---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 01/07/03: 34 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:41 AM - Re: Radio Master Switch (Werner Schneider) 2. 05:39 AM - Re: Trim on e-buss? (willfly) 3. 06:59 AM - Re: 10204 Simpkins (Robert L. Nuckolls, III) 4. 07:05 AM - Re: Trim on e-buss? (Robert L. Nuckolls, III) 5. 07:46 AM - (Gary Casey) 6. 07:46 AM - Avionics Masters (Gary Casey) 7. 08:18 AM - Re: Dual regulator OV protection (David Swartzendruber) 8. 08:27 AM - Re: GPS antenna (Robert L. Nuckolls, III) 9. 08:29 AM - Re: 10198 Clabots (Robert L. Nuckolls, III) 10. 09:29 AM - Re: Antenna Electronics (Robert L. Nuckolls, III) 11. 09:31 AM - Need some help . . . (Robert L. Nuckolls, III) 12. 09:39 AM - Re: Emp wire bundle (Robert L. Nuckolls, III) 13. 10:20 AM - Re: Perm magnet alternator & fuel pump (Robert L. Nuckolls, III) 14. 10:24 AM - Re: Re: AeroElectric-Pulse charger (Robert L. Nuckolls, III) 15. 10:56 AM - Re: Avionics Masters (Walter Casey) 16. 11:02 AM - Re: Antenna Electronics (John Rourke) 17. 11:37 AM - Re: Antenna Electronics (David Lundquist) 18. 11:38 AM - Re: Antenna Electronics (SportAV8R@aol.com) 19. 11:42 AM - Re: Antenna Electronics (Robert L. Nuckolls, III) 20. 11:45 AM - Re: Avionics Masters (Robert L. Nuckolls, III) 21. 11:57 AM - Re: Antenna Electronics (MATTHEW PRATHER) 22. 12:20 PM - Re: Antenna Electronics (Cy Galley) 23. 12:27 PM - Re: Avionics Masters (Cy Galley) 24. 12:47 PM - Re: Antenna Electronics (Rod Kimmell) 25. 01:07 PM - Re: Radio Master Switch (Robert L. Nuckolls, III) 26. 01:13 PM - Good price on battery tester (Robert L. Nuckolls, III) 27. 01:42 PM - Re: Good price on battery tester (BobsV35B@aol.com) 28. 01:55 PM - Dead Dimmer? (John Slade) 29. 06:17 PM - Re: Dead Dimmer? (Robert L. Nuckolls, III) 30. 06:18 PM - Re: Good price on battery tester (Robert L. Nuckolls, III) 31. 06:53 PM - Re: Avionics Masters (Robert L. Nuckolls, III) 32. 06:57 PM - Re: Dead Dimmer? (John Schroeder) 33. 07:19 PM - CESSNA Cardinal NO AVIONICS MASTER (Don Boardman) 34. 07:38 PM - Re: Dead Dimmer? (John Slade) ________________________________ Message 1 _____________________________________ Time: 01:41:51 AM PST US From: "Werner Schneider" Subject: Re: AeroElectric-List: Radio Master Switch --> AeroElectric-List message posted by: "Werner Schneider" > > Yup . . . I've seen it, and others like it for > years. I can't remember if I wrote to this particular > author or not. I used to attempt contact with everyone who > published articles touting the virtues of an avionics > master with respect to protecting radios from airplane > gremlins. My question has always been, "Please identify > for me the source, duration and magnitude of any > transient that might endanger the health and well-being > of any piece of electronics. > . > > Bob . . . > Just started installing my "things" and I have a used Insight engine monitor GEM 602 in the installation instructions (Version 3.0 May 1996) Page 6 .....If the aircraft installation does not include an Avionics Master switch circuit or bus, we recommend that one be installed or a separate switch provided to remove power from the Display during engine starts. Should I really follow the separate switch way (tube display) or just ignore (Bob, do you want the notes in pdf form for asking them =(;o)) Werner (VFR all electric) ________________________________ Message 2 _____________________________________ Time: 05:39:09 AM PST US From: "willfly" Subject: Re: AeroElectric-List: Trim on e-buss? --> AeroElectric-List message posted by: "willfly" I would say the real answer would be determined by the total load you are planning for the E Bus. The heavy load items will be the com/transmitter and transponder. I'm not flying yet but currently have the following on my E Bus; GNC 300XL Nav/Com, GTX 327 transponder, VLM, Elevator Trim, Auto Pilot, AH, DG and EIS system. I plan to limit transponder and com transmissions during E BUS only operation. Steve Glasgow ________________________________ Message 3 _____________________________________ Time: 06:59:57 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: 10204 Simpkins --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > Bob: > >Thanks for your excellent publication and advice. I've been stewing over a >dual-alternator dual-bus Rotax 914 system for a pusher, >and am appalled at how the the hideous current drain of the battery >contactor solenoid eats up the capacity of the standard 914 >generator. Though it would be tolerable for a momentary actuator to have >a high solenoid current, the battery (and crossfeed) contactor is a prime >candidate for improvement. I'm somewhat suprised that with all the >advances in power controllers there isn't a low trigger current (or >voltage) solid-state alternative to the battery contactor. >The only reasons I can think of for this is: > 1. the on resistance is still way too high > 2. the starter currents could fry the solid state contactor > 3. the market is for higher bus voltages > 4. a solid state unit would cost 5 times as much > 5. not enough volume for anybody to be interested >Have you come across a possible replacement, or have you some cautionary >thoughts >on the matter? As you've discovered, such devices exist and have for a number of years. There are high current contactors that use stepped power management to supply fast actuation with low sustaining current but they are not cheap. My question to you is, what features of your load analysis tell you that "power wasteful" contactors are driving your design up to the ragged edge of practicality? What is your second alternator? If it's at least a 40A belt driven machine, then the 18A alternator built onto the back of the Rotax can be treated as if it were an SD-8 or SD-20 pad driven alternator on the back of a Lycoming. You should have gobs of energy to do everything the airplane needs to do an still toss off 20-30 watts for closing less-than-ideal contactors which are more readily acquired and much less expensive. I'd recommend you wire things up using Figure Z-13 where the smaller alternator on the Rotax is used for back-up only. In this configuration, even with dual batteries, the ugly contactors are close only while the big alternator is operating and you have power to burn. If the big alternator is off line, the only relay you need to keep close is the ov protection relay on the smaller alternator which only wastes about 1.5 watts. I will invite you to join us on the AeroElectric List to continue this and similar discussions. It's useful to share the information with as many folks as possible. You can join at . . . http://www.matronics.com/subscribe/ Thanks! Bob . . . |---------------------------------------------------| | A lie can travel half way around the world while | | the truth is till putting on its shoes . . . | | -Mark Twain- | |---------------------------------------------------| ________________________________ Message 4 _____________________________________ Time: 07:05:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Trim on e-buss? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 08:37 AM 1/7/2003 -0500, you wrote: >--> AeroElectric-List message posted by: "willfly" > >I would say the real answer would be determined by the total load you are >planning for the E Bus. The heavy load items will be the com/transmitter >and transponder. > >I'm not flying yet but currently have the following on my E Bus; > >GNC 300XL Nav/Com, GTX 327 transponder, VLM, Elevator Trim, Auto Pilot, >AH, DG and EIS system. I plan to limit transponder and com transmissions >during E BUS only operation. Since you are all electric, do you have a second alternator planned? If you have two alternators, which of the architectures have you selected for wiring things up . . . Z-12, Z-13, or Z-14? Transponder and comm loads are the smallest of loads. The comm in receive mode should be .5A or less, the transponder will run about an amp or so with moderate reply rates. What have you calculated as the total running loads for your present e-bus architecture and why don't you have any lighting and/or turn coordinator on the e-bus? Bob . . . ________________________________ Message 5 _____________________________________ Time: 07:46:15 AM PST US From: "Gary Casey" Subject: AeroElectric-List: --> AeroElectric-List message posted by: "Gary Casey" <> To analyze the situation we need to evaluate all failure modes that would cause an uncommanded full excitation of the alternator field. Yes, I suppose it is possible for the positive side of the field to become shorted to battery voltage, but how would that happen? The wiring is not close to each other, not even internally to the alternator. And if it did short like that any OV system that disconnected the power wouldn't work anyway. If the field had an internal short it would either be a short between windings or a short to ground. In either case the alternator output goes down and doesn't require an over-voltage action. If it did short to ground it presumably will blow the fuse in the field supply, possibly taking the regulator with it. In either case the charging system won't work again until repaired. If the primary regulator had an internal short to ground the fuse will again blow and the secondary regulator would be helpless - still no over-voltage condition. On the other hand, if the voltage regulator sense lead opened, or a number of devices in the regulator failed the regulator output could turn full on, creating an over-voltage. In this case the second regulator would behave as though it were a "proportional" over-voltage module and limit the current to the field. The second regulator should, of course, have a completely independent voltage sense connection. I suppose the failure mode left is a very short duration, single event short to ground, which could cause the output devices in both regulators to fail shorted, but still not blow the in-line fuse. But I think that specific failure mode is very, very rare. Gary Casey ________________________________ Message 6 _____________________________________ Time: 07:46:15 AM PST US From: "Gary Casey" Subject: AeroElectric-List: Avionics Masters --> AeroElectric-List message posted by: "Gary Casey" <> Just as a point of reference, my Cardinal apparently was equipped with an "avionics master relay" which was a normally closed relay between the main buss and the avionics buss. The coil was connected to the starter terminal on the ignition switch so that when the starter was engaged the avionics were turned off. It either only showed up in the service manual, never being installed, or had been removed at some point in its life. Another single point of failure. As far as I can tell there are very minor voltage transients that occur during cranking. The first is when the starter is engaged and the battery voltage takes a virtually instantaneous drop to some lower voltage. During cranking the battery voltage will smoothly rise and fall with each compression stroke, accompanied by a ripple voltage from starter commutator segments. When the starter is released the voltage will step back to a no-load condition, not overshooting. The inductive surge from the starter exists on the STARTER side of the contactor and doesn't exist at the main buss. Car systems shut off some of the electronics during cranking because they only need to shut off the heater blower and the electronics were just hooked to the same switch terminal because it was there. It would be tempting, I suppose, to hook the starter contactor directly to the battery and leave the master off during cranking. But then there would be no way to disconnect the starter if the contactor welded. Gary Casey ________________________________ Message 7 _____________________________________ Time: 08:18:27 AM PST US From: "David Swartzendruber" Subject: AeroElectric-List: RE: Dual regulator OV protection --> AeroElectric-List message posted by: "David Swartzendruber" The failure mode you mention below is one of the ones I was trying to describe. I was not talking about any shorting of the field wire to bus voltage. The other failure mode I was thinking of was shorting of the field winding to itself which would decrease the field resistance, and increase the field current. The pass transistor in the regulator could potentially fail as a result of higher than normal field current, yet not high enough to trip the breaker. You are right about these being somewhat rare, but any OV condition is rare. My preference would be to provide OV protection that didn't have the same failure mode as the regulator. If the regulator is so unreliable that a backup regulator is desired, I would prefer to put it in parallel to the first with the ability to switch between them. Each one would also have OV protection. This still doesn't provide the reliability that one might expect because a fault in the aircraft could take out the first regulator, and then when you switch in the second, it goes too. Also, there are still other single point failures that could take out the alternator system. A second, completely separate alternator system would be my choice if the one alternator, one regulator system was not reliable enough. I believe that one can find a regulator that is as reliable as other parts of the alternator system. Trying to provide redundancy for some components of the system, but not others which are just as likely to fail, seems to be increasing parts count and complexity without the increase in reliability needed to justify it. David Swartzendruber Wichita > I suppose the > failure mode left is a very short duration, single event (or intermittent) short to ground, > which could cause the output devices in both regulators to fail shorted, > but > still not blow the in-line fuse. But I think that specific failure mode > is > very, very rare. > > Gary Casey > ________________________________ Message 8 _____________________________________ Time: 08:27:35 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: GPS antenna --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 11:20 PM 1/3/2003 -0500, you wrote: >--> AeroElectric-List message posted by: j1j2h3@juno.com > >See the current issue of Kitplanes for an article on building an external >GPS antenna. > >Jim Hasper - RV-7 just starting empennage > >Do not archive > > >--> AeroElectric-List message posted by: Whollo80@aol.com > >I'm using a Garmin 90 and sometimes lose coverage on cloudy days. Would >using >one of the externally mounted antennas improve my coverage? Everything >that I >see in Aircraft Spruce is a little bit on the expensive side. Any >thoughts? I've been using GPS antennas from these folk for several years. They have a variety of types including some active (amplified) antennas for as low as $20. http://www.laipac.com/products/gps/GPS%20Active%20Antennas.htm Can't imagine why anyone would want to try and build an antenna at these prices. Bob . . . ________________________________ Message 9 _____________________________________ Time: 08:29:38 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: 10198 Clabots --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 06:59 PM 1/4/2003 -0800, you wrote: >Below is the result of your inquiry. It was submitted by >Gerald Clabots (gclabots@execpc.com) on Saturday, January 4, 2003 at 18:59:39 > >Saturday, January 4, 2003 > >Gerald Clabots > >, >Email: gclabots@execpc.com >Comments/Questions: I plan on ordering you fuse block and fuses, My >question is my pitot tube draws 8.5 amps. Is a 10 amp fuse to small? That >would be 85% of rating. What is a recommended loading of fuses? Pitot heaters are unique in that they have a rather long duration warm-up inrush current. For an 8A pitot heater, I would fuse it at 15A and wire the circuit with 14AWG wire. Every other system in the airplane will be fine with a fuse rated only slightly higher than running current for the device. >Thanks >Gerry Bob . . . |-------------------------------------------------------| | The man who does not read good books has no advantage | | over the man who cannot read them. | | - Mark Twain | |-------------------------------------------------------| ________________________________ Message 10 ____________________________________ Time: 09:29:22 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:37 PM 1/4/2003 -0500, you wrote: >--> AeroElectric-List message posted by: "Duane Bentley" > >Maybe I have some new, defective antennas or I don't understand the >electronics. I've read Bob's chapter on antenna theory, but don't readily >see the answer to my questions. > >I'm installing the various nav & com antennas on my RV6 and decided to do a >continuity check on them before connecting the cables. On the Aeroelectric >transponder antenna, at the connector, the inner pin is insulated from the >outer, and the inner has continuity with the shaft, all as I would expect. > >On my Comant VOR/LOC/GS cat wiskers, the ohm meter says the inner pin and >outer connector are hooked together somewhere inside and have complete >continuity, but the two "whiskers" are insulated from everything. > >The Comant marker beacon antenna also has continuity between the inner pin >and the outer connector shell, but the actual antenna is buried inside the >housing and I can't check that out. > >The bent whip Com antenna is different from the rest. The inner pin and >outer shell are insulated from each other, but there is also no continuity >between the inner pin and the whip. > >So, are the electronics correct, or do I have some defective antenna? As a general rule, antennas cannot always be "tested" with an ohmmeter. Some antennas may have matching networks consisting of various inductors and capacitors that will make continuity measurements confusing or meaningless. Active testing by exciting the antenna with a source at the frequency of interest and measuring resistive and reactive components (SWR) is the only effective means for testing an antenna. As a general rule also, antennas are quite rugged. I cannot recall ever having to replace an antenna that did not suffer some catastrophic damage (collision, lighting stroke, etc). So if your coax feedlines check out, go ahead and stick everything together. If you find performance lacking after every thing is installed, it is MORE likely that you have a problem with a radio but it's easy to test the antenna as installed with test equipment that will be in the possession of every decent avionics shop. Bob . . . ________________________________ Message 11 ____________________________________ Time: 09:31:16 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Need some help . . . --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" We've set a date for the annual weekend seminar in Ft. Worth. It's a rather short coupled date (Mar 22/23). I'd really appreciate it if folks who frequent other list servers would make an announcement for me (assuming list-manager would not dis-approve). Link to the Ft. Worth page is http://www.aeroelectric.com/seminars/Ft.Worth.html Thanks guys . . . Bob . . . |-------------------------------------------------------| | The man who does not read good books has no advantage | | over the man who cannot read them. | | - Mark Twain | |-------------------------------------------------------| ________________________________ Message 12 ____________________________________ Time: 09:39:29 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Emp wire bundle --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 12:02 AM 1/5/2003 -0500, you wrote: >--> AeroElectric-List message posted by: "Larry Bowen" > >I have wire runs going to the empannage area for three things: trim >servo, Pointer ELT, and rudder position/strobe combo light. The ELT and >strobe wires are shielded. (The ELT itself and its antennea are both >beneath the VS.) > >Should there be any problems bundling all three of these wire runs >together? > >- Risks are quite low . . . Bob . . . ________________________________ Message 13 ____________________________________ Time: 10:20:22 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Perm magnet alternator & fuel pump trouble --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:10 AM 1/3/2003 -0500, you wrote: >--> AeroElectric-List message posted by: DHPHKH@aol.com > ><motor coil) may be sensitive to the severe ripple voltage that is present >with the permanent alternators. >> > > Bob, can you expand on the subject of PM alternator ripple? Didn't >realize that, nor the part about an old battery not being able to smooth >things for the system. > > >Thanks >Dan PM alternators in general are single phase devices with an unfiltered ripple voltage equal to full output from the device. 3-phase alternators on the other hand have only about 5% pk-pk ripple after rectification. All of our diagrams show a hefty filter capacitor on each PM alternator installation . . . which should be replaced every 4-5 years. We also recommend periodic battery replacement for the purposes of maintaining both battery capacity and battery filtering effectiveness. Bob . . . ________________________________ Message 14 ____________________________________ Time: 10:24:39 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: AeroElectric-Pulse charger --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 07:02 AM 1/3/2003 -0800, you wrote: >--> AeroElectric-List message posted by: "Jim Robinson" > > >Bob >There was a thread awhile back on battery chargers that helped >desulfonate a battery to prolong it's life. I wonder what was found >out regarding the units. Do they work as stated? Are they worth >buying? any suggestions as to brands/ sources? >Jim Robinson >Glasair 79R I have a sample product that's supposed to recover lost capacity in a battery due to sulfation . . . the limited testing I've been able to conduct haven't been conclusive in support of the claims. I wasn't able to recover a battery that was pulled from service after it failed to start a car . . . I did see some increase in battery capacity for a few cycles of testing. I let the battery sit on the shelf for a month with the de-sulfater installed . . . took it down and attempted to charge and retest . . . battery wouldn't accept any significant charge and it's capacity had dropped to a few percent of new. If it were my airplane, I'd still have to opt for the new-battery-every-year technique for making sure I was carrying the expected reserve capacity. Dave S. You guys were looking at some de-sulfator type products, any new info on that program? Bob . . . ________________________________ Message 15 ____________________________________ Time: 10:56:25 AM PST US Subject: Re: AeroElectric-List: Avionics Masters From: Walter Casey --> AeroElectric-List message posted by: Walter Casey Does anyone remember vacuum tube radios in automobiles. The vacuum tubes required high voltage (over 90V) and to get this voltage the 6V DC had to be converted to AC an run through a transformer. The DC to AC converted was called vibrator and worked like an electric door bell. When you turned on the radio the first thing you heard was the hum of the vibrator. The vibrator was quite prone to failure due to contacts sticking. As I understood it, it was to prevent the contact sticking that the starter button was removed and replaced by the key switch/starter which prevented the radio from being on while the car was started. Old habits die hard. Best wishes, Walter Casey ________________________________ Message 16 ____________________________________ Time: 11:02:03 AM PST US From: John Rourke Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: John Rourke I would agree that an "open circuit" as shown with an ohmmeter is entirely possible in a properly functioning antenna, but if it shows a dead short of 0 ohms from the shielding to the center conductor, I can't think of any way that antenna could function properly. If that is the case, I wouldn't want to initiate any transmission test until the short is found - although I guess today's transceivers can handle that, it still just doesn't sound like a good idea to me. Am I wrong? -John R. P.S.: Other than an RF power/SWR meter, what test equipment ought we to have to run such tests? Robert L. Nuckolls, III wrote: > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > At 09:37 PM 1/4/2003 -0500, you wrote: > >>--> AeroElectric-List message posted by: "Duane Bentley" >> >>Maybe I have some new, defective antennas or I don't understand the >>electronics. I've read Bob's chapter on antenna theory, but don't readily >>see the answer to my questions. >> >>I'm installing the various nav & com antennas on my RV6 and decided to do a >>continuity check on them before connecting the cables. On the Aeroelectric >>transponder antenna, at the connector, the inner pin is insulated from the >>outer, and the inner has continuity with the shaft, all as I would expect. >> >>On my Comant VOR/LOC/GS cat wiskers, the ohm meter says the inner pin and >>outer connector are hooked together somewhere inside and have complete >>continuity, but the two "whiskers" are insulated from everything. >> >>The Comant marker beacon antenna also has continuity between the inner pin >>and the outer connector shell, but the actual antenna is buried inside the >>housing and I can't check that out. >> >>The bent whip Com antenna is different from the rest. The inner pin and >>outer shell are insulated from each other, but there is also no continuity >>between the inner pin and the whip. >> >>So, are the electronics correct, or do I have some defective antenna? > > > As a general rule, antennas cannot always be "tested" with an ohmmeter. > Some antennas may have matching networks consisting of various > inductors and capacitors that will make continuity measurements > confusing or meaningless. Active testing by exciting the antenna > with a source at the frequency of interest and measuring resistive > and reactive components (SWR) is the only effective means for > testing an antenna. > > As a general rule also, antennas are quite rugged. I cannot > recall ever having to replace an antenna that did not suffer > some catastrophic damage (collision, lighting stroke, etc). > So if your coax feedlines check out, go ahead and stick everything > together. If you find performance lacking after every thing is installed, > it is MORE likely that you have a problem with a radio but it's > easy to test the antenna as installed with test equipment that > will be in the possession of every decent avionics shop. > > Bob . . . > > > > > > > > ________________________________ Message 17 ____________________________________ Time: 11:37:11 AM PST US From: "David Lundquist" Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: "David Lundquist" It is entirely possible that a perfectly good antenna can be either open or a dead short when checked with an ohm meter. The ohm meter is only useful if you know what the antenna is supposed to be. Dave Lundquist lundquist@ieee.org ----- Original Message ----- From: "John Rourke" Subject: Re: AeroElectric-List: Antenna Electronics > --> AeroElectric-List message posted by: John Rourke > > I would agree that an "open circuit" as shown with an ohmmeter is > entirely possible in a properly functioning antenna, but if it shows a > dead short of 0 ohms from the shielding to the center conductor, I can't > think of any way that antenna could function properly. > > If that is the case, I wouldn't want to initiate any transmission test > until the short is found - although I guess today's transceivers can > handle that, it still just doesn't sound like a good idea to me. Am I wrong? > > -John R. > > P.S.: Other than an RF power/SWR meter, what test equipment ought we to > have to run such tests? > > > Robert L. Nuckolls, III wrote: > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > > > At 09:37 PM 1/4/2003 -0500, you wrote: > > > >>--> AeroElectric-List message posted by: "Duane Bentley" > >> > >>Maybe I have some new, defective antennas or I don't understand the > >>electronics. I've read Bob's chapter on antenna theory, but don't readily > >>see the answer to my questions. > >> > >>I'm installing the various nav & com antennas on my RV6 and decided to do a > >>continuity check on them before connecting the cables. On the Aeroelectric > >>transponder antenna, at the connector, the inner pin is insulated from the > >>outer, and the inner has continuity with the shaft, all as I would expect. > >> > >>On my Comant VOR/LOC/GS cat wiskers, the ohm meter says the inner pin and > >>outer connector are hooked together somewhere inside and have complete > >>continuity, but the two "whiskers" are insulated from everything. > >> > >>The Comant marker beacon antenna also has continuity between the inner pin > >>and the outer connector shell, but the actual antenna is buried inside the > >>housing and I can't check that out. > >> > >>The bent whip Com antenna is different from the rest. The inner pin and > >>outer shell are insulated from each other, but there is also no continuity > >>between the inner pin and the whip. > >> > >>So, are the electronics correct, or do I have some defective antenna? > > > > > > As a general rule, antennas cannot always be "tested" with an ohmmeter. > > Some antennas may have matching networks consisting of various > > inductors and capacitors that will make continuity measurements > > confusing or meaningless. Active testing by exciting the antenna > > with a source at the frequency of interest and measuring resistive > > and reactive components (SWR) is the only effective means for > > testing an antenna. > > > > As a general rule also, antennas are quite rugged. I cannot > > recall ever having to replace an antenna that did not suffer > > some catastrophic damage (collision, lighting stroke, etc). > > So if your coax feedlines check out, go ahead and stick everything > > together. If you find performance lacking after every thing is installed, > > it is MORE likely that you have a problem with a radio but it's > > easy to test the antenna as installed with test equipment that > > will be in the possession of every decent avionics shop. > > > > Bob . . . > > > > > > > > > > > > > > > > > > ________________________________ Message 18 ____________________________________ Time: 11:38:11 AM PST US From: SportAV8R@aol.com Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: SportAV8R@aol.com In a message dated 01/07/2003 2:02:30 PM Eastern Standard Time, jrourke@allied-computer.com writes: > if it shows a > dead short of 0 ohms from the shielding to the center conductor, I can't > think of any way that antenna could function properly. > I can: balun transformer between feedline and cat-whiskers. The standard arrangement, I believe. Bill B ________________________________ Message 19 ____________________________________ Time: 11:42:00 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 12:57 PM 1/7/2003 -0600, you wrote: >--> AeroElectric-List message posted by: John Rourke > > >I would agree that an "open circuit" as shown with an ohmmeter is >entirely possible in a properly functioning antenna, but if it shows a >dead short of 0 ohms from the shielding to the center conductor, I can't >think of any way that antenna could function properly. There are LOTS of antenna designs that measure zero ohms (or close to it) at the connector that work just fine as an antenna. The ohmmeter is NOT the tool for antenna testing. . . . >If that is the case, I wouldn't want to initiate any transmission test >until the short is found - although I guess today's transceivers can >handle that, it still just doesn't sound like a good idea to me. Am I wrong? > >-John R. > >P.S.: Other than an RF power/SWR meter, what test equipment ought we to >have to run such tests? An SWR meter is good . . . like http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4671&item=1949914808 . . . . or an antenna analyzer like http://www.mfjenterprises.com/products.php?prodid=MFJ-259B is handy. Perhaps your EAA chapter could purchase one and rent/loan it to members. Bob . . . ________________________________ Message 20 ____________________________________ Time: 11:45:47 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Avionics Masters --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 11:54 AM 1/7/2003 -0700, you wrote: >--> AeroElectric-List message posted by: Walter Casey > > >Does anyone remember vacuum tube radios in automobiles. The vacuum >tubes required high voltage (over 90V) and to get this voltage the 6V >DC had to be converted to AC an run through a transformer. The DC to AC >converted was called vibrator and worked like an electric door bell. >When you turned on the radio the first thing you heard was the hum of >the vibrator. The vibrator was quite prone to failure due to contacts >sticking. As I understood it, it was to prevent the contact sticking >that the starter button was removed and replaced by the key >switch/starter which prevented the radio from being on while the car >was started. > >Old habits die hard. My first mobile rig was vibrator power supply powered. Had it installed in a 6-volt, 1941 Pontiac. Here's some more info on this bit of ancient but elegant technology at http://www.geocities.com/vintage_radio/vpwrsup.htm Bob . . . ________________________________ Message 21 ____________________________________ Time: 11:57:33 AM PST US Subject: Re: AeroElectric-List: Antenna Electronics From: "MATTHEW PRATHER" --> AeroElectric-List message posted by: "MATTHEW PRATHER" At the risk of being argumentative, and to somewhat amplify on what Bob said, I believe that an impedance matching balun may be very close to a dc short across its inputs. Check out http://www.kc7nod.20m.com/new_page_1.htm. The reason that doesn't damage a transmitter is that the AC impedance of the inductor will always be greater than the measured DC resistance. What short circuit protection scheme is designed into the output stage of the transmitter shouldn't matter when driving into an inductive load (like a matching transformer). I would imagine that your ADF antenna might look like a DC short because of just such an impedance matcher. This is so because an efficiently sized dipole for lower (ADF) frequencies might be quite large. Not relevant example for transmitter damage, but if you are playing with an ohmeter and your airplane antennas, don't be surprised... Regards, Matt Prather N34RD > --> AeroElectric-List message posted by: John Rourke > > > I would agree that an "open circuit" as shown with an ohmmeter is > entirely possible in a properly functioning antenna, but if it shows a > dead short of 0 ohms from the shielding to the center conductor, I can't > think of any way that antenna could function properly. > > If that is the case, I wouldn't want to initiate any transmission test > until the short is found - although I guess today's transceivers can > handle that, it still just doesn't sound like a good idea to me. Am I > wrong? > > -John R. > > P.S.: Other than an RF power/SWR meter, what test equipment ought we to > have to run such tests? > > > Robert L. Nuckolls, III wrote: >> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" >> >> >> At 09:37 PM 1/4/2003 -0500, you wrote: >> >>>--> AeroElectric-List message posted by: "Duane Bentley" >>> >>> >>>Maybe I have some new, defective antennas or I don't understand the >>> electronics. I've read Bob's chapter on antenna theory, but don't >>> readily see the answer to my questions. >>> >>>I'm installing the various nav & com antennas on my RV6 and decided to >>> do a continuity check on them before connecting the cables. On the >>> Aeroelectric transponder antenna, at the connector, the inner pin is >>> insulated from the outer, and the inner has continuity with the shaft, >>> all as I would expect. >>> >>>On my Comant VOR/LOC/GS cat wiskers, the ohm meter says the inner pin >>> and outer connector are hooked together somewhere inside and have >>> complete continuity, but the two "whiskers" are insulated from >>> everything. >>> >>>The Comant marker beacon antenna also has continuity between the inner >>> pin and the outer connector shell, but the actual antenna is buried >>> inside the housing and I can't check that out. >>> >>>The bent whip Com antenna is different from the rest. The inner pin >>> and outer shell are insulated from each other, but there is also no >>> continuity between the inner pin and the whip. >>> >>>So, are the electronics correct, or do I have some defective antenna? >> >> >> As a general rule, antennas cannot always be "tested" with an >> ohmmeter. Some antennas may have matching networks consisting of >> various inductors and capacitors that will make continuity >> measurements confusing or meaningless. Active testing by exciting >> the antenna with a source at the frequency of interest and >> measuring resistive and reactive components (SWR) is the only >> effective means for testing an antenna. >> >> As a general rule also, antennas are quite rugged. I cannot >> recall ever having to replace an antenna that did not suffer some >> catastrophic damage (collision, lighting stroke, etc). >> So if your coax feedlines check out, go ahead and stick everything >> together. If you find performance lacking after every thing is >> installed, it is MORE likely that you have a problem with a radio >> but it's easy to test the antenna as installed with test equipment >> that will be in the possession of every decent avionics shop. >> >> Bob . . . >> ________________________________ Message 22 ____________________________________ Time: 12:20:44 PM PST US From: "Cy Galley" Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: "Cy Galley" Radio waves are AC and you are measuring DC resistance. ----- Original Message ----- From: "David Lundquist" Subject: Re: AeroElectric-List: Antenna Electronics > --> AeroElectric-List message posted by: "David Lundquist" > > It is entirely possible that a perfectly good antenna can be either open or > a dead short when checked with an ohm meter. The ohm meter is only useful > if you know what the antenna is supposed to be. > > Dave Lundquist > lundquist@ieee.org > > ----- Original Message ----- > From: "John Rourke" > To: > Subject: Re: AeroElectric-List: Antenna Electronics > > > > --> AeroElectric-List message posted by: John Rourke > > > > > I would agree that an "open circuit" as shown with an ohmmeter is > > entirely possible in a properly functioning antenna, but if it shows a > > dead short of 0 ohms from the shielding to the center conductor, I can't > > think of any way that antenna could function properly. > > > > If that is the case, I wouldn't want to initiate any transmission test > > until the short is found - although I guess today's transceivers can > > handle that, it still just doesn't sound like a good idea to me. Am I > wrong? > > > > -John R. > > > > P.S.: Other than an RF power/SWR meter, what test equipment ought we to > > have to run such tests? > > > > > > Robert L. Nuckolls, III wrote: > > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > > > > > > At 09:37 PM 1/4/2003 -0500, you wrote: > > > > > >>--> AeroElectric-List message posted by: "Duane Bentley" > > > >> > > >>Maybe I have some new, defective antennas or I don't understand the > > >>electronics. I've read Bob's chapter on antenna theory, but don't > readily > > >>see the answer to my questions. > > >> > > >>I'm installing the various nav & com antennas on my RV6 and decided to > do a > > >>continuity check on them before connecting the cables. On the > Aeroelectric > > >>transponder antenna, at the connector, the inner pin is insulated from > the > > >>outer, and the inner has continuity with the shaft, all as I would > expect. > > >> > > >>On my Comant VOR/LOC/GS cat wiskers, the ohm meter says the inner pin > and > > >>outer connector are hooked together somewhere inside and have complete > > >>continuity, but the two "whiskers" are insulated from everything. > > >> > > >>The Comant marker beacon antenna also has continuity between the inner > pin > > >>and the outer connector shell, but the actual antenna is buried inside > the > > >>housing and I can't check that out. > > >> > > >>The bent whip Com antenna is different from the rest. The inner pin and > > >>outer shell are insulated from each other, but there is also no > continuity > > >>between the inner pin and the whip. > > >> > > >>So, are the electronics correct, or do I have some defective antenna? > > > > > > > > > As a general rule, antennas cannot always be "tested" with an > ohmmeter. > > > Some antennas may have matching networks consisting of various > > > inductors and capacitors that will make continuity measurements > > > confusing or meaningless. Active testing by exciting the antenna > > > with a source at the frequency of interest and measuring resistive > > > and reactive components (SWR) is the only effective means for > > > testing an antenna. > > > > > > As a general rule also, antennas are quite rugged. I cannot > > > recall ever having to replace an antenna that did not suffer > > > some catastrophic damage (collision, lighting stroke, etc). > > > So if your coax feedlines check out, go ahead and stick everything > > > together. If you find performance lacking after every thing is > installed, > > > it is MORE likely that you have a problem with a radio but it's > > > easy to test the antenna as installed with test equipment that > > > will be in the possession of every decent avionics shop. > > > > > > Bob . . . > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ________________________________ Message 23 ____________________________________ Time: 12:27:20 PM PST US From: "Cy Galley" Subject: Re: AeroElectric-List: Avionics Masters --> AeroElectric-List message posted by: "Cy Galley" What a great site for old radios. Brought back many old memories of my expensive 1948 Buick with the dual point vibrator. Never could get the hash out! Cy Galley, TC - Chair, Emergency Aircraft Repair, Oshkosh Editor, EAA Safety Programs cgalley@qcbc.org or experimenter@eaa.org Always looking for articles for the Experimenter ----- Original Message ----- From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Avionics Masters > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > At 11:54 AM 1/7/2003 -0700, you wrote: > >--> AeroElectric-List message posted by: Walter Casey > > > > > >Does anyone remember vacuum tube radios in automobiles. The vacuum > >tubes required high voltage (over 90V) and to get this voltage the 6V > >DC had to be converted to AC an run through a transformer. The DC to AC > >converted was called vibrator and worked like an electric door bell. > >When you turned on the radio the first thing you heard was the hum of > >the vibrator. The vibrator was quite prone to failure due to contacts > >sticking. As I understood it, it was to prevent the contact sticking > >that the starter button was removed and replaced by the key > >switch/starter which prevented the radio from being on while the car > >was started. > > > >Old habits die hard. > > My first mobile rig was vibrator power supply powered. Had > it installed in a 6-volt, 1941 Pontiac. Here's some more > info on this bit of ancient but elegant technology at > http://www.geocities.com/vintage_radio/vpwrsup.htm > > Bob . . . > > ________________________________ Message 24 ____________________________________ Time: 12:47:58 PM PST US From: "Rod Kimmell" Subject: RE: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: "Rod Kimmell" What looks like a dead short or open to DC current flow on an antenna will look entirely differerent to RF energy whether received or transmitted. Impedance is the AC equivalent of DC resistance and is a combination of resistance, reactance, and frequency. Depending on the antenna design, the DC measurement could be anythings for 0 to infinity. Most VHF/UHF radios, including aircraft, typically expect to see a 50 ohm impedance at the operating frequency. Some antennas have capacitance coupling which would look like an open. Ever wonder how those glass mounted cellular antennas work? Capacitive coupling through the glass. For those interested, any Amateur Radio Relay League Handbook will have more information. Rod -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Cy Galley Subject: Re: AeroElectric-List: Antenna Electronics --> AeroElectric-List message posted by: "Cy Galley" Radio waves are AC and you are measuring DC resistance. ----- Original Message ----- From: "David Lundquist" Subject: Re: AeroElectric-List: Antenna Electronics > --> AeroElectric-List message posted by: "David Lundquist" > > It is entirely possible that a perfectly good antenna can be either > open or > a dead short when checked with an ohm meter. The ohm meter is only > useful if you know what the antenna is supposed to be. > > Dave Lundquist > lundquist@ieee.org > > ----- Original Message ----- > From: "John Rourke" > To: > Subject: Re: AeroElectric-List: Antenna Electronics > > > > --> AeroElectric-List message posted by: John Rourke > > > > > I would agree that an "open circuit" as shown with an ohmmeter is > > entirely possible in a properly functioning antenna, but if it shows > > a dead short of 0 ohms from the shielding to the center conductor, I > > can't think of any way that antenna could function properly. > > > > If that is the case, I wouldn't want to initiate any transmission > > test until the short is found - although I guess today's > > transceivers can handle that, it still just doesn't sound like a > > good idea to me. Am I > wrong? > > > > -John R. > > > > P.S.: Other than an RF power/SWR meter, what test equipment ought we > > to have to run such tests? > > > > > > Robert L. Nuckolls, III wrote: > > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > > > > > > At 09:37 PM 1/4/2003 -0500, you wrote: > > > > > >>--> AeroElectric-List message posted by: "Duane Bentley" > > > >> > > >>Maybe I have some new, defective antennas or I don't understand > > >>the electronics. I've read Bob's chapter on antenna theory, but > > >>don't > readily > > >>see the answer to my questions. > > >> > > >>I'm installing the various nav & com antennas on my RV6 and > > >>decided to > do a > > >>continuity check on them before connecting the cables. On the > Aeroelectric > > >>transponder antenna, at the connector, the inner pin is insulated > > >>from > the > > >>outer, and the inner has continuity with the shaft, all as I > > >>would > expect. > > >> > > >>On my Comant VOR/LOC/GS cat wiskers, the ohm meter says the inner > > >>pin > and > > >>outer connector are hooked together somewhere inside and have > > >>complete continuity, but the two "whiskers" are insulated from > > >>everything. > > >> > > >>The Comant marker beacon antenna also has continuity between the > > >>inner > pin > > >>and the outer connector shell, but the actual antenna is buried > > >>inside > the > > >>housing and I can't check that out. > > >> > > >>The bent whip Com antenna is different from the rest. The inner > > >>pin and > > >>outer shell are insulated from each other, but there is also no > continuity > > >>between the inner pin and the whip. > > >> > > >>So, are the electronics correct, or do I have some defective > > >>antenna? > > > > > > > > > As a general rule, antennas cannot always be "tested" with an > ohmmeter. > > > Some antennas may have matching networks consisting of various > > > inductors and capacitors that will make continuity measurements > > > confusing or meaningless. Active testing by exciting the antenna > > > with a source at the frequency of interest and measuring resistive > > > and reactive components (SWR) is the only effective means for > > > testing an antenna. > > > > > > As a general rule also, antennas are quite rugged. I cannot > > > recall ever having to replace an antenna that did not suffer > > > some catastrophic damage (collision, lighting stroke, etc). > > > So if your coax feedlines check out, go ahead and stick everything > > > together. If you find performance lacking after every thing is > installed, > > > it is MORE likely that you have a problem with a radio but it's > > > easy to test the antenna as installed with test equipment that > > > will be in the possession of every decent avionics shop. > > > > > > Bob . . . > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > direct advertising on the Matronics Forums. ________________________________ Message 25 ____________________________________ Time: 01:07:14 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Radio Master Switch --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 10:40 AM 1/7/2003 +0100, you wrote: >--> AeroElectric-List message posted by: "Werner Schneider" > > > > > > Yup . . . I've seen it, and others like it for > > years. I can't remember if I wrote to this particular > > author or not. I used to attempt contact with everyone who > > published articles touting the virtues of an avionics > > master with respect to protecting radios from airplane > > gremlins. My question has always been, "Please identify > > for me the source, duration and magnitude of any > > transient that might endanger the health and well-being > > of any piece of electronics. > > >. > > > > Bob . . . > > >Just started installing my "things" and I have a used Insight engine monitor >GEM 602 in the installation instructions (Version 3.0 May 1996) Page 6 > > >.....If the aircraft installation does not include an Avionics Master switch >circuit or bus, we recommend that one be installed or a separate switch >provided to remove power from the Display during engine starts. > >Should I really follow the separate switch way (tube display) or just ignore >(Bob, do you want the notes in pdf form for asking them =(;o)) What does Insight say are the consequences of not waiting until after the engine is started to turn on their system? I suspect they've not done their homework on a microcontroller and the thing wanders off into the weeds during brownout. If this is the case, and you want to use the product, put the system on it's own power switch and write a procedure into your manual for keeping it OFF until after the engine is started. Had a builder some years ago find that the display processor on one of his instruments locked up during brownout. He just added a normally closed pushbutton next to the instrument that was in series with the +14V power. After startup, he would hold the button in for a second to interrupt the power and cause the processor to do a normal re-set. Some people put such products on the market thinking they can hide their shortcomings behind somebody else's avionics master switch. The normally closed push-button might be an option for you too . . . you can label Push for WAKE UP Bob . . . ________________________________ Message 26 ____________________________________ Time: 01:13:03 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Good price on battery tester --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" Check out the specials/consignment section of http://www.aeroelectric.com/Catalog/AECcatalog.html Bob . . . |-------------------------------------------------------| | The man who does not read good books has no advantage | | over the man who cannot read them. | | - Mark Twain | |-------------------------------------------------------| ________________________________ Message 27 ____________________________________ Time: 01:42:51 PM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: Good price on battery tester --> AeroElectric-List message posted by: BobsV35B@aol.com In a message dated 1/7/03 3:14:04 PM Central Standard Time, bob.nuckolls@cox.net writes: > Check out the specials/consignment section of > > http://www.aeroelectric.com/Catalog/AECcatalog.html > > Bob . . . > Good Afternoon Bob, The battery tester sounds interesting. Is there anything similar available for twenty-four volt batteries? Happy Skies, Old Bob ________________________________ Message 28 ____________________________________ Time: 01:55:07 PM PST US From: "John Slade" Subject: AeroElectric-List: Dead Dimmer? --> AeroElectric-List message posted by: "John Slade" Bob, My dimmer unit (DIM15-14 - came with the gooseneck light) seems to have died. It gets hot, but doesnt light the lights. I had this problem a few weeks ago, but it came back on. Last week I connected one of the dimmer output's to the LEDs which light up my fuel sight guages. It worked fine, but now it's acting up again. Any suggestions? John Slade Cozy IV #757 ________________________________ Message 29 ____________________________________ Time: 06:17:43 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Dead Dimmer? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:52 PM 1/7/2003 -0500, you wrote: >--> AeroElectric-List message posted by: "John Slade" > >Bob, >My dimmer unit (DIM15-14 - came with the gooseneck light) seems to have >died. It gets hot, but doesnt light the lights. I had this problem a few >weeks ago, but it came back on. Last week I connected one of the dimmer >output's to the LEDs which light up my fuel sight guages. It worked fine, >but now it's acting up again. >Any suggestions? >John Slade >Cozy IV #757 If the dimmer is getting hot but the light doesn't light up, then there is most likely a short circuit that is causing the dimmer to go into thermal shutdown. The short would have to be in wiring between the dimmer and the lamp fixture or in the fixture itself. Bob . . . ________________________________ Message 30 ____________________________________ Time: 06:18:05 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Good price on battery tester --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:40 PM 1/7/2003 -0500, you wrote: >--> AeroElectric-List message posted by: BobsV35B@aol.com > >In a message dated 1/7/03 3:14:04 PM Central Standard Time, >bob.nuckolls@cox.net writes: > > > Check out the specials/consignment section of > > > > http://www.aeroelectric.com/Catalog/AECcatalog.html > > > > Bob . . . > > > >Good Afternoon Bob, > >The battery tester sounds interesting. Is there anything similar available >for twenty-four volt batteries? > >Happy Skies, > >Old Bob Somebody probably makes one for commercial aviation and military applications but you can bet it wouldn't be a $240 device. I'm not aware of any specific products I can guide you toward . . . Bob . . . ________________________________ Message 31 ____________________________________ Time: 06:53:50 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Avionics Masters --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 07:42 AM 1/7/2003 -0800, you wrote: >--> AeroElectric-List message posted by: "Gary Casey" > >< we thought we had a good reason . . . . over the years > the reasoning, experience and technology upon which > the decision was made are long since gone the way of > the buggy whip. > > Bob . . . >> > >Just as a point of reference, my Cardinal apparently was equipped with an >"avionics master relay" which was a normally closed relay between the main >buss and the avionics buss. The coil was connected to the starter terminal >on the ignition switch so that when the starter was engaged the avionics >were turned off. It either only showed up in the service manual, never >being installed, or had been removed at some point in its life. Another >single point of failure. > >As far as I can tell there are very minor voltage transients that occur >during cranking. The first is when the starter is engaged and the battery >voltage takes a virtually instantaneous drop to some lower voltage. During >cranking the battery voltage will smoothly rise and fall with each >compression stroke, accompanied by a ripple voltage from starter commutator >segments. When the starter is released the voltage will step back to a >no-load condition, not overshooting. The inductive surge from the starter >exists on the STARTER side of the contactor and doesn't exist at the main >buss. Car systems shut off some of the electronics during cranking because >they only need to shut off the heater blower and the electronics were just >hooked to the same switch terminal because it was there. > >It would be tempting, I suppose, to hook the starter contactor directly to >the battery and leave the master off during cranking. But then there would >be no way to disconnect the starter if the contactor welded. > >Gary Casey I've had data acquisition systems tied to perhaps 30 different airplanes over the years to look for voltage aberrations. Early explorations were with relatively slow chart recorders. Later measurements used 8000 sample/second data acquisition adapters on a computer. I've never been able to catch a killer starting transient in the wild . . . During contactor bounce, there are some short fuzzy spikes of very low energy content when measured at the bus. If there are any capacitors on the input circuits to powered devices, these little fellers disappear completely. the next most noted artifact is battery voltage at starter inrush current levels that typically pulls the battery down to 6 volts or so for about 2 milliseconds. It rises quickly as the motor begins to turn an passes 8 volts in about 10 milliseconds. After the engine starts and the starter is released, there are no significant transients when the contactor opens. Some folks call the inrush artifact a "spike" and indeed on the oscilloscope, it's pretty pointy . . . but it's relatively long compared to the kinds of real spikes that used to trip our ov modules by a factor of 50 or more. Further, the negative going excursion stays inside the range of voltages any device should expect to see in normal operations . . . zero to 15 volts. I prefer to call it a perfectly acceptable and expected effect of hitting the battery with a 1000A inrush transient and as such should not be a threat to ANY other part of the airplane. DO-160 says so too . . . Bob . . . ________________________________ Message 32 ____________________________________ Time: 06:57:43 PM PST US From: John Schroeder Subject: Re: AeroElectric-List: Dead Dimmer? --> AeroElectric-List message posted by: John Schroeder Bob . . . John Slade mentioned that he can run LED's with the dimmer on your gooseneck lamp. Does the lamp have a LED or LED's? Can you run more than one light off of the dimmer? Thanks, John Schroeder >>My dimmer unit (DIM15-14 - came with the gooseneck light) seems to have >>died. It gets hot, but doesnt light the lights. I had this problem a few >>weeks ago, but it came back on. Last week I connected one of the dimmer >>output's to the LEDs which light up my fuel sight guages. It worked fine, >>but now it's acting up again. > If the dimmer is getting hot but the light doesn't light > ... .> > Bob . . . > > ________________________________ Message 33 ____________________________________ Time: 07:19:52 PM PST US Subject: AeroElectric-List: CESSNA Cardinal NO AVIONICS MASTER From: Don Boardman --> AeroElectric-List message posted by: Don Boardman Hi all, Funny thing, if Cessna put an avionics master in 100,000 airplanes they must have missed my 1971 Cardinal RG ... or maybe this model was supposed to be ahead of it's time? Starting to wire my Murphy Moose soon and I think I will follow Cessna's lead and leave out the avionics master! Bob, I may be bugging you in the near future with some questions as I proceed with my dual alt and single bat system. Thanks for all the generosity you apply to this list, Regards, Don Boardman & Partner, Randy Bowers Murphy Moose #130 M-14PF 400HP, MT-prop, Aerocet 3500 amphibs, Rome, NY ________________________________ Message 34 ____________________________________ Time: 07:38:48 PM PST US From: "John Slade" Subject: RE: AeroElectric-List: Dead Dimmer? --> AeroElectric-List message posted by: "John Slade" > Does the lamp have a LED or LED's? No. Its a very low wattage bulb. > Can you run more than one light off of the dimmer? Bob may give you a more complete answer but yes, you can run any number of LED's off the dimmer. It has five outputs. I use one for the fuel gauges, one for the transponder / radio lights, one for the panel lights and one for the goose neck light. I still have a spare output. My only complaint, other than the fact that it aint working right now, is that it doesnt dim down far enough. Off to check my wiring. John Slade