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Cassegrain Antenna Development
Hi there,
this is my first post here, hope not being off topic :) I was asking myself if there were resources over the net that cover the development of a cassegrain antenna [from the design up to the building] in a homebrew fashion. Thank you for paying attention towards this mail :) Bye bye Emanuele Colucci PS. I already posted this message to rec.radio.amateur.homebrew, but a user suggested to me to post it here too. |
Cassegrain Antenna Development
well, searching for "cassegrain antenna" with google only gives 60,400
links, searching for "cassegrain antenna design and construction" narrows it down to about 4000. "Emanuele Colucci" wrote in message . .. Hi there, this is my first post here, hope not being off topic :) I was asking myself if there were resources over the net that cover the development of a cassegrain antenna [from the design up to the building] in a homebrew fashion. Thank you for paying attention towards this mail :) Bye bye Emanuele Colucci PS. I already posted this message to rec.radio.amateur.homebrew, but a user suggested to me to post it here too. |
Cassegrain Antenna Development
In article , Emanuele
Colucci wrote: Hi there, this is my first post here, hope not being off topic :) I was asking myself if there were resources over the net that cover the development of a cassegrain antenna [from the design up to the building] in a homebrew fashion. Thank you for paying attention towards this mail :) Bye bye Emanuele Colucci PS. I already posted this message to rec.radio.amateur.homebrew, but a user suggested to me to post it here too. Hello, and while I can't point you to any specific sources I would ask why you feel you need to use a Cassegranian feed. This complicates the design in that you need both a parabolic main dish and a hyperbolic reflector. Have you worked out the antenna's frequency band and required radiation pattern/gain? Would a non-Cassegrainian feed (e.g. placing the main radiating/receiving element on a support at the focal point of the reflector) be viable? Sincerely, and 73s from N4GGO, John Wood (Code 5550) e-mail: Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337 |
Cassegrain Antenna Development
"Emanuele Colucci" wrote in message .. . Dave ha scritto: well, searching for "cassegrain antenna" with google only gives 60,400 links, searching for "cassegrain antenna design and construction" narrows it down to about 4000. It's April, 9th, 2009. By this date I still wonder why there are persons so arrogant to think that who asks for advices never looked at google. Have a nice day. Emanuele Colucci because there are those who have never searched with google or any other engine and just want someone to feed them the answers. |
Cassegrain Antenna Development
On Thu, 09 Apr 2009 10:01:32 +0200, Emanuele Colucci
wrote: well, searching for "cassegrain antenna" with google only gives 60,400 links, searching for "cassegrain antenna design and construction" narrows it down to about 4000. It's April, 9th, 2009. By this date I still wonder why there are persons so arrogant to think that who asks for advices never looked at google. Hi Emanuele, This is probably due to the way the question was offered. You want a complete solution to an unknown problem. When such "wish lists" are posted here, they obtain one of several results: 1. An exhaustive reply that is complete to the question asked, but we then have the luxury of reading from the original poster that "that specific solution won't work because...." 2. The beginning of an exhaustive series of postings to draw the specific issues out of the original poster. That has already begun by another poster in this thread. 3. The fire hose is opened (much as above) which is another form of (2) in that you imply you have done a google search, but you haven't expressed what your search terms were - which would, of course, reduce those 60,400 links to something more tractable. You don't offer anything like this in your response except outrage. Each of these possible outcomes inevitable returns to you, and something you could have done first instead of last: What is your problem, why do you think this (a "cassegrain antenna") is the solution, and some fundamental design issues such as 1. Frequency; 2. Bandwidth; 3. Match; 4. Gain; 5. Budget (time and/or money); 6. Specific issues (phase control?); 7. Application issues (EME?). When such things are asked for, students coming here to complete an homework assignment are usually stunned. If you are not a student, then an engineer is always prepared to submit the characteristics required. If you are not a student, nor an engineer, then almost any quick answer could lead you down the path to lost time. You are lucky no one supplied that quick answer, because we have enough miracle antenna designers who come here to do just that. 73's Richard Clark, KB7QHC |
Cassegrain Antenna Development
Hi to everyone and thanks for answering to my message.
Richard Clark ha scritto: Hi Emanuele, This is probably due to the way the question was offered. You want a complete solution to an unknown problem. You and Dave were right. I originally posted the message in the homebrew newsgroup because I was looking for a complete guide to design a cas in order to build a little radiometer working in the "water hole" (1420 ~ 1640 MHz) for an hobbystic aim. The book I used at university to study antennas - Antennas and Radiowave Propagation [by Robert E. Collin] - simply doesn't cover in depth this argument. It just cites the Cassegrain feed system as an alternative to prime focus paraboloidal reflector antennas, because the cassegrain feed does't receive the thermal noise from the ground. I was looking for a complete resource to study the system, and this is why I wrote he to find someone with good advices. Now, the thing I have now understood is that I haven't to be so synthetic while writing a message. So, I would like to study (and eventually build) a radiometer who listens to 1420 ~ 1640 MHz, with a passing bandwidth of 8 MHz, in order to receive a minumum density flux of 240-260 Jy (a Jansky is 10^-26 W / [m^2 * Hz]). I need low antenna temperature (but not as cryogenics ones!). 5. Budget (time and/or money); I can't answer this question yet. Surely, I haven't more than 5-600 euros to spend in the building/buying of the antenna. 6. Specific issues (phase control?); Nothing special: I would like an output signal proportional to the power of the radiation picked up. 7. Application issues (EME?). Amateur radioastronomy. Well, that's all by the moment. Greetings, Emanuele Colucci |
Cassegrain Antenna Development
On Fri, 10 Apr 2009 12:34:34 +0200, Emanuele Colucci
wrote: Hi to everyone and thanks for answering to my message. Richard Clark ha scritto: Hi Emanuele, This is probably due to the way the question was offered. You want a complete solution to an unknown problem. You and Dave were right. I originally posted the message in the homebrew newsgroup because I was looking for a complete guide to design a cas in order to build a little radiometer working in the "water hole" (1420 ~ 1640 MHz) for an hobbystic aim. The book I used at university to study antennas - Antennas and Radiowave Propagation [by Robert E. Collin] - simply doesn't cover in depth this argument. It just cites the Cassegrain feed system as an alternative to prime focus paraboloidal reflector antennas, because the cassegrain feed does't receive the thermal noise from the ground. Hi Emanuele, I have that book and I can see your source material. If it is your choice, that is fine. Other correspondents here can respond to your desire to eliminate thermal noise from the ground in alternative designs. You may have to repeat your query to get their attention as this is not a topic that many have experience with (repetition is for the occasion when they check in on an irregular basis). An alternative is to search this group, specifically, at groups.google.com. I was looking for a complete resource to study the system, and this is why I wrote he to find someone with good advices. Now, the thing I have now understood is that I haven't to be so synthetic while writing a message. So, I would like to study (and eventually build) a radiometer who listens to 1420 ~ 1640 MHz, with a passing bandwidth of 8 MHz, in order to receive a minumum density flux of 240-260 Jy (a Jansky is 10^-26 W / [m^2 * Hz]). I need low antenna temperature (but not as cryogenics ones!). You can get a lot of practical ideas here (construction materials and feed issues); and you can use Collin for the math to simply scale the structure to your frequency band. The design is rather more simple than building it. 5. Budget (time and/or money); I can't answer this question yet. Surely, I haven't more than 5-600 euros to spend in the building/buying of the antenna. That is plenty of money. Do you have any time constraints? 7. Application issues (EME?). Amateur radioastronomy. We have a contributor who has been teaching that for 40 years at a major university, and he studied under the pioneers of that specialty. Search groups.google.com for posts by "Mac N8TT" or use "J. McLaughlin; Michigan, USA" as search terms. Well, that's all by the moment. Greetings, Emanuele Colucci 73's Richard Clark, KB7QHC |
Cassegrain Antenna Development
Hi Richard. Thank you for the answers :)
Richard Clark ha scritto: That is plenty of money. Do you have any time constraints? Yep. I can only use Sundays... But on the other side I have no deadline. We have a contributor who has been teaching that for 40 years at a major university, and he studied under the pioneers of that specialty. Search groups.google.com for posts by "Mac N8TT" or use "J. McLaughlin; Michigan, USA" as search terms. Great! I'll surely look for his messages! Many thanks again. Greetings, Emanuele Colucci |
Cassegrain Antenna Development
On Apr 13, 2:08*am, Emanuele Colucci wrote:
Greetings, Emanuele Colucci W1GHZ has a website on amateur microwave stuff that might be useful (construction practices, etc.) If you have access to a university library or online equivalent, there was a set of articles in the IEEE Antennas and Propagation Magazine (not the transactions on A&P) a few years back covering design of various reflector antennas. The Cassegrain is popular for the reasons you give: low noise from behind the antenna, especially if the secondary reflector is underilluminated. And, it lets you put the electronics right at the feed without having to worry about putting them out at the prime focus. You might also look at the Gregorian or Dragonian configurations, which are offset feed schemes. The Allen Telescope Array is using a form of Gregorian. After that, it's mostly a matter of paper and pencil and working out the curvatures. The biggest challenge is in figuring out what the effect of your construction tolerances is. |
Cassegrain Antenna Development
Dear Emanuele and Group:
I have been mentioned. The other responders have well indicated the key factors of a Cassegrain antenna. They include having the active devices (transmitting or receiving components) at a convenient location and potentially a somewhat better antenna temperature than with a typical parabolic antenna. At Ohio State, working with John D. Kraus, we actually used a form of a Cassegrain antenna - the Big Ear. The Big Ear used a (E-W) wide, vertical parabolic surface to concentrate the radiation from a (E-W) tilting flat reflector that was north of the parabolic surface into a feed that was at ground level. The cost effectiveness was outstanding! I could work below the feed in an underground room accessed through a tunnel under the ground screen. You are commended for initiative in wishing to have a radio telescope. Crafting such an instrument can be an end into itself. However, having an observational goal seems to be desirable if this is more than a construction project. I recommend that you read the ample literature that is available to help you design an observational goal. Note that you need a large size if you are to achieve resolution, which might not be an objective. I worked on the receiving system for a system at NRAO at Green Bank, W.Va. that used a fixed, high gain antenna to observe (once a day) the strength of one source. The antenna used had a predictable gain and, with calibration, the system was able to provide flux measurements (with an attendant uncertainty, of course). Note that the first real radio telescope by Reber was a parabolic dish - it still exists. (He was a really bright, innovative guy.) The presence of antennas used to receive satellite broadcasts that use offset feeds should be considered. Such antennas can have desirable antenna temperatures because of the placement of the feed while not having feed-blockage. Most important is the avoidance of re-inventing the wheel that can be effected by serious study of the literature. That is where I recommend that you start. Kraus' books on antennas and radio-astronomy could be a good place to start. It would be wonderful to be young and have so much learning to look forward to! After over 50 years of studying radio related subjects, I am still excited. The delay in responding is due to the high noise level in this valuable news-group. Ignore, as I do, the theological debates. Pay close attention to those on this group who are knowledgeable. Enjoy the greatest pleasure - that of learning. Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Richard Clark" wrote in message ... On Fri, 10 Apr 2009 12:34:34 +0200, Emanuele Colucci wrote: Hi to everyone and thanks for answering to my message. Richard Clark ha scritto: Hi Emanuele, This is probably due to the way the question was offered. You want a complete solution to an unknown problem. You and Dave were right. I originally posted the message in the homebrew newsgroup because I was looking for a complete guide to design a cas in order to build a little radiometer working in the "water hole" (1420 ~ 1640 MHz) for an hobbystic aim. The book I used at university to study antennas - Antennas and Radiowave Propagation [by Robert E. Collin] - simply doesn't cover in depth this argument. It just cites the Cassegrain feed system as an alternative to prime focus paraboloidal reflector antennas, because the cassegrain feed does't receive the thermal noise from the ground. Hi Emanuele, I have that book and I can see your source material. If it is your choice, that is fine. Other correspondents here can respond to your desire to eliminate thermal noise from the ground in alternative designs. You may have to repeat your query to get their attention as this is not a topic that many have experience with (repetition is for the occasion when they check in on an irregular basis). An alternative is to search this group, specifically, at groups.google.com. I was looking for a complete resource to study the system, and this is why I wrote he to find someone with good advices. Now, the thing I have now understood is that I haven't to be so synthetic while writing a message. So, I would like to study (and eventually build) a radiometer who listens to 1420 ~ 1640 MHz, with a passing bandwidth of 8 MHz, in order to receive a minumum density flux of 240-260 Jy (a Jansky is 10^-26 W / [m^2 * Hz]). I need low antenna temperature (but not as cryogenics ones!). You can get a lot of practical ideas here (construction materials and feed issues); and you can use Collin for the math to simply scale the structure to your frequency band. The design is rather more simple than building it. 5. Budget (time and/or money); I can't answer this question yet. Surely, I haven't more than 5-600 euros to spend in the building/buying of the antenna. That is plenty of money. Do you have any time constraints? 7. Application issues (EME?). Amateur radioastronomy. We have a contributor who has been teaching that for 40 years at a major university, and he studied under the pioneers of that specialty. Search groups.google.com for posts by "Mac N8TT" or use "J. McLaughlin; Michigan, USA" as search terms. Well, that's all by the moment. Greetings, Emanuele Colucci 73's Richard Clark, KB7QHC |
Cassegrain Antenna Development
Thank you John for this message.
J. Mc Laughlin ha scritto: You are commended for initiative in wishing to have a radio telescope. Crafting such an instrument can be an end into itself. However, having an observational goal seems to be desirable if this is more than a construction project. I recommend that you read the ample literature that is available to help you design an observational goal. Yep, I'm still documenting. Perhaps, there are alternatives to a Cas antenna (Yes, I admit, because of exams I haven't crafted it yet, but for me this is a very long term project), like a little array of offset parabolic antennas. Note that you need a large size if you are to achieve resolution, which might not be an objective. I worked on the receiving system for a system at NRAO at Green Bank, W.Va. that used a fixed, high gain antenna to observe (once a day) the strength of one source. The antenna used had a predictable gain and, with calibration, the system was able to provide flux measurements (with an attendant uncertainty, of course). This is interesting! How much time did it take to make a complete radio stellar map? Note that the first real radio telescope by Reber was a parabolic dish - it still exists. (He was a really bright, innovative guy.) Reber's parabolic dish is giant :) My site is situated in countryside, and it could be able to host dishes of max 3 meters of diameter: the data would be transmitted over the internet to my home (near Naples, ITA). The presence of antennas used to receive satellite broadcasts that use offset feeds should be considered. Such antennas can have desirable antenna temperatures because of the placement of the feed while not having feed-blockage. Great. I'll watch for these antennas too! Most important is the avoidance of re-inventing the wheel that can be effected by serious study of the literature. That is where I recommend that you start. Kraus' books on antennas and radio-astronomy could be a good place to start. It would be wonderful to be young and have so much learning to look forward to! After over 50 years of studying radio related subjects, I am still excited. Thanks again for reporting your experiences and the advices! I haven't read Kraus book about radio astronomy: my sources are Collin and some italian books by Flavio Falcinelli. But now I'll surely look for this book too! Greetings, Emanuele Colucci |
Cassegrain Antenna Development
Dear Emanuele:
Do well on your exams. It is that time of the year here as well. It occurred to me that I had quite forgotten that two dishes exist associated with Reber. One is huge and the other is the 9.5 meter dish he built himself. Both are at NRAO. Reber was a true scientist and a great friend of my mentor, Kraus. Here is a story about him: http://www.nrao.edu/whatisra/hist_reber.shtml The maps he published just before the war, were studied by Dutch astronomers who were sequestered during the war. After the war, the Dutch moved the field forward. Reber's interests were many. You will note papers on beans, for which he performed truly original work much of it while we were both at NRAO. After dinner, when one learned not to leave the meat platter too close to him, he would go off to inspect his research garden. He was a collector - not quite the right word, but close - of early radios. I have seen him get them working, construct a box that would just hold the radio, and then store the boxed radio for a future museum. In his testing of old (pre war) radios he discovered that one company had discovered stagger tuning. His note on that subject caused a lot of noise. His observation - known to everyone in the radio field - that the ionosphere was most thin near VK7, resulted in his measuring radiation from space at low frequencies well before satellites. His genius of seeing in common knowledge new possibilities is his hallmark and one that I wish for all who would push knowledge forward. He constructed all of his own measuring instruments, which were strikingly beautiful. I spoke to radio amateurs in VK7 while he was still alive and they told of how beloved he was by the people of that island. By the way, my first name is James, not John. I use "Mac" as it seems more suited to this newsgroup than "Professor." It is just possible that the sort of offset-feed antenna for receiving broadcast signals is not common in Italy. If that is the case, a search will uncover surplus dishes in North America. They tend to be in the one meter size, which might be too small unless used in an array. I am told that surplus, conventional dishes show up from time-to-time as agencies/people move or up-grade. I like the idea of operating remotely. Study, learn, plan, do, observe and you will learn even more. Consider getting an amateur radio license. Warm regards, James / Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Emanuele Colucci" wrote in message ... Thank you John for this message. J. Mc Laughlin ha scritto: You are commended for initiative in wishing to have a radio telescope. Crafting such an instrument can be an end into itself. However, having an observational goal seems to be desirable if this is more than a construction project. I recommend that you read the ample literature that is available to help you design an observational goal. Yep, I'm still documenting. Perhaps, there are alternatives to a Cas antenna (Yes, I admit, because of exams I haven't crafted it yet, but for me this is a very long term project), like a little array of offset parabolic antennas. Note that you need a large size if you are to achieve resolution, which might not be an objective. I worked on the receiving system for a system at NRAO at Green Bank, W.Va. that used a fixed, high gain antenna to observe (once a day) the strength of one source. The antenna used had a predictable gain and, with calibration, the system was able to provide flux measurements (with an attendant uncertainty, of course). This is interesting! How much time did it take to make a complete radio stellar map? Note that the first real radio telescope by Reber was a parabolic dish - it still exists. (He was a really bright, innovative guy.) Reber's parabolic dish is giant :) My site is situated in countryside, and it could be able to host dishes of max 3 meters of diameter: the data would be transmitted over the internet to my home (near Naples, ITA). The presence of antennas used to receive satellite broadcasts that use offset feeds should be considered. Such antennas can have desirable antenna temperatures because of the placement of the feed while not having feed-blockage. Great. I'll watch for these antennas too! Most important is the avoidance of re-inventing the wheel that can be effected by serious study of the literature. That is where I recommend that you start. Kraus' books on antennas and radio-astronomy could be a good place to start. It would be wonderful to be young and have so much learning to look forward to! After over 50 years of studying radio related subjects, I am still excited. Thanks again for reporting your experiences and the advices! I haven't read Kraus book about radio astronomy: my sources are Collin and some italian books by Flavio Falcinelli. But now I'll surely look for this book too! Greetings, Emanuele Colucci |
Cassegrain Antenna Development
"Emanuele Colucci" wrote in message ... Thank you John for this message. J. Mc Laughlin ha scritto: You are commended for initiative in wishing to have a radio telescope. Crafting such an instrument can be an end into itself. However, having an observational goal seems to be desirable if this is more than a construction project. I recommend that you read the ample literature that is available to help you design an observational goal. Yep, I'm still documenting. Perhaps, there are alternatives to a Cas antenna (Yes, I admit, because of exams I haven't crafted it yet, but for me this is a very long term project), like a little array of offset parabolic antennas. Note that you need a large size if you are to achieve resolution, which might not be an objective. I worked on the receiving system for a system at NRAO at Green Bank, W.Va. that used a fixed, high gain antenna to observe (once a day) the strength of one source. The antenna used had a predictable gain and, with calibration, the system was able to provide flux measurements (with an attendant uncertainty, of course). This is interesting! How much time did it take to make a complete radio stellar map? Note that the first real radio telescope by Reber was a parabolic dish - it still exists. (He was a really bright, innovative guy.) Reber's parabolic dish is giant :) My site is situated in countryside, and it could be able to host dishes of max 3 meters of diameter: the data would be transmitted over the internet to my home (near Naples, ITA). The presence of antennas used to receive satellite broadcasts that use offset feeds should be considered. Such antennas can have desirable antenna temperatures because of the placement of the feed while not having feed-blockage. Great. I'll watch for these antennas too! Most important is the avoidance of re-inventing the wheel that can be effected by serious study of the literature. That is where I recommend that you start. Kraus' books on antennas and radio-astronomy could be a good place to start. It would be wonderful to be young and have so much learning to look forward to! After over 50 years of studying radio related subjects, I am still excited. Thanks again for reporting your experiences and the advices! I haven't read Kraus book about radio astronomy: my sources are Collin and some italian books by Flavio Falcinelli. But now I'll surely look for this book too! Greetings, Emanuele Colucci Hi Emanuele The probability of your realizing any success with parabolas less then 10 feet diameter using cassegrain systems is extremely low at L-band. I realize that you are able to decide for yourself, which antenna system is best for your project. I do want to alert you to the fact that the beam from the "source radiator", behind the dish, needs to be shaped to be concentrated on the reflector at the focus. There is not enough room in a 3 meter dish to provide access to a primary feed with the narrow beam required for realizing the benefits of a cassegrain feed. I have has some succes with a 1 meter off center fed dish at L-band (1.691 GHz) for redceiving signals from a geosynchronouis satellite. The feed I designed for that dish might be of some use to you. Jerry KD6JDJ |
Cassegrain Antenna Development
Jerry wrote:
"Emanuele Colucci" wrote in message ... snip I haven't read Kraus book about radio astronomy: my sources are Collin and some italian books by Flavio Falcinelli. But now I'll surely look for this book too! Greetings, Emanuele Colucci Hi Emanuele The probability of your realizing any success with parabolas less then 10 feet diameter using cassegrain systems is extremely low at L-band. I realize that you are able to decide for yourself, which antenna system is best for your project. I do want to alert you to the fact that the beam from the "source radiator", behind the dish, needs to be shaped to be concentrated on the reflector at the focus. There is not enough room in a 3 meter dish to provide access to a primary feed with the narrow beam required for realizing the benefits of a cassegrain feed. I have has some succes with a 1 meter off center fed dish at L-band (1.691 GHz) for redceiving signals from a geosynchronouis satellite. The feed I designed for that dish might be of some use to you. You might also look at the design for the Allen Telescope Array, which is a Gregorian feed, and is offset. All of these are useful to have minimum noise contribution from the surrounding earth.. if the feed over-illuminates the secondary reflector, you are still looking at cold sky, unlike with a prime focus sort of feed, where overillumination looks at the dirt behind the reflector. There's a set of articles in IEEE Antennas and Propagation Magazine (not the transactions) a few years back that has all the equations and design rules for all of the various reflector configurations. As for reflector sources.. 1.5m parabolic reflectors intended for offset feet are readily available in Europe. They're used by British Expatriates in places like the Canary Islands to get BskyB broadcasts (since they're well out of the satellite footprint, they need more gain than the usual 50cm sort of dish on the side of your house). A couple years ago, I remember googling for reflectors of this size for a project and ran across this kind of thing. The reflectors were real cheap (10-15 pounds), but shipping to the US would cost many times that. They seem NOT to be readily available surplus here in the US.. VSAT stations in Alaska might be the only application. |
Cassegrain Antenna Development
Thanks to James for the advices and to Jerry and Jim for the news.
Jerry: I'd like to know more about your solution, if you agree. :) Jim Lux ha scritto: There's a set of articles in IEEE Antennas and Propagation Magazine (not the transactions) a few years back that has all the equations and design rules for all of the various reflector configurations. Where I can find these articles? Best wishes, Emanuele Colucci |
Cassegrain Antenna Development
"Emanuele Colucci" wrote in message ... Thanks to James for the advices and to Jerry and Jim for the news. Jerry: I'd like to know more about your solution, if you agree. :) Jim Lux ha scritto: There's a set of articles in IEEE Antennas and Propagation Magazine (not the transactions) a few years back that has all the equations and design rules for all of the various reflector configurations. Where I can find these articles? Best wishes, Emanuele Colucci Hi Emanuele I submit that, if you intend to actually build an antenna for L-Band and are restricting its diameter to 3 meters, you need not consider a cassegrain feed. The reflector at the focus is too small to allow the primary feed to illuminate it with a high percentage of the available source at the rear of the dish. For one example, let the cassegrain reflector be 1/2 meter diameter and be spaced 1meter from the apex of the dish. Wouldnt that suggest that the primary beam, from behind the dish will have a beamwidth of about 30 degrees (at -3dB)?? If the cassegrain reflector is made bigger, that blocks more of the parabolic dish apperature. If the cassegrain reflector is made smaller, that increases the need for a high gain primary feed. It is my contention that, if you want to research Cassegrain antennas, that is a worthy project. If you want to build a functing L-Band telescope with 3 meter dishes, dont include cassegrain feeds in the project. Jerry KD6JDJ |
Cassegrain Antenna Development
Emanuele Colucci wrote:
Thanks to James for the advices and to Jerry and Jim for the news. Jerry: I'd like to know more about your solution, if you agree. :) Jim Lux ha scritto: There's a set of articles in IEEE Antennas and Propagation Magazine (not the transactions) a few years back that has all the equations and design rules for all of the various reflector configurations. Where I can find these articles? Best wishes, Emanuele Colucci You might want to take a look at W1GHZ's online book http://www.w1ghz.org/antbook/conf/Mu...r_antennas.pdf He gives a procedure, and refers to a variety of sources, among them, the ones I was thinking of: The articles I was thinking of were by Christophe Granet at CSIRO in Australia, and published in Tom Milligan's "Antenna Designer's Notebook" column in the A&P Magazine April 1998, "Designing Axially Symmetric Cassegrain or Gregorian Dual-Reflector Antennas from Combinations of Prescribed Geometric Parameters" June 98, Minimum blockage Dec 99, Displaced axis dual reflector antenans (4 types) Dec 2001, Dragonian Dual-Reflector June2002, Offset Cassegrain or Gregorian Dec 2003, Designing ..offset.. Part 2, Feed-horn Blockage Conditions. There's some FORTRAN available too, from Tom Milligan. |
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