My Latest LACE TAG

[Tim Irvine]

I successfully tested this new tag design in a race Saturday night in Picayune, MS for a glow run. I designed this to be a reuse tag. I used a Dog bone Monza D4 chip on the inside of the Bow. I did put a poly label with my logo and a number on the outside of the chip. I am including the antenna setup that was simple to setup and provided great coverage. I used 4 MTI Antennas, 2 overhead, two ground level at the finish line, and put my TR200 up as a backup. The mat you see is ONLY for the wire from the far side antenna, but it makes a great finish line stripe.

 I am constantly testing and thinking of a better way as I am sure you all are too. The only missed reads were people who did not wear the chips. Except I did have one lady who tucked the chip inside her sock. I had about 20 people crease the chip (folding it in half despite the included instructions. Those chips still read. I had one poor soul somehow have his fall off a the starting line. On the chip design I used a sheet of Poly (using Poly folders from Office Depot)  and cut it to the desired size. (1 1/4 x 5 1/2) and then used a hole punch to put a hole in each end of the poly strip. I put the dog bone on one side and the poly label on the other side. If you have any questions, let me know.

[Tim Irvine]

As I continue to test this new chip concept, I wanted to post results. I used the Lace Tags again this Saturday on a super small race I had. In addition to it being a wet situation, I decided to only setup my TR200, TR265, and TR290. I had the TR265 in Position 1, the TR290 in Poisition 2, and the TR200 in Position 3. I went with this setup as a possible transition setup and the rain was actually a bonus to see how the new Lace Chips would work in the rain. The first 15 people across read just fine. Then one missed. I ran him down and his chip had fallen off. (ugh), then a few more did not read. I began to see what was missing, and the TR265 and the TR290 were missing the most. Surprisingly the TR200 was bailing them out. Here are my conclusions as to why the missed reads and the major differences from this race and the dry race on May 13th.

1. In Picayune I used the FX9500 with two overhead antennas facing down, two on each side of the finish line and 1 with the TR200 further and the only read I missed was the folks who can't tie their shoes and the chips fell off.

2. Saturday the label I put on one side did get wet and likely was part of the problem. The labels are polypro labels, but they still got pretty wet. I may look at using shaprie to write the number on the chips. Ideally, if I can find a place to stamp them with permanent ink.

3. In the latter stages of the race as I looked at some of the way the chips were worn on missed reads, I found the chip to be worn correctly, but on the inside of the shoe. This is where the overhead antennas make a huge difference. Plus the FX900 is pretty powerful.  

4. I don't know, but I am thinking the TR290 could have been too close to the TR265. I tried to space them enough, but anything is possible.

5. Finally, I purchased two new cables that I used on Saturday for both the TR200 and TR265. 25 foot long LMR195. 

  So you can see there were a lot of variables to consider.

 

     In conclusion, I know the Picayune setup works well. I also think if I add a mat with the TR200 and TR265 and maybe shorter cables, I will be good on this for a setup for a transition. The TR290 needs more testing to see where I can use it. I may decide to use it for an announcer screen or kiosk at this point. It does work, but, a little shaky. Then again, it was raining. Not sure how the rain affected it. 

    Stay tuned.

[Dioxin]

That's a horrendous way to use a Dogbone tag.

The tag is designed to pick up RF signals at roughly 4x its length.

Length (of the foil part) of a Dogbone tag is 94mm. Signal wavelength is then 4x94mm=376mm = 0.376m.

RF frequency = Light speed/wavelength = 300,000,000/0.376 = 800MHz.

This is around the region of the 860MHz to 960MHz band that the readers operate in.

When you bend the tag that way you not only half its length and de-tune it, you also have one half of the antenna pointing roughly the same direction as the other half so the signals cancel instead of adding. The chip in the centre of the tag is relying on a difference in the signal from opposite ends of the foil antenna.

The tag is designed to be used flat. If you need a shorter tag then use something else which will cope better.

There are tags of different shapes and sizes which are differently tuned and won't need to be bent that way.

My experience with Dogbones and water were ok.

If I dip the tag in water and take it out it is seen immediately by the reader. i.e. drops of surface water on the tag are almost irrelevant.

But if your tag is up against something which absorbs the water, such as a t-shirt or a paper bib, then it starts to get badly affected by the water.

[tiberiu.gindu]

The last software version does not report which antenna picked up what tag(s).

Previous versions were reporting, when turning on an option "store RFID activity" (checkbox), which tag was seen by which antenna & how many times - during a passage of the tag.

Actually, it was a list of records, not the number of reads; but one could easily count the records using export to Excel and pivot tables.

Signal strenght was never reported.

I agree such info would help a lot for analysing various setups, tags, equipment, posioning of antenna or of tags, using foam spacers or not etc.

[Brian Agee]

Another bit of advice:   15' feet is about as far as you should go with LMR195 cable - and this is with a much bigger reader than the TR200/TR265. For the TR265 Package we actually provide a 10' LMR240 cable.

[Dioxin]

25 feet of LMR195 cable will have about 3dB losses so you will lose about 50% of your signal in the cable. 

For comparison, I use a very slightly better cable (it would have 2.5dB loss over 25 feet) but mine is only 1m long as I position my reader next to the antenna. My cable losses are then just 7%.

So if you transmit 1W of power down your 25 foot cable, only 0.5W will reach the antenna. If I transmit 1W of power, 0.93W reaches the antenna.

If you are using a reader with a single antenna attached then I suggest you consider doing the same and make the antenna cable as short as possible by positioning the reader next to the antenna. This might mean increasing the length of other cables to the reader but they don't affect your signal strength.

I don't know anything about the TR readers but the FX9500 can be set to compensate to some extent for cable losses. It's in the admin pages when you log on to the web interface.

The reader will increase its output at the connector to try and keep the transmit power at the antenna at the desired level. So, in your case, it might try and double the transmit power expecting half of it to be lost in the cable so you end up with the desired power at the antenna.

This is only useful if your local laws restrict your transmit power to less than the FX9500 can supply.

[Tim Irvine]

Be that as it may, the config with the FX9500 proved to work beautifully with the dogbones on the May 13th Picayune race, so I have to disagree with you that this is a horrendous way to use a Dogbone tag. I did pretty extensive testing before I put them in a race using that application.

 What I did this past Saturday was a worst case option and of course it wasn't pretty. That was me stretching the boundaries of what the chips/antennas can and can't do. The chip option was an add on so the race was manually timed and nobody was missed.

For the LMR195 cable length, I knew that was a mistake, but I tested it anyway, I have plans to cut those cables in half and maybe even shorter to lessen the length from the antenna to the reader and velcro the Thinkify reader to the back of the antenna. I will use longer USB cables to get the distance I need from computer to reader. That is part of the next test I am planning. 

  Again, I have to disagree strongly about the shoe placement of the dogbone. There isn't a lot of difference in the bow I created and the D-tag loop Chronotrack uses. The bow keeps the tag from the body (as long as it is worn correctly) and as long as the antenna has a clear view of the tag, from overhead down, of from each side, I have no issues reading it.

   But I continue to test, and will continue to do that to see where the absolute best placement for not only tags, and gear should be. 

   I do appreciate the feedback and I consider everything you say as I test. From the start, my goal has been to be able to use a chip in a way that gives me the best chance for success. If this bow design turns out to not be it, that's fine, but I think ideally a chip on the shoe will help me achieve some simple goals I have.

1. Better control where the chip reads. A mat may be the best option to ensure this, but again, I am stretching the boundaries.

2. No missed reads. Getting there. Nothing is worse.

3. shorten the time I spend putting the chips together. This is the most time consuming part of any race for me. 

  Thanks again for the input. You give me lots to consider.

[JK Race Timing Systems]

Hi

I must tend to agree with Tim on 1 point.

Bending a tag does not necessarily shorten or detune a tags optimum frequency response. It may make it less sensitive from a polarisation point of view but the degradation should be minimal.

A commercially available Triathlon type tag is a good example of this.

If you cut one open you will see that it too is pretty much a dogbone folded over a clear perspex block before being hermetically sealed.

The only thing I would like to say is that if using this type of positioning on the top of the foot while using a mat as opposed to a tag off the side of the shoe is that it does have a lot of water to pass through ( The wet shoe/Sock and then the water content of the foot itself.

I personally will always believe that a bib on the chest is always the best option if you are prepeared to put the work in to building a gantry but I know it doesnt work for all.

[Dioxin]

I've just done some tests with both configurations of Dogbone tag.

The first was straight and the second was bent in the way shown above.

That tags were rotated to 25 points/directions within a hemisphere all 45degrees apart, 3m from the circularly polarised antenna.

As expected, the only time the straight tag did worse was when it was nearly end on to the antenna. This occurred 5 out of the 25 positions but 4 of those 5 are directly end on to the antenna for the straight tag.

The rest of the time, 20 out of 25, the straight tag was considerably stronger.

Graph attached:

Blue is the straight Dogbone signal strength and red is the curved dogbone signal strength.

The scale is in dBm as given by the chip reader. Each vertical division is 5dB and you can see that, other than when end on to the antenna, the straight tag returns a significantly higher signal.

Then I compared detection rate, rather than signal strength, at about 9m from the antenna.

Over the same 25 positions, the Straight was seen 19 out of 25 positions and the curved 10 out of 25 positions.

Provided you can avoid the straight tag being end on to the antenna then it's way better than the curved tag.

This is easily achieved. For bib mounted tags, place them vertically so they're never end on to a side antenna.

For shoe mounted tags mount them along the length of the shoe, not across the shoe so, again, they are never end on to a side antenna.

The above only applies to side antennae. Things are different for timing mats.

[Tim Irvine]

Great data Dioxin! One question I have is what kind of antenna are you using?

[SR Aaron]

Hey Dioxin,

Nice data! It really comes down to your reader, antennas, chips, and cables. Actual "data" will always be different from timer to timer because of these variables. For example, Dogbone with 4D or R6 chips (between the two, there's a HUGE difference on how well they read), or the FX7400 or FX9500 (HUGE difference), or LMR195 vs LMR240 vs LMR400 (HUGE difference and the correct type depends on length), type of antenna and direction (so many variables that make HUGE differences).
If you maximize your read strength in all of these areas then its very rare to miss a read no matter how the chip is used. We time 55+ events a year, running, paddle boarding, snow... no foam, horizontal chip placement on back of bib, heavy RAIN throughout the year... 100% reads at nearly every event.

The people that don't have bibs or have already finished never read though... :)

Hope this inspires some of you to research.
Aaron

[Dioxin]

The tests were with an FX7500 reader and a Motorola AN480-CR antenna.

The centre antenna was about 0.7m above the ground and the chips under test were 1m above ground.

Cable length and reader don't really matter as it was the same reader, cable and antenna for both chips, but the cable was about 1m long CLF200.

The chips were from the same batch of Dogbone Monza R6 and I unfolded the bent chip afterwards and retested and both gave very similar readings so chip differences are slight.

I know the folded tag is for use on a shoe so maybe I should have had the chips lower to the ground but both suffer badly when close to the ground.

I can redo the test lower to the ground if anyone really thinks it's important but I expect both tags to be affected to about the same extent.

[Pete Wareham]

What is difference between dogbone d4 and r6?

Which reads better from bib (mat antenna)?

[Dioxin]

The R6 has a better and more consistent read range.

[Oscar's Race Results]

I have of late been using Alien 9654's directly mounted flat on bibs.  Had first 2 misses of the year on 6/30 on faster runners finishing downhill.  Disposable $.13 chips are a convenient option for race directors and I am in a highly competitive environment. I know I need to better position my antennas for larger races. I am in love with my handsome FINISH banner and out of sight cables in the arch.  I would have to re-engineer all of that to do overhead antennas.  How much better would overhead antennas do than a couple of tripods  back from the Finish line about 3' with antennas angled at 45 degrees?  

[JK Race Timing Systems]

Hi Oscar

What reader have you running on that system.

If its an 8 port fx9500 would you consider setting the first 4 (Truss antennae) to bistatic mode and leave the rest as monostatic.

I am testing Bistatic mode at the moment and results are excellent.

I cant tell if its any better as the last 3 races for me have been 100% reads but I certainly feel more confident with the bistatic setup.

Try it if you have the ability and the gear ( Circular polarised antennae Left and right polarisation)

Regards

JK

[Tim Irvine]

I Use 2 overhead on my truss using my custom mounts and two on the side. Those 4 are on FX9500 (A) and on the second FX9500 I only use 2 antennas when the chute narrows. This has proven to work well for me. Sometimes I hook up my TR265 as a catchall in the rear of the chute. 

  I have yet to use the FX7400 in the mix on a race with the FX9500's.

  I did do a race using my lace tag design back in the spring with only the FX7400 (2 overhead on the truss) and 2 on the sides. plus the TR265. I had 100% reads.

 Anytime you have runners coming in hot to the finish, a loose antenna pattern can result in missed reads. My first chip races back in 2012 I had a similar situation where runners came in hot and I missed. Since then, I have adjusted the setup and overcome this.

   Also, the Smartrac dogbone R6 is the chip I use. It is dependable.