Turbotronic

Got a few of these into stock today and thought I would share with everyone my experiences with both systems, as it relates to our requirements for turbine aircraft.
I will be comparing the JR DSX 12, JR DSX9 (DSM2) and another JR DSX9 (DSM J)
For now I just want to post a few pictures comparing the insides of both systems i.e DSM2 vs DSMJ.
Later I hope to do more in depth views of the technologies.
First off there is no difference of any sort in hardware design, so any differences will be in firmware. Both systems use the Cypress CYRF6936 RF front end and an CY8C214 microprocessor on the satelite RX PCB's. These PCB's are also identical to the ones in the main RX with the exception of the satelite RX's having another ground plane antenna as well i.e. is is connected to the ground plane of the PCB directly.
The balance of the circuitry in the main RX on the main PCB consists of a CY8C29466 SoC Microprocessor, a Micrel 3.3V regulator, some bypass caps and connectors. The PCB itself is a double layer throughplated FR board with ENIG (emersion Nickle and Gold plated) finish. The connector pins to Servos and Sattelite RX's are flash gold plated. Interestingly neither of the processors use crystal oscillators, instead relying on the internal oscilator source with a claimed accuracy of +- 2.5%. Components used and basic circuit layout is identical between all three systems.

Turbotronic

Well I just had to have a look inside the new JR MP80 brushless servo. Now this is a good piece of engineering with a quality feel bar none. The case parts, gears etc fit together so well you cant help be impressed. The motor is of course a sensored type ( sensorless is not really suitable for servos). It is driven by the usual tripple H-brige mosfett output stage ( 3 x FDS8858CZ ) with 7A odd amp rating. The CPU is a dsPIC33FJ12 micro, very suited to this application.
Gears are of course all metal. Calimed performance figures are:
MP80S 12KG/cm and 0.09sec/60 deg. That is pretty fast.
MP80T 25Kg/cm and 0.19 sec/60 deg. ie twice the torque and half the speed.
I am hoping to run some bandwidth test which should be interesting to compare for folks using gyros and for UAV autopilots.
I also have the DS6301 and DS6305 to look at later.

Turbotronic

I am almost done with my technical evaluation but so far the DSM-J is my clear favourite. With near Instantaneous recovery from brownout and loss of signal it is considerably faster in this respect than the DSM2.
Next step is to do a spectrum analyser test to discover the extent of the hopping sceme itself.
Andre

CustomPC

Hi,

Did you test for the lowest voltage that the DSM J receivers can operate at?

I've always liked JR Radios but i don't like DSM2 so the release of DSM J is my wish come true.

I'm ready to go with a new 11X in DSM J in the very near future.

Turbotronic

Hi,
There is no difference beteween the 2 apart from software. The PCB's for DSMJ is in fact marked "SPEKTRUM...". All components are identical. I cannot be sure if the software is a 100% JR or a Spektrum product. The serial protocols from Satelite to RX is identical as well. DSM J is still DSM but with fast channel switching, making it a hybrid of FHSS and DSM.
If my understanding is correct syncronization is achieved innitially via DSM mode and from thereon it switches channels. I would hope that they have a good scheme for in-flight resync, posibbly using a single pre-selected DSM channel.
As far as battery voltage brownout issues go there will be no difference.
On the radios I have DSM2 clearly took a few seconds to reconnect whereas DSMJ was near instantaneous. Both radios are brand new and should have the latest software.
Best regards
Andre

CustomPC

Hi,

Can you tell me if there are any EU or FCC approval labels on the DSM J module.

One of the requirements for a 2.4Ghz radio to be legal in my country is to be either FCC or EU approved (or both).

What are the requirements in South Africa?

Turbotronic

There are no external FCC or EU markings at all on either type. In SA we have ICASA as approving body but hardly any ISM equipment has it. The actual TX module that is the RF generator has an FCC ID of R8UGWJ4USHN33 ( Unigen RF USB module) used in all Spektrum/JR TX's.
So I do not see a problem but the FCC nr will probably also be affixed on the outside.
This module is sold for about $10 or so in the US with this approval.
Andre

CustomPC

Thanks

I've sent the info to the radio guru that does testing and approvals for our governing body..