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#11
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ELT antenna in composite planes.
A quarter wave with ground plane has a donut pattern with a hole on top. No sir, a vertical dipole has a donut pattern with a hole on the top. A quarter wave with a ground plane has a donut sliced longitudinally (like slicing a bagel for cream cheese) with a hole on the top. Practically zero radiation on the back side of the ground plane. Also, my logic tells me (gain reciprocity notwithstanding) that a ducky radiates better than receives - there is simply not enough antenna surface to collect signal like in a larger antenna. But for ELT transmission is what counts. Oh, my dear Lord. First the man cites the reciprocity property of antennas (which in a hundred years has yet to be disproven) but HIS logic says that a ducky has to transmit better than it hears. Sorry, sir, I want nothing more to do with this conversation. You evidently belong with those geniuses who sell magnets to put in the carburetor to double the gas mileage. Jim |
#12
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ELT antenna in composite planes.
On Oct 31, 7:33 pm, "RST Engineering" wrote:
A quarter wave with ground plane has a donut pattern with a hole on top. No sir, a vertical dipole has a donut pattern with a hole on the top. A quarter wave with a ground plane has a donut sliced longitudinally (like slicing a bagel for cream cheese) with a hole on the top. Practically zero radiation on the back side of the ground plane. Aw comon. Now we are nit picking to win an argument. My main intended point was that it has a hole on top irregardless if its a half or full donut. Also, my logic tells me (gain reciprocity notwithstanding) that a ducky radiates better than receives - there is simply not enough antenna surface to collect signal like in a larger antenna. But for ELT transmission is what counts. Oh, my dear Lord. First the man cites the reciprocity property of antennas (which in a hundred years has yet to be disproven) but HIS logic says that a ducky has to transmit better than it hears. Please take a look at http://en.wikipedia.org/wiki/Radiation_pattern . Reciprocity refers to radiation/reception "pattern" (geometry) being the same and not to total radiation/reception efficiency. The second equation says the total power actually received depends on A(theta,phi) the "effective area or effective aperture of the antenna" for a receiving antenna - i.e. the size of the antenna. A small tuned antenna can send most of its power out (not necessarily directionally) but will receive much less signal than a large antenna simply because it has small receiving area. We are confusing directional gain with RF power transmission efficiency. Sorry, sir, I want nothing more to do with this conversation. You evidently belong with those geniuses who sell magnets to put in the carburetor to double the gas mileage. Why do you have to use insults? If you really don't want to comment just don't. |
#13
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ELT antenna in composite planes.
Cy,
That reminds me. I recently built and tried out the MicroTrak 300 APRS tracker ( .3 watt transmitter) in my aircraft. It managed over 25 miles direct on a ducky. Not bad for transmission. My ducky is about 9" long. My comparison you quoted was more based on comparing the typical aircraft radio "transmission" range and the similar range of the APRS ducky tracker - both are about 5watts, both VHF. It would be interesting to compare an aircraft tuned ducky reception vs transmission range. Maybe I'll do that someday. All I need is a second standard aircraft radio/antenna and a second aircraft to talk to. On Oct 31, 7:32 pm, "Cy Galley" wrote: Your reference that your 5 watt will work out 60 miles. Unfortunately the old style ELT has only a .1 watt transmitter which is 1/50 the output of your example. I do not have the expertise to tell how this will reduce the distance, but I will bet it does curtail the range quite a bit. -- Cy Galley EAA Safety Programs Editor |
#14
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ELT antenna in composite planes.
Because, you stupid imbecile, if you don't get answers to your posts, people
might really believe the bull**** that you are passing on as fact. And then it takes me HUNDREDS of HOURS to tell people why your stuff isn't right. Don't you understand that? Or pass your credentials on as a professional antenna designer and we'll carry this discussion on at a whole different level. Jim Why do you have to use insults? If you really don't want to comment just don't. |
#15
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ELT antenna in composite planes.
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#16
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ELT antenna in composite planes.
Dave,
It was about a couple thousand feet above ground - about what I locally fly. And it was probably more than 60 miles range. Up at 12K msl above Washington state mountains had one digi got me about 100 miles. My rough comparison is with normal radio aircraft reception at say 8000 msl - aircraft to aircraft communication fizzles out about 60? miles. So the ducky isn't bad "transmission" range in direct line of sight situations. But it seems bad in reception. Yeah the current APRS catch is the HAM license. Wish somehow it was easier to get a tracker for GA use. APRS tracking can be a great safety factor. On Oct 31, 10:32 pm, Dave S wrote: wrote: 60 miles coverage on the ground? to what elevation of a receiving antenna? Details.. details.. As for APRS.. while I applaud it, the "catch" is that you have to have a HAM radio licence and ham radio equipment to utilize the existing VHF packet network. Dave |
#18
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ELT antenna in composite planes.
Yeah the current APRS catch is the HAM license. Wish somehow it was easier to get a tracker for GA use. APRS tracking can be a great safety factor. Its not really that difficult, conceptually. Especially when they revise the bandplan to the next narrowing of the bandwidth. Dedicate an aviation channel or two nationwide (I'm sure the band planners can spare ONE or TWO when the next doubling of available frequencies occurs) packet reception. Digipeaters wouldn't really be needed, provided enough igates exist on enough tall towers. If enough aircraft in an area had this, it would also allow tracker equipped aircraft to see OTHER tracker equipped aircraft as a sort of poor man's TIS/TCAS, but the beaconing rate would need to be much faster to support that in real time. There is no monopoly on using APRS on HAM only, and you can put a TNC on theoretically any radio, only infrastructure concerns. Use smart beaconing, so that when traveling straight line, beaconing is minimized, and use corner-pegging logic so that a beaconed datapoint defines when a course change occurs. By setting up a system with smart beaconing you could handle hundreds of beaconing aircraft in an area, with minimal collisions. |
#19
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ELT antenna in composite planes.
One doesn't crash 1000 feet in the air and line of sight is what really
works. That's why they use a satellite which helps immensely when down in the trees and valleys -- Cy Galley EAA Safety Programs Editor Always looking for ideas and articles for EAA Sport Pilot New address - wrote in message ups.com... Dave, It was about a couple thousand feet above ground - about what I locally fly. And it was probably more than 60 miles range. Up at 12K msl above Washington state mountains had one digi got me about 100 miles. My rough comparison is with normal radio aircraft reception at say 8000 msl - aircraft to aircraft communication fizzles out about 60? miles. So the ducky isn't bad "transmission" range in direct line of sight situations. But it seems bad in reception. Yeah the current APRS catch is the HAM license. Wish somehow it was easier to get a tracker for GA use. APRS tracking can be a great safety factor. On Oct 31, 10:32 pm, Dave S wrote: wrote: 60 miles coverage on the ground? to what elevation of a receiving antenna? Details.. details.. As for APRS.. while I applaud it, the "catch" is that you have to have a HAM radio licence and ham radio equipment to utilize the existing VHF packet network. Dave |
#20
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ELT antenna in composite planes.
Cy,
That is assuming the ELT will always work. During a crash the ELT may be destroyed and/or your personal satellite PLB may not go off if you are injured. According to APOA, ELT failure rate is about 27% - not too good, not good for Foster, the man with the satellite signal watch. The 406's failure rate is about 19% - still not too good ( see http://www.montanapilots.org/ ). At 1000 AGL with a 12/1 glide ratio the plane is no more than about two miles from the last point - and you roughly know the direction. But seldom APRS will not get detected at 500 AGL. The standard ($1000+) 406 ELT accuracy is about two miles. A $3000+ 406 will transmit your position to the satellite from your aircraft gps navigation - assuming that your avionics will work after the crash. Hmmm... $1000, $3000??? An APRS tracker is only couple hundred bucks - NO subscription fees. On Nov 5, 9:59 pm, "Cy Galley" wrote: One doesn't crash 1000 feet in the air and line of sight is what really works. That's why they use a satellite which helps immensely when down in the trees and valleys -- Cy Galley EAA Safety Programs Editor Always looking for ideas and articles for EAA Sport Pilot New address - |
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