---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 04/23/06: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:33 AM - Re: antenna (Robert Sultzbach) 2. 07:33 AM - Re: antenna (Robert Sultzbach) 3. 07:36 AM - Re: firewall penetrations (Ken) 4. 09:11 AM - Re: firewall penetrations (Eric M. Jones) 5. 10:23 AM - Re: antenna (Robert L. Nuckolls, III) 6. 12:08 PM - Re: antenna (Brian Lloyd) 7. 01:18 PM - Re: Re:Garmin 296 power/battery (Dale Ensing) 8. 01:35 PM - Re: antenna (Robert G. Wright) 9. 01:37 PM - Re: antenna (simon miles) 10. 02:39 PM - Re: antenna (Brian Lloyd) 11. 03:28 PM - Re: antenna (Robert L. Nuckolls, III) 12. 03:53 PM - Re: antenna (Robert L. Nuckolls, III) 13. 09:30 PM - Re: Old Stuff (Mauri Morin) ________________________________ Message 1 _____________________________________ Time: 07:33:50 AM PST US From: Robert Sultzbach Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: Robert Sultzbach --- "Robert G. Wright" wrote: > --> AeroElectric-List message posted by: "Robert G. > Wright" > > On Comant's spec sheets for DME/Transponder > antennae, what is the > significance of "Power RF?" > > > > Rob > > > > > > > browse > Subscriptions page, > FAQ, > http://www.matronics.com/Navigator?AeroElectric-List > > > Admin. > > > > > > > > > > > ________________________________ Message 2 _____________________________________ Time: 07:33:50 AM PST US From: Robert Sultzbach Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: Robert Sultzbach --- "Robert G. Wright" wrote: > --> AeroElectric-List message posted by: "Robert G. > Wright" > > On Comant's spec sheets for DME/Transponder > antennae, what is the > significance of "Power RF?" > > > > Rob > > > > > > > browse > Subscriptions page, > FAQ, > http://www.matronics.com/Navigator?AeroElectric-List > > > Admin. > > > > > > > > > > > ________________________________ Message 3 _____________________________________ Time: 07:36:57 AM PST US From: Ken Subject: Re: AeroElectric-List: firewall penetrations --> AeroElectric-List message posted by: Ken Hi Eric Except for not having magnetos, I have that and more all going through a single firewall opening. More than a hundred wires for dual efi and ignition etc. I preferred two openings but space was tight and one opening turned out to be easier for me. Most low voltage efi sensors are shielded. Power and ground wires such as fuel injector wires or contactor coil feeds are twisted/braided pairs where convenient in accordance with good aeroelectric book wiring practice. All ground wires (except the two firewall to engine ground straps) go through that opening which I think is a good thing. FWIW just this week I investigated the signals with a scope and could find no evidence of crosstalk or problems due to routing everything through the same opening. I had expected to find some magnetic coupling but did not. I even temporarilly rerouted the normally noisy ignition coil feeds (high current pulses with 100 volt or so spikes) but it made no difference to anything that I scoped. Separate subject but the 1994 subaru DIS ignition coils (4 cylinder) are physically one unit with a minor effort to isolate the iron cores a bit. I believe I did see evidence of secondary coupling evidenced by short duration high voltage spikes in the high voltage circuit when the alternate coil fires. Could of been just crosstalk in the spark plug wires but I suspect magnetic coupling at the coils. Ken Erich_Weaver@URSCorp.com wrote: >--> AeroElectric-List message posted by: Erich_Weaver@URSCorp.com > > >Listers: > >Lots of wire hanging around my RV-7A right now, waiting to be tamed. Im >following the Z-13/8 architecture and using a GRT EFIS/EIS. I labeled >items on the Z-13 figure as being either aft or forward of the firewall, >then sorted through the various EFIS/EIS wire call-outs to make a list of >all the wires needing to go through the firewall so I could plan wire paths >a little better: > >1 battery bus to battery contactor >2 battery contactor to the S704-1 relay for the backup alternator >3 battery contactor to main bus >4 master switch to battery contactor >5 push to start switch to starter contactor >6 regulator for back-up alternator to backup alternator (two wires) >7 regulator for main alternator to main alternator >8 left ignition switch to p-mag (two wires) >9 right ignition switch to p-mag (two wires) >10 Groundpower switch to groundpower contactor >11 EIS to CHT(8 wires) >12 EIS to EGT wires (8 wires) >13 EIS to Hall effect current sensor (two wires) >14 Tach (EIS to P-mag) >15 EIS to OAT sensor (not sure where to put OAT sensor yet) >16 EIS to VDO oil pressure sensor >18 EIS to oil temp sensor >19 EIS to fuel pressure sensor (two wires) > >I would like to minimize the number of firewall penetrations. Are any of >the above wires likely to cause problems with any others when bundeled >together? Did I overlook any wires? > >For practical reasons only, Im considering two penetrations for the wires, >one for the various contactor wires near the left side of the firewall, and >the other for everything else, near the center or slightly to the left. > >Any thoughts from those that have been there before would be appreciated > >thanks guys > >Erich Weaver > > >Erich Weaver >URS Corporation >130 Robin Hill Rd >Santa Barbara CA 93117 >805-964-6010 >FAX 805-9640259 > ________________________________ Message 4 _____________________________________ Time: 09:11:10 AM PST US Subject: AeroElectric-List: Re: firewall penetrations From: "Eric M. Jones" --> AeroElectric-List message posted by: "Eric M. Jones" Many times we copy successful methods long after new and better ways of doing things are available. The idiom of firewall penetration devices using leather washers and two crescent-shaped stainless parts came from the days of metal-cowled airplanes and "A petrol-proof flexible tubing at last: an invention of the greatest importance to aviation NACA TM-48 October 1921". The FAA firewall-penetration flame test was designed for metal airplanes and engines where burning was a common hazard. My hunch is that too much attention is paid to this relatively minor task. What might make more sense?--Armored fuel lines, fuel shutoffs, Purple-K; and a flame detector under the cowl. My Glastar instructions include a stainless steel firewall--but it looks like extreme overkill to me. 3M Dot Paper will pass the FAA test and weighs a tiny fraction of stainless steel sheet. Consider fire safety as a complete system. Those towel bar holders and firestop should not be depended upon as the whole solution. -------- Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge, MA 01550 (508) 764-2072 emjones@charter.net Read this topic online here: http://forums.matronics.com/viewtopic.php?p=30164#30164 ________________________________ Message 5 _____________________________________ Time: 10:23:34 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:08 PM 4/22/2006 -0500, you wrote: >--> AeroElectric-List message posted by: "Robert G. Wright" > > >On Comant's spec sheets for DME/Transponder antennae, what is the >significance of "Power RF?" > > >Rob Hmmm . . . seems my reply was truncated. For antennas, there's a design limit for the maximum power you can expect it to handle. For example, a simple DME/Transponder antenna for mounting to the bottom of an airplane could be severely taxed at say 10,000 watts. It could be a current issue where some part of the antenna might be overheating and be damaged (not a problem with DME/Transponder antennas because while PEAK power is perhaps 100-200 watts, the average power is measured in milliwatts. If it's a voltage issue (gaps in construction or capacitors arc over) then peak power is a significant concern irrespective of average power. In any case, a DME/Transponder antenna you purchase for use on an aircraft isn't going to be at-risk for damage by any radio installed for that purpose at the power levels commonly supplied. A 50-ohm antenna accepting 250 watts of power sees peak currents on the order of 2.5 amps and peak voltages on the order of 110 volts. Generally not a big thing in the aviation antenna world. The same company may well make antennas rated in the killowatts where such things are a design challenge. They may have a data sheet format that says "tho shalt put a power rating on thy product" so even the lowly DME/Transponder antenna gets a power rating. This gives rise to the neophyte's dilemma, "Gee, there's a power rating stated for this product I might want to buy for my airplane . . . how and why would I consider this as significant for my buy-decision?" The answer in this case is, "No big deal." 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 6 _____________________________________ Time: 12:08:32 PM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: Brian Lloyd Robert G. Wright wrote: > --> AeroElectric-List message posted by: "Robert G. Wright" > > On Comant's spec sheets for DME/Transponder antennae, what is the > significance of "Power RF?" Transmitting antennas are usually rated for how much transmitter output power they can handle. Remember that transponders and DMEs have transmitters and transmit with peak power levels on the order of 200-300 watts. They transmit in short bursts so that the average power is low but still, the peak voltages and currents are those of the 300W level. This can cause arcing internally to the antenna if it isn't rated for this power level. But if the antenna says it is for a DME or transponder, you are pretty safe using it for that function. -- Brian Lloyd 361 Catterline Way brian-yak at lloyd dot com Folsom, CA 95630 +1.916.367.2131 (voice) +1.270.912.0788 (fax) I fly because it releases my mind from the tyranny of petty things . . . - Antoine de Saint-Exupery ________________________________ Message 7 _____________________________________ Time: 01:18:17 PM PST US From: "Dale Ensing" Subject: Re: AeroElectric-List: Re:Garmin 296 power/battery --> AeroElectric-List message posted by: "Dale Ensing" Thanks Bob, you said "We have three laptops in the family that use L-I batteries for portable use and ALL are used as many hours or more with external power plugged in. None of the instruction manuals suggest that this is a 'bad' thing to do." Bob, The laptop experience is one of the reasons I asked the question. My wife gave me her laptop when she needed to upgrade for her business. She had always used the laptop with external power. When I tried to use the battery I found it now has a very short endurance. Maybe 10 minutes. I know NiCads develope a memory...do L-I also do that? Have tried cycling the L-I but no luck. Dale Ensing do not archive ________________________________ Message 8 _____________________________________ Time: 01:35:14 PM PST US From: "Robert G. Wright" Subject: RE: AeroElectric-List: antenna --> AeroElectric-List message posted by: "Robert G. Wright" Bob, you're so quick on replies, you even beat me to labeling myself the neophyte that I am! I'm just trying to wrap myself around all the info out there on airframe and panel wiring that Revision 11 just can't hold. I'm weighing the desire to do all my own wiring (time and learning) against farming the panel out to $omeone el$e just to have it correct. Too bad there're no avionics seminars around my area for the next foreseeable future.... Rob > >On Comant's spec sheets for DME/Transponder antennae, what is the >significance of "Power RF?" > > >Rob Hmmm . . . seems my reply was truncated. For antennas, there's a design limit for the maximum power you can expect it to handle. For example, a simple DME/Transponder antenna for mounting to the bottom of an airplane could be severely taxed at say 10,000 watts. It could be a current issue where some part of the antenna might be overheating and be damaged (not a problem with DME/Transponder antennas because while PEAK power is perhaps 100-200 watts, the average power is measured in milliwatts. If it's a voltage issue (gaps in construction or capacitors arc over) then peak power is a significant concern irrespective of average power. In any case, a DME/Transponder antenna you purchase for use on an aircraft isn't going to be at-risk for damage by any radio installed for that purpose at the power levels commonly supplied. A 50-ohm antenna accepting 250 watts of power sees peak currents on the order of 2.5 amps and peak voltages on the order of 110 volts. Generally not a big thing in the aviation antenna world. The same company may well make antennas rated in the killowatts where such things are a design challenge. They may have a data sheet format that says "tho shalt put a power rating on thy product" so even the lowly DME/Transponder antenna gets a power rating. This gives rise to the neophyte's dilemma, "Gee, there's a power rating stated for this product I might want to buy for my airplane . . . how and why would I consider this as significant for my buy-decision?" The answer in this case is, "No big deal." 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 9 _____________________________________ Time: 01:37:23 PM PST US From: simon miles Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: simon miles I'm intrigued. Why does a transponder or DME draw such high power? My radio only draws about 5 watts and that seems to work perfectly well - or is the peak draw actually much higher? Simon Miles. Brian Lloyd wrote: > --> AeroElectric-List message posted by: Brian Lloyd > > > > Robert G. Wright wrote: >> --> AeroElectric-List message posted by: "Robert G. Wright" >> >> On Comant's spec sheets for DME/Transponder antennae, what is the >> significance of "Power RF?" > > Transmitting antennas are usually rated for how much transmitter output > power they can handle. Remember that transponders and DMEs have > transmitters and transmit with peak power levels on the order of 200-300 > watts. They transmit in short bursts so that the average power is low > but still, the peak voltages and currents are those of the 300W level. > This can cause arcing internally to the antenna if it isn't rated for > this power level. > > But if the antenna says it is for a DME or transponder, you are pretty > safe using it for that function. > ________________________________ Message 10 ____________________________________ Time: 02:39:10 PM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: Brian Lloyd simon miles wrote: > --> AeroElectric-List message posted by: simon miles > > I'm intrigued. Why does a transponder or DME draw such high power? My > radio only draws about 5 watts and that seems to work perfectly well - > or is the peak draw actually much higher? It doesn't draw high power. It is just that it transmits very short bursts of high power so while the peak power is high, the average power (which is what your power bus has to deliver to the radio) is very low. Think of it this way. It might transmit with 100W for 1/100th of a second every second. The peak power is 100W but the average power is 1W. The durations and rates are different than that in real life but it gives you the idea how it works. -- Brian Lloyd 361 Catterline Way brian-yak at lloyd dot com Folsom, CA 95630 +1.916.367.2131 (voice) +1.270.912.0788 (fax) I fly because it releases my mind from the tyranny of petty things . . . - Antoine de Saint-Exupery ________________________________ Message 11 ____________________________________ Time: 03:28:32 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: antenna --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 03:33 PM 4/23/2006 -0500, you wrote: >--> AeroElectric-List message posted by: "Robert G. Wright" > > >Bob, you're so quick on replies, you even beat me to labeling myself the >neophyte that I am! I'm just trying to wrap myself around all the info out >there on airframe and panel wiring that Revision 11 just can't hold. I'm >weighing the desire to do all my own wiring (time and learning) against >farming the panel out to $omeone el$e just to have it correct. Too bad >there're no avionics seminars around my area for the next foreseeable >future.... We are ALL neophytes at many things. I presume your presence here on the List is search out useful things to apply to your decision making and/or to enhance your abilities to take on new tasks. It's my pleasure and that of many others to share what we've learned toward your goals. Bob . . . ________________________________ Message 12 ____________________________________ Time: 03:53:54 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: antenna --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 08:08 PM 4/23/2006 -0700, you wrote: >--> AeroElectric-List message posted by: Brian Lloyd > > >simon miles wrote: > > --> AeroElectric-List message posted by: simon miles > > > > > I'm intrigued. Why does a transponder or DME draw such high power? My > > radio only draws about 5 watts and that seems to work perfectly well - > > or is the peak draw actually much higher? > >It doesn't draw high power. It is just that it transmits very short >bursts of high power so while the peak power is high, the average power >(which is what your power bus has to deliver to the radio) is very low. > >Think of it this way. It might transmit with 100W for 1/100th of a >second every second. The peak power is 100W but the average power is 1W. >The durations and rates are different than that in real life but it >gives you the idea how it works. Brian nails it. Consider that power is a rate thing and does not consider duration. For example, cruising down the road may require 40-50 horsepower from your engine . . . but how does that translate to energy? To speak of energy, you must consider duration. Driving 500 miles might take ten hours . . . so while the power was 50 h.p., the energy was 500 horsepower-hours. You can have a 100 watt lightbulb on the ceiling that you turn on for one second out of each hour. Peak power is 100 watts, energy is 100/3600 watt-hours or 1/36th of a watt-hour. Your transponder puts out a stream of 0.45 microsecond wide pulses at 100W, or what ever the "power rating" of your transponder is. See http://www.airsport-corp.com/modec.htm The strings happen over a span of 21 uS and repeats several times each time the REPLY light on your transponder lights up. One might say that the AVERAGE power for a reply of all "1" in the bit stream approaches 50 watts . . . but this is still very periodic and even when your're being painted by several radar sites, the average power over say 10 seconds is less than 1 watt which accounts for about 100 millampers of the input power to your transponder . . . the rest being lost in running associated circuitry and losses in the transmitter's high power output stage. Tying this back to the antenna power rating question, knowing that peak power is as much as 200W, the designer might have some voltage issues to consider but from an average power handling perspective, current stresses to the antenna are trivial. Bob . . . ________________________________ Message 13 ____________________________________ Time: 09:30:10 PM PST US From: "Mauri Morin" Subject: Re: AeroElectric-List: Old Stuff --> AeroElectric-List message posted by: "Mauri Morin" How 'bout the one for resistor color stripes????? Bad Boys Rape Our Young Girls But Violet Gives Willingly Black Brown Red Orange Yellow Green Blue Violet Gray White 0 1 2 3 4 5 6 7 8 9 Mauri Morin Polson, MT RV-8 N808M (reserved) C180 N2125Z Flying SEMPER FI