2.4 PT Dropouts

rayhuang

Thom y-sorry for the late post, but my 20 yr old amp and bookshelf speakers flanking the 27" TV in my training room (basement) just seems so inadequate all of a sudden!!

vladav

Jesse,

I can understand your troubleshooting question (I'm a systems analyst).

Frankly, I would never mount it to my stem and be satisfied. If I crash the head is vunerable, and when riding in the drops I can't see the display unless it's far enough forward. So the mounting position is not arbitrary for me.

My setup has 3 electronic devices near each other - 2.4 Servo, Garmin 305H/R+CAD, Blackburn LED light.

The garmin only has output to the HR strap (If at all?). Other than that it's a passive RF device.

The light potentially sends out interference - but no apparent correlation between the light's presence (Mounted or not) nor it's operation. I get Servo/Hub drops either way.

As for the QC improvements - I only know when my shop received the hub (02-01-07).

I believe it shipped direct from Saris, but I can check if it helps?
I assume the serial number on Hub/Servo will tell you?
Was the weak link the in the Hub or the Servo?

Thanks for the support!
Dave

Steve_B

Dave,

Sorry for butting in. I work on wireless stuff for a living.

I agree with Jesse's line of thought 100%. Can you change the mounting position as an experiment? It wouldn't have to be permanent. Just to see the effect on the dropouts.

Also, the first thing that I'd do is turn off all that other electronic stuff on your bars. You say the Garmin is "passive". It's not though, not totally. The receiver can possibly be a source of interference to the 2.4 and, depending upon architecture, it might have a small oscillator inside too. Turn it off.

Both of these need to be evaluated over the preiod of a few hours because your complaint was over a period of hours.

If there's no change in the dropout situation with either or both of these, you're free to go back to how you had it.

Steve_B

Experiment 1: The problem is that depending upon where the interference (if that's the problem) is coming from, you may or may not be helping the situation by putting a shield on only part of the unit. It depends on a few things.

BTW, Lambda/4 in free space is about 31 mm and in copper mesh I think it's more like 41 mm. I'm not sure that you need the shield to be Lambda/4. It's not a quarter- wavelength stub, it's just a shield, which usually can be of arbitrary size, really. (We have whole rooms here at work made of mesh that do the same thing.)

I like your thinking though. If it made a difference, it might lead you in a direction.

Experiment 2: The shark fin antenna was for the "non-wireless" (older) systems. I don't know if they worked at 2.4 GHz as well. (It would be easy to find out though.) If they don't, don't plan on using a shark-fin antenna because it wouldn't be resonant at or near 2.4 GHz. Not only that, how would you plan on attaching to the receiver inside the yellow computer?

If you're going to build a repeater with coax and all that, you're reverting to the old school wired version. It's the same thing. Interesting how things go in cycles, huh?

vladav

Do I denote a hint of 'undig your heels sir' (if so it's warranted ) Even so, why would so many others be experiencing similar results?

Thanks for the inputs Steve & Jesse!

Steve,
Plan of action: since everything is wireless - I'll alternate carrying them in my jersey pockets. One on the bar, one in the pocket... agreed? Plenty of distance + water (torso) to attenuate.

It'll take a few days to test thoroughly...

RF science facinates me - it's so messy and clean at the same time

(BTW, maybe I can bend your ear on PM about our warehouse RF challenges )

vladav

Yeah easy to find out - hoping I don't have to...

I was hoping/guessing that the same circutry to recieve the wired signal from the Sharkfin is still there in the 2.4 servo. The pins are there for the cradle upload...

Attaching a reciever? (Probably applying practical knowledge to my guesswork? See how you are!) If you have a stub at one end and a stub at the other, you will get a transmission, correct? (Albeit with a ton of db loss.) That's what I was thinking anyways...

vladav

Okay well I really only have 2 test rides: Not enough for anything conclusive but interesting nonetheless.

03-11-07, placed Garmin in jersey pocket, left the Servo in my normal handlebar postion (Ref pics above.) For first half of ride power cable to light was disconnected, for second half the light was connected and turned on.

03-13-07, placed the Servo in my seat pack. (Specalized narrow pack contents: 1 tube, 1 CO2, 2 plastic levers.) Garmin on handlebar.
The orientation of the servo was: display facing hub. Drawing imaginary line perp from face would intersect ground perhaps a foot or two behind contact patch. So display facing down and back.

Should mention I have 2 cadence sensors placed on chain stay. Garmin(over)/PT(under).

WKO+ Ride files attached(remove .txt extension). The gaps are already picked out and saved with detail of where, when, what, etc.
(I’m assuming all use WKO+. If not I can post text.)

03-11: 2:20 Hour ride; 12 drops, 8.8 minutes lost data.
MotionBased GPS dashboard for 03-11 test

03-13: 1:09 hour ride; 7 drops (The first one only kindof counts, I’ll give it a mulligan), 1.7 minutes missed data.
MotionBased GPS dashboard for 03-13 test
This was the first time I noticed data other than power within a gap. Notably cadence. I’m led to believe that the cadence snsr has a relatively weak signal too since it had to be so close to the Servo.
HR would have been sporadic since the strap didn’t have LoS. (Same w/garmin in pocket.)

It is weird how some gaps are minutes long but when selected only add up to a single data point (1.x seconds.) Maybe a WKO+ thing?


IMPORTANT: this time I did not wear my tin foil heat-conduction layer between helmet and head… (just 3 pocket protectors for jersey pockets – Gu in pocket = yuk.)

Regards,
Dave

Attached Files

	Dav_Vlad_3_11_2007.wko.txt (67.0 KB, 6 views)
	Dav_Vlad_3_13_2007.wko.txt (43.4 KB, 1 views)

marmatt

sorry to chime in so late,but I have had intermittent drops with my 2.4 but didn't want to send it in. Any advice as to wether this would actually help and/or what the turn around is.

BergHügi

hallo from Germany,

I'am using a PT 2.4 since 2 weeks druing 9 rides and 850 km. During the first 7 rides, when I was using a Garmin 301 simultaniously, I had about 10 dopouts of the hub per hour but no dropout of the heard rate. On the weekend the Garmin stayed at home and astonishing I had only 9 short hub drop outs (shorter than 3 seconds) during 9 hours ride.

powertap

To be clear there is no interference issue, it is an RF power issue on the hub end of things. This is why position of the Computer is important in this particular case as the hub cannot be moved.

Despite this obviously being a unit in need of repair, I'll offer some additional experimentation ideas since you seem to be game.

1. Put the computer on the stem or the left part of your bar (in the photos you don't have anything there) The antenna in the computer is somewhat positional, this is why putting it in the back packet may not work so well. In addition, the computer doesn't like to be too close to humans.
2. Try putting it back int he saddle pack WITHOUT anything else in it (no CO2, tube etc)
3. Mount the CPU on your top tube.

Again, these aren't things that we would have the typical customer do but in the name of experimentation it could be interesting.

Jesse Bartholomew
PowerTap Product Manager

Addict07

Jesse: Thanks for participating in this forum. I am curious about how these problems have been handled. Obviously this has been a bumpy new product launch for your company and as you can see from the numerous threads on this site and others, the 2.4 is starting to develop a bad reputation through word of mouth.

Why didn't you guys just recall the early units? I'm assuming you can trace the RF power issue to a range of serial numbers or other identifying characteristics? Why are you letting these end up in customer hands, where they then get built into wheels and then cause an immediate poor purchase experience when they don't work? Then when we contact customer service, after explaining the problem, why are we instructed to buy new batteries instead of just shipping it back to you? Then when ultimately the new batteries and trying to "refind" the hub don't work, why are we expected to ship the wheel back on our dime, when it's your quality problem? And instead of immediately shipping me a new, working unit, I have to go without any data for 2 weeks or so until you repair the original unit and send it back to me. I dropped $1500, why am I being inconvenienced?

I read all about Saris' supposedly great customer service, and while your people are pleasant enough to deal with, I find your process completely lacking. I know all the things I mention above cost money for Saris to do, but for most of us, the $1500 we spent on this is the largest cycling investment we have other than the bike itself. We chose your product over an Ergomo, and most of us could even afford an SRM if we really wanted to. I can't believe we are being treated as if we bought a malfunctioning $20 light.

Not to dump on you personally, I'm sure these are all management decisions...

kennybear

I was ready to buy a powertap 2.4 but I just ordered a Ergomo, I just don't have the time to pretest the pt for Saris.

Alex Simmons

You'll just need a PT then to calibrate the ergomo...

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kennybear

Got it covered, my training partner has one :-)