problem persisted. We also found 1 very leaky B&C connector and fixed it, we routed the comm coax from the center of the plane to the fuselage side wall. We tried the AAE dipole with the built in balun and it seemed better than the Archer 006. We had a nice long pc of RG 58 coax that
I was able to walk around the hangar with ranging 20-30 feet from the Glasair and keyed up and things were alot better at a distance and when we keyed up close to the plane the problems were worse but better than the Archer 006 with no balun.
Our grounding seems good with a few exceptions. All the avionics and all panel electrics... lights, pitot heat, strobes etc are brought out to one common ground 10g wire that then goes to the copper strip avionics ground under the panel and that strip is in turn grounded to the engine block via 4g wire. Recall from my email a few months back that the panel is profesionally built and that company set up the 10 ground for us to run to the av ground bus. The 2 batteries negitives are brought together on 2 g and then through the center console through the fire wall to the engine block near were the avionics ground bus attaches to the block. There is good ground continuity from the avionics ground bus back to the batteries with resistance in the 300 mohm range. The exceptions to the grounding are that the ray allan trim and flap indicators, the trim connection from the stick to the relays and then to the trim motor and the flap connection from the flap momentary DPDT to the flap
motor may all or partly be doubly grounded. These connections were all provided for by the panel maker and therefore the ground accounted for through the 10g avionics ground wire. We ran into trouble using his connections because the wiring for them wasn't big enough so I think they are powered and grounded separetly but still connected to some extent via the panel makers original wiring.
So we may have a ground loop somewhere. So my thought is to disconnect items from the avionics ground bus in an organised way and key up and see if things improve before we resort to chokes etc.
That's alot to ask you to read and think on but if you made it this far what do you think.
Tom
>
> From: MPPalmer(at)aol.com (MPPalmer(at)aol.com)
> Date: 2008/06/13 Fri PM 04:29:31 EDT
> To: glasair-list(at)matronics.com (glasair-list(at)matronics.com)
> Subject: Radiated or conducted
| Quote: |
> I've written about this before, so I'm going to keep this brief. (Search the
|
> archives for "radiated" and "conducted."
>
> There are two ways EMI can get into your radios. Either by the power cord
> (conducted) or by antenna. (radiated.) I don't know about this PC you're using.
> If it's battery powered and you get interference, then your problem is
> radiated. It could be the CPU or the screen drivers. In any event, metal shielding is
> the usual solution. If you put your gizmo in an enclosed metal box (for
> testing) and the radio noise goes away, it's radiated.
>
> If your PC is powered by the aircraft bus and the noise goes way when powered
> independently, by a separate battery, then the solution is beads, capacitors,
> etc. on the power lines. Usually it's easier to squelch conducted than
> radiated RFI.
>
> Of course, it could be a mixture of both kinds of interference.
>
> Mike Palmer <><
===========
> ist" target="_blank">http://www.matronics.com/Navigator?Glasair-List
===========
MS -
k">http://forums.matronics.com
===========
e -
-Matt Dralle, List Admin.
t="_blank">http://www.matronics.com/contribution
===========
| Quote: | | http://www.matronics.com/Navigator?Glasair-List |
0123456789
Checked by AVG. Date: 15/06/2008 5:52 PM
Checked by AVG.
15/06/2008 5:52 PM
[quote][b]
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bobf(at)feldtman.com
Guest
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| Posted: Sun Jun 15, 2008 7:18 pm Post subject: Radiated or conducted |
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My 430W is quiet as a mouse in my aerocommander.. Look up Palomar engineers - that is where I get mine. haven't heard of MGL avionics.
bobf
On 6/15/08, Tom Goddard <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)> wrote:[quote]
Our radios are GNS 430W and a Garmin SL40. I have not tried any ferrites yet. Can you suggest any? I have hear that MGL avionics sells good ones… have you heard of them?
Tom
From: owner-glasair-list-server(at)matronics.com (owner-glasair-list-server(at)matronics.com) [mailto:owner-glasair-list-server(at)matronics.com (owner-glasair-list-server(at)matronics.com)] On Behalf Of Robert Feldtman
Sent: June 14, 2008 3:04 PM
To: glasair-list(at)matronics.com (glasair-list(at)matronics.com)
Subject: Re: Glasair-List: Radiated or conducted
did you try putting ferrite beads or toroids on the 12 input into your radios? What kinda of radios do you have. I have a GX-65 apollo and think it is very noise sensitive - (poor noise rejection)... and am fighting RFI from the spark plug wires on my LOM engine in my glastar. Some radios just have better noise rejection than others. on the transmitting side, some radios have much poorer harmonic radiation rejection as well - I think you have done a great job with the antennas figuring them out and doubt the ground is the problem. We'll see what experts say on the blog here. I always learn something.
bobf
On Sat, Jun 14, 2008 at 11:02 AM, <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)> wrote:
--> Glasair-List message posted by: <tomgoddard(at)ns.sympatico.ca (tomgoddard(at)ns.sympatico.ca)>
Hi Mike,
You responded to an email of mine on this topic several months ago about comm RFI EMI getting into everything in our panel and you suggested to sort it out to put a dummy load on the comm pigtail and key up and see what happened... we did that and all the trouble went away except the Tru Trak AP still had a heading change. So we concluded that we have both Radiated and conducted RF troubles. We did VSWR testing on our old antennas and they weren't too bad but changed them anyway from the Glasair Aviation copper foil dipole to the Bob Archer 006 with a well made connection and a proper install. Recall Bob Archer does not advocate the use of a balun. The VSWR didn't improve much... about 2-2.5 The problem persisted. We also found 1 very leaky B&C connector and fixed it, we routed the comm coax from the center of the plane to the fuselage side wall. We tried the AAE dipole with the built in balun and it seemed better than the Archer 006. We had a nice long pc of RG 58 coax that
I was able to walk around the hangar with ranging 20-30 feet from the Glasair and keyed up and things were alot better at a distance and when we keyed up close to the plane the problems were worse but better than the Archer 006 with no balun.
Our grounding seems good with a few exceptions. All the avionics and all panel electrics... lights, pitot heat, strobes etc are brought out to one common ground 10g wire that then goes to the copper strip avionics ground under the panel and that strip is in turn grounded to the engine block via 4g wire. Recall from my email a few months back that the panel is profesionally built and that company set up the 10 ground for us to run to the av ground bus. The 2 batteries negitives are brought together on 2 g and then through the center console through the fire wall to the engine block near were the avionics ground bus attaches to the block. There is good ground continuity from the avionics ground bus back to the batteries with resistance in the 300 mohm range. The exceptions to the grounding are that the ray allan trim and flap indicators, the trim connection from the stick to the relays and then to the trim motor and the flap connection from the flap momentary DPDT to the flap
motor may all or partly be doubly grounded. These connections were all provided for by the panel maker and therefore the ground accounted for through the 10g avionics ground wire. We ran into trouble using his connections because the wiring for them wasn't big enough so I think they are powered and grounded separetly but still connected to some extent via the panel makers original wiring.
So we may have a ground loop somewhere. So my thought is to disconnect items from the avionics ground bus in an organised way and key up and see if things improve before we resort to chokes etc.
That's alot to ask you to read and think on but if you made it this far what do you think.
Tom
>
> From: MPPalmer(at)aol.com (MPPalmer(at)aol.com)
> Date: 2008/06/13 Fri PM 04:29:31 EDT
> To: glasair-list(at)matronics.com (glasair-list(at)matronics.com)
> Subject: Radiated or conducted
| Quote: |
> I've written about this before, so I'm going to keep this brief. (Search the
|
> archives for "radiated" and "conducted."
>
> There are two ways EMI can get into your radios. Either by the power cord
> (conducted) or by antenna. (radiated.) I don't know about this PC you're using.
> If it's battery powered and you get interference, then your problem is
> radiated. It could be the CPU or the screen drivers. In any event, metal shielding is
> the usual solution. If you put your gizmo in an enclosed metal box (for
> testing) and the radio noise goes away, it's radiated.
>
> If your PC is powered by the aircraft bus and the noise goes way when powered
> independently, by a separate battery, then the solution is beads, capacitors,
> etc. on the power lines. Usually it's easier to squelch conducted than
> radiated RFI.
>
> Of course, it could be a mixture of both kinds of interference.
>
> Mike Palmer <><
===========
> ist" target="_blank">http://www.matronics.com/Navigator?Glasair-List
===========
MS -
k">http://forums.matronics.com
===========
e -
-Matt Dralle, List Admin.
t="_blank">http://www.matronics.com/contribution
===========
Checked by AVG. Date: 15/06/2008 5:52 PM
Checked by AVG.
15/06/2008 5:52 PM
| Quote: |
target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://www.matronics.com/Navigator?Glasair-List
click="return top.js.OpenExtLink(window,event,this)">http://forums.matronics.com
_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://www.matronics.com/contribution
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