---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 01/20/05: 21 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:44 AM - Re: Re: Odyssey Battery (Rob Logan) 2. 08:12 AM - Re: GPS wiring? (Lockamy, Jack L) 3. 09:02 AM - Re: Aircraft Theft Protection (Robert L. Nuckolls, III) 4. 09:20 AM - Re: GPS wiring? (rd2@evenlink.com) 5. 10:16 AM - Re: Re: Odyssey Battery (Terry Watson) 6. 10:33 AM - Re: Dynon Efis (Steve Sampson) 7. 10:49 AM - Re: Re: 1/4 wave groundplane? (Malcolm Thomson) 8. 11:34 AM - Re: Re: Odyssey Battery (Rob Logan) 9. 11:53 AM - Re: Re: 1/4 wave groundplane? (Rob Logan) 10. 12:01 PM - Re: Re: 1/4 wave groundplane? (Steve Sampson) 11. 12:07 PM - Re: Re: 1/4 wave groundplane? (Robert L. Nuckolls, III) 12. 02:52 PM - Re: Re: 1/4 wave groundplane? (Malcolm Thomson) 13. 02:52 PM - Switching GPS Data Signals () 14. 06:22 PM - Re: Effects of feedline length on Standing Wave Ratio (Robert L. Nuckolls, III) 15. 06:25 PM - Re: Re: 1/4 wave groundplane? (Robert L. Nuckolls, III) 16. 06:30 PM - Re: Switching GPS Data Signals (Robert L. Nuckolls, III) 17. 06:54 PM - Re: Switching GPS Data Signals (rv-9a-online) 18. 07:04 PM - Bent whip "radiators" question (Turbo Tom) 19. 07:30 PM - Re: Switching GPS Data Signals (Brian Kraut) 20. 08:29 PM - Re: Switching GPS Data Signals (rv-9a-online) 21. 09:46 PM - Re: Z13a Pre-flight alt test procedure? (Mike Holland) ________________________________ Message 1 _____________________________________ Time: 07:44:00 AM PST US From: "Rob Logan" Subject: Re: AeroElectric-List: Re: Odyssey Battery --> AeroElectric-List message posted by: "Rob Logan" > There is nothing "wrong" with the Odyssey battery . . . > the notion that BATTERY MAINTENANCE should include either ... > replacement of the battery IN SPITE of the fact that it still cranks Odyssey PC680 battery is listed as > 30% state of charge still provides sufficient starting amps > 50% state of charge after 2 years if stored at room temperature > eight year design life or > 400 [cycles] when fully discharged or > 500 [cycles] when discharged to 80% so at 150 cycles a year, that replace every third annual. but http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4519882933 claims its 7.27'' x 3.11'' x 6.67'' in http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4520579883 claims its 7.0" in length, 3.0" wide, and 6 9/16" tall. not sure what http://www.bandc.biz/BC116-1.pdf is but its claims 7.1" 6.6" 3.0" did the first guy just get his size wrong or am I missing something or how big is the non MJ PC680? ________________________________ Message 2 _____________________________________ Time: 08:12:01 AM PST US Subject: Re: AeroElectric-List: GPS wiring? From: "Lockamy, Jack L" --> AeroElectric-List message posted by: "Lockamy, Jack L" Mickey, Go to www.ebay.com. Do a search for Garmin 010-10082-00. This should get you a large list of available cables at much better prices than you will get from buying direct from Garmin. I think I paid $10 for the cable I'm using on my Garmin 196 connected to a TRIO Avionics Autopilot. Jack Lockamy Camarillo, CA -7A FWF (almost done...) ________________________________ Message 3 _____________________________________ Time: 09:02:57 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Aircraft Theft Protection --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 01:40 AM 1/20/2005 -0500, you wrote: >--> AeroElectric-List message posted by: Dww0708@aol.com > >During" oneday on the flight line "an old man started his 182 with one of >those chain gangs on the prop, snapped three of the four engine mounts >before >he realized what he had done. I mean you could see the cross grain of the >castings where they exceeded their yield strength, probably makes you go >sentimental. That BE 1900 looks like it is covered in Gill Liner >internally. Did >yall do that cargo mod. I did a few cargo mods on some DO228 s. Love >hearing stuff from the Big Shops. David At least he didn't get off the ground before he became aware of a critical check-list item. Wonder if he looked into his fuel tanks too . . . Don't know anything about this particular airplane. It was sitting inside the avionics hangar at RAS Wichita two weeks ago during the ice storm and was outside on the ramp Monday when I took the picture. Bob . . . ________________________________ Message 4 _____________________________________ Time: 09:20:34 AM PST US From: rd2@evenlink.com Subject: Re: AeroElectric-List: GPS wiring? --> AeroElectric-List message posted by: rd2@evenlink.com I got one for 196 from ebay last year, cheap. Sometime thereafter 1/2 of the 4-hole connector broke off (apparently couldn't take the PA winter), so I had to get one from Garmin (the connector seems made from better material). Now it's holding up (cable is always connected in the airplane, GPS unit is taken out disconnected/connected almost every day). Maybe just my experience... Rumen do not archive _____________________Original message __________________________ (received from Lockamy, Jack L; Date: 08:10 AM 1/20/2005 -0800) --> AeroElectric-List message posted by: "Lockamy, Jack L" Mickey, Go to www.ebay.com. Do a search for Garmin 010-10082-00. This should get you a large list of available cables at much better prices than you will get from buying direct from Garmin. I think I paid $10 for the cable I'm using on my Garmin 196 connected to a TRIO Avionics Autopilot. Jack Lockamy Camarillo, CA -7A FWF (almost done...) ________________________________ Message 5 _____________________________________ Time: 10:16:59 AM PST US From: "Terry Watson" Subject: RE: AeroElectric-List: Re: Odyssey Battery --> AeroElectric-List message posted by: "Terry Watson" Rob, Here's a page that has a PDF reference for the specs on Odyssey batteries: http://www.batterymart.com/c-odyssey.html Terry did the first guy just get his size wrong or am I missing something or how big is the non MJ PC680? ________________________________ Message 6 _____________________________________ Time: 10:33:41 AM PST US From: "Steve Sampson" Subject: RE: AeroElectric-List: Dynon Efis --> AeroElectric-List message posted by: "Steve Sampson" Kevin - thanks for that. I was testing the ASI the other day in the hanger by pressurising the pitot line and was amazed to see the Dynon compass swing quite aggressively. I guess it percieved it as an acceleration as the pressure came on and the software moved the compass to counteract the non existant acceleration error. (It was facing about 240)I think that clears that up. This is a D10 with a remote compass and the software that was current last year at S&F. I dont have the version number to hand. Steve. RV9a 9036 G-IINI PS Have you tested your entire pitot system with the Dynon Pitot/AoA head on. I dont see how to do it because Dynon have a built in leak. Its very small but they have confirmed it is meant to be there. > I'd like to confirm one thing - did you have the Dynon EFIS connected to the pitot and static systems? The reason I ask is that I understand that they use the airspeed input to partially correct for acceleration errors. The unit might behave strangely if it saw accelerations but no airspeed. Thanks for the Dynon report. -- Kevin Horton RV-8 (finishing kit) Ottawa, Canada -- No virus found in this outgoing message. Checked by AVG Anti-Virus. ________________________________ Message 7 _____________________________________ Time: 10:49:19 AM PST US From: "Malcolm Thomson" Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Malcolm Thomson" Bob, I have been given some conflicting information regarding "ground planes" and this post leaves me still more confused about this business of ground planes. I have an airplane which is nearly all carbon. Unlike fiberglass, I am told that all antenna's must be on the outside of the carbon structure just like you would place them on an metal airplane. The basis for this is that "carbon acts like metal and does not let the radio frequencies through". With this said, one might assume then that the carbon will also act as a ground plane but I am also told that it does not. So, do I need to add a ground plane? If so, what would be the approach? Should I install some thin aluminum inside the aircraft, mount the antenna's on the outside, their bolts passing through the carbon and aluminum thereby making the electrical connection to the ground plane? What is the smallest ground plane you'd recommended for a COM antenna and does the antenna have to be mounted in the middle of it? Thanks Malcolm. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Subject: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" --> At 06:35 PM 1/19/2005 +0000, you wrote: >--> AeroElectric-List message posted by: "Steve Sampson" > > >Oops! That was meant to go to aeroelectric > > > -----Original Message----- > > From: Steve Sampson [mailto:Steve@lbho.freeserve.co.uk] > > Sent: 19 January 2005 18:09 > > To: RV Squadron (E-mail) > > Subject: [rvsqn] 1/4 wave groundplane > > > > Bob - I would welcome your comments. > > > > In the bumph the PFA (roughly the British EAA) gives out there is > > some stuff about aerials. It includes...... > > > > "Even some professional radio installers seem to think that if the > > braid of the feeder coax is firmly connected to the metal fuselageat > > the base of the aerial, then it will do the job. Wrong! At any given > > frequency the length of the driven element ...is calculated to be > > resonant as a 1/4 wavelength................................But the > > 'counterpoise' or other half must also be of similar dimensions so > > as to present the trans/rec witha 1/2 wavelength total. The entire > > fuselage however presents no such thing and completely unbalances > > the system................causing a variety of problems, not least > > interference and much degraded performance........ At the base of > > the aerial the braid should also be connected to a tuned groundplane > > either in the form of a down going insulated wire or number of wires > > measuring 5% less in length than the driven > > element..........................It doe not matter that the airframe > > is also connected at its centre..................the oscilating > > pulses in the aerial will choose the resonant path both > > ways........................................." > > > > What is your reaction to this? I have never seen this reccomendation > > before. He seems to be trying to turn a 1/4 wave into a dipole with > > half the aerial inside and half outside. Surely this would cause > > energy to bounce around inside a metal aircraft? The writer is not "wrong" but he's making a mountain out of a molehill. An airplane is not a perfect world for antennas. Further, his concerns for "degraded performance" generally don't surface as significant realities. VHF Comm antennas have been installed on aircraft for over 60 years. Installations range from nearly ideal (antenna sits on large area of metal "radiating" several wavelengths in all directions. 747s and their like make really good airborne antenna farms. As the airplane gets smaller, the real estate for ground plane goes down. As the airplane becomes fabric over tube, opportunities for using existing features on the airplane as a ground plane or "counterpoise" degrades further and ultimately becomes non-existent on the glass-n- plastic machines. Yes, if you went to the antenna range and quantified performance of the various compromise antennas that have flown on ultra-lights through 747s, one could cheer the data plots on the 747 installation and cry in lots of beer over the results of tests for the ultra-light. Let us consider the most compromised antenna of all - the "rubber duckie" common to bizillions of hand held radios ranging from CB frequencies (27 Mhz) to near microwave (wi-fi products at 5 Ghz). NONE of these products are favored with anything like the ideal antenna when it comes to ground planes. Your hand-held vhf comm transceiver not only has a foreshortened antenna (it should be 23.6 inches long), it has only your very small body capacity to couple thorough to approach anything like a useful ground plane. Bottom line for USEFULNESS of ANY antenna installation is whether or not it serves the intended purpose while avoiding interference with other systems (some folks can use the outside-antenna comm transceiver with no problems while hand-held comm with rubber-duck in cockpit drives some panel mounted stuff zonkers). I've often remarked here on the list about the disparity of comments on Bob Archer's wing tip comm antennas (VERY compromised). One user says, "piece of crap" while another says, "greatest thing since sliced bread". Turns out that one guy never needs to talk to stations more than 10 miles away and the other guy was gunching about not hitting an RCO 40 miles away while he was flying 2000 feet above the terrain. We KNOW that a hand-held performs MUCH better plumbed into the ship's external antenna (no matter how compromised) than it does using just a rubber-duck from the cockpit. However, I'm not going to pitch the rubber-ducks on my hand-helds in favor of an "ideal" antenna with an optimal ground plane. This umbrella sized device would be difficult to open and use in the cockpit. All this stuff applies only to resonant, un-amplified antennas that drive low impedance feedlines (50 ohm coax). There's a whole other world of antennas like amplified GPS antennas, loran antennas, ADF antennas, AM antenna on your car, etc. which are e-field receptors and have their own special worlds that do not (indeed some cannot) depend on any kind of resonant counterpoise or ground plane. The writer was perfectly founded in the physics of the ideal antenna structure but appears unaware of the practical realities of antenna compromise that have performed to the degree EXPECTED and ACCEPTED on airplanes of all sizes for for decades. He may be familiar with the efforts that antenna designers expend to get the most from a broadcast or ground based communications antenna where the GOAL is ANTENNA performance. Our goal is to optimize FLIGHT SYSTEM performance wherein most situations will tolerate "degraded" antenna performance. Please feel free to forward this note to the original author and invite him to join us here on the List. Bob . . . ________________________________ Message 8 _____________________________________ Time: 11:34:17 AM PST US From: "Rob Logan" Subject: Re: AeroElectric-List: Re: Odyssey Battery --> AeroElectric-List message posted by: "Rob Logan" > http://www.batterymart.com/c-odyssey.html this lists the PC680 as Length 7 in. Width 3 1/16 in. Height 6 5/8 in. but has a link to http://www.batterymart.com/pdf_files/odyssey_guide.pdf that lists the PC680 as 7.27" 3.11" 6.67" so I'm still confused.... how big is a PC680? will it fit in a box I made for a B&C 16Ah battery? Rob ________________________________ Message 9 _____________________________________ Time: 11:53:33 AM PST US From: "Rob Logan" Subject: Re: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Rob Logan" > What is the smallest ground plane you'd recommended for a COM antenna > and does the antenna have to be mounted in the middle of it? mounted my antennas to the outside carbon, but attached 4 copper radials (striped house wire) to the nut plates... the length of the ground planes isn't nearly as critical as the vertical. what matters is the SWR, or reflected energy back into the radio, this can be adjusted by coax feed length if you can't cut your floxed in radials like me. http://mars.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=22 > The writer is not "wrong" but he's making a mountain out of > a molehill. An airplane is not a perfect world for antennas. 4 radials of "close" size are easy to glass in (3 would work, but more than 4 is overkill) and fine tune SWR with feed length.. no math required... one would notice loss of impedance fuel level converters for 30secs long before the tower asks you to "say again" -Rob ________________________________ Message 10 ____________________________________ Time: 12:01:15 PM PST US From: "Steve Sampson" Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Steve Sampson" Bob - thanks for that. As I thought, theoretically correct but not pragmatic. The story of so much in UK engineering in the last 60 years. Steve. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Robert L. Nuckolls, III Subject: AeroElectric-List: Re: 1/4 wave groundplane? -- No virus found in this outgoing message. Checked by AVG Anti-Virus. ________________________________ Message 11 ____________________________________ Time: 12:07:50 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 11:48 AM 1/20/2005 -0700, you wrote: >--> AeroElectric-List message posted by: "Malcolm Thomson" > > >Bob, I have been given some conflicting information regarding "ground >planes" and this post leaves me still more confused about this business >of ground planes. > >I have an airplane which is nearly all carbon. Unlike fiberglass, I am >told that all antenna's must be on the outside of the carbon structure >just like you would place them on an metal airplane. The basis for this >is that "carbon acts like metal and does not let the radio frequencies >through". Correct . . . > With this said, one might assume then that the carbon will >also act as a ground plane but I am also told that it does not. . . . sorta correct. We tried using carbon fiber as ground plane on several projects and abandoned the idea. It's EASY to add a good ground plane in most cases . . . so why not? >So, do I need to add a ground plane? If so, what would be the approach? >Should I install some thin aluminum inside the aircraft, mount the >antenna's on the outside, their bolts passing through the carbon and >aluminum thereby making the electrical connection to the ground plane? >What is the smallest ground plane you'd recommended for a COM antenna >and does the antenna have to be mounted in the middle of it? The ground plane is easiest to fabricate and install if you cut strips of aluminum or copper foil about 1" wide and 22 inches long. RADIATE minimum of 4, maximum of 8 radials from base of antenna on inside of fuselage. Run along contours. If you have to "hop" over structure or stiffeners, don't change length of material, just run it, secure it with adhesive and let it be. The radials should connect to a common plate under the footprint of the antenna. If you make the plate out of brass and the radials out of brass shim stock, all can be neatly soldered together at the center. On a graphite airplane, a solid pieced of brass shim stock conformed to the inside contours for as far as practical in each direction with a max desired dimension of 22" from base of antenna would be an attractive compromise too. Other antennas are built the same way . . . transponder antennas can use a full circular disk of brass or aluminum, 5.2" in diameter. See chapter on antennas in the 'Connection. Now, if for some reason you can only get three or two radials installed, the thing will probably do just fine anyhow. Antennas on airplanes can be VERY poor compared to the best-we-know-how-to- do and still function adequately. Bob . . . ________________________________ Message 12 ____________________________________ Time: 02:52:10 PM PST US From: "Malcolm Thomson" Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Malcolm Thomson" Bob, how significant is the use of brass vs. aluminum? Thanks. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" --> At 11:48 AM 1/20/2005 -0700, you wrote: >--> AeroElectric-List message posted by: "Malcolm Thomson" > > >Bob, I have been given some conflicting information regarding "ground >planes" and this post leaves me still more confused about this business >of ground planes. > >I have an airplane which is nearly all carbon. Unlike fiberglass, I am >told that all antenna's must be on the outside of the carbon structure >just like you would place them on an metal airplane. The basis for >this is that "carbon acts like metal and does not let the radio >frequencies through". Correct . . . > With this said, one might assume then that the carbon will also act >as a ground plane but I am also told that it does not. . . . sorta correct. We tried using carbon fiber as ground plane on several projects and abandoned the idea. It's EASY to add a good ground plane in most cases . . . so why not? >So, do I need to add a ground plane? If so, what would be the approach? >Should I install some thin aluminum inside the aircraft, mount the >antenna's on the outside, their bolts passing through the carbon and >aluminum thereby making the electrical connection to the ground plane? >What is the smallest ground plane you'd recommended for a COM antenna >and does the antenna have to be mounted in the middle of it? The ground plane is easiest to fabricate and install if you cut strips of aluminum or copper foil about 1" wide and 22 inches long. RADIATE minimum of 4, maximum of 8 radials from base of antenna on inside of fuselage. Run along contours. If you have to "hop" over structure or stiffeners, don't change length of material, just run it, secure it with adhesive and let it be. The radials should connect to a common plate under the footprint of the antenna. If you make the plate out of brass and the radials out of brass shim stock, all can be neatly soldered together at the center. On a graphite airplane, a solid pieced of brass shim stock conformed to the inside contours for as far as practical in each direction with a max desired dimension of 22" from base of antenna would be an attractive compromise too. Other antennas are built the same way . . . transponder antennas can use a full circular disk of brass or aluminum, 5.2" in diameter. See chapter on antennas in the 'Connection. Now, if for some reason you can only get three or two radials installed, the thing will probably do just fine anyhow. Antennas on airplanes can be VERY poor compared to the best-we-know-how-to- do and still function adequately. Bob . . . ________________________________ Message 13 ____________________________________ Time: 02:52:10 PM PST US From: Subject: AeroElectric-List: Switching GPS Data Signals --> AeroElectric-List message posted by: I am currently wiring the panel for my Zodiac 601XL. I am installing a Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I also have on order a Blue Mountain EFIS Lite Gen 3, which has a built in GPS. I would like to be able to use my Garmin 295 and the EFIS Lite to supply the GPS data. Does anyone have any comments on the advisability of using a "2-8" type DPDT switch to change the GPS data in/out from the above two sources? I have no idea if putting the signals through a switch would result in unacceptable signal loss. Tony Graziano Zodiac 601XL; N493TG ________________________________ Message 14 ____________________________________ Time: 06:22:27 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Effects of feedline length on Standing Wave Ratio --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > What is the smallest ground plane you'd recommended for a COM antenna > > and does the antenna have to be mounted in the middle of it? > >mounted my antennas to the outside carbon, but attached 4 >copper radials (striped house wire) to the nut plates... the >length of the ground planes isn't nearly as critical as >the vertical. what matters is the SWR, or reflected energy >back into the radio, this can be adjusted by coax feed >length if you can't cut your floxed in radials like me. >http://mars.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=22 > > > The writer is not "wrong" but he's making a mountain out of > > a molehill. An airplane is not a perfect world for antennas. >4 radials of "close" size are easy to glass in (3 would work, but >more than 4 is overkill) and fine tune SWR with feed length.. no >math required... one would notice loss of impedance fuel level >converters for 30secs long before the tower asks you to "say again" Antenna feedline has no effect on SWR. When SWR is very poor, the transmitter may be HAPPIER attempting to transfer energy to the antenna/feedline system but SWR is SWR is SWR. The PRIMARY effect on SWR is overall length of the radiating element . . . i.e. the antenna itself. SECONDARY effects that stack on top of each other is the sum of the reactances of what purports to be a 'ground plane' combined with any attempts with lumped constant inductors and capacitors to optimize the 1/4-wave antenna feed-point impedance to 50 ohms. It naturally falls close to 35 ohms. It's always a good thing to do an SWR plot of a multi-frequency antenna (COMM runs 118-135 MHz) and see if the SWR is MINIMUM near the center of the range of interest (126.5) and that it doesn't get outrageously high at the ends. SWR of 3:1 is generally quite acceptable. It may be that minimum occurs somewhere OTHER than right in the middle but as long as it's less than 3:1 over the range, the antenna is at least a reasonable LOAD for energies put out by the transmitter. This says NOTHING about the antenna's efficiency as a radiator (and conversely a receptor) of radio frequency energies. One WISHES that the whole 50 ohms impedance of a 1:1 antenna also represents its RADIATION resistance as well. Never quite so. Very sad antennas can have RADIATION resistances in the 1-10 ohm range while the rest is resistive losses. A 50 ohm resistor has an impedance of 50 ohms but a radiation resistor in the milliohms range. This is why they make good "DUMMY LOADS". See: http://www.aeroelectric.com/Pictures/DummyLoad.jpg . . . this is a VERY poor antenna but the transmitter doesn't know it. SWR is 1:1 but it radiates little or nothing. Be very suspicious of any instructions suggesting that you "adjust the length of the feedline for improved matching or reduction of SWR". This is a big red flag that says something is seriously wrong with the design of the antenna and/or feedline system. Bob . . . ________________________________ Message 15 ____________________________________ Time: 06:25:13 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 03:51 PM 1/20/2005 -0700, you wrote: >--> AeroElectric-List message posted by: "Malcolm Thomson" > > >Bob, how significant is the use of brass vs. aluminum? Brass and copper can be soldered to . . . VERY long lived joints. Aluminum is an acceptable performer but must be "fastened" with high pressure methods to achieve and maintain gas-tight joints over the lifetime of the airplane. If you must use aluminum, I'd rivet the radials on. When a rivet swells in the properly sized hole . . . it's about as gas tight as you can get . . . but my personal preference is for copper or brass. I just LUV soldering things together. Bob . . . ________________________________ Message 16 ____________________________________ Time: 06:30:55 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Switching GPS Data Signals --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:50 PM 1/20/2005 -0600, you wrote: >--> AeroElectric-List message posted by: > >I am currently wiring the panel for my Zodiac 601XL. I am installing a >Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for >tracking. I also have on order a Blue Mountain EFIS Lite Gen 3, which has >a built in GPS. I would like to be able to use my Garmin 295 and the EFIS >Lite to supply the GPS data. > >Does anyone have any comments on the advisability of using a "2-8" type >DPDT switch to change the GPS data in/out from the above two sources? I >have no idea if putting the signals through a switch would result in >unacceptable signal loss. Digital signals are essentially "lossless" . . . and dependent on how much LOAD the receiving device places on the transmitting device. My designs are always robust with respect to the transmitter. My gizmos can "talk" to dozens of devices interested in serial data with no degradation. When you have multiple transmitters or sources, then some kind of either-or switching arrangement is in order. Given that most GPS data is one-way (meaning that it's simply spewed out with no regard for how the receiving equipment is accepting it) a simple single pole, two position switch (1-3) should suffice to select between the two sources. All the grounds can run together and the switch used to select which source signal line drives the receivers. Bob . . . ________________________________ Message 17 ____________________________________ Time: 06:54:23 PM PST US From: rv-9a-online Subject: Re: AeroElectric-List: Switching GPS Data Signals --> AeroElectric-List message posted by: rv-9a-online One issue with the Garmin 295 is (I believe) that it's serial output does not put out true-RS-232C signal levels, but rather TTL level signals. Normally, this should not be a problem, but it may may make the GPS serial data signals more susceptible to interference. Level converters are available to fix this, send me an email off-line if you are interested and I'll send you a link. Vern Little, RV-9A tgrazian@bellsouth.net wrote: >--> AeroElectric-List message posted by: > >I am currently wiring the panel for my Zodiac 601XL. I am installing a Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I also have on order a Blue Mountain EFIS Lite Gen 3, which has a built in GPS. I would like to be able to use my Garmin 295 and the EFIS Lite to supply the GPS data. > >Does anyone have any comments on the advisability of using a "2-8" type DPDT switch to change the GPS data in/out from the above two sources? I have no idea if putting the signals through a switch would result in unacceptable signal loss. > >Tony Graziano >Zodiac 601XL; N493TG > > > > ________________________________ Message 18 ____________________________________ Time: 07:04:24 PM PST US From: "Turbo Tom" Subject: AeroElectric-List: Bent whip "radiators" question --> AeroElectric-List message posted by: "Turbo Tom" > > See: http://www.aeroelectric.com/Pictures/DummyLoad.jpg > > . . . this is a VERY poor antenna but the transmitter > doesn't know it. SWR is 1:1 but it radiates little or > nothing. > That was very well-explaned, Bob! The super-low SWR but non-radiator illustration was outstanding. I for one, would like to know just what effects the bending of the typical 1/4-wave whip 'aft' would have on radiation [transmission and reception]. How do those composite streamlined "Commant" [sp] stack up against a straight or bent wire on the bottom of the fuselage of the typical RV? They all seem to work "OK", but do you have an opinion on which is best, or worse. I've seen quite a few bent wires lately that were swept completely aft, and not all that far from the belly. Are there practical differences? One last related question; if the antenna is mounted between the gearlegs, [mine are aluminum] does that have a real-world effect? TT RV-8 ATL GA ________________________________ Message 19 ____________________________________ Time: 07:30:29 PM PST US From: "Brian Kraut" Subject: RE: AeroElectric-List: Switching GPS Data Signals --> AeroElectric-List message posted by: "Brian Kraut" NMEA standard is RS-422, not 232, although it is quite common for devices to put out TTL levels which works fine. RS-422 is much more imune to noise than 232. RS-422 is a differential signal that goes to +5V on a logic 1 and -5V on a logic 0. TTL goes to +5V on a logic 1 and 0V on a logic 0. Since in their infinite wisdom the originators of NMEA decided to use a RS-422 transmitter as standard and an optocoupler as an input in this weird mismatched arrangement the -5V gets clipped to 0V by the optocoupler in the receiver end so it is essentially TTL anyway. Because some transmitters, including the devices I manufacture, use a real RS-422 driver where the A and B signal lines are isolated from ground and some use TTL with a ground reference I recommend using a double pole, double throw toggle switch to switch both sides of the signal simultaneously. The shields can all be tied together. While a single pole switch works almost all of the time, a double pole switch works every time. Some manufacturers also have a shield connection at the receive side of the signal, but it is normally common practice, in marine electronics anyway, to connect the shield only on the transmit side to prevent ground loops. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of rv-9a-online Subject: Re: AeroElectric-List: Switching GPS Data Signals --> AeroElectric-List message posted by: rv-9a-online One issue with the Garmin 295 is (I believe) that it's serial output does not put out true-RS-232C signal levels, but rather TTL level signals. Normally, this should not be a problem, but it may may make the GPS serial data signals more susceptible to interference. Level converters are available to fix this, send me an email off-line if you are interested and I'll send you a link. Vern Little, RV-9A tgrazian@bellsouth.net wrote: >--> AeroElectric-List message posted by: > >I am currently wiring the panel for my Zodiac 601XL. I am installing a Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I also have on order a Blue Mountain EFIS Lite Gen 3, which has a built in GPS. I would like to be able to use my Garmin 295 and the EFIS Lite to supply the GPS data. > >Does anyone have any comments on the advisability of using a "2-8" type DPDT switch to change the GPS data in/out from the above two sources? I have no idea if putting the signals through a switch would result in unacceptable signal loss. > >Tony Graziano >Zodiac 601XL; N493TG > > ________________________________ Message 20 ____________________________________ Time: 08:29:51 PM PST US From: rv-9a-online Subject: Re: AeroElectric-List: Switching GPS Data Signals --> AeroElectric-List message posted by: rv-9a-online The Trio datasheet appears to allow either RS-422 single ended, RS-422 differential, RS-232, or perhaps even TTL inputs. Of these, the most robust would be RS-422 differential, but not many GPS devices provide it. Many devices (Garmin panel units for example) provide RS-232 levels (+/- 10 volts approx), and some (portable GPS) provide TTL levels. Of the last two, the RS-232 level is more noise immune (the marking level of -10V has about 11 volts of noise immunity, the spacing level of +10 volts around 8 volts of noise immunity). TTL levels, or single-ended RS-422 provide about 1 to 2 volts of noise immunity. These are estimates from memory, but you can see that single ended 5 Volt signals are not as robust as RS-232 levels. Differential RS-422 run as a twisted pair with a shield is the best.... but not common. What does this mean to Tony who's head is probably spinning right now? Not too much. Unless you are in a high electrical noise environment you can probably safely ignore the subtleties and just run your wires through the switches. If you have autopilot problems later, this would be one area to investigate, however. Vern Little Brian Kraut wrote: >--> AeroElectric-List message posted by: "Brian Kraut" > >NMEA standard is RS-422, not 232, although it is quite common for devices to >put out TTL levels which works fine. RS-422 is much more imune to noise >than 232. > >RS-422 is a differential signal that goes to +5V on a logic 1 and -5V on a >logic 0. TTL goes to +5V on a logic 1 and 0V on a logic 0. Since in their >infinite wisdom the originators of NMEA decided to use a RS-422 transmitter >as standard and an optocoupler as an input in this weird mismatched >arrangement the -5V gets clipped to 0V by the optocoupler in the receiver >end so it is essentially TTL anyway. > >Because some transmitters, including the devices I manufacture, use a real >RS-422 driver where the A and B signal lines are isolated from ground and >some use TTL with a ground reference I recommend using a double pole, double >throw toggle switch to switch both sides of the signal simultaneously. The >shields can all be tied together. While a single pole switch works almost >all of the time, a double pole switch works every time. > >Some manufacturers also have a shield connection at the receive side of the >signal, but it is normally common practice, in marine electronics anyway, >to connect the shield only on the transmit side to prevent ground loops. > >Brian Kraut >Engineering Alternatives, Inc. >www.engalt.com > >-----Original Message----- >From: owner-aeroelectric-list-server@matronics.com >[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of >rv-9a-online >To: aeroelectric-list@matronics.com >Subject: Re: AeroElectric-List: Switching GPS Data Signals > > >--> AeroElectric-List message posted by: rv-9a-online > > >One issue with the Garmin 295 is (I believe) that it's serial output >does not put out true-RS-232C signal levels, but rather TTL level >signals. Normally, this should not be a problem, but it may may make >the GPS serial data signals more susceptible to interference. Level >converters are available to fix this, send me an email off-line if you >are interested and I'll send you a link. > >Vern Little, RV-9A > >tgrazian@bellsouth.net wrote: > > > >>--> AeroElectric-List message posted by: >> >>I am currently wiring the panel for my Zodiac 601XL. I am installing a >> >> >Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I >also have on order a Blue Mountain EFIS Lite Gen 3, which has a built in >GPS. I would like to be able to use my Garmin 295 and the EFIS Lite to >supply the GPS data. > > >>Does anyone have any comments on the advisability of using a "2-8" type >> >> >DPDT switch to change the GPS data in/out from the above two sources? I >have no idea if putting the signals through a switch would result in >unacceptable signal loss. > > >>Tony Graziano >>Zodiac 601XL; N493TG >> >> >> >> > > > > ________________________________ Message 21 ____________________________________ Time: 09:46:57 PM PST US From: "Mike Holland" Subject: Re: AeroElectric-List: Z13a Pre-flight alt test procedure? --> AeroElectric-List message posted by: "Mike Holland" Bob, I have the SD8, with indicator light and wired per Z13. What problem is there with having both alternators active? If the SD8 will come on-line at idle speed the indicator light would go out and that would indicate it was active without having to shut down the main alternator. If it matters I have Hall effect sensors on both B leads. Thanks