Hi Lou,
I think you will have a couple of challenges. But, this could be fun.
The issue with weight on your rotisserie is partly a matter of mass, but mostly of balance. Find a way to mount the dish so that it doesn't apply a big torque to the motor. Back when AO-40 was still transponding, I had a 3' x 2' BBQ grill dish. When I mounted it, I used the LNB as a counter weight on a shaft behind the dish to offset some of the torque it applied, being mounted on the side of the cross-boom. http://home.wavecable.com/~ko6th/Dsc00201.jpg Even my little Alliance TV rotor (mounted sideways as an Elevation rotor) could move it just fine. One of the things I did which might have helped was that the mechanical connection between the rotors and the antennas had some "give" to them. The idea was that doing so prevented the motor from stalling when it tried to start moving. No idea if it helped, but that was the theory. All that said, your dish (one of them) is even heavier. I would be concerned if you tried this with two unless you can really balance things.
The other issue could be the size of the dish, compared to the wavelength you are capable of receiving. From what I remember when building the AO-40 station, 2.4 ghz needed a dish at least a few feet in diameter for good performance, and your dish was designed for 5.8 ghz. If you're only looking below 2 ghz, it might be disappointing. Are you committed to using the SDRPlay? Something like the HackRF can go to 6 ghz, for example. Lacking that, you're going to need a down-converter. For AO-40, there were several models of HBO receiver setups that we re-purposed, for example, my Drake 2880. They naturally receive in the 2.5 ghz -2.7 ghz range, if there's anything interesting left in that band. They were easy to move to nearby bands by re-crystaling the LO.
Last thought is regarding sensitivity. These SDR devices aren't noted for being really sensitive, nor very selective (poor front-end filtering), though some are significantly better than others. If you can focus on a single RF segment, a narrow band, low noise preamp at the antenna will go a long ways towards actually hearing something. Receiving AO-40, with its 10 watt transmitter only 30,000 miles away, required me to invest in a good preamp at the feed point in order for my Drake down converter to produce anything audible, and even then it was right above the noise. Modern SDRs are probably a good bit better than the Drake / ICOM IC-R7000 receiver lash-up I used, but you're looking for something potentially a lot weaker.
Then again, this hobby is all about experimenting and seeing what works. Good luck, and let us know what you find!
Greg KO6TH
Lou Michaels wrote:
A pair of 25'' 5.8ghz 29dBi Teletronics International dishes fell into my lap this week and I'm trying to decide on some projects.
Here's a pic: https://i.imgur.com/W9oeVSv.jpg
I have a G5500 rotor from my previous ground station, and I'm thinking of doing some solar radio astronomy or transponder chasing.
Without the covers, the dishes weigh 13.2lbs each. Could the G5500 safely handle the load of one or two of these dishes? I'm not considering roof mounting, and prefer to do things closer to the ground for the time being.
Via a SDRPlay, my highest receive capability is 2ghz. Short of changing the feed, what might I do or be able to use to bring the frequency down to something more manageable or will the dish still feed signals at lower frequencies?
I'm not beyond changing the feed, or building transverters, but some searching isn't producing more than commercial wifi applications.
Anyone have any plans, ideas, advice or direction to offer?
Thanks in advance!
Cheers, Lou W2LMM
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