When do we get "spread-spectrum" technology?  
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When do we get "spread-spectrum" technology? - 10/23/2005 3:37 PM   
Capt Jim


 

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Spread-spectrum technology has been available for surface vehicles, but not airborne vehicles, until just recently. I see that a complete "spread-spectrum" receiver/transmitter system is now available for the foamies, and micro helis...but not for the more conventional forms of aircraft. That suggests a possible limited range scenario??? Does anyone have any good info as to when we can expect to see "spread-spectrum" technology available for the rest of us...desperatly wanting to relieve ourselves from our biggest vulnerability.....radio interference.
Thanks.
Jim

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RE: When do we get "spread-spectrum" technology? - 10/23/2005 7:42 PM   
Geistware



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Status: offline 		From what I understand. The power output limit for 24 Ghz is 100mw. That is not enough power for out larger planes. Also the antenna is very directional so two is needed to ensure proper 360 degree coverage. With the FCC power limit, I don't see this being available in the USA for quite some time.

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RE: When do we get "spread-spectrum" technology? - 10/23/2005 9:33 PM   
Capt Jim


 

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Status: offline 		Aha...there always a problem! Thanx for the heads up.....maybe this is what it takes to get me into a flying damm foamie. hehheh. My 1/4 scale Cub will never forgive me.
jim

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RE: When do we get "spread-spectrum" technology? - 10/23/2005 10:14 PM   
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Status: offline 		Spektrum has just announced there 6 channel DSM radio for parkflyers and indoor flyers (airplanes and heli).
Not long now!

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RE: When do we get "spread-spectrum" technology? - 10/24/2005 5:56 AM   
submikester


 

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Status: offline 		Think about how far you can go with your 2.4 Ghz cordless phone, or your 802.1a/b/g wireless network card.

The Spread-Spectrum technologies are based on the same 2.4Ghz technology that those are one and while designed to work well together in my experience range is always an issue. Jumping up to 5ghz makes range better but it still isn't nearly what we have with our current systems.

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RE: When do we get "spread-spectrum" technology? - 10/25/2005 4:18 AM   
aeajr



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Status: offline 		Spread is available now and has a 3000 foot range. They are marketing it for electrics.

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RE: When do we get "spread-spectrum" technology? - 10/25/2005 3:01 PM   
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Status: offline 		Spread spectrum is used for the downlink for my Eagletree telemetry system. In the high power mode(100 mw) it has never dropped out on me. I tried to get my aircraft to 1000 feet but I had to stop at 850 feet because I could no longer see it well enough to be able to control it. It also seemed like I was missing control pulses although I can't say that for sure.

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RE: When do we get "spread-spectrum" technology? - 10/25/2005 11:04 PM   
mr.rc-cam



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Status: offline 		Actually, the power output on the FCC Part 15 approved long range SS devices is as high as 1 watt. The magic is that the average power is zero on a spread spectrum RF signal. If done correctly, the effective radiated power appears as random noise. In absence of the spread spectrum technology, the allowed RF power is well under 1mW (0.001 watt) for Part 15 transmitters.

Having said that, I suspect that the new Spread Spektrum R/C system from Horizon is based on much less than 1 Watt. I would expect it to be a ~100mW design and use a receiver that has very good sensitivity (with a mere -104dBm or better sensitivity spec it could offer out-of-sight range). Keep in mind that the Spektrum system is designed for moderate range park flyer use, so a few hundred yards of range is plenty in that case.

My gut feeling is that spread spectrum R/C will not be the Holy Grail as some wish it will be. It will have many advantages, but I just don't expect it to be perfect for every R/C'er.

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RE: When do we get "spread-spectrum" technology? - 10/25/2005 11:33 PM   
BillS


 

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Status: offline 		Last year at the NAS Oceana air show several drones were being displayed including a helicopter. We were told they used Spread Spectrum.

Bill


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RE: When do we get "spread-spectrum" technology? - 10/26/2005 6:57 PM   
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Status: online 		In this airborne application, you have to take into account the orientation and polarization of the antennas (both in the airplane and on the ground). This is much less of an issue, when you have 3 or 4 times the usable range (ie beyond your eyesight) in most 72 Mhz narrow band systems.

These 2.4 GHz systems are paying a pretty big penalty in path loss at such a high frequency as well.

My partner and I demoed a system spread spectrum system to the AMA 2 years ago, it used 4 antennas in the plane. Flying at long ranges in fast airplanes with 2.4 GHz is not easy AT ALL.

I am sure we will find out the practical range of this system from Horizon soon enough, when they start getting on the market. My hat is off to them for getting this system out there.

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RE: When do we get "spread-spectrum" technology? - 10/30/2005 4:06 PM   
dirtybird


 

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Status: offline 		Do you know who invented Spread Spectrum transmission?
Heddy Lemarr! For you youngsters she was the Marylin Monroe of her day. Or Pamala Andersson if you don't know who MM was.
She held the initial patent. The patent had long expired before anyone had any use for it.

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