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Author Topic: Corner reflector instead of yagi  (Read 2036 times)
K5TED
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Posts: 96




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« on: October 16, 2017, 06:55:44 PM »

Anyone using corner reflectors for sat comms? The Arrow dual band looks interesting.
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N4UFO
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Posts: 515




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« Reply #1 on: October 17, 2017, 06:37:37 AM »

Hi Ted,

Not that I am aware of... portable or handheld, the vast majority of folks use an Arrow, followed by an Elk and then homebrew handheld yagis a distant third. And while the Elk is okay for permanent setup outside, I'm told the Arrow is not designed for all weather without doing some weatherproofing.

At home, it's usually yagis of various sorts, either single polarity of dual/circular polarity. (Probably the optimum would be switchable dual polarity instead of circular.) If one has an AZ-EL rotor, one can use a bit of gain, but a lot is not necessary... the days of 20+ element yagis is over; for the time being at least. (I have 7 on VHF and 11 on UHF myself.) If you try to use yagis set to a fixed elevation (15-20 degrees) a simple TV rotor will do, but you need to limit the gain to about 3 elements on VHF and 5-7 on UHF. Why? because when the bird goes over head you will lose it. In case you asked, 'fixed elevation?', yes, the birds will spend the vast majority of the time between 0 and 30-40 degrees of your local horizon... and when they do go 'overheard' they are not there for long, because they will 'whip on by' relative to your position. So, setting up some low gain yagis tilted up about 15-20 degrees is a trick to get around not having an AZ-EL rotor.  But keep in mind the 'fixed elevation' trick doesn't work worth a flip on SO-50. SO-50's downlink is so weak (1/4 watt to a 1/4 wave whip) you need to be pointed right at it with a gain antenna.

For use with my AZ-EL rotors, I picked up a couple of used Cushcraft yagis... Diamond makes some inexpensive yagis that would also be quite good (5 or 10 elements on VHF, 10 or 15 on UHF). If one wants to experiment with dual polarity, the M2 'LEO pack' would be a good choice and can be purchased through the AMSAT website getting you a discount and a donation to AMSAT.  Smiley

Last and certainly the least... folks using omnidirectional antennas. Folks trying to work SO-50 with a regular 2m/uhf omni antenna can't hear the bird and create a lot of QRM. A number of folks have tried using 'eggbeater' or similar style antennas on the linear birds, but even with preamps, the claims made about their performance bring up serious questions, in my opinion. Most folks claiming they work fine have likely never used any other antennas and simply don't know what they are NOT hearing. Or they are trying to sell them so they can put up some yagis...  Wink

Want to try out satellites for the first time? Arrow is a good choice, but keep in mind it's meant for handheld. And while some people try mounting them on tripods, experienced ops have learned that ends up being far more work and does not perform as well as simply holding it. It takes a bit, but two hands can manage if you arrange your gear correctly.  Cheesy  The Arrow is also a good choice because it's duarable and easily portable. BUT, if someone wants to homebrew up something just to 'get a taste' to see if they like satellites, here is some good info:

http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf

http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf

Keep in mind, follow dimensions and specs to the latter, use GOOD coax (LMR-240UF or Wireman #118) and keep it as short as possible. Despite what the calculations and the experts will tell you, a foot or two can make a difference. Some very experienced hams that are new to satellites will argue this point, but many sat elmers have seen a newbie having problems and after being advised to shorten their feedlines by a foot or two, suddenly can hear the satellite.

I realize I went WAY beyond the question asked, but I was kind of trying to anticipate the next set of questions and having this information out here is good for the 'lurkers' out there as well.  Grin

73 & GL!  Kevin N4UFO
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W5PFG
Member

Posts: 149




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« Reply #2 on: October 17, 2017, 09:38:58 AM »

I'm not aware of anyone trying a corner reflector yagi these days.  I've not tried, personally.
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