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"Poor Mans" 2.4 Ghz Spectrum Analyzer

Old 07-01-2012, 01:42 AM
  #26  
kyleservicetech
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Originally Posted by solentlife View Post
Hi Denny ... sorry to drag out an old post ...

I read somewhere that depending on how the Tx signal is set up - there are different power levels allowed. As I understood from the article 'limited' freq hopping / allocation allowed a radio to be higher powered, but general bandwidth hopping was seriously limited in power. Maybe this is part of the reason that the Futaba signal appears tighter ? It's not unusual for radio signals to have side lobes / splatter as the power is increased or lesser quality components used ?
I find it interesting that in days of 35Mhz FM ..... JR went their own route with FMSSSSS - using a different intermediate freq in their Tx / Rx's .... so it meant you could only use JR crystals. Rest of the RC was using another. later JR amended their gear to join the general world and have same intermediate .... isn't it strange that 2.4Ghz seems to have done similar - in fact even worse as each manufacturer / brand seems to have it's own version of freq control / allocation.
Will we see a coming together of 2.4Ghz in future to a single system format ? I hope so ... It was so simple in the old days .... a pendant and number on your Tx ... a peg from the control board .... go fly. No peg - No fly. Today ? Who knows what the hell is going on up there in the ether ....

Nigel
Interesting info
I've checked the 2.4 Ghz chips used in my Spektrum DX7 and AR7000 receivers. These type chips are generally transceivers, capable of both transmitting and receiving.

It looks like Spektrum/JR transmitters first look for open channels, then broadcast on unused channels. Futaba, if my el-cheapo Spectrum Analzyer is correct, just broadcasts on every available channel regardless if other transmitters are using several channels. At least that is what showed up on my Spectrum analyzer.

Don't think we will ever see interchangeable receivers from different suppliers work with the Spectrum/JR/Futaba type radios. Likely a lot of $$$$ goes into designing these transmitters and receivers, and likely most of those $$$$ goes into the computer code required to run both the transmitters and respective receivers.
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Old 05-01-2013, 07:44 PM
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Just thought I would add a line or 2 on the subject of spectrum.......
I have found a site that helped me with this, as I am not an electronics guru and have always wanted to know...... Check it out....

Will post link in next message....
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Old 05-01-2013, 07:44 PM
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The link is: http://www.rcmodelreviews.com/spreadspectrum01.shtml

Really good stuff on how r/c stuff works....
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Old 05-02-2013, 01:56 AM
  #29  
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Originally Posted by Channel 19 View Post
The link is: http://www.rcmodelreviews.com/spreadspectrum01.shtml

Really good stuff on how r/c stuff works....
Thanks, I've run across this before.

FYI, the Spektrum DSSS (Direct Sequence Spread Spectrum) and DSMX is much more advanced and far more complex than the "Simple" FHSS frequency hopping used by Futaba and other mfgs. The frequency hopping mode of operation goes back to World War II. From what I can determine, Spektrums DSMX is a combination of both DSSS and FHSS, making the DSMX very difficult to interfere with. However, assuming quality equipment, both types work, and work very well in most flying locations.

Methinks in a very crowded radio area like a very large model airplane fun fly, DSMX might have it over the FHSS systems. Spektrum has a video where they turn on 100 2.4 Ghz radios, then move the pilot and his transmitter several hundred feet away, then fly the model over the 100 transmitters. Try that with 72 Mhz, and you will have a "Dial a crash!".

Take a look at this, yeah it is involved!! There are web sites that get into the mathematics of how DSSS works, and those sites are far more complex.

http://www.eetimes.com/design/commun...rum-Technology
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Old 08-09-2013, 04:52 AM
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Default 2.4 Ghz frequency spectrum analyzer Update

This is a sad update for what was a very good and very well priced unit. The mfg has discontinued it, and it is getting very hard to find.

What is worse, since the mfg has discontinued it, the mfg is not supporting Windows 8. So if you have Windows 8, it can't be installed. And if you had an older computer that has had the Windows 8 upgrade, the analyzer won't work with Windows 8.
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Old 08-09-2013, 03:58 PM
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Crap. There's gotta be another one out there somewhere.
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Old 08-09-2013, 06:41 PM
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Originally Posted by CNY_Dave View Post
Crap. There's gotta be another one out there somewhere.
Yeah
I've found one or two of them. Problem is, price starts at $120 each.
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Old 08-12-2013, 04:07 AM
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Cheaper than $20,000!
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Old 08-12-2013, 04:14 AM
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Originally Posted by CNY_Dave View Post
Cheaper than $20,000!

Yeah
But still a long way from the $40 I paid for the one I have that don't work with Windows 8
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