2M Foamy

To discuss all things relating to flying models via remote video

2M Foamy

Postby Mark Hitchman » Thu Apr 12, 2012 12:54 am

This is my last flight of my 2 Meter foam glider before I switch to CP antenna. The area has 110KV power lines which I fly over and a river bed to get some extra interference :)
The next flight will be with a Skew Planer on the VTX and a Helical on the receiver for a direct comparison.

http://www.youtube.com/watch?v=DoKYtZqVj2A
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Re: 2M Foamy

Postby RCModelReviews » Thu Apr 12, 2012 1:50 am

So what VTX/freq are you using?
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Re: 2M Foamy

Postby Mark Hitchman » Thu Apr 12, 2012 2:12 am

1010 Mhz, my 5.8 ghz receiver and transmitters just arrived :)
Will be good to do a comparison
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Re: 2M Foamy

Postby RCModelReviews » Thu Apr 12, 2012 2:27 am

To give you an indication -- I can reliably get to 2KMs with a 200mW 5.8GHz transmitter using a conventional 2dBi transmitter antenna and 5dBi receiver antenna.

Switching to CP antennas reduces that range slightly (which is to be expected because they're lower gain) but the increase in noise as you near the limits of range is far more predictable and gradual. This gives great confidence when flying at the limits of FPV range as you don't get those prolonged dropouts that occur with conventional dipoles.

I've got a 500mW 5.8GHz transmitter here which I would expect to extend the useful range to about 3Kms with CP antennas and I'm building a 9dBi helical to test in conjunction with my diversity controller.

The nice thing about 5.8GHz is that the receiver modules are only about US$10 a pop so it becomes really practical to have an antenna-farm with diversity to give you good long range without sacrificing coverage around the landing area.

I'm expecting that the maximum practical range with 5.8GHz and hi-gain antennas will be in the region of 8-10Kms.
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Re: 2M Foamy

Postby Mark Hitchman » Thu Apr 12, 2012 3:15 am

Yeah those 5.8 receivers are amazing, the size of a postage stamp :)
pity about the range though, never worked out why the higher frequencies are not better closer to the ground than lower frequencies. The freznel zone is smaller so why would they not be better?
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Re: 2M Foamy

Postby RCModelReviews » Thu Apr 12, 2012 3:47 am

The problem with higher frequencies when near the ground is that the "ground clutter" absorbs too much signal. Lower frequencies tend to pass right through the ground clutter without obstruction but up at 5.8GHz everything (trees, bushes, damp air etc) becomes a brick-wall.

The solution is (of course) to set an orbiting relay up at a higher altitude (an RC model with an FY21/31 orbiting a fixed point). That plane can receive the video from the FPV model on one frequency and re-transmit back to the ground-station on another.

Starts getting pretty complex then though.
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