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Help with Student Project.
I've voulenteered to help the SDSU mechanical engineering studens get
telemetry from their rocket see: http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. I have all the electronics working, I'm using a commercial 910Mhz telemetry radio, I have every thing working except the antenna. For the last launch I burred a dipole in the plywood fin, alas the rocket did not launch it caught fire and burned up the fins. (It did not burn as far as the electronics.) The new fins are carbon fiber composite so no antenna there... The rocket will get to mach 2 so small wires sticking out will probably break or burn up. I have enough power and ground side gain that I need no gain from the rocket, an isotropic radiator with 3db of loss would be fine. Any suggestions? My ideas and thoughts: 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket near the engine. Pros: simple. Cons: lots of metal to block the signal and mess up the pattern. Not clear if the ionized exhaust will block the signal. Antenna pattern is almost exactly wrong. (Telemetry really needed for recovery tracking so ionization fading is not a deal killer) 2)Horizontal dipole at the bottom plate of engine. All the problems of #1 except pattern. 3)Put Fiberglass windows in the electronics bay near the nose of the rocket. One window on each side, Driving two hosrizontal dipoles with a power splitter, one dipole on each side. Pros: Easy to do. Cons: I don't know what the pattern would be like, or exactly how I shoudl phase the two antennas on opposite sides. (Some metal between then so not a clean situation.) Resources: It have a minicircuits SMA 2 way power splitter, and can make precise metal parts (0.002" or better). I do not have any antenna testing equipment that is any good at 900Mhz. so any suggestions... Paul (Kl7JG) |
Wonder if the rocket body is tall enough to tape thin wires
to the sides for a dipole, or 1/4 wave... IE: a dipole for 910 mhz would be about 6.1 inches or so...3.05 inches per leg of the dipole, if center fed...Seems you could wrap the thin 3 inch legs around the rocket body, and make a "circle" dipole of sorts...You could stagger the ends, so they aren't close together, or you could even run it vertical...Magnet wire would be ok, if you could get some strong tape, glue, epoxy, silicone, etc, to stick it to the body...The "bump" on the body wouldn't be that drastic I don't think, but you'd have to talk to your rocket guys about that....MK |
Good Lord, forget the power splitter and all the rest of that stuff. Find a
place on the rocket that you can have a simple copper foil dipole fed with a coax "split tube balun". You need more info on how to do that? Just post here and I'll do what I can. Jim Weir SDSU Class of '67 |
Your question is interesting, mach II, wow!
I found this page, it deals with models constructed of carbon fiber--and their worries about it affecting antenna/signals: http://www.rcuniverse.com/forum/carb...2747045/tm.htm A guy or two there have claimed to have done some tests, how relevant these are to you, you will have to discern.... If their claims are correct, and operation of an antenna around, under or near carbon fiber is possible--how about copper foil tape on the fins--under a gelcoat??? Just an idea.... Warmest regards, John wrote in message ... | I've voulenteered to help the SDSU mechanical engineering studens get | telemetry from their rocket see: | http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. | | I have all the electronics working, I'm using a commercial 910Mhz | telemetry radio, I have every thing working except the antenna. | | For the last launch I burred a dipole in the plywood fin, alas | the rocket did not launch it caught fire and burned up the fins. | (It did not burn as far as the electronics.) | | The new fins are carbon fiber composite so no antenna there... | | The rocket will get to mach 2 so small wires sticking out will | probably break or burn up. | | | I have enough power and ground side gain that I need no gain | from the rocket, an isotropic radiator with 3db of loss would be fine. | | | Any suggestions? | | | My ideas and thoughts: | | 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket | near the engine. | | Pros: | simple. | Cons: | lots of metal to block the signal and mess up the pattern. | Not clear if the ionized exhaust will block the signal. | Antenna pattern is almost exactly wrong. | | (Telemetry really needed for recovery tracking so ionization fading is | not a deal killer) | | | 2)Horizontal dipole at the bottom plate of engine. | All the problems of #1 except pattern. | | | | | 3)Put Fiberglass windows in the electronics bay near the nose of the | rocket. One window on each side, Driving two hosrizontal dipoles with | a power splitter, one dipole on each side. | | Pros: Easy to do. | Cons: | I don't know what the pattern would be like, or exactly how I shoudl | phase the two antennas on opposite sides. (Some metal between then so | not a clean situation.) | | Resources: | It have a minicircuits SMA 2 way power splitter, and can make precise | metal parts (0.002" or better). | I do not have any antenna testing equipment that is any good at | 900Mhz. | so any suggestions... | | | Paul (Kl7JG) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
I'm surpised no one has asked how much transmit power is available, and how
high the rocket is expected to fly. Regardless, unless a micropower transmitter is being used, it seems to me that a very simple quarter wave nose tip made if 1/8" rod or similar material would only protrude a few inches above the nose and would probably do the job. At this frequency, even a tiny metal mass inside the nose would probably be a sufficiently good counterpoise for feeding it. This seems like a simple problem (or 'no problem'). I'm surprised at the complex solutions. Joe W3JDR wrote in message ... I've voulenteered to help the SDSU mechanical engineering studens get telemetry from their rocket see: http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. I have all the electronics working, I'm using a commercial 910Mhz telemetry radio, I have every thing working except the antenna. For the last launch I burred a dipole in the plywood fin, alas the rocket did not launch it caught fire and burned up the fins. (It did not burn as far as the electronics.) The new fins are carbon fiber composite so no antenna there... The rocket will get to mach 2 so small wires sticking out will probably break or burn up. I have enough power and ground side gain that I need no gain from the rocket, an isotropic radiator with 3db of loss would be fine. Any suggestions? My ideas and thoughts: 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket near the engine. Pros: simple. Cons: lots of metal to block the signal and mess up the pattern. Not clear if the ionized exhaust will block the signal. Antenna pattern is almost exactly wrong. (Telemetry really needed for recovery tracking so ionization fading is not a deal killer) 2)Horizontal dipole at the bottom plate of engine. All the problems of #1 except pattern. 3)Put Fiberglass windows in the electronics bay near the nose of the rocket. One window on each side, Driving two hosrizontal dipoles with a power splitter, one dipole on each side. Pros: Easy to do. Cons: I don't know what the pattern would be like, or exactly how I shoudl phase the two antennas on opposite sides. (Some metal between then so not a clean situation.) Resources: It have a minicircuits SMA 2 way power splitter, and can make precise metal parts (0.002" or better). I do not have any antenna testing equipment that is any good at 900Mhz. so any suggestions... Paul (Kl7JG) |
You might take a look at slot antennas.
wrote in message ... I've voulenteered to help the SDSU mechanical engineering studens get telemetry from their rocket see: http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. I have all the electronics working, I'm using a commercial 910Mhz telemetry radio, I have every thing working except the antenna. For the last launch I burred a dipole in the plywood fin, alas the rocket did not launch it caught fire and burned up the fins. (It did not burn as far as the electronics.) The new fins are carbon fiber composite so no antenna there... The rocket will get to mach 2 so small wires sticking out will probably break or burn up. I have enough power and ground side gain that I need no gain from the rocket, an isotropic radiator with 3db of loss would be fine. Any suggestions? My ideas and thoughts: 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket near the engine. Pros: simple. Cons: lots of metal to block the signal and mess up the pattern. Not clear if the ionized exhaust will block the signal. Antenna pattern is almost exactly wrong. (Telemetry really needed for recovery tracking so ionization fading is not a deal killer) 2)Horizontal dipole at the bottom plate of engine. All the problems of #1 except pattern. 3)Put Fiberglass windows in the electronics bay near the nose of the rocket. One window on each side, Driving two hosrizontal dipoles with a power splitter, one dipole on each side. Pros: Easy to do. Cons: I don't know what the pattern would be like, or exactly how I shoudl phase the two antennas on opposite sides. (Some metal between then so not a clean situation.) Resources: It have a minicircuits SMA 2 way power splitter, and can make precise metal parts (0.002" or better). I do not have any antenna testing equipment that is any good at 900Mhz. so any suggestions... Paul (Kl7JG) |
nah, he needs a fractal patch or two.
"Fred W4JLE" wrote in message ... You might take a look at slot antennas. wrote in message ... I've voulenteered to help the SDSU mechanical engineering studens get telemetry from their rocket see: http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. I have all the electronics working, I'm using a commercial 910Mhz telemetry radio, I have every thing working except the antenna. For the last launch I burred a dipole in the plywood fin, alas the rocket did not launch it caught fire and burned up the fins. (It did not burn as far as the electronics.) The new fins are carbon fiber composite so no antenna there... The rocket will get to mach 2 so small wires sticking out will probably break or burn up. I have enough power and ground side gain that I need no gain from the rocket, an isotropic radiator with 3db of loss would be fine. Any suggestions? My ideas and thoughts: 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket near the engine. Pros: simple. Cons: lots of metal to block the signal and mess up the pattern. Not clear if the ionized exhaust will block the signal. Antenna pattern is almost exactly wrong. (Telemetry really needed for recovery tracking so ionization fading is not a deal killer) 2)Horizontal dipole at the bottom plate of engine. All the problems of #1 except pattern. 3)Put Fiberglass windows in the electronics bay near the nose of the rocket. One window on each side, Driving two hosrizontal dipoles with a power splitter, one dipole on each side. Pros: Easy to do. Cons: I don't know what the pattern would be like, or exactly how I shoudl phase the two antennas on opposite sides. (Some metal between then so not a clean situation.) Resources: It have a minicircuits SMA 2 way power splitter, and can make precise metal parts (0.002" or better). I do not have any antenna testing equipment that is any good at 900Mhz. so any suggestions... Paul (Kl7JG) |
Doesn't his original post "indicate" he wishes a "horizontal" polarized ant,
as opposed to vertical nose rod? At least, that is why I dismissed the "obivious." Warmest regards, John "W3JDR" wrote in message news:1cIee.3075$fQ2.31@trnddc05... | I'm surpised no one has asked how much transmit power is available, and how | high the rocket is expected to fly. | | Regardless, unless a micropower transmitter is being used, it seems to me | that a very simple quarter wave nose tip made if 1/8" rod or similar | material would only protrude a few inches above the nose and would probably | do the job. At this frequency, even a tiny metal mass inside the nose would | probably be a sufficiently good counterpoise for feeding it. | | This seems like a simple problem (or 'no problem'). I'm surprised at the | complex solutions. | | Joe | W3JDR | | | wrote in message | ... | I've voulenteered to help the SDSU mechanical engineering studens get | telemetry from their rocket see: | http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. | | I have all the electronics working, I'm using a commercial 910Mhz | telemetry radio, I have every thing working except the antenna. | | For the last launch I burred a dipole in the plywood fin, alas | the rocket did not launch it caught fire and burned up the fins. | (It did not burn as far as the electronics.) | | The new fins are carbon fiber composite so no antenna there... | | The rocket will get to mach 2 so small wires sticking out will | probably break or burn up. | | | I have enough power and ground side gain that I need no gain | from the rocket, an isotropic radiator with 3db of loss would be fine. | | | Any suggestions? | | | My ideas and thoughts: | | 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket | near the engine. | | Pros: | simple. | Cons: | lots of metal to block the signal and mess up the pattern. | Not clear if the ionized exhaust will block the signal. | Antenna pattern is almost exactly wrong. | | (Telemetry really needed for recovery tracking so ionization fading is | not a deal killer) | | | 2)Horizontal dipole at the bottom plate of engine. | All the problems of #1 except pattern. | | | | | 3)Put Fiberglass windows in the electronics bay near the nose of the | rocket. One window on each side, Driving two hosrizontal dipoles with | a power splitter, one dipole on each side. | | Pros: Easy to do. | Cons: | I don't know what the pattern would be like, or exactly how I shoudl | phase the two antennas on opposite sides. (Some metal between then so | not a clean situation.) | | Resources: | It have a minicircuits SMA 2 way power splitter, and can make precise | metal parts (0.002" or better). | I do not have any antenna testing equipment that is any good at | 900Mhz. | so any suggestions... | | | Paul (Kl7JG) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
I forgot to include the part of his original post which suggested this to
me, here it is: "Antenna pattern is almost exactly wrong." ....when he was referring to a vertical antenna hanging from the tail (probably melt in the exhaust!) Warmest regards, John "John Smith" wrote in message ... | Doesn't his original post "indicate" he wishes a "horizontal" polarized ant, | as opposed to vertical nose rod? | | At least, that is why I dismissed the "obivious." | | Warmest regards, | John | | "W3JDR" wrote in message news:1cIee.3075$fQ2.31@trnddc05... || I'm surpised no one has asked how much transmit power is available, and | how || high the rocket is expected to fly. || || Regardless, unless a micropower transmitter is being used, it seems to me || that a very simple quarter wave nose tip made if 1/8" rod or similar || material would only protrude a few inches above the nose and would | probably || do the job. At this frequency, even a tiny metal mass inside the nose | would || probably be a sufficiently good counterpoise for feeding it. || || This seems like a simple problem (or 'no problem'). I'm surprised at the || complex solutions. || || Joe || W3JDR || || || wrote in message || ... || I've voulenteered to help the SDSU mechanical engineering studens get || telemetry from their rocket see: || http://www-rohan.sdsu.edu/~sharring/sdsurocket.html. || || I have all the electronics working, I'm using a commercial 910Mhz || telemetry radio, I have every thing working except the antenna. || || For the last launch I burred a dipole in the plywood fin, alas || the rocket did not launch it caught fire and burned up the fins. || (It did not burn as far as the electronics.) || || The new fins are carbon fiber composite so no antenna there... || || The rocket will get to mach 2 so small wires sticking out will || probably break or burn up. || || || I have enough power and ground side gain that I need no gain || from the rocket, an isotropic radiator with 3db of loss would be fine. || || || Any suggestions? || || || My ideas and thoughts: || || 1)Simple 1/4 wave vertical sticking out the bottom plate of the rocket || near the engine. || || Pros: || simple. || Cons: || lots of metal to block the signal and mess up the pattern. || Not clear if the ionized exhaust will block the signal. || Antenna pattern is almost exactly wrong. || || (Telemetry really needed for recovery tracking so ionization fading is || not a deal killer) || || || 2)Horizontal dipole at the bottom plate of engine. || All the problems of #1 except pattern. || || || || || 3)Put Fiberglass windows in the electronics bay near the nose of the || rocket. One window on each side, Driving two hosrizontal dipoles with || a power splitter, one dipole on each side. || || Pros: Easy to do. || Cons: || I don't know what the pattern would be like, or exactly how I shoudl || phase the two antennas on opposite sides. (Some metal between then so || not a clean situation.) || || Resources: || It have a minicircuits SMA 2 way power splitter, and can make precise || metal parts (0.002" or better). || I do not have any antenna testing equipment that is any good at || 900Mhz. || so any suggestions... || || || Paul (Kl7JG) || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || | | |
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