Re: does anyone have OI and RC radio issues
 

that just went right over my head??

Re: does anyone have OI and RC radio issues
 

I appologize if some of my references or terminology was confusing to others. My intent was to respond to Eric's proposed test and to answer a question as to the 'what's inside' question.

Eric suggested that he was going to run some high(er) frequency RF succeptability testing, and I suggested that, based upon my observations, that the problem might be easier to expose by subjecting the device to lower frequency pulsed transients.

EN (EuroNorme) 61000 describes a number of different product compliance tests, and among them is a specific fast transient test where interconnecting cabling is laid in a coupling trough and subjected to this test.

I also stated that a lower frequency AM (Amplitude Modulated) signal can sometimes expose weaknesses with a given product design that a transient test will expose.


As to the FCC (Federal Communications Commission) OET (Office of Engineering and Technology) EA (Equipment Authorization) reference, if you look on the back of any unlicensed device which intentionally generates RF (Radio Frequency) emissions, you should find a manufactuer and product code identifier. With that identifier, you can look up information regarding that specific device, on the FCC's website, as that information becomes part of a public file. The direct link to this information was provided earlier in this rather lengthly thread, so I didn't see the need to re-post it.

I think it is unfair to IFI that we publicly speculate as to what the root cause of this problem is, or is not, without factual information in hand. However, as someone experienced with product design, including RF design, I will state that I do not believe that "cell phones" are the problem here. As I indicated in my response, our build location is not located near any RF sources (i.e. transmitters), let alone any that would be synchronized in time with the actuation of the motors.

Ultimately, whatever the cause of the problem affecting a few of us may be, the responsibility to resolve it lies upon the manufactuer and or FIRST to work out a solution. Those among us, such as Eric, with equipment to perform testing that IFI may not otherwise be able to accomplish on their own, may be able to provide some additional data to IFI that would help them.

I hope that helps,

Re: does anyone have OI and RC radio issues
 

How about a machine shop, given the number of different types of equipment and such in a machine shop, would any of that equipment be enough to disrupt RC to OI communictaions for a few seconds? Same goes for a wood shop?

Re: does anyone have OI and RC radio issues
 

The comment about cracking the box was in regard to seeing if the automatic gain control (assuming the IFI RF frontend was using this) was kicking in to some unknown response. With a few oscilloscope leads we could check to see if this was occurring.

We performed no lab testing before shipping the modem back, so other than some more recent comments about potential motor interference the only thing I had to go on was the cell phone comment. It seems unlikely to me as well, but if I'm scanning at 30MHz it's just as easy to let the equipment continue up to 900MHz. Our Biconilog antenna is good to 1Gig, and somewhat shoddy to 3Gig. From 3-9 I've got a log antenna, and past that you'd need a horn which doesn't calibrate well for the 10m FCC testing we typically perform.

I'm pretty limited in the EFT testing I can perform, however we have some loops lying around that might work, albeit in a completely non-calibrated fashion. Certainly anything I try in that realm will be pretty non-scientific.

If IFI chooses to end speculation after a few more radios have been in their lab, that would be fantastic. Like last year's 8.2V problem, there were some intelligent discussions trying to determine what the problem is. The more people with something useful to contribute looking at the problem, the better.

Ninja Edit: Thanks for filling in the details of our acronym-laden conversation Dave. I tried to give some detail to my earlier posts so this doesn't lose meaning to others following the thread.

Re: does anyone have OI and RC radio issues
 

E and Dave,
I went to the FCC files and looked over the pictures. Anyone else notice the internal antenna? Is it a dipole with the external antenna or a separate transmit or receive antenna?
I would like to know how many teams having problems have the modem mounted against a metal surface. If any team is having regular problems, could you try holding the modem outside the robot and check for same issues you had when the modem was mounted on the robot?

Re: does anyone have OI and RC radio issues
 

They're definitely separate antennae, one for transmit one for receive. During my discussion with Corey this past weekend, some of his suggestions were to mount the modem vertically, orient the external antenna away from the internal antenna, and to keep it away from any metallic structure nearby that could be acting as a ground plane. At the time, both modems were screwed to pieces of plywood, one for the driver station, and one that was C-clamped to our drivetrain with no structures surrounding it. Implementing those suggestions still resulted in a number of cutouts on Saturday afternoon and Sunday.

IFI should have our modems on Tuesday assuming UPS does its job. Right now, last year's modems are working flawlessly so paying double or triple for to overnight them wasn't worth the cost.

--Eric

Re: does anyone have OI and RC radio issues
 

Eric,
Did Corey indicate which antenna was the transmit?

Re: does anyone have OI and RC radio issues
 

I dont think this would be the problem. We work in GM and the WHOLE machineshop is around the corner, we havnt had any problems with the radio as of yet. So maybe it just might be your connections or something other thats simple. Maybe your radio has been brainwashed by another team not to work? :ahh:

Re: does anyone have OI and RC radio issues
 

Nope. Without knowing more about their link budget, it's not immediately clear which should be which.

Judging from the photos and clever use of MS-paint, the internal antenna is roughly 1/4 wave, and the external roughly 1/2wave for the 902-928MHz band. Assuming no poorly placed metallic structures, and that you aren't purposefully pointing the antennas end-wise at each other, you should get a nice fat pattern off both. Once again, for the interested reader, RFCafe has lots of fun info about antennas, power, patterns, etc. IN particular, check out http://www.rfcafe.com/references/ele...a_patterns.htm

I've got to hand it to the IFI RF guys though, they tuned their transmit strength to be JUST under the FCC limits. Particularly on the RC side :) If there is a signal strength problem, it's not on the transmit side.

I'd say those are my 2 cents, but at this point I'm up to about a buck's worth.

--Eric

Re: does anyone have OI and RC radio issues
 

So beyond a relocation of the mounting of our radio, 1075 needs to phone up IFI and ship the radios back? They seem to be much less reliable than the old Ewave models... I'm not sure why we switched either, considering Ewave engineered those radios FOR us. Our old radios were rebranded Ewave Screamer422s for reference, Ewave's website even states that they were specifically designed for us.

Re: does anyone have OI and RC radio issues
 

If you have the same problems other people in this thread have shown, you've tried mounting them vertically, and not deep inside your robot, then call them up and get an RMA. Since so far there isn't a mass posting of "my radio doesn't work", if you don't have any problems I wouldn't send it back.

Re: does anyone have OI and RC radio issues
 

The parts adjacent to the shield appear as though they might be the first and 2nd IF filters, probably 455kHz and perhaps 10.7MHz or higher, and are only stuffed on one of the boards. So my guess would be that the internal antenna is Tx, and the external is Rx. It seems odd they wouldn't just diplex the external antenna.

As to the Tx power, I was a bit surprised to see that was considered passing and do note a "unc." in the pass/fail column but saw no discussion on it in the report... but certainly that is not a problem for us to consider here as the error is potentially on the side of a tiny bit too much power.

I have my doubts that this is a link budget, antenna tuning, external interference (cell phone or otherwise) issue, but speculation and facts are two different things and IFI is in the best position right now to analyze the facts.

Thanks,

Re: does anyone have OI and RC radio issues
 

Correct, and I'd like to echo that as well, and in part is the reason why I started a new thread, so that we could be very clear that IF you have a problem as some of us have described, that you need to contact IFI and discuss the situation with them, and if they determine that it is necessary, to RMA the unit back to them.

As of Monday this week, only 2 of the 4 teams reporting a problem had sent in their radio's for examination by IFI. I overnighted our teams radios to make that 3 out of 5.

The burden falls upon IFI and FIRST to determine how to address this issue and whether or not it is something they feel warrants additional attention.

As with last years problem, with what I think was a silicon bug in the user processor, that was worked around by a change to the linker file, some people had experienced the problem and others had not. IFI and FIRST were proactive in making sure that by competition time, all teams had been given the information they needed to make the updates, and I think we should be confident that the same level of effort would be applied to this problem, IF (and I must stress IF) this is later determined to be a problem that potentially affects everyone.

The FUD factor (Fear, Uncertainty, and Doubt) might be running a bit high here, but logical thinking will resolve whatever this issue may be, which again has only been reported by a few teams.

Thanks,

Re: does anyone have OI and RC radio issues
 

all of IFI's suggestions were tried for our robot. Ex. mounting radio's vertically, away from suggested places, etc. Still the same problem.

Hopefully we will all find out soon the specific(s) on what may be causing these symptoms.:D

Re: does anyone have OI and RC radio issues
 

Team 359 UPDATE!!!
We finally tested our new radios from IFI. We tested for two hours with 3 fully charged batteries.
NO. of problems with radio during that time.........NONE!!!!!!!!!!!!!!!

Our conclusion is whatever technical possible reasons it could have been, simply put, the ones that came in our kit was defective, and the new ones that we got work PERFECTLY. Not one time did we lose signal between the OI and the RC.

I hope its as simple as everyone else who have similar problems, to have their radios replaced.

Aloha!:D