---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 07/20/15: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:10 AM - Re: Re: Radio Buzz (Robert L. Nuckolls, III) 2. 06:13 AM - Re: Radio Buzz (Robert L. Nuckolls, III) 3. 06:14 AM - Re: Re: Radio Buzz (Robert L. Nuckolls, III) 4. 09:15 AM - Re: Radio Buzz (Ross Home) 5. 11:46 AM - Re: Radio Buzz (rayj) 6. 12:26 PM - Re: Radio Buzz (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:10:53 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Radio Buzz At 05:06 PM 7/19/2015, you wrote: > >Is the AFS 5600 EFIS wired according to the installation >manual? Usually shielded cables are grounded at the source end >only, but not always. Can you identify one or more wires from the >AFS 5600 EFIS that are causing the noise? > Is the squelch on the com radio adjusted too sensitive? As a general rule, no appliance slated to use in airplanes should require ANY special attention on the part of the installer to mitigate a noise issue. The qualification testing for TC aircraft puts your black box out on a copper-top table, wires it up to function stand-alone with no less than 2 meters of "ship's wiring" and it should be neither sensitive to or an emitter of unfriendly energy sources. If any manufacturer suggests 'adding filters, moving wires, adjusting antenna locations, etc. . . they are admitting to their lack of due diligence in design/fabrication of their product. Bob . . . ________________________________ Message 2 _____________________________________ Time: 06:13:48 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Radio Buzz At 06:16 PM 7/19/2015, you wrote: >I will try to rig a short antenna. As it is, I get about 6-9 inches >from the EFIS to set off the sniffer (a handheld radio) > >Ross Mickey Your zeroing in on the root cause . . . I have an h-t antenna that's only about an inch long with a 1/2" disk soldered to the end. This can be used to probe wires, openings in enclosures, lcd screens, etc. Of course, this only works with noise sources that have strong amplitude modulated components . . . but if you can 'hear' it in your nav-comm, you can generally 'sniff it' with a hand-held. Bob . . . ________________________________ Message 3 _____________________________________ Time: 06:14:46 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Radio Buzz At 08:00 PM 7/19/2015, you wrote: > >If I dim my Dynon D-180 screen, it makes noise in the headset. I >leave the screen on full bright (never fly at night) and the noise >is not noticeable. >Joe Unfortunately, all too common . . . Bob . . . ________________________________ Message 4 _____________________________________ Time: 09:15:42 AM PST US From: "Ross Home" Subject: RE: AeroElectric-List: Radio Buzz With my dumbed down handheld sniffer I have identified the major culprit and perhaps a second. The main interference (80%-90%) is from an 18" piece of unused OAT wire that is plugged into the main harness with pos, signal and shield all pinned in the harness. In talking with AFS tech support, the three options are, 1) connect the pos and signal wires together 2) connect the signal and shield together or 3) unpin all three wires from the harness and remove the whole thing. The second culprit is a couple of the serial port wires (2 of the 4). These are emanating some interference which is probably caused by my error. I connected a black the wire coming out of the premade harness (which is connected to the four shield wires for the serial ports) to ground rather than to the chassis of the EFIS. The new harnesses from AFS (mine is two years old) do not have this but take care of connecting the serial shields to the chassis in the pinning of the harness. I will check these out on Weds when I get back to the hangar. Thank you all for your help. Ross From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Monday, July 20, 2015 6:12 AM Subject: Re: AeroElectric-List: Radio Buzz At 06:16 PM 7/19/2015, you wrote: I will try to rig a short antenna. As it is, I get about 6-9 inches from the EFIS to set off the sniffer (a handheld radio) Ross Mickey Your zeroing in on the root cause . . . I have an h-t antenna that's only about an inch long with a 1/2" disk soldered to the end. This can be used to probe wires, openings in enclosures, lcd screens, etc. Of course, this only works with noise sources that have strong amplitude modulated components . . . but if you can 'hear' it in your nav-comm, you can generally 'sniff it' with a hand-held. Bob . . . http://www.matronics.com/Navigator?AeroElectric-List http://www.matronics.com/contribution ________________________________ Message 5 _____________________________________ Time: 11:46:08 AM PST US From: rayj Subject: Re: AeroElectric-List: Radio Buzz Does the disk make the the "detector" directionally sensitive, like I'm guessing a loop would? Raymond Julian Kettle River, MN The things we admire in men, kindness and generosity, openness, honesty, understanding and feeling are the concomitants of failure in our system. And those traits we detest, sharpness, greed, acquisitiveness, meanness, egotism and self-interest are the traits of success. And while men admire the quality of the first they love the produce of the second. -John Steinbeck, novelist, Nobel laureate (1902-1968) On 07/20/2015 08:12 AM, Robert L. Nuckolls, III wrote: > At 06:16 PM 7/19/2015, you wrote: >> I will try to rig a short antenna. As it is, I get about 6-9 inches >> from the EFIS to set off the sniffer (a handheld radio) >> >> Ross Mickey > > Your zeroing in on the root cause . . . I have > an h-t antenna that's only about an inch long with > a 1/2" disk soldered to the end. This can be used > to probe wires, openings in enclosures, lcd screens, > etc. > > Of course, this only works with noise sources that have > strong amplitude modulated components . . . but if you > can 'hear' it in your nav-comm, you can generally 'sniff > it' with a hand-held. > > > Bob . . . > > * > > > * > ________________________________ Message 6 _____________________________________ Time: 12:26:49 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Radio Buzz At 11:14 AM 7/20/2015, you wrote: With my dumbed down handheld sniffer I have identified the major culprit and perhaps a second. The main interference (80%-90%) is from an 18" piece of unused OAT wire that is plugged into the main harness with pos, signal and shield all pinned in the harness. In talking with AFS tech support, the three options are, 1) connect the pos and signal wires together 2) connect the signal and shield together or 3) unpin all three wires from the harness and remove the whole thing. I would vote for removing any unused wires from the connector. The second culprit is a couple of the serial port wires (2 of the 4). These are emanating some interference which is probably caused by my error. I connected a black the wire coming out of the premade harness (which is connected to the four shield wires for the serial ports) to ground rather than to the chassis of the EFIS. The new harnesses from AFS (mine is two years old) do not have this but take care of connecting the serial shields to the chassis in the pinning of the harness. Hmmmm . . . there's no good reason for serial wires to radiate. Single wire data at the higher speeds (20-100 kBits/sec) were subject to some electro-static coupling issues but the designers of RS232 transmitters offered connections for a capacitor to slow the transition edges of the data. Twisted pair data architectures eliminated this risk. I'm disappointed that the EFIS designers didn't do a better job of managing this but yes, at VHF, the long pig-tail on the shield ground could add enough impedance to allow those pesky edges to couple out. This may well be an instance where the long pigtail not only added the series impedance, it became the VHF friendly radiator for the noise. I will check these out on Weds when I get back to the hangar. Let us know what you discover . . . be sure to let the supplier know too . . . they MIGHT see fit to fix this at the next upgrade opportunity. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.