---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 01/16/21: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:10 AM - Re: Antenna Ground Planes (Alec Myers) 2. 05:42 AM - don't count on control wire to turn IR alternator off (johnbright) 3. 05:53 AM - Re: OV relay and crowbar (johnbright) 4. 09:04 AM - Re: Antenna Ground Planes (AdventureD) 5. 09:47 AM - Re: Re: Antenna Ground Planes (Charlie England) 6. 10:11 AM - Re: Antenna Ground Planes (Robert L. Nuckolls, III) 7. 11:04 AM - Re: Alternator Ground (rparigoris) 8. 11:14 AM - Re: Antenna Ground Planes (user9253) 9. 05:10 PM - Re: Antenna Ground Planes (AdventureD) 10. 06:43 PM - Re: Antenna Ground Planes (user9253) 11. 07:33 PM - Re: Alternator Ground (rparigoris) ________________________________ Message 1 _____________________________________ Time: 04:10:46 AM PST US From: Alec Myers Subject: Re: AeroElectric-List: Antenna Ground Planes A ground plane works the same way as a mirror: the boundary condition for th e electric field at the surface of an infinite (or ground connected) ground p lane is that no electric field component can exist parallel to the surface o f the ground plane. To enforce this electric currents are induced in the gro und plane to produce a cancelling field - equivalent to a reflected antenna m irrored in the plane. If the ground plane is small or not connected to the t ransmitter circuit then those currents are impeded to a greater or lesser ex tent. The effectiveness of a ground plane is improved if it is electrically connec ted to the circuit that=99s connected to the antenna so those currents flow more easily. But it will still have some effect even if it=99s n ot. The higher the frequency the more effective a floating ground plane will be: at light frequencies a smooth metal surface is an almost perfect ground pla ne (mirror) even when not electrically connected to anything else. Bob - how did I do? On Jan 16, 2021, at 02:35, Bob Verwey wrote: =EF=BB Dan there are no dumb questions...even though i dont know the answer to your question...lol On Sat, 16 Jan 2021, 06:05 AdventureD, wrote: tions.com> > > Here is a dumb question about ground planes. Does the ground plane serve t o direct the signal to the antenna irrespective of whether the antenna is "c onnected" to the ground plane, or must the antenna itself be electrically co nnected to the ground plane? > > I am asking because the tech says the best approach to the ground plane in my e-glass composite is conductive paint on the belly. what I am wondering is how, after the conductive paint is painted over, one ensures that the an tenna is "grounded" to the conductive paint ground plane. I think it may be the case that the ground plane has nothing to do with "grounding" the anten na to the ground plane, but rather that the purpose of the ground plane is t o absorb signal for the antenna located in the middle of it (whether or not t he antenna "touches" the ground plane. > > As you can see, I obviously don't know how antenna ground planes work. > > Appreciate your help, > Dan > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=500260#500260 > > > > > > > ========== > - > Electric-List" rel="noreferrer noreferrer" target="_blank">http://www. matronics.com/Navigator?AeroElectric-List > ========== > FORUMS - > eferrer noreferrer" target="_blank">http://forums.matronics.com > ========== > WIKI - > errer noreferrer" target="_blank">http://wiki.matronics.com > ========== > b Site - > -Matt Dralle, List Admin. > rel="noreferrer noreferrer" target="_blank">http://www.matronics.com/c ontribution > ========== > > > ________________________________ Message 2 _____________________________________ Time: 05:42:08 AM PST US Subject: AeroElectric-List: don't count on control wire to turn IR alternator off From: "johnbright" I don't know about all internally regulated alternators but it is common for the control wire to turn the alternator on but have no ability to turn it off. In any case, as stated in AeroElectric Connection book: The 'control input to the alternator has no direct ability to open the field supply circuit and halt a runaway condition. Ref attached image snip from AeroElectric Connection book. -------- John Bright, RV-6A, at FWF, O-360 Z-101 single batt dual alt SDS EM-5-F. john_s_bright@yahoo.com, Newport News, Va https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500266#500266 Attachments: http://forums.matronics.com//files/aec_r12ac1_page_3_3_153.jpg ________________________________ Message 3 _____________________________________ Time: 05:53:26 AM PST US Subject: AeroElectric-List: Re: OV relay and crowbar From: "johnbright" I don't know about all internally regulated alternators but it is common for the control wire to turn the alternator on but have no ability to turn it off. In any case, as stated in AeroElectric Connection book: The 'control input to the alternator has no direct ability to open the field supply circuit and halt a runaway condition. Ref attached image snip from AeroElectric Connection book. -------- John Bright, RV-6A, at FWF, O-360 Z-101 single batt dual alt SDS EM-5-F. john_s_bright@yahoo.com, Newport News, Va https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500267#500267 Attachments: http://forums.matronics.com//files/aec_r12ac1_page_3_3_193.jpg ________________________________ Message 4 _____________________________________ Time: 09:04:18 AM PST US Subject: AeroElectric-List: Re: Antenna Ground Planes From: "AdventureD" I think youre saying that around an antenna will work to some degree even if it is not electrically connected to the antenna. If that is true, conductive paint will work to some degree even if sealed over by actual paint. To make it even better, should the inside of the hole drilled to accept the antenna be coated with the conductive paint so there is a connection between the ground plane and the antenna. From what you are saying, it appears that that would make the ground plane work even better. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500268#500268 ________________________________ Message 5 _____________________________________ Time: 09:47:19 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Re: Antenna Ground Planes On Sat, Jan 16, 2021 at 11:10 AM AdventureD wrote: > dobrien@microfoundations.com> > > I think you=99re saying that around an antenna will work to some de gree even > if it is not electrically connected to the antenna. If that is true, > conductive paint will work to some degree even if sealed over by actual > paint. To make it even better, should the inside of the hole drilled to > accept the antenna be coated with the conductive paint so there is a > connection between the ground plane and the antenna. From what you are > saying, it appears that that would make the ground plane work even better .. > > Even on a composite airframe, you'll likely need some form of doubler to spread the mechanical loads out from the mount. Why not just use properly dimensioned aluminum sheet inside the fuselage? Weight gain of an ounce or three, and guaranteed ground plane in addition to the doubler function. If the plane is 'glass (not carbon), the best idea was already offered: put the entire assy inside the fuselage. Charlie ________________________________ Message 6 _____________________________________ Time: 10:11:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Ground Planes At 06:06 AM 1/16/2021, you wrote: If the ground plane is small or not connected to the transmitter circuit then those currents are impeded to a greater or lesser extent. The higher the frequency the more effective a floating ground plane will be: at light frequencies a smooth metal surface is an almost perfect ground plane (mirror) even when not electrically connected to anything else. Bob - how did I do? Very good! At a hammer-n-tongs level I like to envision ground planes from two perspectives. The common terrestrial version utilizes what I would call a 'resonant' ground plane. The goal of a ground plane is to provide a minimal loss (lowest practical metallic resistance) non-radiating conductor to concentrate radiation energy in the vertical element. Consider a vertical dipole antenna with a feedline attached to the center. You have two elements in the same plane that share energy management tasks for emitting and receiving energy. Now, fold the bottom element 90 degrees to horizontal. Intuitively, one can see that this element is now in vigorous argument with the vertical element for squirting energy off into the ether. Each element has a load impedance on the order of 30 ohms. Suppose we added a second horizontal element opposite the first. Now we have TWO radiating elements with a combined load impedance of 15 ohms . . . now we can calculate that energy fed to the base will have a 15:30 division ratio with most of energy going to the 'good guy'. Okay, let's add two more radials elements disposed 90 degrees from the first two. Now we have a load impedance of 30/4 or 7.5 ohms for the combination of bad guys . . . and 80% of the energy at the end of the feedline goes to the 'good guy'. 4-radials is a practical place to stop adding . . . the difference between 80 and 100% of energy going to the 'good guy' is not observable in practice. But we don't need to stop there. If you droop the radials at about 45 degrees, you increase the theoretical feed point impedance of 30 ohms (close but not quite 1:1 swr for 50 ohm feedline) the match is a bit better and one of several potential losses in the system is reduced. Drooping also reduces the radiation angle of the antenna so as to focus more attention at the horizon as opposed to the Andromeda galaxy. On the other hand, you can add an infinite number of radials forming a solid disk. Now the theoretical load impedance of the plane approaches zero ohms . . . a good thing you can do to improve performance. Now, here comes those pesky machines known as airplanes . . . with envelopes and structures that are not very friendly for seeking an optimal antenna installation. In a plastic airplane, you can choose to go the enhanced or optimized route for achieving a suitable ground plane. At ADSB/XPNDR frequencies the optimized route is pretty easy. The disk is relatively small. At VHF frequencies, the disk is unmanageably larger so optimization with 4 or more 'radials' becomes the technique of choice. The short answer is that mounting antennas on the outside of a metal airplane offers a perfectly satisfactory ground plane although the infinite number of radials are not resonant. No big deal. In a plastic airplane, the ground plane needs to be fabricated and going the resonant mode with either a disk (optimal) or radials (enhanced) works good, last a long time. The native conductive qualities of materials in composite airplanes whether carbon-fiber, paint or any spray on coatings don't even begin to approach the much-desired quest for close-to-zero-ohms qualities of the optimized ground plane. Bob . . . Un impeachable logic: George Carlin asked, "If black boxes survive crashes, why don't they make the whole airplane out of that stuff?" ________________________________ Message 7 _____________________________________ Time: 11:04:27 AM PST US Subject: AeroElectric-List: Re: Alternator Ground From: "rparigoris" Hi AdventureD "if the alternator is already grounded via attachment to the case, why would that be needed?" See my post on this thread about the V tail bonanza alternator. I located a bad connection between the two halves of the alternator. Running a separate wire to ensure the back hald of the alternator isn't a bad idea if you didn't want to disassemble alternator. Ron P. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500272#500272 ________________________________ Message 8 _____________________________________ Time: 11:14:37 AM PST US Subject: AeroElectric-List: Re: Antenna Ground Planes From: "user9253" > I think youre saying that around an antenna will work to some degree even if it is not electrically connected to the antenna. If that is true, conductive paint will work to some degree even if sealed over by actual paint. To make it even better, should the inside of the hole drilled to accept the antenna be coated with the conductive paint so there is a connection between the ground plane and the antenna. From what you are saying, it appears that that would make the ground plane work even better. Nobody above said that conductive paint will work as an antenna ground plane except the OP's misinformed tech. Yes, conductive paint does have some conductive properties. It also has high resistance, too high to make an effective ground plane. After installing the com antenna, check its SWR with a meter. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500273#500273 ________________________________ Message 9 _____________________________________ Time: 05:10:24 PM PST US Subject: AeroElectric-List: Re: Antenna Ground Planes From: "AdventureD" > Nobody above said that conductive paint will work as an antenna ground plane except the OP's misinformed tech. Yes, conductive paint does have some conductive properties. It also has high resistance, too high to make an effective ground plane. After installing the com antenna, check its SWR with a meter. Funny thing is a bunch of Lancair guys believe (and say they have experienced) that conductive paint works. Let's suppose it doesn't work. Does the existence of the conductive paint over e-glass do any harm when the antenna is put on the outside of the plane? If one put 4 or 6 or 8 copper strips radiating out from the coax attach point on the inside of the eglass plane, that would still work as well as if the conductive paint weren't there, would it not? On the other hand, if I wanted to put a strikefinder antenna on the bottom of the inside of the fuselage, I assume that conductive paint could interfere with the signal to the strikefinder antenna on the inside of the plane, yes? In that sense, would the conductive paint actually do harm? [/quote] Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500278#500278 ________________________________ Message 10 ____________________________________ Time: 06:43:10 PM PST US Subject: AeroElectric-List: Re: Antenna Ground Planes From: "user9253" An antenna will work without a ground plane. But how well? The opinion of others is subjective. The best way to know how well an antenna works is with a SWR meter. Conductive paint will not do any harm at all to the performance of an exterior antenna. It will not do much good either. Use whatever paint looks good. Use a ground plane consisting of 4 wires or copper strips inside of the fuselage. I am not knowledgeable about a strikefinder. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=500279#500279 ________________________________ Message 11 ____________________________________ Time: 07:33:26 PM PST US Subject: AeroElectric-List: Re: Alternator Ground From: "rparigoris" Hi AdventureD For SD20 connector: https://bandc.com/product/replacement-field-connector-for-alternators-l-40-bc410-h-bc425-1-sk35-lom30/ as far as field wires, they are to be paralleled to regulator. I have a SD20S and just twisted 2 wires together from regulator to go to both field wires. One is not a ground. You can just make a short paralleled wire as well. Here's install manual: https://bandc.com/wp-content/uploads/2018/05/install-instructions-bc410_revC.pdf As far as grounding for SD20, it's grounded by the 4 mounting nuts. I'm going the belt and suspenders route and running an extra ground from one of the screws on the brush side of case to engine ground. Note they want you to cross tighten to 20 inch lbs, then go to 60 to 70 inch lbs. I'm going to weld up a 12 point torque adapter for my 1/4" torque wrench. Manual tells you torque value for B+ nut. Best not tighten to the old stand by of stripping and backing off 1/2 turn! Ron P. 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