900 Mhz - Page 5 - RC Groups
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Dec 22, 2012, 08:42 PM
No, you are mistaken. They really are -150dBm to -165dBm (and more now!) sensitivity. Here are just a few examples from dozens of GPS receiver chips available:

http://gpstekreviews.com/2007/04/14/...rmance-survey/
http://microcontrollershop.com/produ...oducts_id=4597
http://www.u-blox.com/en/gps-chips/s...ngle-chip.html

Spread spectrum signals are 'wide' band transmissions, but the definition of 'wide' is subject to opinion. As pointed out in the datasheet for the AT86RF212 the bandwidth is selectable from 240KHz to 1.2MHz. Wider is better for fighting interference.

Spread spectrum systems do not add noise. They do in fact reduce the effects of noise. Here is an article describing how spread spectrum works, including noise suppression and processing gain:

http://www.eetimes.com/design/commun...rum-Technology

I spent 18 months of my life helping debug and test a 2.4GHz front-end chip, and building more than 50 different prototype designs for testing. I think I have a pretty good handle on how all of this stuff works. The information I have presented is absolutely correct, verified by Atmel (and other 900MHz RF chipset manufacturers) with real world testing, providing application notes to the public for projects that you can build yourself and test.
Last edited by JimDrew; Dec 22, 2012 at 08:50 PM.
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Dec 22, 2012, 11:35 PM
Registered User
I think your specification is mistaken
check this out.
http://en.wikipedia.org/wiki/High_Sensitivity_GPS
Dec 23, 2012, 12:05 PM
LOL! "This article does not cite any references or sources." Not surprising it is incorrect. That 'W' should be a 'M' instead. Seriously, do some research on the chipset manufacturers and see what they show for sensitivity. I already linked several examples, but you can find dozens of others.
Apr 16, 2013, 10:46 AM
Thermals, Tom
RyanNX211's Avatar
Quote:
Originally Posted by JimDrew
We plan to make 900MHz as common as our 2.4Ghz, with indentical modules and receivers.
While my interest in 900mhz was piqued a while ago, I have no problem with 2,4 Nanos at this point.

It was good to hear at Toledo that you're holding off on this as we don't want to draw unnecessary attention for our ability to fly our models really far away.
Otherwise, I might commit to waiting and not making a decision.
Apr 16, 2013, 02:53 PM
Registered User
jim don't know how you are so diplomatic with that guy just reading his post are annoying

don


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