Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
"mr1956" wrote in message ... I am looking for some help developing a properly tuned piano wire antenna for an all metal experimental rocket. This particular vehicle currently uses a Digi International 9Xtream 100 mw transmitter which operates using Frequency Hopping Spread Spectrum from 910 to 918 MHz. The first flight used a .062" diameter length of piano wire cut so that the exposed length was about 1/2 wavelength. The wire antenna was isolated from the metal airfame with a small nylon penetrator and connected to the transmitter via about a 12" length of RG-178 coax. The coax was terminated at the antenna via two small jumpers (soldered to the center conductor and shield). The shield was grounded on the metal airframe transforming the entire rocket into an artificial ground plane (the antenna was also swept back at about a 45 degree angle to reduce drag. During this first flight we observed a range of about 10 miles, about half of the published range of this transmitter. The RF system is used as a downlink for GPS data and we did not get a good radio link after ignition until the rocket had descended to about 50,000 feet. Maximum velocity was about Mach 3 which is why a conventional antenna cannot be used as it will be melted by friction. For the second version, we are thinking of using a slightly smaller diameter piano wire for a 1/4 wave length antenna as I think this may be more suitable for a system using an artificial ground plane. In addition, I plan to terminate the RG-178 coax directly at the antenna and seal it with potting compound. This new antenna will be mounted totally on the exterior of the airframe and angled back only about 10 degrees to give a better radiation pattern. However, I would really like to properly tune this new antenna and was wondering if anyone in this group has any ideas as to how to do this. Doing a tuned RCL circuit at this frequency is proving to be difficult using discrete components, to say the least. I do not have an SWR, but do have an RF millivolt meter as well as the means to measure the capacitance between the antenna and metal airframe. Any help will be appreciated as I would hate to fly this thing again and not get it back because our RF downlink had insufficient range. C. Newport Hi C Have you considered flush antennas, like slots? Is is practical to use antenna directivity at the ground station to increase the "range"? It might be advantageous to use Linear Polarization on the rocket and Circular Polarization on the ground. For impedance measurement at L band, it is possible to build a slotted line using plumbing supplies. That presumes that you already have access to a signal generator and a detector to record the signal generator's output. A home built slotted line will have difficulty regestaring low VSWRs. But, once it is known that the load impedance is close to the line impedance (low VSWR), a directional coupler can be used to match more precisely. I have built a "plumber's delight" slotted line that works well at 130 MHZ. The high quality directional couplers are affordable on eBay. Note - If I can do it, it cant be too complicated! Jerry KD6JDJ |
#2
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
On Sun, 24 May 2009 04:04:52 GMT, "Jerry"
wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. Slot antennas are also a power waste. You need 4 slots, run by a power splitter, in order to insure that at least one antenna is oriented in the direction of the receiver. Meanwhile, the other 3 slot antennas are radiating power to nobody in particular. Say goodby to about 3/4th of your tx power. Receive sensitivity is not affected. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#3
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
"Jeff Liebermann" wrote in message ... On Sun, 24 May 2009 04:04:52 GMT, "Jerry" wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. Slot antennas are also a power waste. You need 4 slots, run by a power splitter, in order to insure that at least one antenna is oriented in the direction of the receiver. Meanwhile, the other 3 slot antennas are radiating power to nobody in particular. Say goodby to about 3/4th of your tx power. Receive sensitivity is not affected. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Hi Jeff Why are you so negative?? I have designed and built lots of slot antennas that were widely used on military aircraft. The efficiency is quite good. I am sure a smart guy like you could design a slot antenna and locate it for those guys with the 3G rocket. There hasnt been any text that restricts where the slot could be located. As I read the original post, they werent receiving signal from the accending rocket. Maybe they only want to receive data that was recorded after the rocket reached it's peak. There are lots of information that you and I dont yet know. But, my major question for you is "Why are you so negative?". Jerry KD6JDJ |
#4
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
On Sun, 24 May 2009 07:30:03 GMT, "Jerry"
wrote: "Jeff Liebermann" wrote in message .. . On Sun, 24 May 2009 04:04:52 GMT, "Jerry" wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. Slot antennas are also a power waste. You need 4 slots, run by a power splitter, in order to insure that at least one antenna is oriented in the direction of the receiver. Meanwhile, the other 3 slot antennas are radiating power to nobody in particular. Say goodby to about 3/4th of your tx power. Receive sensitivity is not affected. Hi Jeff Why are you so negative?? I have designed and built lots of slot antennas that were widely used on military aircraft. The efficiency is quite good. I am sure a smart guy like you could design a slot antenna and locate it for those guys with the 3G rocket. There hasnt been any text that restricts where the slot could be located. As I read the original post, they werent receiving signal from the accending rocket. Maybe they only want to receive data that was recorded after the rocket reached it's peak. There are lots of information that you and I dont yet know. But, my major question for you is "Why are you so negative?". Jerry KD6JDJ I don't think I'm being particularly negative or offensive. I offered what I consider to be a more reasonable alternative (CP turnstile antenna) and ran the path loss calculations to insure that it would work. I also itemized why a slot antenna would be an inferior solution. My main point is that with a vertically ascending rocket, the antenna pattern should be primarily ahead and behind the rocket, not perpendicular. I've seen one paper design that used insulated fins for the 4 turnstile antenna elements. However, I haven't seen the actual rocket. I also built a 2.4GHz antenna system for a model airplane for a video downlink. The initial design was a slot antenna system in the fuselage, which worked great when the aircraft was overhead, but did badly when near the horizon and out of the antenna pattern. Two vertical monopoles and a power splitter did much better, especially since it worked well in inverted flight. I must admit that I haven't designed a slot antenna system for a high power Mach 3 rocket. I did build a small "G" motor rocket without telemetry but that doesn't count for much. Anyway, we're both guessing. Without a clue as to the size, geometry, and construction of the rocket, the configuration of the ground station antenna, the location of the ground station, and the approximate trajectory (probably straight up), we can only speculate as to the optimal design. My guess is that this a level 1 rocket with an "H" or "I" motor which could barely tolerate the slight increase in diameter required for multiple slot antnnas. Wire or fin antennas don't add anything. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#5
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
Jeff Liebermann wrote:
On Sun, 24 May 2009 04:04:52 GMT, "Jerry" wrote: Have you considered flush antennas, like slots? Slot antennas have the maximum lobe perpendicular to the rocket axis. There's very little signal below the rocket. This is why tracking stations are far away from the launch site. If the rocket were overhead, and going straight up, there's no signal. That was my first thought on side mounted antennas. The best solution would be something on the fins if that were possible with the airframe design. -- Jim Pennino Remove .spam.sux to reply. |
#6
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
On May 24, 12:04*am, "Jerry" wrote:
"mr1956" wrote in message ... I am looking for some help developing a properly tuned piano wire antenna for an all metal experimental rocket. This particular vehicle currently uses a Digi International 9Xtream 100 mw transmitter which operates using Frequency Hopping Spread Spectrum from 910 to 918 MHz. The first flight used a .062" diameter length of piano wire cut so that the exposed length was about 1/2 wavelength. The wire antenna was isolated from the metal airfame with a small nylon penetrator and connected to the transmitter via about a 12" length of RG-178 coax. The coax was terminated at the antenna via two small jumpers (soldered to the center conductor and shield). *The shield was grounded on the metal airframe transforming the entire rocket into an artificial ground plane (the antenna was also swept back at about a 45 degree angle to reduce drag. During this first flight we observed a range of about 10 miles, about half of the published range of this transmitter. The RF system is used as a downlink for GPS data and we did not get a good radio link after ignition until the rocket had descended to about 50,000 feet. *Maximum velocity was about Mach 3 which is why a conventional antenna cannot be used as it will be melted by friction. For the second version, we are thinking of using a slightly smaller diameter piano wire for a 1/4 wave length antenna as I think this may be more suitable for a system using an artificial ground plane. *In addition, I plan to terminate the RG-178 coax directly at the antenna and seal it with potting compound. This new antenna will be mounted totally on the exterior of the airframe and angled back only about 10 degrees to give a better radiation pattern. However, I would really like to properly tune this new antenna and was wondering if anyone in this group has any ideas as to how to do this. Doing a tuned RCL circuit at this frequency is proving to be difficult using discrete components, to say the least. I do not have an SWR, but do have an RF millivolt meter as well as the means to measure the capacitance between the antenna and metal airframe. Any help will be appreciated as I would hate to fly this thing again and not get it back because our RF downlink had insufficient range. C. Newport * Hi C * Have you considered flush antennas, like slots? * Is is practical to use antenna directivity at the ground station to increase the "range"? * It might be advantageous to use Linear Polarization on the rocket and Circular Polarization on the ground. * For impedance measurement at L band, it is possible to build a slotted line using plumbing supplies. * That presumes that you already have access to a signal generator and a detector to record the signal generator's output. * A home built slotted line will have difficulty regestaring low VSWRs. But, once it is known that the load impedance is close to the line impedance (low VSWR), a directional coupler can be used to match more precisely. * I have built a "plumber's delight" slotted line that works well at 130 MHZ. * The high quality directional couplers are affordable on eBay. * Note - If I can do it, it cant be too complicated! * * * * * * * * * * * * Jerry * KD6JDJ I have looked at slotted or flush wrap around antennas but integrating one into the existing design would be difficult due to the wall thickness of the metal. Something like that would have to be mounted flush and I would be worried about the wind blast peeling the thing off. Certainly, there is much that can be done but I am unfortunately not Wallops Island and have limited resources like anyone else. |
#7
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
"mr1956" wrote in message ... On May 24, 12:04 am, "Jerry" wrote: "mr1956" wrote in message ... I am looking for some help developing a properly tuned piano wire antenna for an all metal experimental rocket. This particular vehicle currently uses a Digi International 9Xtream 100 mw transmitter which operates using Frequency Hopping Spread Spectrum from 910 to 918 MHz. The first flight used a .062" diameter length of piano wire cut so that the exposed length was about 1/2 wavelength. The wire antenna was isolated from the metal airfame with a small nylon penetrator and connected to the transmitter via about a 12" length of RG-178 coax. The coax was terminated at the antenna via two small jumpers (soldered to the center conductor and shield). The shield was grounded on the metal airframe transforming the entire rocket into an artificial ground plane (the antenna was also swept back at about a 45 degree angle to reduce drag. During this first flight we observed a range of about 10 miles, about half of the published range of this transmitter. The RF system is used as a downlink for GPS data and we did not get a good radio link after ignition until the rocket had descended to about 50,000 feet. Maximum velocity was about Mach 3 which is why a conventional antenna cannot be used as it will be melted by friction. For the second version, we are thinking of using a slightly smaller diameter piano wire for a 1/4 wave length antenna as I think this may be more suitable for a system using an artificial ground plane. In addition, I plan to terminate the RG-178 coax directly at the antenna and seal it with potting compound. This new antenna will be mounted totally on the exterior of the airframe and angled back only about 10 degrees to give a better radiation pattern. However, I would really like to properly tune this new antenna and was wondering if anyone in this group has any ideas as to how to do this. Doing a tuned RCL circuit at this frequency is proving to be difficult using discrete components, to say the least. I do not have an SWR, but do have an RF millivolt meter as well as the means to measure the capacitance between the antenna and metal airframe. Any help will be appreciated as I would hate to fly this thing again and not get it back because our RF downlink had insufficient range. C. Newport Hi C Have you considered flush antennas, like slots? Is is practical to use antenna directivity at the ground station to increase the "range"? It might be advantageous to use Linear Polarization on the rocket and Circular Polarization on the ground. For impedance measurement at L band, it is possible to build a slotted line using plumbing supplies. That presumes that you already have access to a signal generator and a detector to record the signal generator's output. A home built slotted line will have difficulty regestaring low VSWRs. But, once it is known that the load impedance is close to the line impedance (low VSWR), a directional coupler can be used to match more precisely. I have built a "plumber's delight" slotted line that works well at 130 MHZ. The high quality directional couplers are affordable on eBay. Note - If I can do it, it cant be too complicated! Jerry KD6JDJ I have looked at slotted or flush wrap around antennas but integrating one into the existing design would be difficult due to the wall thickness of the metal. Something like that would have to be mounted flush and I would be worried about the wind blast peeling the thing off. Certainly, there is much that can be done but I am unfortunately not Wallops Island and have limited resources like anyone else. Hi C It looks like your "wire" antenna might actually be OK for your project. You have demonstrated that it works when the rocket is nearly 10 miles away when you hoped for 20 miles. Evidently, the antenna doesnt need to function while the rocket is accending. Are you able to improve the ground based antenna The equipment you now have would need only 6 dB improvement to provide the 20 mile range. I'd like to know more about your ground based antenna system. Jerry KD6JDJ (who has lots of small diameterTeflon dielectric coax to donate to a real project) |
#8
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
On May 24, 9:48*am, "Jerry" wrote:
"mr1956" wrote in message ... On May 24, 12:04 am, "Jerry" wrote: "mr1956" wrote in message .... I am looking for some help developing a properly tuned piano wire antenna for an all metal experimental rocket. This particular vehicle currently uses a Digi International 9Xtream 100 mw transmitter which operates using Frequency Hopping Spread Spectrum from 910 to 918 MHz. The first flight used a .062" diameter length of piano wire cut so that the exposed length was about 1/2 wavelength. The wire antenna was isolated from the metal airfame with a small nylon penetrator and connected to the transmitter via about a 12" length of RG-178 coax. The coax was terminated at the antenna via two small jumpers (soldered to the center conductor and shield). The shield was grounded on the metal airframe transforming the entire rocket into an artificial ground plane (the antenna was also swept back at about a 45 degree angle to reduce drag. During this first flight we observed a range of about 10 miles, about half of the published range of this transmitter. The RF system is used as a downlink for GPS data and we did not get a good radio link after ignition until the rocket had descended to about 50,000 feet. Maximum velocity was about Mach 3 which is why a conventional antenna cannot be used as it will be melted by friction. For the second version, we are thinking of using a slightly smaller diameter piano wire for a 1/4 wave length antenna as I think this may be more suitable for a system using an artificial ground plane. In addition, I plan to terminate the RG-178 coax directly at the antenna and seal it with potting compound. This new antenna will be mounted totally on the exterior of the airframe and angled back only about 10 degrees to give a better radiation pattern. However, I would really like to properly tune this new antenna and was wondering if anyone in this group has any ideas as to how to do this. Doing a tuned RCL circuit at this frequency is proving to be difficult using discrete components, to say the least. I do not have an SWR, but do have an RF millivolt meter as well as the means to measure the capacitance between the antenna and metal airframe. Any help will be appreciated as I would hate to fly this thing again and not get it back because our RF downlink had insufficient range. C. Newport Hi C Have you considered flush antennas, like slots? Is is practical to use antenna directivity at the ground station to increase the "range"? It might be advantageous to use Linear Polarization on the rocket and Circular Polarization on the ground. For impedance measurement at L band, it is possible to build a slotted line using plumbing supplies. That presumes that you already have access to a signal generator and a detector to record the signal generator's output. A home built slotted line will have difficulty regestaring low VSWRs. But, once it is known that the load impedance is close to the line impedance (low VSWR), a directional coupler can be used to match more precisely. I have built a "plumber's delight" slotted line that works well at 130 MHZ. The high quality directional couplers are affordable on eBay. Note - If I can do it, it cant be too complicated! Jerry KD6JDJ I have looked at slotted or flush wrap around antennas but integrating one into the existing design would be difficult due to the wall thickness of the metal. Something like that would have to be mounted flush and I would be worried about the wind blast peeling the thing off. *Certainly, there is much that can be done but I am unfortunately not Wallops Island and have limited resources like anyone else. * Hi C * It looks like your "wire" antenna might actually be OK for your project. You have demonstrated that it works when the rocket is nearly 10 miles away when you hoped for 20 miles. * Evidently, the antenna doesnt need to function while the rocket is accending. * Are you able to improve the ground based antenna * The equipment you now have would need only 6 dB improvement to provide the 20 mile range. * I'd like to know more about your ground based antenna system. * * * * * * * * * * * * *Jerry * *KD6JDJ * * *(who has lots of small diameterTeflon dielectric coax *to donate to a real project) Jerry: The "ground station" is not much; just a small receiver with a standard 1/2 wave dipole attached using an sma connector. The receiver is battery powered and connected to a laptop using a standard serial cable. We had thought about using a Yagi during the previous flight but it just got left by the wayside with everything else that had to be done. The basic telemetry and downlink system is manufactured by Ozark Aerospace (Erik Hall) but uses a Digi Int. 9Xstream radio modem (www.ozarkaerospace.com and I use the ARTS TX-900G and RX-900). I actually built my own transmitter and GPS system using a 5 watt data radio and Garmin GPS with a small Li-Ion battery pack. But that system was "lost" during a not so successful flight in Texas a few years ago. Hence, for this design I opted to buy something off the shelf that already worked. Most people using this system have fiberglass airframes so for them it is a simple matter to use a commercially available antenna mounted inside of the airfame. But this is an all metal design so I had the telemetry board made so I could connect my own antenna. FYI, the rocket is 15 feet long, 6" in diameter and weighs over 100 lbs empty and close to 200 lbs. on the pad. It is all aluminum, except for the nose cone which is laminated birch. I'm using metal for the airframe because it just easier to work with and the first 8 feet of the rocket is metal anyway as that is the motor case. The published range for this Digi Int. transmitter is 20 miles, though people doing amateur high-altitude balloon flights have reportedly observed even better reception from high altitudes (i.e., over 80 K feet). This rocket did about 85,000 feet last September at Black Rock, Nevada so it is doubtful that we will get GPS data at apogee anyway due to the COTS limitations. But I'd like to get as much as possible and will probably eventually convert to the 9Xtend modem which goes up to one watt xmit power. Curt |
#9
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
Hi C It looks like your "wire" antenna might actually be OK for your project. You have demonstrated that it works when the rocket is nearly 10 miles away when you hoped for 20 miles. Evidently, the antenna doesnt need to function while the rocket is accending. Are you able to improve the ground based antenna The equipment you now have would need only 6 dB improvement to provide the 20 mile range. I'd like to know more about your ground based antenna system. Jerry KD6JDJ (who has lots of small diameterTeflon dielectric coax to donate to a real project) Jerry: The "ground station" is not much; just a small receiver with a standard 1/2 wave dipole attached using an sma connector. The receiver is battery powered and connected to a laptop using a standard serial cable. We had thought about using a Yagi during the previous flight but it just got left by the wayside with everything else that had to be done. The basic telemetry and downlink system is manufactured by Ozark Aerospace (Erik Hall) but uses a Digi Int. 9Xstream radio modem (www.ozarkaerospace.com and I use the ARTS TX-900G and RX-900). I actually built my own transmitter and GPS system using a 5 watt data radio and Garmin GPS with a small Li-Ion battery pack. But that system was "lost" during a not so successful flight in Texas a few years ago. Hence, for this design I opted to buy something off the shelf that already worked. Most people using this system have fiberglass airframes so for them it is a simple matter to use a commercially available antenna mounted inside of the airfame. But this is an all metal design so I had the telemetry board made so I could connect my own antenna. FYI, the rocket is 15 feet long, 6" in diameter and weighs over 100 lbs empty and close to 200 lbs. on the pad. It is all aluminum, except for the nose cone which is laminated birch. I'm using metal for the airframe because it just easier to work with and the first 8 feet of the rocket is metal anyway as that is the motor case. The published range for this Digi Int. transmitter is 20 miles, though people doing amateur high-altitude balloon flights have reportedly observed even better reception from high altitudes (i.e., over 80 K feet). This rocket did about 85,000 feet last September at Black Rock, Nevada so it is doubtful that we will get GPS data at apogee anyway due to the COTS limitations. But I'd like to get as much as possible and will probably eventually convert to the 9Xtend modem which goes up to one watt xmit power. Curt Hi Curt I strongly suspect that you can use the antenna you now have on the rocket. There is a possibility that you hadnt optimized the pointing of the stub on the base station. You might be able to get enough system gain by using a simple Turnstile Antenna at the ground station ( Wikipedia ). If you decide you want more signal than you get with a Turnstile, it would be easy to build a 900 MHz Helix or Crossed Yagii. It seems very important to use a Circularly Polarized antenna at the ground station. Jerry |
#10
|
|||
|
|||
Piano Wire Antenna for Experimental Rocket
On May 24, 2:59*pm, "Jerry" wrote:
Hi C It looks like your "wire" antenna might actually be OK for your project.. You have demonstrated that it works when the rocket is nearly 10 miles away when you hoped for 20 miles. Evidently, the antenna doesnt need to function while the rocket is accending. Are you able to improve the ground based antenna The equipment you now have would need only 6 dB improvement to provide the 20 mile range. I'd like to know more about your ground based antenna system. Jerry KD6JDJ (who has lots of small diameterTeflon dielectric coax to donate to a real project) Jerry: The "ground station" is not much; just a small receiver with a standard 1/2 wave dipole attached using an sma connector. *The receiver is battery powered and connected to a laptop using a standard serial cable. We had thought about using a Yagi during the previous flight but it just got left by the wayside with everything else that had to be done. The basic telemetry and downlink system is manufactured by Ozark Aerospace (Erik Hall) but uses a Digi Int. 9Xstream radio modem (www.ozarkaerospace.comand I use the ARTS TX-900G and RX-900). *I actually built my own transmitter and GPS system using a 5 watt data radio and Garmin GPS with a small Li-Ion battery pack. But that system was "lost" during a not so successful flight in Texas a few years ago. Hence, for this design I opted to buy something off the shelf that already worked. Most people using this system have fiberglass airframes so for them it is a simple matter to use a commercially available antenna mounted inside of the airfame. But this is an all metal design so I had the telemetry board made so I could connect my own antenna. FYI, the rocket is 15 feet long, 6" in diameter and weighs over 100 lbs empty and close to 200 lbs. on the pad. It is all aluminum, except for the nose cone which is laminated birch. I'm using metal for the airframe because it just easier to work with and the first 8 feet of the rocket is metal anyway as that is the motor case. The published range for this Digi Int. transmitter is 20 miles, though people doing amateur high-altitude balloon flights have reportedly observed even better reception from high altitudes (i.e., over 80 K feet). This rocket did about 85,000 feet last September at Black Rock, Nevada so it is doubtful that we will get GPS data at apogee anyway due to the COTS limitations. But I'd like to get as much as possible and will probably eventually convert to the 9Xtend modem which goes up to one watt xmit power. Curt * Hi Curt * I strongly suspect that you can use the antenna you now have on the rocket. *There is a possibility that you hadnt optimized the pointing of the stub on the base station. *You might be able to get enough system gain by using a simple Turnstile Antenna at the ground station ( Wikipedia ). * If you decide you want more signal than you get with a Turnstile, it would be easy to build a 900 MHz Helix or Crossed Yagii. * It seems very important to use a Circularly Polarized antenna at the ground station. * * * * * * * * * * * * * Jerry I am familiar with the Helix antenna and the Yagi, but not a "crossed yagi." Am I correct in assuming that the crossed yagi is simply two yagis with the reflectors at right angles to each other (so that it looks like a cross when viewed from the end)? Directionality on the ground station is an issue though. Once the rocket goes out of sight (it was only visible for about three seconds of a nine minute flight), pointing the receiving antenna in the right direction and elevation would be guess work. I know that the yagi must be much more directional than the 1/2 wave dipole used before but how much I do not know. I would imagine it is determined by the number and spacing of the elements. I also think that having the transmitting antenna more perpendicular to the airfame will help during apogee and descent. Curt |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|