Old vs New antenna: a.k.a. Is Bigger Better?

Eyeux · February 3, 2021, 3:05pm

As some have noticed I’ve been making some noise about me being torn between old and new “flex wedge” antenna formats.

On the “verge” of Apex launch, Walletmoor being here and payment implant options growing by the day, I get to ask myself what is the difference between the 2 antenna formats?

So here it is a (hopefully) comprehensive suite of tests I ran.
Would be great if other folks with either of those implant form-factors could chip in to add their experiences!

These are the 2 implants I have with me to compare:

FlexMN “wedge”, with new antenna (from now on referred as “new”):

Flex DF2 “wedge”, with old antenna (from now on referred as “old”):

Both are HF, but they are different chips. Worth noting that I do expect the magic Ntag chip on the new antenna to perform worst than a payment conversion on that same antenna.
Still, so far this is only my assumption.

So Let the comparison begin!

RESILIENCE:

First of all, just by looking at it I can see clearly a lot more robustiness on the connections from the chip to the new antenna than the old one. (I assume a big drive for this coming from the FlexNExT connection issues.)

Yet when I think of a strip/wedge form-factor the necessity of such improvement is directly correlated to the placement:

If I place the strip/wedge directly on top of a bone or otherwise non-flexible surface, then the forces acting against the connection are minimal. So a robustiness gain is not so needed. Ex: on top of a metacarpal bone, or on the flat middle of your arm, following the arm’s direction.
If I want to place the strip/wedge at a high stretch/mobility place, then this gain in robustness becomes more valuable. The constant stretching of the skin, and therefore of the pocket, will start to apply force against the connections. Hence why added robustness becomes a nice factor. Ex: Finger Phallange, inner side of the wrist.
If I am to position the strip/wedge in a perpendicular way to the flat surface, then either (or both) the antenna would be constantly resting in a stress position, or very succeptible to mechanical trauma applying strenght over the connections. Both are very solid arguments in favor of sacrificing range in favour of robustiness, especially since stress force under resting conditions will inevitably lead to contact failure on weak enough soldering/connection. Ex: across the back of the hand. On the wrist, perpendicular to the arm’s length.

Thoughts:

This gain in robustness might allow the tag to be placed in ways/places where the old antenna could fail.
This gain allows for added peace of mind when planning your install
This improvement might be rendered moot depending on your choice of placement and lifestyle.

READ DISTANCE:

Here I’ve measured distance with a digital caliper. Still handheld, so allow for some deviation.

Measured by approaching the tag from above, slowly, until I got a read.

Repeated the approach about 15 times for each and only counted when I got a read.

Utilised an ACR122, a DT KBR reader and my phone.

These are the results:
Reader . . . . . . . NEW . . . . . . . OLD

KBR(DT) . . . . . ~0.3cm . . . . . ~1.5cm

ACR122 . . . . . . ~0.3cm . . . . . ~1.5cm

Phone . . . . . . . . . 0 . . . . . . . . ~1cm

Thoughts:

not any significant difference between readers
with a phone, I could only get a read on the new antenna after touching it on the phone and rubbing around.
There was much more consistency with the old antenna.
The new antenna would very seldom read from almost 0.6cm away, but some cases needed to touch the reader or just failed to read.
Range seems to be quite different here, but not to a level I really care, personally speaking. If I got to touch the reader, so be it. Although, if I’m thinking of a payment implant, given that most antennas sit behind a touch screen, that might be an issue.

READABILITY TESTS

Here comes what I’m mostly interested in: How easily will I get a read.

This is particularly important if we’re talking about a payment implant, where I sure don’t want to have to be doing weird gestures and jumping around the terminal until it finally goes through or I give up.

For a payment implant I don’t care about range or whatnots nearly as much as I care about consistency.

That said, the objective here is to see how consistent/easy is to get an UID read out of the chip.
I’m only reading UID to minimise the fact that I only have 2 implants in the strip/wedge format, and each one has a different chip in it.

These are the tests I’ve done:

Approach the tag to the reader, slowly, from above down.
Swipe the tag through the reader, sideways, with a fast motion. Back and forth movement.
Swipe the tag through the reader, sideways, with a slow motion. Back and forth movement.

Each of these was repeated 40 times.
All of them passing the chip less than 0.3mm away from the reader.

Each repetition was performed against

DT’s KBR reader
ACR122

Results:

Slow Above
Reader . . . . . . New . . . . . . . . . . Old
KBR . . . . . . . . 26 / 40 . . . . . . . . 40/40
ACR . . . . . . . . 14 / 40 . . . . . . . . 40/40

Slow Sideways
Reader . . . . . . New . . . . . . . . . . Old
KBR . . . . . . . . 29 / 40 . . . . . . . . 40/40
ACR . . . . . . . . 21 / 40 . . . . . . . . 40/40

Fast Sideways
Reader . . . . . . New . . . . . . . . . . Old
KBR . . . . . . . . 06 / 40 . . . . . . . . 38/40
ACR . . . . . . . . 06 / 40 . . . . . . . . 36/40

Thoughts:

Maybe my magic Ntag is just far too slow?
Even then, the difference here is far too drastic to be completely unrelated to the antenna.
Maybe it is my old antenna/DF chip that are way too performatic, and that raised my expectation?
“fast sideways” is roughly as fast as I usually approach my card to a terminal.
Maybe my new antenna is messed up?
So far I am really put down by the new antenna. I just hope others are having better results.

“SWEET SPOT”:

Here I messed around with approaching from different angles, moving about,angling the chip, etc…

Whenever I got a read, I would try repeating the same motion back and forth slowly, maintaining angles, about 4 times to check if there was consistency.

Thoughts:

old antenna: I didn’t even needed this, since it reads all the time even from weird angles. I can get reads even almost perpendicular to the KBR’s antenna (where even my fobs fail to read).
new antenna: both on phone, KBR and ACR, I couldn’t find a single “sweet spot”. it’s just terribly fiddly. Even when I got a position and place where it reads more often than the others (parallel to the back of the D on DT’s KBR), it still fails to read almost every other time while repeating the motion.

PAYMENT TERMINALS:

As the last test, I went out and messed about with some payment terminals in self checkouts at Tesco, Wilko and Saisburys (UK).

I first tested out my old antenna’s blinkie, and noticed that there is a “beep” on the screen and it obviously fails to read the “card”.
Since this was quite consistent, I decided to compare both implants.

old antenna: Fairly easy to get the “beep”. To the point I had to change my habit of presenting my card held between index and pinkie, because sometimes it reads my old antenna tag first.
new antenna: I figured out that a security guard finds my actions worrying and reaches me faster than I can get a “beep” using the new antenna. I did got a couple beeps, but only after much fiddling and always had to be touching the screen.

Thoughts:

Here, more than in any other test, I believe the chip is playing a larger part than the antenna. but even then the difference is awestriking.

FINAL THOUGHTS

I can’t take my tests as canonical since they were performed with different chips!
I can see why the new format might be better for most people! And for DT as well, especially since it grants both a lot of security, peace of mind and subsequently a lot less stress!
That said, for for myself, given that I always plan my implants with taking the best advantage of the placement as I can, I don’t see any desperate need to increase resilience. Yet I do see a gigantic gain from readability!
The range and readability of the old antenna is just insane! With a borrowed Wiegand reader I even got it to read through my hand (like a FlexNExT on an ACR).
For everyday use, having so much reliability is a must for me. Both while working at a computer (where I swipe my implant a LOT), and when opening a door while carrying heavy boxes or groceries with both hands… Is essential!
Not even caring that much about the range gain (which would be, by itself, enough to make me consider sacrificing resilience), and only thinking from that format being so easy to get a read from… Makes it a no-brainer for me to predilect the “Old” antenna. This is a personal opinion, not a statement of superiority from one format over another!

So… Anyone else fancy chipping in your experiences?

Mariarangok · February 3, 2021, 3:54pm

I wish I could’ve done some proper testing like that. But there’s even a running joke about me not owning a ruler.
I can say that the payment implant got a read with my iphone (while in the pouch) well over 1cm away,
Since its been in my arm, no read from my phone but I tested the ACR reader this mornign and got consistent reads. I made a video but its really bad (TV on in the background, awful angle, one handed stuff) I will try to make another that showcases better the read distance but for now I’m hopeful.

Eyeux · February 3, 2021, 4:04pm

Thanks!!

The more you can add the better!

Despite being as thorough as I could with my tests, I’m still in the precarious situation where my new antenna is attached to a grey market chip…

amal · February 3, 2021, 4:51pm

That is an amazing work up… I would say the biggest issue is different chips will give different results. I can also say we are continuing to experiment with the new antenna design to further maximize performance… still little tweaks to make here and there I think.

Pilgrimsmaster · February 3, 2021, 5:58pm

I see that Amal has replied as to what I was thinking whilst reading your great write-up and also what you have mentioned yourself.

I can only add that my custom payment is probably a different chip from the walletmor chip and I have the wedge antenna; I get consistent 10mm read range.
My first new Flex antenna implant will hopefully be the FlexMN no blinkie so My comparison would likely be the same as yours.

Satur9 · February 3, 2021, 10:05pm

Definitely worth highlighting this. We’ll continue to develop and test new antenna designs, but every chip/antenna combo will have unique performance characteristics. Please do not take the performance of this particular chip in the new flex form factor as indicative of the whole series.

I made this video a while back to explain how we test tuning of the implants, and it might help clear up some concepts for you.

DonFire · February 4, 2021, 8:20am

How much of a bump in the resonant frequency are you aiming for due to the changes encountered when implanted, and could this be why sometimes new flex wedge is not performing well when only in the pouches?

Satur9 · February 4, 2021, 4:16pm

So I personally don’t have enough data to say for certain what the difference in resonant frequency is between an implant inside and outside the body, but Amal has said there’s usually between a 100-400kHz reduction. That would mean the surrounding tissue is introducing between 1-4pF of parasitic capacitance, which affects the tuning. We try and overshoot the inductance to account for this.

Yes this would apply for any implant. Usually not a huge difference in performance for simply reading the UID, but for write operations requiring more power it can be significant. As seen in that video the curve of power draw slopes away exponentially around the resonant frequency, so small differences matter.

Eyeux · February 5, 2021, 9:14am

Damn! I wasn’t seeing notifications from this post!!

Definitely. I just wasn’t expecting it to be so much of a difference. Especially on some aspects, such as range.

I mean… on fast swipes, especially seeing other folks with the proper flexMN commenting on their read speeds being slow (just like mine), it makes sense to think the main culprit would be the chip, not the antenna. (can’t process the read request fast enough for a fast swipe)

I hope I made it clear enough that the chip is a big issue regardless, and that this Thread was more of a call for people to share than a concluded thing.

Feel free to edit it if you think it needs more clarity, @Pilgrimsmaster !

Makes perfect sense: Performance difference between a DF2 and a payment chip should be much smaller than a Gray chip and a DF.

Although this gets me leaning towards the other theory I already brought up:

Maybe I do have an over performing implant on the old antenna?
I have a consistent 15mm range, which is even more than yours. Sometimes I can get way more than that. With particular strong readers, I can get an UID read through my hand.

Could it be possible that my Blinkie helps my old antenna overperform? Through some field distortion or whatchammacallit?
I begun thinking about the experiments where you can increase an antenna’s coupling/range by holding a magnet in just the right place.

Regardless, looking forward to your new antenna implant experience!

That is a great video!
Very well done, professional and clear!
Thanks a lot for sharing!

And that is also a great point!

amal · February 5, 2021, 9:24am

Actually the magic ntag chip itself has a coupling sensitivity… things kinda have to be just right… the chips ability to modulate the field and detect modulations is pretty crappy… so there is even a huge difference between getting solid reads with my pixel 2 and pretty unstable reads with my pixel 5 at the same “range”… even programming the magic ntag with the proxmark3 required me to hold it 2cm from the antenna, as laying it directly on the antenna resulted in write errors.

Eyeux · February 5, 2021, 9:34am

Not unexpected, but had I known this to be cannon, would have put a lot more warnings on the original post!

Still happy with the FlexMN “wedge”, though!

My main concern is to explore the antenna differences before getting a payment option.

Ottomagne · February 5, 2021, 10:08am

Interesting. I’m able to lay mine on the antenna and get consistent reads. Just goes to show how finicky this stuff can be

Eyeux · February 5, 2021, 10:22am

“write”

That can also explain why we both failed at our write attempts.

anon3825968 · February 5, 2021, 3:39pm

To be brutally honest, this chip sounds sketchy as fuck. You’re using it instead of a genuine NXP solely because of the packaging, correct?

Who’s next in line to receive a full-size antenna flexMN? I am so gonna wait for that person to report their experience with the chip before implanting mine… and the next person, and probably the one after that also…

By all means take your time to solve the blinkies problem. I’m in no hurry whatsoever.

Ottomagne · February 5, 2021, 4:20pm

Let me rephrase - when I put my flexMN directly on the HF antenna, I’m able to get consistent reads and writes. I’ve converted mine successfully into an NTAG216 (according to the magic write script -c), but my issue subsists as my phone can’t successfully write. @amal mentioned somewhere that the magic script doesn’t set a signature though, so it’s possible that maybe that’s causing the phone to refuse to write to what it perceives as a non-official tag? Not completely sure, but beyond the long read/write times, I’ve not had a significantly difficult time getting it to couple correctly. I think I’m gonna try to carve out some time this weekend to try and work on getting it working.

Eyeux · February 5, 2021, 7:51pm

Is there a “genuine” magic Ntag?

Of the proxmark, or of the Phone?
Just trying to squeeze as much clarity I can, to understand this when I’m about to try the same.

anon3825968 · February 5, 2021, 8:03pm

My understanding is that the magic is completely accidental: I understood that Amal was looking for a chip in a MOBx package with capacitance compatible with his existing antennae to create a flexNExT replacement, and none of the genuine articles were suitable, but the magic chip was.

Or maybe I misunderstood the genesis of the flexMN.

Anyhow, I have a bad feeling about this, and I clearly have a feeling that the two current flexMN owners are trying really hard to convince themselves that the chip is okay. I’m rarely wrong when I have bad feelings like that. So I’m hopeful, but I’m not too hopeful…

Ottomagne · February 5, 2021, 8:04pm

Reads and writes on the proxmark, only reads on the phone. In fact, I took my tag to my prox earlier today, noticed some weird config settings on my tag. Wiped it using the magic write script, which set it as an NTAG213 (just like Amal said), then I configured it as an NTAG216. This time, the settings looked more correct, and the phone reads it as having 888 bytes of memory, so it looks like my previous issue was something having to do with the configuration I had done before. I’m still not able to write to it with my phone though - both NFC Tools and TagWriter fail when trying to write even the smallest amount of data to the chip.

My next step is to try and manually write some ndef data in and see if I can get a phone to read it.

Eyeux · February 5, 2021, 8:11pm

If I am one of these two, your feeling is misplaced.

I am quite satisfied with the chip so far, actually. Although I haven’t played with it nearly enough.

I can’t care much about that chip being fiddly to read nor it’s range. I see the Magic Ntag as a hacker chip, which I’ll use to do hacky things. (Hence why I didn’t want blinkies in it)

If it has another NDEF entry, then it is a bonus. If it cannot use NDEF, then it’s as expected. I mean… this is a gray chip, what would I expect?

If it’s that fiddly, then I wouldn’t be surprised a phone can’t spit out enough oomph for a write operation, tbh.

anon3825968 · February 5, 2021, 8:20pm

Yes you were one of the two

Okay, my feeling was misplaced: you’re not disappointed because you don’t care that it’s fiddly. My bad. But then by your own admission, it is fiddly. Exactly what I’m afraid of, because I care.

The flexNExT’s bullseye had its fatal durability problem, but one thing it wasn’t was fiddly: it provided a solid hit all the way through my wrist with a desktop reader, and any old cellphone could read the entire 868 bytes of my NDEF in 0.2 seconds (yes, I timed it).

That’s what I need in the flexMN: it’ll be the replacement for the flexNExT that I used to open difficult doorlocks with and share business contacts with, with people who have no more than a split second to spare. If it’s a fiddly hacker chip that doesn’t perform reliabily and quickly, it is a very big concern to me.