---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 01/15/14: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:12 AM - Re: ELT Antenna (msmeredith) 2. 05:32 AM - Re: ELT Antenna (msmeredith) 3. 07:09 AM - Re: Re: ELT Antenna (The Kuffels) 4. 10:18 AM - Re: ELT Antenna (msmeredith) 5. 10:51 AM - Re: ELT Antenna (msmeredith) 6. 12:46 PM - Re: Change to Shottky? (Robert L. Nuckolls, III) 7. 01:30 PM - Re: Change to Shottky? (Roger Evenson) 8. 02:53 PM - Re: ELT Antenna (Robert L. Nuckolls, III) 9. 05:32 PM - Re: Re: ELT Antenna (The Kuffels) 10. 06:46 PM - Re: Re: ELT Antenna (Stuart Hutchison) 11. 07:17 PM - Re: Re: ELT Antenna (Kelly McMullen) 12. 07:47 PM - Re: Re: ELT Antenna (Tim Andres) 13. 07:55 PM - Re: Re: ELT Antenna (Kelly McMullen) ________________________________ Message 1 _____________________________________ Time: 05:12:15 AM PST US Subject: AeroElectric-List: Re: ELT Antenna From: "msmeredith" The longer answer involves not only the shielding effect caused by the aluminum but also the feed mismatch, both of which will reduce signal output. But the application is so direct there is no doubt you could be heard by a satellite. If you wish to be sure, build a mock up with foil over cardboard and scrap tubing. See how it works with and without the foil. Don't forget the rules about when and how to test ELTs. Tom Kuffel[/quote] Tom, Good idea. What do I need to measure the output with this mockup? -------- Mark Meredith Super Chipmunk N7DW Read this topic online here: http://forums.matronics.com/viewtopic.php?p=416930#416930 ________________________________ Message 2 _____________________________________ Time: 05:32:14 AM PST US Subject: AeroElectric-List: Re: ELT Antenna From: "msmeredith" stuart(at)stuarthutchison wrote: > I'll be making an > angled mount with fibreglass fairing like a COM antenna for the underside of > my Rocket, since I also have a manual 406 GPS PLB. > Kind regards, Stu > > F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY > www.teamrocketaircraft.com > -- Stu, I've thought about the "impact" of a rollover which is why I added the rollbar. But think I'll stick with an assumption the airplane is still airborne or upright in big pieces if the ELT is ever activated! I have a very small cockpit and don't plan to carry a PLB. There are very few places to put even a portable GPS for trips, so I went with the installed ELT (best I can tell, aircraft has never had one since it was built in 1951). Kannad has an internal antenna also so works without the whip in a handheld mode, though I'd need a screwdriver and a good hand to access it... -------- Mark Meredith Super Chipmunk N7DW Read this topic online here: http://forums.matronics.com/viewtopic.php?p=416931#416931 ________________________________ Message 3 _____________________________________ Time: 07:09:01 AM PST US From: "The Kuffels" Subject: Re: AeroElectric-List: Re: ELT Antenna Mark, << works with and without the foil. .... Good idea. What do I need to measure the output with this mockup? >> The ELT still transmits on 121.5 so any aircraft band hand held will do the job. Most hand helds have a signal strength indicator but a better way (although tedious) is to see how far away (over flat ground) you can hear it without the foil/cardboard. Then try it with the shield. No guarantee it will be just as good at 406MHz but the odds are likely. Or contact a local amateur radio club (find at arrl.org). Many ham UHF hand helds can receive 406MHz. You will easily find a ham who would enjoy helping with your experiment. << But think I'll stick with an assumption the airplane is still airborne or upright in big pieces if the ELT is ever activated! >> My experience suggests this is not a valid assumption. When this is true, the people are ambulatory, can remove the ELT from its mount, attach the portable antenna, or just talk on the aircraft radio. But in most crashes I have seen, if the occupants are badly injured (and so really need an ELT) then most external antennas are no longer working. Carrying a PRB in your pocket might be a good Plan B. If you do run the test, let us know the results. Tom Kuffel ________________________________ Message 4 _____________________________________ Time: 10:18:18 AM PST US Subject: AeroElectric-List: Re: ELT Antenna From: "msmeredith" [quote="kuffel(at)cyberport.net"]Mark, The ELT still transmits on 121.5 so any aircraft band hand held will do the job. Most hand helds have a signal strength indicator but a better way (although tedious) is to see how far away (over flat ground) you can hear it without the foil/cardboard. Then try it with the shield. No guarantee it will be just as good at 406MHz but the odds are likely. Or contact a local amateur radio club (find at arrl.org). Many ham UHF hand helds can receive 406MHz. You will easily find a ham who would enjoy helping with your experiment. > My experience suggests this is not a valid assumption. When this is true, the people are ambulatory, can remove the ELT from its mount, attach the portable antenna, or just talk on the aircraft radio. But in most crashes I have seen, if the occupants are badly injured (and so really need an ELT) then most external antennas are no longer working. Carrying a PRB in your pocket might be a good Plan B. If you do run the test, let us know the results. Tom Kuffel > [b] Tom, Thanks. I'll run the test and let you know. I have some extra .025 alum so will use that for the mockup. -------- Mark Meredith Super Chipmunk N7DW Read this topic online here: http://forums.matronics.com/viewtopic.php?p=416949#416949 ________________________________ Message 5 _____________________________________ Time: 10:51:13 AM PST US Subject: AeroElectric-List: Re: ELT Antenna From: "msmeredith" kuffel(at)cyberport.net wrote: > Mark, > > > > The ELT still transmits on 121.5 so any aircraft band hand held will do the job. Most hand helds have a signal strength indicator but a better way (although tedious) is to see how far away (over flat ground) you can hear it without the foil/cardboard. Then try it with the shield. No guarantee it will be just as good at 406MHz but the odds are likely. > > Or contact a local amateur radio club (find at arrl.org). Many ham UHF hand helds can receive 406MHz. You will easily find a ham who would enjoy helping with your experiment. > > > > > My experience suggests this is not a valid assumption. When this is true, the people are ambulatory, can remove the ELT from its mount, attach the portable antenna, or just talk on the aircraft radio. But in most crashes I have seen, if the occupants are badly injured (and so really need an ELT) then most external antennas are no longer working. Carrying a PRB in your pocket might be a good Plan B. > > If you do run the test, let us know the results. > > Tom Kuffel Tom and other listers, Second thoughts. My bent comm and blade transponder antennas are under the belly amidships behind the wing, close to the ELT transmitter's position above them. If I mount the ELT whip antenna underneath also, can I bend the steel rod beyond the black base so it's shaped similar to my comm antenna? Would I need a large bend radius to prevent it from breaking, and would this affect the transmit functionality? I could move it forward a foot or so (just aft the flaps) to separate it from the comm antennas. I just need to be careful not to tune my radio to 121.5 when testing the ELT. Of course that round antenna base will be a big source of drag, but mounting it underneath would solve the rollover and aesthetic issues. Though now the assumption is the landing gear stay with the airplane! -------- Mark Meredith Super Chipmunk N7DW Read this topic online here: http://forums.matronics.com/viewtopic.php?p=416954#416954 ________________________________ Message 6 _____________________________________ Time: 12:46:33 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Change to Shottky? At 01:20 PM 1/14/2014, you wrote: At Bob's suggestion, I've been looking at double anode - single cathode arrangements in a TO-247 case, wired so that current goes through both diodes. My average amperage will be 6-7 amps (12 to 14 total) and I can find packages that will have voltage drops of 0.3 volts or less. The tradeoff is higher leakage, but I don't see how a few tens of mA will cause problems. With only 4 watts or so, Bob suggested using the aluminum already behind the panel. Even if you don't have enough sheet aluminum, there are light-weight heat sinks for the TO-247 package that only cost a couple of bucks and weigh an ounce or so. The TO-247 does have to be solder connected and mounted with an electrically resistive pad, which adds little to cost or weight. You're not going to find Schottky devices with rated for such low voltage drops at their rated current. To push the drop down, you use oversized to grossly oversized diodes lightly loaded and yes, your drop will go down a tad. The advantage of Schottky diodes is that they have less voltage drop than silicon diodes. Silicon is approx 0.7 volts and Schottky about 0.5 volts. The advantage being that Schottkys dissipate a little less energy. Using your numbers for typical load: Existing diode: P = IE 6 * .7 = 4.2W Schottky diode: 6 * .5 = 3.0W I agree w/ your conclusion, probably not worth changing anything for a delta of 1.2W.' Agreed . . . The only time the diode is 'wasting' energy is when the alternator is running and if you're running a 40A+ alternator, the energy 'savings' is trivial. I wired Z11 with the earlier recommended endurance bus diode w/15 watt heatsink. My loads are 11.5 amps intermittent maximum, 6.1a. typical, and if alternator quits, I could shut things off to get to about 3.3 amps for comfortable endurance use. I see 13.1-13.3 volts on this bus during flight. I have had no issues in 350 hours. That heatsink is WAaayyyy bigger than you need for this application. Since completing my RV in 2010, I have been absent from the aeroelectric list. I have noticed that the Shottky diode is now recommended. It's an OPTION . . . one of several. Did a search to attempt to 'catch up' with the discussion and have tentatively concluded that this change would be purely optional, and not 'highly recommended' for some electrical reason. EXACTLY. I would not recommend anyone swap out an existing rectifier installation. The Schotty devices are attractive for new construction. My product uses the airframe for heat management . . . a bit more compact than the rectifier . . . There are VERY few incarnations of the e-bus that demands a finned heat-sink for the rectifier. Either the silicon junction rectifier -OR- the Schottky device should exist quite happily simply sinked to the airplane. Products like this http://tinyurl.com/mfp9k7a probably make sense in a composite airplane but I suspect that few installations in metal airplanes need the extra heat-sink. I'm on a weight reduction kick, so my only objective to change to the Shottky would only be to eliminate the 1/2 lb. of the heat-sink. 1/2 pound? Which heat-sink are you using? Bob, et al: I'm looking for some assurance. Have I missed something pertinent to this decision or am I on track? Is this a metal airplane? Have you looked at simply bolting the diode to local sheet metal? Bob . . . ________________________________ Message 7 _____________________________________ Time: 01:30:06 PM PST US From: Roger Evenson Subject: Re: AeroElectric-List: Change to Shottky? Bob: To answer your questions, this is an RV7, all metal airplane. The heat sink I used was the 15 watt one, the larger of the two offered at B&C. It weighs 7 oz. I will remove it and install directly to the aluminum subpanel. Would you change your recommendation if you knew I was in Arizona, occasionally flying in 100+ temperatures? Thanks. Roger ----- Original Message ----- From: "Robert L. Nuckolls, III" Sent: Wednesday, January 15, 2014 1:43:39 PM Subject: Re: AeroElectric-List: Change to Shottky? At 01:20 PM 1/14/2014, you wrote: At Bob's suggestion, I've been looking at double anode - single cathode arrangements in a TO-247 case, wired so that current goes through both diodes. My average amperage will be 6-7 amps (12 to 14 total) and I can find packages that will have voltage drops of 0.3 volts or less. The tradeoff is higher leakage, but I don't see how a few tens of mA will cause problems. With only 4 watts or so, Bob suggested using the aluminum already behind the panel. Even if you don't have enough sheet aluminum, there are light-weight heat sinks for the TO-247 package that only cost a couple of bucks and weigh an ounce or so. The TO-247 does have to be solder connected and mounted with an electrically resistive pad, which adds little to cost or weight. You're not going to find Schottky devices with rated for such low voltage drops at their rated current. To push the drop down, you use oversized to grossly oversized diodes lightly loaded and yes, your drop will go down a tad. The advantage of Schottky diodes is that they have less voltage drop than silicon diodes. Silicon is approx 0.7 volts and Schottky about 0.5 volts. The advantage being that Schottkys dissipate a little less energy. Using your numbers for typical load: Existing diode: P = IE 6 * .7 = 4.2W Schottky diode: 6 * .5 = 3.0W I agree w/ your conclusion, probably not worth changing anything for a delta of 1.2W.' Agreed . . . The only time the diode is 'wasting' energy is when the alternator is running and if you're running a 40A+ alternator, the energy 'savings' is trivial. I wired Z11 with the earlier recommended endurance bus diode w/15 watt heatsink. My loads are 11.5 amps intermittent maximum, 6.1a. typical, and if alternator quits, I could shut things off to get to about 3.3 amps for comfortable endurance use. I see 13.1-13.3 volts on this bus during flight. I have had no issues in 350 hours. That heatsink is WAaayyyy bigger than you need for this application. Since completing my RV in 2010, I have been absent from the aeroelectric list. I have noticed that the Shottky diode is now recommended. It's an OPTION . . . one of several. Did a search to attempt to 'catch up' with the discussion and have tentatively concluded that this change would be purely optional, and not 'highly recommended' for some electrical reason. EXACTLY. I would not recommend anyone swap out an existing rectifier installation. The Schotty devices are attractive for new construction. My product uses the airframe for heat management . . . a bit more compact than the rectifier . . . There are VERY few incarnations of the e-bus that demands a finned heat-sink for the rectifier. Either the silicon junction rectifier -OR- the Schottky device should exist quite happily simply sinked to the airplane. Products like this http://tinyurl.com/mfp9k7a probably make sense in a composite airplane but I suspect that few installations in metal airplanes need the extra heat-sink. I'm on a weight reduction kick, so my only objective to change to the Shottky would only be to eliminate the 1/2 lb. of the heat-sink. 1/2 pound? Which heat-sink are you using? Bob, et al: I'm looking for some assurance. Have I missed something pertinent to this decision or am I on track? Is this a metal airplane? Have you looked at simply bolting the diode to local sheet metal? Bob . . . ________________________________ Message 8 _____________________________________ Time: 02:53:30 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: ELT Antenna At 09:04 PM 1/14/2014, you wrote: Hi - I'm installing a Kannad Integra 406AF ELT with built in GPS. The cheapest antenna for this ELT is the whip, which is what I bought with it. The blade/vane for this unit are hundreds/thousands more expensive. But now I'm trying to figure out where to put the whip! It's a monstrosity. I presume you're talking about the AV-200 described in Kannad's manual . . . . http://tinyurl.com/olaccxt This is an unusual Chippy - it's single seat open cockpit, and I installed an 8 foot long turtleback/headrest to conceal a rollover bar behind the rear seat. It's .025 alum, about a foot high/wide at the cockpit then tapering to about 4 inches at the fin. I'd like to mount the antenna 2 feet back on the top of the main fuselage structure, so the rubber part is inside the turtleback, then poke the steel whip out the top through a small hole/grommet. That approach would be unobtrusive, avoid an ugly 2 foot tall antenna with fat black base, and avoid beefing up the turtleback top to support it. My question: would the ELT still be heard with the bottom 8 inches or so of base hidden under .025 alum? Probably not. That "bottom 8" is probably the 406 mHz part of the antenna. Further, given that this product doesn't have a separate GPS antenna, I'm assuming that the single antenna assembly serves the GPS receiver as well. I think you should take pains to install per the manufacturer's recommendations. Bob . . . ________________________________ Message 9 _____________________________________ Time: 05:32:53 PM PST US From: "The Kuffels" Subject: Re: AeroElectric-List: Re: ELT Antenna Mark, << If I mount the ELT whip antenna underneath also >> This is probably the worst location for an ELT antenna. Any kind of brush at an off-airport landing will wipe it off the fuselage. << can I bend the steel rod beyond the black base so it's shaped similar to my comm antenna? >> Don't know why not. << Would I need a large bend radius to prevent it from breaking, >> No idea. If the antenna there is just a steel rod as you say, then bending it around a 1" pipe or so should work. But once again, this is a very bad location. << would this affect the transmit functionality? I could move it forward a foot or so (just aft the flaps) to separate it from the comm antennas. >> The nearness of other VHF antennas will affect performance more than a bend. The above fuselage location has two ground planes of isolation from your Com antenna. Is it time yet to consider making the cover out of fiberglass instead of aluminum? Tom Kuffel ________________________________ Message 10 ____________________________________ Time: 06:46:58 PM PST US From: "Stuart Hutchison" Subject: RE: AeroElectric-List: Re: ELT Antenna The ELT antenna is almost never radiating and when it is activated, COM radio performance is unlikely to be relevant. Bob may be able to confirm, but I believe the ELT antenna proximity to VHF COM antennas can be problematic because radio transmissions have been known to activate the ELT. I acknowledge Mark's comment about the possibility of an underbelly antenna being wiped off, which is why the base of mine will be firmly mounted (midships) angled aft at about 45 deg (rather than bend the whip element) and the fat part faired with fibreglass to minimise/absorb antenna impact damage and or carve a path through the brush/grass. Perhaps different with a tricycle undercarriage, but I can expect the taildragger to be upside down if I land in scrub (with the main wheels so far forward and a heavy engine), so my priority is to have the antenna less shielded by the aircraft when inverted. If it were mounted on top, then it may also wiped off as the aircraft comes to rest inverted or be pinned flat against the ally skin. Preserving the coax link between the transmitter and antenna is a known problem in major crashes, so keep the coax run short, protected and flexible too if possible. Kind regards, Stu F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY www.teamrocketaircraft.com -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The Kuffels Sent: Thursday, January 16, 2014 12:32 PM Subject: Re: AeroElectric-List: Re: ELT Antenna --> Mark, << If I mount the ELT whip antenna underneath also >> This is probably the worst location for an ELT antenna. Any kind of brush at an off-airport landing will wipe it off the fuselage. << can I bend the steel rod beyond the black base so it's shaped similar to my comm antenna? >> Don't know why not. << Would I need a large bend radius to prevent it from breaking, >> No idea. If the antenna there is just a steel rod as you say, then bending it around a 1" pipe or so should work. But once again, this is a very bad location. << would this affect the transmit functionality? I could move it forward a foot or so (just aft the flaps) to separate it from the comm antennas. >> The nearness of other VHF antennas will affect performance more than a bend. The above fuselage location has two ground planes of isolation from your Com antenna. Is it time yet to consider making the cover out of fiberglass instead of aluminum? Tom Kuffel ________________________________ Message 11 ____________________________________ Time: 07:17:52 PM PST US From: Kelly McMullen Subject: Re: AeroElectric-List: Re: ELT Antenna Almost all ELTs, especially the older ones do in fact radiate anytime they are near high powered VHF transmitters in the FM, TV, etc bands. That radiation will in fact severely affect Com radio reception. The antenna for ELT is integral to its TSO so no home brew antennas fullfill the TSO. While I think most DAR's are somewhat tolerant as to antenna placement, most install instructions do call for installation on top of the fuselage, and the install instructions are also part of the TSO approval. So while you may have valid points about final resting of a crash being upside down, during the touchdown, prior to rollout odds are very high that any belly antenna will be wiped off the airframe. IMHO, with about equal experience between tail wheel(mostly off pavement in Alaska) and nose dragging aircraft, in off field landing situations of soft surface, nose wheel is far more likely to cause flipping than tail wheel. Non-compliance with TSO is between you and your DAR, but most discussed here will be at least technical non-compliance. Kelly On 1/15/2014 7:47 PM, Stuart Hutchison wrote: > > The ELT antenna is almost never radiating and when it is activated, COM > radio performance is unlikely to be relevant. Bob may be able to confirm, > but I believe the ELT antenna proximity to VHF COM antennas can be > problematic because radio transmissions have been known to activate the ELT. > > I acknowledge Mark's comment about the possibility of an underbelly antenna > being wiped off, which is why the base of mine will be firmly mounted > (midships) angled aft at about 45 deg (rather than bend the whip element) > and the fat part faired with fibreglass to minimise/absorb antenna impact > damage and or carve a path through the brush/grass. Perhaps different with > a tricycle undercarriage, but I can expect the taildragger to be upside down > if I land in scrub (with the main wheels so far forward and a heavy engine), > so my priority is to have the antenna less shielded by the aircraft when > inverted. If it were mounted on top, then it may also wiped off as the > aircraft comes to rest inverted or be pinned flat against the ally skin. > Preserving the coax link between the transmitter and antenna is a known > problem in major crashes, so keep the coax run short, protected and flexible > too if possible. > > Kind regards, Stu > > F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY > www.teamrocketaircraft.com > > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The > Kuffels > Sent: Thursday, January 16, 2014 12:32 PM > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Re: ELT Antenna > > --> > > Mark, > > << If I mount the ELT whip antenna underneath also >> > > This is probably the worst location for an ELT antenna. Any kind of brush > at an off-airport landing will wipe it off the fuselage. > > << can I bend the steel rod beyond the black base so it's shaped similar to > my comm antenna? >> > > Don't know why not. > > << Would I need a large bend radius to prevent it from breaking, >> > > No idea. If the antenna there is just a steel rod as you say, then bending > it around a 1" pipe or so should work. But once again, this is a very bad > location. > > << would this affect the transmit functionality? I could move it forward a > > foot or so (just aft the flaps) to separate it from the comm antennas. >> > > The nearness of other VHF antennas will affect performance more than a bend. > > The above fuselage location has two ground planes of isolation from your Com > antenna. > > Is it time yet to consider making the cover out of fiberglass instead of > aluminum? > > Tom Kuffel > > ________________________________ Message 12 ____________________________________ Time: 07:47:51 PM PST US Subject: Re: AeroElectric-List: Re: ELT Antenna From: Tim Andres DAR approval not needed as the ELT is not even required unless there are 2 or more seats, or for phase 1 testing. Not saying its wise or will work, but it will not be required to be present for airworthiness. Tim > On Jan 15, 2014, at 7:16 PM, Kelly McMullen wrote: > > > Almost all ELTs, especially the older ones do in fact radiate anytime they are near high powered VHF transmitters in the FM, TV, etc bands. > That radiation will in fact severely affect Com radio reception. > The antenna for ELT is integral to its TSO so no home brew antennas fullfill the TSO. While I think most DAR's are somewhat tolerant as to antenna placement, most install instructions do call for installation on top of the fuselage, and the install instructions are also part of the TSO approval. > So while you may have valid points about final resting of a crash being upside down, during the touchdown, prior to rollout odds are very high that any belly antenna will be wiped off the airframe. IMHO, with about equal experience between tail wheel(mostly off pavement in Alaska) and nose dragging aircraft, in off field landing situations of soft surface, nose wheel is far more likely to cause flipping than tail wheel. > Non-compliance with TSO is between you and your DAR, but most discussed here will be at least technical non-compliance. > Kelly >> On 1/15/2014 7:47 PM, Stuart Hutchison wrote: >> >> The ELT antenna is almost never radiating and when it is activated, COM >> radio performance is unlikely to be relevant. Bob may be able to confirm, >> but I believe the ELT antenna proximity to VHF COM antennas can be >> problematic because radio transmissions have been known to activate the ELT. >> >> I acknowledge Mark's comment about the possibility of an underbelly antenna >> being wiped off, which is why the base of mine will be firmly mounted >> (midships) angled aft at about 45 deg (rather than bend the whip element) >> and the fat part faired with fibreglass to minimise/absorb antenna impact >> damage and or carve a path through the brush/grass. Perhaps different with >> a tricycle undercarriage, but I can expect the taildragger to be upside down >> if I land in scrub (with the main wheels so far forward and a heavy engine), >> so my priority is to have the antenna less shielded by the aircraft when >> inverted. If it were mounted on top, then it may also wiped off as the >> aircraft comes to rest inverted or be pinned flat against the ally skin. >> Preserving the coax link between the transmitter and antenna is a known >> problem in major crashes, so keep the coax run short, protected and flexible >> too if possible. >> >> Kind regards, Stu >> >> F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY >> www.teamrocketaircraft.com >> >> >> >> -----Original Message----- >> From: owner-aeroelectric-list-server@matronics.com >> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The >> Kuffels >> Sent: Thursday, January 16, 2014 12:32 PM >> To: aeroelectric-list@matronics.com >> Subject: Re: AeroElectric-List: Re: ELT Antenna >> >> --> >> >> Mark, >> >> << If I mount the ELT whip antenna underneath also >> >> >> This is probably the worst location for an ELT antenna. Any kind of brush >> at an off-airport landing will wipe it off the fuselage. >> >> << can I bend the steel rod beyond the black base so it's shaped similar to >> my comm antenna? >> >> >> Don't know why not. >> >> << Would I need a large bend radius to prevent it from breaking, >> >> >> No idea. If the antenna there is just a steel rod as you say, then bending >> it around a 1" pipe or so should work. But once again, this is a very bad >> location. >> >> << would this affect the transmit functionality? I could move it forward a >> >> foot or so (just aft the flaps) to separate it from the comm antennas. >> >> >> The nearness of other VHF antennas will affect performance more than a bend. >> >> The above fuselage location has two ground planes of isolation from your Com >> antenna. >> >> Is it time yet to consider making the cover out of fiberglass instead of >> aluminum? >> >> Tom Kuffel > > > > > ________________________________ Message 13 ____________________________________ Time: 07:55:27 PM PST US From: Kelly McMullen Subject: Re: AeroElectric-List: Re: ELT Antenna Agreed if a single seater is all that is involved. On 1/15/2014 8:47 PM, Tim Andres wrote: > > DAR approval not needed as the ELT is not even required unless there are 2 or more seats, or for phase 1 testing. Not saying its wise or will work, but it will not be required to be present for airworthiness. > > Tim > >> On Jan 15, 2014, at 7:16 PM, Kelly McMullen wrote: >> >> >> Almost all ELTs, especially the older ones do in fact radiate anytime they are near high powered VHF transmitters in the FM, TV, etc bands. >> That radiation will in fact severely affect Com radio reception. >> The antenna for ELT is integral to its TSO so no home brew antennas fullfill the TSO. While I think most DAR's are somewhat tolerant as to antenna placement, most install instructions do call for installation on top of the fuselage, and the install instructions are also part of the TSO approval. >> So while you may have valid points about final resting of a crash being upside down, during the touchdown, prior to rollout odds are very high that any belly antenna will be wiped off the airframe. IMHO, with about equal experience between tail wheel(mostly off pavement in Alaska) and nose dragging aircraft, in off field landing situations of soft surface, nose wheel is far more likely to cause flipping than tail wheel. >> Non-compliance with TSO is between you and your DAR, but most discussed here will be at least technical non-compliance. >> Kelly >>> On 1/15/2014 7:47 PM, Stuart Hutchison wrote: >>> >>> The ELT antenna is almost never radiating and when it is activated, COM >>> radio performance is unlikely to be relevant. Bob may be able to confirm, >>> but I believe the ELT antenna proximity to VHF COM antennas can be >>> problematic because radio transmissions have been known to activate the ELT. >>> >>> I acknowledge Mark's comment about the possibility of an underbelly antenna >>> being wiped off, which is why the base of mine will be firmly mounted >>> (midships) angled aft at about 45 deg (rather than bend the whip element) >>> and the fat part faired with fibreglass to minimise/absorb antenna impact >>> damage and or carve a path through the brush/grass. Perhaps different with >>> a tricycle undercarriage, but I can expect the taildragger to be upside down >>> if I land in scrub (with the main wheels so far forward and a heavy engine), >>> so my priority is to have the antenna less shielded by the aircraft when >>> inverted. If it were mounted on top, then it may also wiped off as the >>> aircraft comes to rest inverted or be pinned flat against the ally skin. >>> Preserving the coax link between the transmitter and antenna is a known >>> problem in major crashes, so keep the coax run short, protected and flexible >>> too if possible. >>> >>> Kind regards, Stu >>> >>> F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY >>> www.teamrocketaircraft.com >>> >>> >>> >>> -----Original Message----- >>> From: owner-aeroelectric-list-server@matronics.com >>> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The >>> Kuffels >>> Sent: Thursday, January 16, 2014 12:32 PM >>> To: aeroelectric-list@matronics.com >>> Subject: Re: AeroElectric-List: Re: ELT Antenna >>> >>> --> >>> >>> Mark, >>> >>> << If I mount the ELT whip antenna underneath also >> >>> >>> This is probably the worst location for an ELT antenna. Any kind of brush >>> at an off-airport landing will wipe it off the fuselage. >>> >>> << can I bend the steel rod beyond the black base so it's shaped similar to >>> my comm antenna? >> >>> >>> Don't know why not. >>> >>> << Would I need a large bend radius to prevent it from breaking, >> >>> >>> No idea. If the antenna there is just a steel rod as you say, then bending >>> it around a 1" pipe or so should work. But once again, this is a very bad >>> location. >>> >>> << would this affect the transmit functionality? I could move it forward a >>> >>> foot or so (just aft the flaps) to separate it from the comm antennas. >> >>> >>> The nearness of other VHF antennas will affect performance more than a bend. >>> >>> The above fuselage location has two ground planes of isolation from your Com >>> antenna. >>> >>> Is it time yet to consider making the cover out of fiberglass instead of >>> aluminum? >>> >>> Tom Kuffel >> >> >> >> > > ------------------------------------------------------------------------------------- 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.