Much has already been written about reducing ANT+ interference, including this Zwift Insider article. Conventional wisdom and many forum and Facebook user groups advocate placing your ANT+ dongle close to the trainer. Others are adamant that a powered USB hub is the only answer.
USB Port and Power Draw
There are also numerous suggestions on the ‘net that your USB port needs to deliver 500ma to prevent dropouts. So I decided to look into that! Using the free version of USBDeview from nirsoft.net, I noted that although my ports can deliver 500mA, neither of my two ANT+ devices ever draw more than 100mA.
I plugged the ant+ stick into the port shown below as delivering 500mA to a webcam and the power dropped to 100mA on that port.
I checked this with a very well respected Zwift PC guru who gets very clean ANT+ signals and he confirmed the same on his ports.
As a third test, Eric (Zwift Insider editor) ran the test on his own system. Same results – all ANT+ sticks were drawing 100mA:
A sample size of only three, but seems pretty solid evidence that 100mA draw is absolutely fine.
ANT+ Dongle Positioning
Next, it was time to try a number of varying positions for my ANT+ adapters. The results were surprising!
The dongles used in these tests were the Anself USB ANT+ stick and Garmin USB ANT+ stick (see Recommended ANT+ Sticks for Zwift).
The four positions I tried are shown in the picture below. All analysis was done with the excellent Zwiftalizer – The Logfile Analyzer for Zwift. Ideally, we want zero searches and as few avg rxfails as possible.
Directly into the PC – Position 1
First off I plugged one ANT+ adapter directly into the PC. As expected this gave the worst results as the PC is in front of my bike. Although not dreadful, there were 5 times that the devices tried to repair, and over 51% fails.
Anself direct into PC (pos 1) 
Garmin direct into PC (pos 1)
Under the trainer – Position 2
I next tried to position the stick just under the KICKR v5.
The Garmin had less searches than the Anself, but more fails. All tests were done in the same position, same USB port, and same extension cable.
Anself behind trainer 
Garmin behind trainer
Under the bottom bracket – Position 3
Moving the dingles forward seemed to improve things a little, still with one search for the KICKR but less Avg fails:
Anself under bottom bracket (pos 3) 
Garmin under bottom bracket (pos 3)
Under the front wheel – Position 4
Since moving the adapter forwards improved the signal, I took it even further forwards and placed it just under the front wheel. So further away from the KICKR, but this got the best results yet!
The Garmin doesn’t perform as well as the Anself in this position, which is strange as the pedals are very close to the ant+ adapter now.
Anself under front wheel (pos 4) 
Garmin under front wheel (pos 4)
Powered USB Hub (Position 4)
Anself in powered USB hub (pos 4) 
Garmin in powered USB hub (pos 4)
ANT+ Adapter raised off the floor
I also raised the Ansell off the floor in Position 4, and looped it over a cardboard box (to try and minimise any further interference. This actually made the signal worse for me.
Summary Table and Conclusions
Here is a summary including the averaging of the searches and RXfails for each adapter in each of the 4 positions. It’s clear that position 4 gets the lowest avg fails and searches for the Anself, whereas the Garmin appears to prefer position 3. It is also interesting, that for me, the powered USB hub made no huge improvement to a quality shielded USB extension cable placed in the appropriate position.
It’s also interesting to note that the Anself performs better than the Garmin in terms of avg fails, despite being less than half the price! (See them on Amazon here: Anself USB ANT+ stick / Garmin USB ANT+ stick).
In large group rides
I tried position 4 with the Anself in a Tour De Zwift catchup ride with 250+ people and I’m confident that it’s the best position now for me.
Note: the Wahoo KICKR doesn’t have the ability to turn off the standard ANT+ unlike the Tacx NEO, so the dual ANT and FEC creating the small interference troughs shown at regular intervals.
I hope this helps you in your quest to get a rock-solid ANT+ signal to your PC!
Questions or Comments?
Share below!
I don’t much use ANT+ except for my Garmin Vivoactive watch as an HRM. For this, position is key to avoid regular dropouts – I really have to keep it on the same side as my PC (with a modern powered USB), so I wear it on my right wrist. Left wrist results in dropouts even though the range is only 50cm difference. I found the same was true for my ANT+ Powertap pedals before I got a smart trainer – position and distance were crucial. Didn’t know about Zwiftalyzer but I will check that out. Good work here –… Read more »
I used ant+ for a period (when I had to use a pc) with nothing but trouble. As soon as I returned to using my laptop with bluetooth all problems vanished.
Have you tested on the floor vs elevated/floating. One of the common ant+ tips is don’t lay the usb stick directly on the floor.
Yes good point, I meant to include that!! I had it up high, draped over a cardboard box and made it worse for me.
.
@Casey article now updated with the results of it being raised up, thanks for the prompt!
Interesting, below is my current setup based on previous experience, like ANT+ & PC/ Laptops don’t mix without a lead to keep them apart ANT+ is 700m & 90deg (to the side) of the PC box. BT is straight out 1m20 from the PC tower, by the bike front axle (bike is at 45 deg to PC tower). Bike itself is steel (a retired CX/Gravel) and has power sockets nearby, so a dirtier environment for the BT to cope with, but less then a bike length to the Kickr Core & Tickr X that complete the setup. Usually run the… Read more »
I would love to see Zwift’s data on split of user by platform and connection type. My guess is that the use of Ant+ will reduce as a proportion of the Zwift base, as the convenience of platforms like iPad continue to rise. It seems to me that it’s PC users that are hanging onto Ant+, mostly due to the historically poor Bluetooth implementation on Windows.
yeah that would be very interesting!! Any split of user base would be fascinating to see!! I also think not so long ago Bluetooth devices only supported one connection, so if you wanted any dual recording ANT+ was the only answer. And then there is the HUGE improvement in graphics you get from a PC with a GPU vs an iPad.
Lots of us with ANT+ only power meters too!
I currently located my ANT+ dongle right below my bottom bracket. However I have often thought that the best position would be to the side of the trainer. My experiment would be to find out where the ANT+ antenna is in my trainer and place my ANT+ dongle straight out to the side of the antenna location on the trainer.
I wish trainer manufacturers would just add an USB port.
Great Article! Another comparation using Bluetooth would be great!
I’ve not found a way to get similar info on Bluetooth connections, searches etc
Made some tests. 1) Real power consumption of ANT+-adapter is ~10 mA (100 mA is just the limit), so no sense to use powered USB-hub. 2) Same adapter can “see” my heart rate monitor even if i stand at 8 meters behind my bike.
Interesting stuff, thanks for sharing!! The more tests/data we can do the better we can all get our ant+ performance!!
Using a powered USB Hub is mainly not about the current 10..100mA, but some (mostly older, e.g. the Garmin USB ANT+ from ~10yrs ago, which many of us got with the older Freerunner Watch or as used Part from 2nd Hand) USB ANT+ sticks require nearly 4.8..5V to operate properly and when using an USB extension cord, this Voltage drops to 4.2V and even below. This is then the case where a powered USB Hub helps really a lot. A cheap USB Tester, similar to yours, shows this very good and the powered USB Hub was in my case the… Read more »
I spent many an hour playing this game also! There is also interference potential from the PC Wifi and home networks. I use 5 GHz for the Wifi now, the best stick orientation depends on it’s radiation pattern i.e. what direction and polarisation the antenna radiates, likewise for the smart trainer. I have never seen data for the sticks or the trainers, so it’s all trial and error. It may be possible to be too close also and then cause overload of the ANT+ transceiver and data errors.
from what I’ve read there are only certain channels on the 2.4 GHz WiFi that interfere, as per this article. How to Fix ANT+ Dropouts in Zwift – Zwift Insider
Yes that’s true Greg, at least in theory, however it does not allow for the probability that the wifi is much stronger (higher power + good antennas) than the ANT+ or Bluetooth signals and will probably spread out much wider than the simplistic diagram showing the normal modulation bandwidth. So i moved to 5 GHz on the PC to make sure.
Andy Brown – your comment on radiation pattern particularly resonated with me. I had my desktop unit oriented so the front faced my Yahoo KICKR – USB ports in the back faced away from the KICKR. I had a good ANT+ dongle in one of the USB ports. I could not get Zwift to work right. I tried all sorts or arrangements including USB extension cords. Then one day I turned the desktop box around so the back panel was now facing the KICKR, i.e., no desktop metal between the ANT+ and the KICKR. Bingo! Everything worked fine.
Every bodies home have different levels of interference and unfortunately what works for one person can’t be assumed to be the best solution and may not provide any help to others. Also different trainers will have the ANT+ broadcast in different positions. For example, personally my Garmin ANT+ stick is plugged directly into my laptop which sits on my Wahoo Desk in from of my Kickr Bike. I don’t get any drop outs and 2.97% Avg RXFAILS on my Kickr Bike. I get far higher Avg RXFAILS from my chest based heart rate monitor implying that this has a weaker… Read more »
I think the port on your machine makes a difference too.. For months I have been using my work laptop (MS Surface book) and used to get a few drop outs on every ride / race.. Just last week we replaced our home laptop and so I tried that, exactly the same setup but on 5 rides now not one drop out. The new laptop has a 3.2 Gen 1 port in almost exactly the same place as the 3.0 Gen 1 port on my work laptop. In both instances I place the laptop on a DJ music stand in… Read more »
Why would you put your dongle in a place to catch sweat when you could just put it off to the side a little bit and out of the splash zone?
Nevermind, I didn’t see the cardboard hanging test the first time through the article.
Would be interesting to compare the KurtKinetic Extended Range ANT+ dongle https://www.kurtkinetic.com/accessories-products/extended-range-ant-usb-dongle
Just have to measure it with an USB Volt / Amp meter.
See the attached image. Shows.01 A or about 10 mA for a Garmin Ant+ stick in use (i.e. Zwift running, connected to Power2Max for power and cadence and Garmin HRM, all sending data.)
4.85V on USB is kinda low.
I have mine, a Garmin, taped to the left leg of my Kickr. Never had an issue. With the amount I sweating I do (and it’s common to have a puddle beneath me in the summer months) the thought of placing and ANT+ dongle below the bottom bracket seems to be a recipe for disaster.
I’m not a heavy sweater so mine remains dry. You could pop it into a small plastic bag which others have done.
I’ve only used Ant+ since being a Beta tester for Zwift. I have a long cable USB extension and an Ant+ dongle at the end which is directly next to the trainer. I never had issues until recently, now it’s quite regular all riders disappear and around 6 seconds later they re appear. My issue is due to Zwift, not the Ant+ connection.
Does the log file at zwiftalizer show you anything regarding network or other dropouts? There was a great article on here last week about firewalls causing this for some people.
My old Toshiba laptop has built in Bluetooth. It is located some 10 feet in front of my trainer in the 11 o’clock position. It just works. No USB extension cables, no dongles, and it just works. ANT+ has a short range and it’s just not suitable for a remote connection like computer to trainer.
Same here, I got my USB Bluetooth Dongle on my PC across the room (distance about 3m to the trainer) and in the four months that I’ve been using Zwift (about 5 days of total activity) I never had a single dropout. HR strap ist connected to the Dongle, too. I wonder why people even bother using ANT+ (if they have the option to use BT).
Which dongle do you have? I bought one and Windows recognises it fine but it doesn’t show up in Zwift. Did you have to do anything specific?
I had an extension cable closer to the sensors and had quite some drop outs. Now the dongle is directly in my notebook and the dropouts are gone. So the QTY of a cable matters is my conclusion. btw, my trainer is (still) USB it selves.
Interesting stuff. Tried it plugged into the PC in my very early days of Zwift with the odd drop out. Got an extension and moved it under the bottom bracket, far enough back that sweat isn’t a problem, for my left crank, single sided power meter. Never had a single problem since then, thankfully, 4 years and counting.
I have an Elite Suito and have been trying different set ups. I now have the Anself ant+ dongle by the side and this works well. I have just been using Bluetooth only for the trainer too but sometimes my avatar stops for a break for about 30 seconds while I am still working. Very annoying. Any ideas why?
I position my ANT+ using a USB extender near my crank so it is close to both my cadence and power sensors and I rarely have problems. Thanks for the article. I am using the original cadence and speed sensors from Garmin, I cannot remember what the ANT+ adaptor is but If Garmin sells one I probably would have bought it all at the same time.
Interesting article. Thanks for the research. I started using the Kickr Snap a couple of months after its release. I purchased two Garmin dongles at the time. Still use them. The dongles have been plugged into at least 3 different W10 laptops with the laptop on a stand in front of the bike. I used the Snap for years and currently use a couple of H3s. I do not recall any connecting issues and very few stutters in game. No real stop dropouts. My WiFi network has 2.4 GHz on a non-standard channel due to neighborhood interference. I use 5… Read more »
I mentioned the age of my Garmin dongles…I wonder if that might have something to do with issues…Older and stouter vs newer and lack of QA.
I got this ANT+ from Amazon with an extension base: https://www.amazon.ca/gp/product/B0891W89XW/
It was plug and play, no driver installation was required on Windows 10. I have it mounted on the side of my laptop pedestal desk. Halfway between desktop and floor.
I checked last session on Zwiftalizer, Avg Rxfails=8.91%, Searches=0.
I had no dropouts during any of the rides using this adapter, I’m very happy with it. Much more reliable than using BlueTooth which used to have connection issues and dropouts.
See location on my laptop pedestal
Closeup of the ANT+ dongle and the extension base.
Time now for Eric to update his ANT+ dropouts article where he pedals the myth that a higher power USB port is necessary!
I find Bluetooth works better than Ant+ but Zwift tends to find Ant+ first, but when using Ant+ it has more breaks in service – my buddy is left standing on the road too often
I get very low (sometime next to 0) RXFAILS but searches can be quite high and this seems to be completely unrelated to sensor or device . The only constant is 1. Dongle and 2. Environment . Zwiftalizer is insistance that my ANT “device” signal is up and down like a fiddlers elbow but does not say which device it is referring to . Since all are showing equivalent search levels, either all of the sensors are in trouble , that seems unlikely or it is a common factor. If it was environment why would that not result also in… Read more »
under ant+ signal quality on zwiftalizer it shows you the name of the devices and the searches/fails for each individual device, and then a summary of searches. Have you got an example screenshot from that part of zwiftalizer?
I have a Kickr v5 and went through a similar phase of examining various Ant+ and BLE setup locations and results. The best and very consistent solution for me is to use Ant+ with a Anself dongle which produces great results as verified by Antilizer and my session experiences. I also connect a Garmin HR monitor and sometimes a Garmin Edge 1030 to the same Ant+ dongle, with no issues. The only time the Kickr’s BLE is used is to rarely connect my phone apps directly to the trainer. The best location I chose was to use a 10ft USB… Read more »
J’utilise un iMac avec MacOs sous Big Sur et une clé ANT CYCPLUS achetée sur Amazon 15€
Mon HT se trouve à plus de 2 mètres et je ne rencontre aucun problème avec Zwift :o)
I have my dongle on the extension placed in the 1″-1.5″ wide space between the flywheel and the housing at the rear, and have not had one single dropout since being placed there.