---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 12/24/06: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:44 AM - Daisy-Chaining Stereo Inputs (Mark Chamberlain) 2. 09:39 AM - Re: Daisy-Chaining Stereo Inputs (Robert L. Nuckolls, III) 3. 10:49 AM - Re: Some experiments fail (Robert L. Nuckolls, III) 4. 11:10 AM - Oops! (Robert L. Nuckolls, III) 5. 11:39 AM - Over Voltage (Sally Kilishek) 6. 12:00 PM - Re: Some experiments fail (Robert L. Nuckolls, III) 7. 12:01 PM - Re: Daisy-Chaining Stereo Inputs (Robert L. Nuckolls, III) 8. 12:05 PM - Re: Oops! (Mickey Coggins) 9. 01:14 PM - Back-Up Battery ground (Carlos Trigo) 10. 01:38 PM - Re: Re: Daisy-Chaining Stereo Inputs () 11. 01:55 PM - Re: Oops! (Chuck Jensen) 12. 08:21 PM - Headphone Out connection to Aircraft Mic input (Scott Winn) ________________________________ Message 1 _____________________________________ Time: 04:44:15 AM PST US From: "Mark Chamberlain" Subject: AeroElectric-List: Daisy-Chaining Stereo Inputs Hi All and Happy Christmas! I am trying to get stereo input from multiple sources (MP3, GPS, Traffic etc.) in to my FlightCom 403 intercom. I figured it might work by just "daisy-chaining" them together but if I have more than one plugged it at once I get some sort of nasty feedback. Is there some sort of device I need in between them so they can't "see" each other? Thanks for your help, Mark - N234C Flying - 48 hours ________________________________ Message 2 _____________________________________ Time: 09:39:05 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Daisy-Chaining Stereo Inputs At 05:41 AM 12/24/2006 -0700, you wrote: >Hi All and Happy Christmas! > >I am trying to get stereo input from multiple sources (MP3, GPS, Traffic >etc.) in to my FlightCom 403 intercom. I figured it might work by just >"daisy-chaining" them together but if I have more than one plugged it at >once I get some sort of nasty feedback. Is there some sort of device I >need in between them so they can't "see" each other? > >Thanks for your help, The problem is not so much one of "feedback" as it is for "loading". Each source, while not supplying energy to the signal stream presents a potential for being a load. this means that while one source is being used, it sees multiple loads that may affect both signal intensity and frequency response. MUCH better that you use an isolation (mixing) amplifier if you want to use multiple sources simultaneously or a simple two-pole, three-position switch (like miniature 4-pole, on-on-on switch) for selecting each source one at a time. However, you won't damage anything with the daisy chaining experiment. Give it a try. It might prove satisfactory to your needs . . . it's just not the best we know how to do. Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > --------------------------------------------------------- ________________________________ Message 3 _____________________________________ Time: 10:49:48 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Some experiments fail At 09:28 PM 12/23/2006 -0400, you wrote: > >Harold, > >1. I think that is actually a water drain hole. > >2. If someone did the engineering and flight testing required to use >a static source on a pitot tube, it would be specific to one exact >mounting location and mounting angle on only one type of aircraft. >It wouldn't be practical for Dynon to do the flight testing required >to define a mounting location for each type of aircraft that people >would want to mount this pitot on. Each aircraft type would probably >require at least a dozen hours of flight testing, with mod work >required to move the pitot tube around every two or three flights. >Huge job. There are a number of probes that offer both static and pitot pressure sensing. Obviously, the dynamic portion has an opening on the end and the static portion is generally ported to the external environment through a ring of holes just behind the nose opening. Pitot-Static probes, as you already know, have two fluid fittings instead of one. They are much more difficult to build under the current ice-survival rules. See complex maze of passages JUST to handle ice crystals and ingested moisture for a pitot-only tube at: http://www.aeroelectric.com/Pictures/Pitot_Tube/Pitot_Tube_Heater.jpg It may now be impossible if not simply impractical to combine both functions into a single device. But for non-aviation, precision airflow measurements, combined pitot-static probes are quite common. See: http://www.unitedsensorcorp.com/pitot_frame.html http://www.flowkinetics.com/measurement.htm If I can put my hands on one of the older pitot-static probes I've had laying around here, I'll post some photos. But Kevin is right-on with his observations of the difficulty for achieving acceptable pitot-static measurements in a consumer environment (read repeatable from airplane to airplane and known, stable boundaries on accuracy). You wouldn't believe the hoops we've jumped through to meet the new RVSM (reduced vertical separation minimums) that have effectively doubled the number of over-water airways by stacking airplanes in at twice the old vertical density. Now, one of the really hot items on the pilot's pre-flight inspection is to spit-polish the areas around the pitot static system ports to make sure that no contamination has altered the aircraft's ability to detect and hold an assigned altitude. Even after all the fussing is over and the type-certificate is awarded, few if any systems are perfect. This give rise to the Calibrated Airspeed and Calibrated Altitude differential charts found in many pilot's operating handbooks. Good pitot static measurements become exponentially difficult as your need for accuracy drops below 2 or 3 percent. The pitot static systems installed on our flight test aircraft are big, heavy, and would look really ugly installed on your RV. The J-3 stuck a piece of copper tube out in the breeze ahead of and below the wing. The performance was adequate for that class of airplane and the way it was used. I used to show my renters how to comfortably operate that airplane with the panel completely covered. But as we move up in performance and our demands on knowing the real numbers go up, it can be difficult and expensive to get them all right under all conditions. Bob . . . ________________________________ Message 4 _____________________________________ Time: 11:10:10 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Oops! . . . and you thought failure to drop the wheels on your Bonanza was expensive! See: http://www.zianet.com/tedmorris/dg/bombers4.html Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > --------------------------------------------------------- ________________________________ Message 5 _____________________________________ Time: 11:39:20 AM PST US From: Sally Kilishek Subject: AeroElectric-List: Over Voltage I'm using a generic Ford regulator (Wells VR749) and a B&C OVM-14 overvoltage module wired as per Z-22 in my RV8. It worked fine for a short time, but after about 4 hours of flying, the overvoltage indicator light started flickering. Bus voltage is rising above 15 volts (one time as high as 16 volts), then dropping back below 15 volts and immediately rising again. It looks to me like the regulator isn't regulating and that the OV module is cutting off the field excitation until voltage drops below 15. I've replaced the regulator twice, but the problem continues. Is there somewhere else I should be looking? George N57GK __________________________________________________ ________________________________ Message 6 _____________________________________ Time: 12:00:03 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Some experiments fail At 08:07 PM 12/23/2006 -0500, you wrote: >After 4 hours of fiddling, I was able to drop the SWR to 7.3 by moving the >point where it attaches to the tube. I actually was able to get it to >drop to 1 at one point. I installed a T connector...the antennae on the >leg, the line coming off one side of the top and a 50 ohm termination on >the other side. I don't think that counts though. Sounds like you're attempting to "gamma-match" the mast of your pitot tube as a useful radiator. http://www.vk1od.net/GammaMatch/gamma.htm For this technique to begin to be successful, the overall length of the mast must be close to 1/4 wavelength at the frequency of interest. In the case of comm antennas, let us assume a center frequency of 126 Mhz. So 300/126 yields 2.4 meters for full-wave or .6 meteres for 1/4-wave. In the clumsy system currently favored by the intellectually unwashed, this comes to 23.4 inches. This is the length of pitot tube you need to start with. Now, a Google search of "gamma match" on the 'net will yield a wealth of data on the physics and techniques of gamma matching. In a nutshell, your goal is to attach a 50 ohm feedline to some point along the antenna's length so as to achieve the best match . . . obviously, the antenna's impedance at the base is damned-small-ohms and up in the gazillion-ohms range at the top. SOMEWHERE between the base and the top, we should find the utopian 50 ohm point. Problem is that any conductor you use to run between end of the coax and the physical attach point on the antenna has significant INDUCTANCE at our frequency of interest. This is why all the articles you'll find on gamma-matching will incorporate two variables. Physical attach-point on the radiator and an adjustable capacitance for "series-resonating" the offending inductance and making it disappear. You don't describe the details of your experiment but if you have a better description and perhaps photos to share, we can help you move this exercise forward. Just know that the first essential elements are overall length (at least 1/4 wave), feed point location and inductive reactance elimination by use of variable capacitor. These features go ONLY to achievement of an acceptable standing wave ratio. Once the antenna appears to be efficiently accepting (or delivering) energy, then one can turn to issues of radiation efficiency. Is the polarization optimized? Is the radiation pattern acceptably devoid of performance killing nulls? Is the radiation resistance a significant if not major portion of the antenna total impedance. I've seen antennas with 1:1 swr having impedances of 50 ohms and radiation resistances on the order of 1 ohm . . . the thing gets about 2% of applied energy launched into the ether while the rest is a feeble and inefficient attempt to de-ice the antenna. For those of us who are interested in the simple-ideas that support antenna performance, may I suggest a peek at: http://www2.arrl.org/tis/info/whyantradiates.html Antennas are really interesting pieces of technology and it doesn't take a lot of equipment and even less "black art" to fabricate useful designs. I would only caution that if the goal is to achieve a 1/4 to 1/2-knot more speed by reducing antenna drag on your OBAM aircraft, be aware that the return on investment for the $time$ expended might be disappointingly small. If the goal is to understand more about how these critters work, then your return on investment can be considerably better. Bob . . . ________________________________ Message 7 _____________________________________ Time: 12:01:43 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Daisy-Chaining Stereo Inputs >> >>I am trying to get stereo input from multiple sources (MP3, GPS, Traffic >>etc.) in to my FlightCom 403 intercom. I figured it might work by just >>"daisy-chaining" them together but if I have more than one plugged it at >>once I get some sort of nasty feedback. Is there some sort of device I >>need in between them so they can't "see" each other? >> >>Thanks for your help, > > The problem is not so much one of "feedback" as it is > for "loading". Each source, while not supplying energy > to the signal stream presents a potential for being a load. > this means that while one source is being used, it sees multiple > loads that may affect both signal intensity and frequency > response. MUCH better that you use an isolation (mixing) amplifier > if you want to use multiple sources simultaneously or a simple > two-pole, three-position switch (like miniature 4-pole, on-on-on > switch) for selecting each source one at a time. > > However, you won't damage anything with the daisy chaining > experiment. Give it a try. It might prove satisfactory to your > needs . . . it's just not the best we know how to do. I forgot to add. There's a brief discussion of multiple source audio mixing in the current update chapter to the 'Connection which you're free to download at: http://aeroelectric.com/articles/Rev11/18Audio_R11.pdf Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > --------------------------------------------------------- ________________________________ Message 8 _____________________________________ Time: 12:05:35 PM PST US From: Mickey Coggins Subject: Re: AeroElectric-List: Oops! > > . . . and you thought failure to drop the wheels on your > Bonanza was expensive! See: > > http://www.zianet.com/tedmorris/dg/bombers4.html > Ugh. That's a good way to avoid getting promoted. -- Mickey Coggins http://www.rv8.ch/ #82007 finishing do not archive ________________________________ Message 9 _____________________________________ Time: 01:14:01 PM PST US From: "Carlos Trigo" Subject: AeroElectric-List: Back-Up Battery ground Since I will have to put some wheight in the tail of my RV-9A because of W&B issues, I am planning to install a small battery (probably around 4.5Ah, depending on its own wheight) to act as a back-up battery for some avionics (EFIS and Auto-pilot). For the (+) terminal of that future battery, I already passed a AWG#14 tefzel wire all the way from the tail to the back of instrument pannel, but for the (-) wire, I am thinking that I could attach it to a ground lug that I already have in the tail, which is directly connected to the "Main" battery (-) terminal, and where are also connected the ground wires from the tail light, the tail strobe beacon and the elevator trim motor. Can I connect that battery's (-) terminal to the tail ground lug ? Is there a possibility for ground loop ? Carlos ________________________________ Message 10 ____________________________________ Time: 01:38:20 PM PST US From: Subject: Re: Re: AeroElectric-List: Daisy-Chaining Stereo Inputs > > From: "Robert L. Nuckolls, III" > Date: 2006/12/24 Sun AM 11:37:39 CST > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Daisy-Chaining Stereo Inputs > > > At 05:41 AM 12/24/2006 -0700, you wrote: > > >Hi All and Happy Christmas! > > > >I am trying to get stereo input from multiple sources (MP3, GPS, Traffic > >etc.) in to my FlightCom 403 intercom. I figured it might work by just > >"daisy-chaining" them together but if I have more than one plugged it at > >once I get some sort of nasty feedback. Is there some sort of device I > >need in between them so they can't "see" each other? > > > >Thanks for your help, > > The problem is not so much one of "feedback" as it is > for "loading". Each source, while not supplying energy > to the signal stream presents a potential for being a load. > this means that while one source is being used, it sees multiple > loads that may affect both signal intensity and frequency > response. MUCH better that you use an isolation (mixing) amplifier > if you want to use multiple sources simultaneously or a simple > two-pole, three-position switch (like miniature 4-pole, on-on-on > switch) for selecting each source one at a time. > > However, you won't damage anything with the daisy chaining > experiment. Give it a try. It might prove satisfactory to your > needs . . . it's just not the best we know how to do. > > Bob . . . It might be worthwhile to ask what he means by 'daisychaining'. The most common meaning in my world is plugging one device into the next, then that device into the next, etc. If he's doing that, there might easily be 'feedback' issues depending on how each device handles 'ins' & 'outs'. Charlie ________________________________ Message 11 ____________________________________ Time: 01:55:24 PM PST US Subject: RE: AeroElectric-List: Oops! From: "Chuck Jensen" Voice Recorder... Landing Checklist Complete? Check. Ohhhhh, myyyyy. They obviously need one of those squat switches I have on my Velocity which warns a person when you get slow, and the gear isn't down and locked. I think I'll put that in their suggestion box....I could even fax them a wiring diagram! Chuck Jensen Do Not Archive -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Mickey Coggins Sent: Sunday, December 24, 2006 3:05 PM Subject: Re: AeroElectric-List: Oops! --> > > . . . and you thought failure to drop the wheels on your Bonanza was > expensive! See: > > http://www.zianet.com/tedmorris/dg/bombers4.html > Ugh. That's a good way to avoid getting promoted. -- Mickey Coggins http://www.rv8.ch/ #82007 finishing do not archive ________________________________ Message 12 ____________________________________ Time: 08:21:31 PM PST US From: "Scott Winn" Subject: AeroElectric-List: Headphone Out connection to Aircraft Mic input List, I have an audio 'alert audio' output that is a headphone out with a 3.5mmaudio jack. My intercom doesn't have an audio input, but I do have passenger 3 and passenger 4 mic inputs available since my aircraft is only 2 place. What kind of a circuit would be needed to connect a headphone out to a microphone input on an aviation intercom? I know there is power on the audio line, can it be coupled with an audio transformer to protect the headphone circuit from the DC power? Would additional components be necessary? Has anyone made such a circuit before? I want both the pilot and the co-pilot to hear the alerts, so a Mic input seems like it would work well if it can be adapted. --Scott ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.