It's a good thing you want the less technical version - because I'm a software engineer by trade. I really wish I knew a lot more about antennas & electronics. With amateur radio astronomy - a lot of it depends on what you are trying to observe, i.e. what frequency range you are working in and how strong are the sources you are observing. For solar, and Jupiter-Io events I think a Yagi is perfect. For radio-meteor detection - an AM radio is all you need. I'm not familiar with using a cylindrical parabola - so I would have to defer to someone that actually knows what they are talking about. <g> What I am doing is aimed more at detecting galactic hydrogen - i.e. 1420 MHz (also known as the "water hole"). So, I hope it's okay if I answer the advantages/disadvantages from that perspective: Parabolic dish: - this is what I am using Advantages: Cheap - most people are giving them away. Aperture - More aperture so more signal Resolution - the larger size gives you better resolution (but it's still terrible when compared to optical frequencies) Disadvantages: Ugly - lets face it - these things aren't very "purdy" Massive - they weigh a lot so they need to be mounted in concrete Pointing - because of the size you need to either do "drift scans" or get fairly expensive rotators. Single Yagi Advantages: As you mentioned - you can build one at home Lighter weight - so you can probably get a cheaper rotator or set them up on a temporary basis and just move them by hand Disadvantages: Custom - if you want one for 1420 MHz you will have to build it or buy a custom one - which adds up to more money Less signal strength - so you will need a longer integration time to get any signal Higher noise - I believe they aren't as good at off axis noise rejection as a dish Yagi Array (S&T had some great articles about building one) Advantages: Highest resolution A lot easier to set up than an array of dishes Disadvantages: Requires additional electronics to create in interferometer - but this is certainly doable. Requires a pretty good sized yard You have to space the antennas according to the frequency that you are monitoring I hope this is at least somewhat helpful. Clear skies, Dale.
-----Original Message----- From: utah-astronomy-bounces+dale.hooper=sdl.usu.edu@mailman.xmission.com [mailto:utah-astronomy- bounces+dale.hooper=sdl.usu.edu@mailman.xmission.com] On Behalf Of Kim Hyatt Sent: Thursday, September 08, 2005 12:30 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] amateur radio astronomy
Hi Dale. I'm afraid I can't help you at all with your problem, but your post reminded me of something I haven't really thought about for some time.
One of my earliest astronomy projects was the construction of a radio telescope, 'way back in high school. Since I'm not ashamed of my age, I'll divulge the year: 1971. (Everyone's supposed to say, "Why Kim, I had no idea you were that old. You look SO young!) Unfortunately, I became distracted by other things and abandoned the project before it got very far. Anyway, at first I had planned to purchase a surplus military parabolic dish to use for an antenna, but it was too costly. I finally determined to build a Yagi array, but not before I realized that a cylindrical parabaloid would have also been very easy to build and with very little skill or exotic materials required. I don't recall why I settled on the Yagi array, I have simply forgotten too much of the physics involved. And that finally brings me to a question I have for you and others: What would be the advantages/disadvantages of one type of antenna over another? I would still rule out the conventional parabolic dish because of the relative complexity of its construction for a basement tinkerer like me. However, the cylindrical parabaloid is still quite easy to construct with some plywood, a simple plot of a parabola on a piece of paper for a pattern, and some hardware fabric or insect screen to cover the surface. Can anyone enlighten me? Remember, you need to explain in terms my few remaining viable brain cells can comprehend.
Thanks all.
----- Original Message ----- From: "Dale Hooper" <Dale.Hooper@sdl.usu.edu> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Thursday, September 08, 2005 9:19 AM Subject: [Utah-astronomy] Sept. QST source for RT upgrade help
| I'm hoping that Gary Liptrot or one of the other amateur radio operators | on the list might be able to help me with this - | | | | I'm trying to determine the best way to upgrade my radio telescope so | that it is fully-steerable. | | | | It's my understanding that the September issue of QST magazine has a | good review of available rotators. But, I've been unable to find a way | to purchase the magazine without joining ARRL. I've tried the Logan | Borders, Hastings, and Wal-Mart as well as amazon.com with no joy. So, | if you could let me know where I could purchase a copy, it would be | greatly appreciated. | | | | Clear skies, | | Dale. |