SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Closed Thread
Thread Tools
Old Oct 14, 2008, 07:08 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,781 Posts
"If it was actually capable of listening to all 40 channels inside of 94ms (or
320ms for that matter), then shouldn't it relink inside that same period of time"

I think this is what you like to call a strawman arguement. If the receiver is cycling through all 40 channels in 94 msecs, when will it be listening on the channel the transmitter is using since the Tx it is not on continuosly? Maybe that is why the 6100 takes its time re-aquiring?
teamdavey is online now Find More Posts by teamdavey
Sign up now
to remove ads between posts
Old Oct 14, 2008, 09:12 PM
Registered User
Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
28,654 Posts
Maybe so. If that's the case, then it's even more pointless.
Note that they specially tout fast re-link time as one of the benefits of a
scheme that still has DSSS at its foundation. Besides Tx and Rx
clocks should stay synchronized for a longer than the second
it takes to break the Rf link, so Rx should be listening when Tx is transmitting.
That's pretty fundamental to any SS system that isn't on-air 100% of the time.

ian
Daemon is online now Find More Posts by Daemon
RCG Plus Member
Old Oct 14, 2008, 09:46 PM
Registered User
Melbourne, Australia
Joined May 2006
6,407 Posts
Quote:
Originally Posted by teamdavey
"It still seems a somewhat creative interpretation of the letter of the law rather than its intent, but never-the-less, valid."

It says what it says, if the intent was something different, then it should say something else - no?
Having been involved in telecommunications standards for a couple of decades it is my view that it is extremely hard to make them crystal clear and totally unambiguous. In this case there is some wriggle room in the wording IMO that was probably not intended but is available even so.
kgfly is online now Find More Posts by kgfly
Old Oct 14, 2008, 09:53 PM
Registered User
Melbourne, Australia
Joined May 2006
6,407 Posts
Quote:
...While the equipment is operating (transmitting and/or receiving) each channel of the hopping sequence shall be occupied at least once during a period not exceeding four times the product of the dwell time per hop and the number of
channels....
I agree with Daemon that it is hard to see how DSM complies with this aspect. My understanding is that the Tx only transmits on two of the 40 channels, period, so it does not comply. It also seems most unlikely that once connected to the Tx, the Rx scans the other channels. So it would appear to me that only during power-on time for the Tx (where it scans all channels to select the two to use) and power-on for the Rx (where it scans all channels to find the bound Tx) do they comply, but during normal operation they don't.

In the end, if the authorities have given it their blessing, that's all that really matters to the RC world.
kgfly is online now Find More Posts by kgfly
Old Oct 14, 2008, 10:30 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,781 Posts
"Besides Tx and Rx
clocks should stay synchronized for a longer than the second
it takes to break the Rf link, so Rx should be listening when Tx is transmitting.
That's pretty fundamental to any SS system that isn't on-air 100% of the time.'

That was not the point I was making - forget it.
teamdavey is online now Find More Posts by teamdavey
Old Oct 14, 2008, 10:32 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,781 Posts
"In the end, if the authorities have given it their blessing, that's all that really matters to the RC world."

Exactly!
teamdavey is online now Find More Posts by teamdavey
Old Oct 15, 2008, 06:18 AM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,331 Posts
I just read here that a small 1-antenna RX for small planes is planned (soon).
This makes the system more and more tempting.
Julez is offline Find More Posts by Julez
Old Oct 15, 2008, 06:31 AM
Holger Rusch
Prof. Dr. YoMan's Avatar
Germany, Karlsruhe
Joined Apr 2003
415 Posts
Quote:
Originally Posted by Julez
This makes the system more and more tempting.
Julez, you know, less that 15 channels FHSS gives no more than 20mW EIRP legaly in the EU for this system.

They should implement full hopping as even XPS/IFS in version 3 will do it to be
EN300-328 conform.

Looking forward on how Jeti and Spektrum will manage this.
Prof. Dr. YoMan is offline Find More Posts by Prof. Dr. YoMan
Old Oct 15, 2008, 12:28 PM
Registered User
slowswede's Avatar
Joined Jan 2007
180 Posts
Quote:
Originally Posted by Prof. Dr. YoMan
Looking forward on how Jeti and Spektrum will manage this.
Spectrum does.. I guess Jeti does too, somehow..

This is Spectrums explanation:

FHSS modulation shall:
either:
a) make use of at least 15 well defined, non-overlapping hopping channels
separated by the channel bandwidth as measured at 20 dB below peak
power;
or if capable of adaptive frequency hopping:
b) at least be capable of operating over a minimum of 90 % of the band
specified in table 1, from which at any given time a minimum of 20
channels or hopping channels shall be used.
For both cases, the minimum channel separation shall be 1 MHz, while the dwell
time per channel shall not exceed 0,4 s.
While the equipment is operating (transmitting and/or receiving) each channel of
the hopping sequence shall be occupied at least once during a period not
exceeding four times the product of the dwell time per hop and the number of
channels. Systems that meet the above constraints shall be tested according to the
requirements for FHSS modulation.


In short:

As long as you are listening to 15 or more channels in a given timeframe it seems that you cover a loophole and clause (a) applies.. Listening does not really mean recieving anything, just a scan, if TX or RX both have to do so, I dunno..

Somewhere read that the next revision of EN300-328 (after V1.7.1) perhaps will drop the DSSS/FHSS difference, next year perhaps?
slowswede is offline Find More Posts by slowswede
Old Oct 15, 2008, 06:04 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,781 Posts
Others have stated that some form of acceptable "media access protocol" will be required. Apparently stamping all over the band meets that definition , so anything goes - right?

Seriously, does any one out there actually know what is planned (as opposed to hearing what they want to hear)?
teamdavey is online now Find More Posts by teamdavey
Old Oct 16, 2008, 10:45 AM
Registered User
slowswede's Avatar
Joined Jan 2007
180 Posts
Found something, it seems that it was agreed on a tcam meeting that the current 300-328 is out of date allready and too restrictive:

http://64.233.183.104/search?q=cache...lnk&cd=1&gl=uk
slowswede is offline Find More Posts by slowswede
Old Oct 16, 2008, 02:49 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,781 Posts
Thank you - and the critical "appropriate mitigation techniques" discussion is in there.
teamdavey is online now Find More Posts by teamdavey
Old Oct 23, 2008, 05:12 AM
Registered User
Berlin, Germany
Joined Mar 2002
316 Posts
The TU Module in an Multiplex Cockpit SX with te 4Ch RX.
The binding can be done with the JetiBox or with a jumper. It has a lot of new functions: you can set a the RX voltage on which the TX starts to beep. The TX beeps when it looses connection to the RX!, you can define the chanels to the servo pins assignment (e.g. Ch 7 to pin 4)
I will fly it on weekend during a HLG contest. We will make some range tests as well.
Viktor is offline Find More Posts by Viktor
Old Oct 23, 2008, 06:30 AM
mostly gliders
liukku's Avatar
Skellefteċ, Sweden
Joined Sep 2003
962 Posts
Quote:
Originally Posted by Viktor
The TU Module in an Multiplex Cockpit SX with te 4Ch RX.
The binding can be done with the JetiBox or with a jumper. It has a lot of new functions: you can set a the RX voltage on which the TX starts to beep. The TX beeps when it looses connection to the RX!, you can define the chanels to the servo pins assignment (e.g. Ch 7 to pin 4)
I will fly it on weekend during a HLG contest. We will make some range tests as well.
Thank you Victor
This is what I have been waiting for. Keep up the good job.

/Ville
liukku is online now Find More Posts by liukku
RCG Plus Member
Old Oct 23, 2008, 07:00 AM
Registered User
ricoalonso's Avatar
USA, KS, Derby
Joined Mar 2003
1,475 Posts
Viktor:

Is there a distinction between the Tx beep when the Rx batt is low and the Tx beep when it looses contact with the Rx?

Thanks for sharing your experiences with the Jeti 2.4 system.

Rico.
ricoalonso is offline Find More Posts by ricoalonso
Closed Thread


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Polk Hobby 72Mhz or a 2.4ghz system skotman Radios 5 Apr 27, 2007 08:38 AM
Discussion XPS 2,4ghz system and FDR..? merengue Eagle Tree Systems 4 Apr 27, 2007 05:41 AM
Discussion 6EX-2.4GHz system Rox DIY Electronics 4 Apr 10, 2007 09:07 AM
Sold (pics added)ALULA 3 servo, complete setup with 2.4ghz system rcaddition Aircraft - Sailplanes (FS/W) 2 Apr 09, 2007 11:47 PM
Discussion Spektrum DX6 6-channel DSM 2.4Ghz System cpd1343 Dock Talk 38 Feb 23, 2007 05:53 PM