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Old Mar 21, 2013, 05:16 PM
Sweetrex is offline
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Major Differences in FASST and S-FHSS


I can't find a discussion (although I'm sure it exists somewhere) about the major differences in the FASST and S-FHSS radio systems by Futaba. One thing I do see is a HUGE difference in pirces on the Rx's and Tx's. Can anyone comment? I'm not a competition level flyer and I don't have planes bigger than maybe the biggest parkflyers and maybe a bit bigger than that or faster than 120mph.
Last edited by Sweetrex; Mar 21, 2013 at 05:21 PM.
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Old Mar 21, 2013, 06:03 PM
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The actual RF chips are different. FASST uses the ML2724 (+their own chip for the DSSS modulation), where as S-FHSS uses the CC2500. The CC2500 is the same chip that is used in FrSky/Hitec/Graupner and other systems.

FASST is both DSSS modulation (like DSM2) and FHSS (frequency hopping) - much like DSMX. Where as S-FHSS is just FHSS - like FrSky/Hitec/Graupner systems.

Futaba seems to target FASST (and FASSTest) as their premium system and S-FHSS as a more 'eco' system. However I suspect this is in part to not upset existing users of FASST systems. It would have been commerically suicide, but they could have dumped FASST and moved to S-FHSS without users noticing a difference.

Finally S-FHSS and FASST aren't compatible with one or the other. HOWEVER there are new Futaba transmitters out there that support both FASST and S-FHSS - notably the Futaba 18MZ and 14SG.

Si.
Old Mar 21, 2013, 09:10 PM
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Quote:
Originally Posted by SimonChambers View Post
The actual RF chips are different. FASST uses the ML2724 (+their own chip for the DSSS modulation), where as S-FHSS uses the CC2500. The CC2500 is the same chip that is used in FrSky/Hitec/Graupner and other systems.

FASST is both DSSS modulation (like DSM2) and FHSS (frequency hopping) - much like DSMX. Where as S-FHSS is just FHSS - like FrSky/Hitec/Graupner systems.

Futaba seems to target FASST (and FASSTest) as their premium system and S-FHSS as a more 'eco' system. However I suspect this is in part to not upset existing users of FASST systems. It would have been commerically suicide, but they could have dumped FASST and moved to S-FHSS without users noticing a difference.

Finally S-FHSS and FASST aren't compatible with one or the other. HOWEVER there are new Futaba transmitters out there that support both FASST and S-FHSS - notably the Futaba 18MZ and 14SG.

Si.
Thank you, Si.
Old Mar 21, 2013, 09:30 PM
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Thanks Simon. I like to have all of the chip specs and FCC reports.

http://www.sparc.uni-mb.si/Sistemida..._Sheet_1_2.pdf
Old Mar 22, 2013, 01:47 AM
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Frsky FASST compatibles are using same ML2724 as Futaba and sells for less than $30, so the difference is only in their marketing scheme.
Old Mar 22, 2013, 07:37 AM
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So I can use FrSky stuff interchangeably?
Old Mar 22, 2013, 08:45 AM
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Not any Frsky stuff, they have two production lines, own ACCST system, and FASST compatibles.
Only the FASST compatibles can be used with a Futaba transmitter.
Old Mar 22, 2013, 10:20 AM
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A clone must use the same chip so that it can clone the firmware.
Old Mar 22, 2013, 10:49 AM
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Nope, is not a clone, is a compatible.
And is not necessary to use same chip.
A receiver has two parts: the RF part, a chip called transceiver, and the logic part, which is a microprocessor. Both are consumer chips, without anything secret or proprietary inside, and aren't so new technology as you could believe, mostly are developed between 2003 and 2006.
CC2500 transceiver is used in Hitec, Graupner, Frsky, and nobody call any of them a cloe of the other
What make a system is the FH protocol and decoding scheme, which are programs executed by the microprocessor. You make a clone when you obtain the program from whatever source, either illegal or immoral
When you use a logic analyzer to intercept the dialog between RF part and microprocessor, and create from the scratch another software who does the same thing, this is not a clone, is reverse engineering, and implies a lot more brain than the first. Also, some don't consider this fact as illegal, unless explicitly specified, which is a very fuzzy part if intellectual property.
Old Nov 09, 2013, 05:16 AM
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fhss vs dsmx


spectrum analysis
Old Nov 09, 2013, 09:47 AM
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Modraude, would you care to comment on the differences as seen in the two spectrum analysis plots????

Or anybody else ???
Old Nov 09, 2013, 10:57 AM
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Quote:
Originally Posted by Airman74 View Post
Modraude, would you care to comment on the differences as seen in the two spectrum analysis plots????

Or anybody else ???
i think that the largest size of spikes and the more homogeneus time distribution on waterfall display of dsmx is the effect of dsss...
i would like that someone can confirm this.. i just measure...
Old Nov 09, 2013, 11:51 AM
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Not comparing apples to apples there.

A fare comparison would be Speky DSMx with JR DMSS or Futaba’s FASSTest, these are Hybrid systems with wider bandwidth signal (much better)
In fact Futaba’s FASSTest and JR’s DMSS looks very similar on a spectrum analyser.

Doug
Old Nov 09, 2013, 12:14 PM
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Originally Posted by DougV View Post
Not comparing apples to apples there.

A fare comparison would be Speky DSMx with JR DMSS or Futaba’s FASSTest, these are Hybrid systems with wider bandwidth signal (much better)
In fact Futaba’s FASSTest and JR’s DMSS looks very similar on a spectrum analyser.

Doug
so they are similar to the orange dsmx compatible showed on left image?
Old Nov 09, 2013, 03:54 PM
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The difference between Futaba S-FHSS and FASST is range. This is due to Tx RF output power and Rx sensitivity.

The Futaba S-FHSS transmitters come with reduced RF output power. The receivers have less sensitivity. "S" might stand for "short" (range).

Ok, here are the numbers.

The popular T14SG in FASST:
P = 16.83dBm (w/o G = 1.5 dBi Antenna Gain)

The 18MZ in FASST:
P = 16.145dBm (w/o G = 1.5 dBi Antenna Gain)


T6J:
P = 15.83dBm (w/o Antenna Gain 2.0dBi)

T8J:
P = 13.242dBm (w/o Antenna Gain G = 2.0 dBi)

Cheers!
Last edited by Pippin; Nov 09, 2013 at 04:17 PM.


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