Cycling Jersey radio interference

[Ade]

I have known for sometime that a cycling jersey can cause interference
with my ANT+ heart rate monitor. Typically my heart rate goes insanely
high when the jersey starts flapping about on a descent at the start of
my ride.

Recently, whilst cycling, I have started listing to podcasts on a
Bluetooth headset connected to a phone in my back pocket. The headphone
reception was incredibly poor, prone to breaking up. The headphones are
fine everywhere else. So my guess is that the jersey is responsible for
radio interference again.

What do people think? Is this a dumb idea? If not what is the best
solution. Should I eat more so my jersey flaps around less?

[John B.]

On Thu, 22 Jul 2021 00:43:26 +0100, Ade <Ade.sp...@gmail.com>
wrote:

Or buy a smaller jersey (:-)
--
Cheers,

John B.

[Jeff Liebermann]

On Thu, 22 Jul 2021 00:43:26 +0100, Ade <Ade.sp...@gmail.com>
wrote:

It's not your jersey. It's interference between ANT+ and Bluetooth.
If you lookup the specs on your BT headset, it will be either BLE
(bluetooth low energy) or Bluetooth 5.x. Both are different in how
they handle interference problems. ANT+, BT-5 and BLE all operate in
a frequency range of 2400 to 2524MHz band. If you try to operate both
ANT+ and either BT-5 or BLE at the same time, you will see mutual
interference.

"BLE vs ANT+ Interference Troubleshooting Tips"
<https://support.zwift.com/en_us/ble-vs-ant-interference-troubleshooting-tips-ryUhOTnzH>

If you need me to dig deeper, I'll need the manufacturer names and
model numbers for the ANT+ heard rate monitor, phone, and BT headset.

--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

[Ralph Barone]

Just on the long shot that it’s static electricity discharge that’s messing
your ANT+ signal, try using a fabric softener or anti-static spray on your
jersey and see if it fixes anything.

[Jeff Liebermann]

My initial guess(tm) is a bit more complexicated. Ade didn't specify
the type of "phone" but my guess(tm) is that it's a smartphone with
Wi-Fi, cellular voice, cellular data, and Bluetooth turned on and
running. I'll take them one at a time:

1. Wi-fi is constantly looking for an access point to talk to. It
blasts out beacons and responds to any access point it hears with a 4
way handshake. Eventually, it probably fails when it can't negotiate
an encryption key exchange. All this takes some air time, which can
easily jam either BT or AMP+.

2. Cellular voice varies with the protocol, but basically does
something similar to Wi-Fi. However, instead of listening for access
points, the handset (smartphone) belches broadcasts announcing to the
world "I'm here. I want to connect" and waits for a response from the
base station. If there's nobody around, it tries again and again at
full power (typically about 250 mw). While not on the same frequency,
the typical all digital BT headset receiver doesn't have much
selectivity and can be easily blocked by a strong signal. The
distance between the back pocket phone and the BT earpieces is about
60 mm (about 2ft), which is rather close.

3. Cellular data is similar to cellular voice. In the case of LTE
(4G), cellular voice is yet another data channel and identical to
cellular data. To keep things simple, I'll assume that 3G phones
don't exist and that everyone has upgraded to LTE.

4. Bluetooth uses a completely different protocol as Wi-Fi. Wi-Fi is
DSSS (direct sequence spread spectrum) while BT is FHSS (frequency
hopping spread spectrum). When these two meet to do battle for who
can communicate, BT usually wins. To make matters worse, the original
specs called for BT to hop over the entire 2.4 GHz band, thus insuring
that coexistence with Wi-Fi is not going to happen. So, later version
of BT were allowed to spread into 3 sub-bands and switch sub-bands to
reduce interference. This helps, but does not completely eliminate
the interference.

The key here is that all the devices are on the same 2.4GHz band, all
are fairly close to each other, and all are susceptible to
interference from the others.

As for the jersey causing the problem, I think it's more a matter of
bad observation. The OP stated that

"Typically my heart rate goes insanely high when the
jersey starts flapping about on a descent at the start
of my ride".

Kinda sounds like the jersey flapping happens at the same location
every time (descent at the start of the ride). In other words, it's
the location that's causing the problem where there might be yet
another 2.4GHz source of interference at that location. The jersey is
just along for the ride.

Hint: RF is magic.

[Ralph Barone]

It could also be static electricity from the jersey being picked up by the
HRM electrodes. Static electricity is magic too :-)

Let’s leave this to science. With any luck, the OP will try something and
report back on the results and we’ll have a better idea as to what’s going
on.

[AMuzi]

Darn it, Jeff.
I was hoping someone here would suggest a big MOLTENI chest
tattoo instead of the jersey.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[Frank Krygowski]

Of course, I believe the last statement. But I'd have said "black magic."

Given your explanation, it sounds like it would make sense to try
turning off the phone's Wi-fi and cellular voice, at least (Airplane
mode?) to see if that helps.

Those shouldn't be needed while riding anyway.

--
- Frank Krygowski

[Tom Kunich]

Question: do you have a high end Jersey with a metal rather than plastic zipper?

[funkma...@hotmail.com]

The OP doesn't say whether problem occurs when the phone _isn't_ present. Try leaving the phone at home (or at least powered off) and see of the problem persists. If not, Jeff is Correct, it's some sort of interference (known as RFI) from the phone.

Once the link between the ANT sensor and receiver has been established, It should take a lot more than bluetooth or wifi polling (scanning, hopping, whatever you wish to call it) to cause any issues. In any case, a simple jamming effect of a BLE radio in close proximity would more likely cause the HRM data to drop out rather than show a very high reading. ANT+ is coded such that two ANT+ devices can co-exist without stepping on each others data, so it should stand to reason that the ANT link ignores the occasional blip when BLE is asking for a link - the protocols are different to the point that they should ignore even a poll.

To be clear, I'm not saying it doesn't or can't happen, just that it shouldn't.

One thing to consider is the possibility that either the HRM sensor, the receiver, or both are dual band ANT/BLE (I have an HRM/head unit which does both). The OP should make sure that isn't the case, and if it is, make sure he/she is actually linking with ANT rather then BLE. I have my HRM configured to run in ANT+ but I can't turn off BLE on the head unit. If I have my phone BLE on and it links before I've established the ANT link, the head unit get very confused. It causes enough problems that I don't use my bluetooth headphones on my rides, I stick to a wired set.

BLE has an annoying habit of allowing a different master to take over a slave simply by issuing a request. This is from personal experience when I'm listening to my bluetooth speaker poolside, and my daughter decides she wants to listen to something else. She just clicks 'connect' on her phone now I'm stuck with beyonce over king crimson ("lark's tongue in aspic? ew daddy!").

As Jeff points out RF is magic. Some of my past co-workers went so far as to call it voodoo. Then there's Clarkes' Third Law:

"Any sufficiently advanced technology is indistinguishable from magic."

[Jeff Liebermann]

I beg to differ. RF is a rather ordinary flavor of magic. The key
principle in magic is that the casual observer is unable to undestand
how it works. With black magic, one adds a metaphysical layer.
However, this is not really the case with RF. All that is required to
understand RF is a lifetime of working with RF devices, tool,
products, methods, and theory. I think I understand how RF works but
am lacking in many areas. For example, I still have problems
understanding Maxwell's Equations:
<https://en.wikipedia.org/wiki/Maxwell%27s_equations>
So, rather than spending another lifetime learning them, I prefer to
label them as magic, and ignore them unless pressed. In other words,
magic is what we do NOT want to learn.

>Given your explanation, it sounds like it would make sense to try
>turning off the phone's Wi-fi and cellular voice, at least (Airplane
>mode?) to see if that helps.
>
>Those shouldn't be needed while riding anyway.

Agreed.
1. Turn on "airplane mode". That will turn off cellular voice,
cellular data, Wi-Fi, and Bluetooth.
2. Once in airplan mode, you can turn on or off each of these
services individually.

Notice I didn't say anything about distracted riding, where not being
able to hear traffic sounds is considered a hazard. In California,
it's not legal to drive a car wearing two earphones because the driver
cannot hear sirens, horns, or gunshots (used to signal lane changes).
It should be the same for cycling. I probably should have mentioned
this previously, but was distracted by RF related issues. Sorry.
<https://www.bicyclelaw.com/road-rights-listen-up/>

[Lou Holtman]

It happened to me also several times, also with no phone so interference with the phone/bluetooth can be ruled out in my cases. Conditions when this happened:
- beginning of the ride when I not yet sweaty.
- low humidity conditions and windy,
- downhill.
I settled for the flapping shirt an insufficient lubrication of the chest contacts of the strap. It always went away on the next uphill (when it counts) and later in the ride (sweaty).
I must say it has been a long time ago since the last time it happened.

Lou

[John B.]

On Thu, 22 Jul 2021 10:50:50 -0400, Frank Krygowski
<frkr...@sbcglobal.net> wrote:

Good Lord! Without the hand phone and the GPS and the electronic maps
one might become lost and unable to find their way home and be reduced
to living on the streets and begging for food.
--
Cheers,

John B.

[Mike A Schwab]

Check any other pocket contents for blocking the signal (candy bar wrappers, repair kits, etc) by placing the object on top of the phone. And certainly agree on turning off wifi when you aren't in range of any. Your body (water, etc) could be blocking the signal too.

[Ade]

I have used the phone and heart rate monitor for years. In winter when I
wear layers of stuff, they is no problem with the heart rate monitor.

I can even simulate the wild heart rate effect by sitting at home
agitating the jersey with my hand. Spraying my jersey with water before
a ride also gets rid of the effect.

I was more interested in why the Bluetooth headset had problems.
Podcasts are download and hence local to the phone. The headset works
fine in a moving car, even when listening to internet broadcasts or
talking over voip.

There is something different about the bike. I will experiment. First I
will run removing the ANT+ stuff.

> Notice I didn't say anything about distracted riding, where not being
> able to hear traffic sounds is considered a hazard. In California,
> it's not legal to drive a car wearing two earphones because the driver
> cannot hear sirens, horns, or gunshots (used to signal lane changes).

I was only listening to people talking on the podcast, not heavy metal.
I can still hear traffic.

Fortunately we don't have guns where I live. I've only been to the USA
once and then I lived in NYC, which felt very safe, very similar to
home. Maybe the West Coast is different?

When I say safe maybe I'm wrong, but we worry about traffic. I noticed
flowers by the road side for a kid who was killed on my standard bike
route last weekend. He was hit by a drunk driver whilst riding an
electric scooter.

[sms]

Are the ANT+ heart rate sensor and the Bluetooth headset both connected
to the phone, or is the ANT+ sensor connected to a separate display? If
you have a phone with ANT+ (many Android phones, but not iPhones, see
<https://www.thisisant.com/directory/filter/~/60/~/>) you might try
pairing the ANT+ sensor with the phone.

[Ade]

ANT+ heart rate monitor is Garmin Edge 800 (not BLE), Phone is a Nexus
5X (not ANT+).

Both very old technology, the Garmin is so old it might predate my smart
phone usage, i.e. the heart rate problem is not caused by a smart phone.
I think the Garmin must predate my smart phone usage because I can't see
why I would want maps on a bike computer in the age of the Google Maps
smart phone.

[Jeff Liebermann]

On Fri, 23 Jul 2021 13:32:39 +0100, Ade <Ade.sp...@gmail.com>
wrote:

>There is something different about the bike. I will experiment. First I
>will run removing the ANT+ stuff.

You might want to disclose the makers and model numbers of the
equipment you're using.

How ANT+ Wireless Compatibility Works
<https://pezcyclingnews.com/toolbox/how-wireless-compatibility-works-with-ant/>
ANT communicates in a crowded radio-frequency space,
because Wi-Fi and all your near-field consumer items
like cordless phone extensions are transmitting in
the same band (Yes, your Wi-Fi CAN interfere with
your ANT+ devices!).

>I can even simulate the wild heart rate effect by sitting at home
>agitating the jersey with my hand. Spraying my jersey with water
>before a ride also gets rid of the effect.

Try riding with a T-shirt instead of a jersey and see if there's
anything wrong with your jersey. Water is a very good RF attenuator.
I used to partially cover dish antennas with wet towels on 2.4GHz
wireless links to test fade margin (how far the signal can be reduced
before data errors increase). I would expect a wet jersey to make
things worse, not better.

>I was more interested in why the Bluetooth headset had problems.
>Podcasts are download and hence local to the phone. The headset
>works fine in a moving car, even when listening to internet
>broadcasts or talking over voip.

Well, the likely suspect would be the new BT headset. I bought a
cheap clone of the original Apple AirPods for about $15. They barely
work. Range is suppose to be 10 to 18 meters, but it can barely do 2
meters. Worse, the range decreases as the battery discharges. Junk.
I borrowed a pair of real Apple AirPods, which worked reliably to 6
meters. Borrow someone else's BT earphones and see how they work.
(This is called repair by substitution).

My guess(tm) is still interference. I once had to deal with
intermittent interference complaint that mobile backup cameras and
local wireless parking lot security cameras were failing to
communicated around lunch time. It turned out to be a leaky microwave
oven at a nearby delicatessen. My guess(tm) is that any Bluetooth
headset would have been similarly affected.

>There is something different about the bike. I will experiment.
>First I will run removing the ANT+ stuff.

I don't think it's the bicycle, unless it contains a hidden NSA
installed secret tracking transmitter. Is there any other device on
your bicycle that uses 2.4GHz wireless? Additional ANT+ devices?
Wireless bicycle computah? Wireless rear view helmet camera and
display? Wireless shifting (SRAM Red eTap)? Wireless hotspot? 2.4GHz
microwave death ray? A similar problem was caused by a "fruit dryer"
built from a converted industrial microwave oven that wiped out Wi-Fi
links over about a 500 meter radius. Find a different route that
includes a downhill section and check if the problem persists.

>Fortunately we don't have guns where I live. I've only been to
>the USA once and then I lived in NYC, which felt very safe, very
>similar to home. Maybe the West Coast is different?

Yes, it's different. We have this problem called "road rage" which is
often accompanied by a shooting:
<https://www.google.com/search?q=freeway+road+rage+shooting>
I've never seen any of this myself, but I read about all too often in
the media.

[Jeff Liebermann]

On Fri, 23 Jul 2021 18:00:32 +0100, Ade <Ade.sp...@gmail.com>
wrote:

>ANT+ heart rate monitor is Garmin Edge 800 (not BLE), Phone is a Nexus
>5X (not ANT+).

Garmin Edge 800 doesn't have BLE or regular Bluetooth. It uses USB
communicate. The Edge 810 does have Bluetooth. The Edge 800 was
first available in Nov 2010. The Edge 800 only uses GPS satellites.
The LG Nexus 5X does GPS and GLONASS. In general, more satellites
means faster lock time, more accuracy, fewer dropouts, etc. Bluetooth
is 4.2 with A2DP (Advanced Audio Distribution Profile):
<https://www.gsmarena.com/lg_nexus_5x-7556.php>
Released Nov 2015.

>Both very old technology, the Garmin is so old it might predate my smart
>phone usage, i.e. the heart rate problem is not caused by a smart phone.
>I think the Garmin must predate my smart phone usage because I can't see
>why I would want maps on a bike computer in the age of the Google Maps
>smart phone.

Leaving GPS running on a smartphone tends to rapidly run down the
battery. A dedicated GPS mapping device has fewer tasks and less
hardware running, and therefore will have a longer battery life.
Garmin 800 spec says battery life can be up to 15 hrs. My guess is
your LG Nexus 5x can do about 6 hrs with average use and maybe 8 to 10
hrs if you turn off the un-needed hardware and services.

[Ade]

On 23/07/2021 22:21, Jeff Liebermann wrote:

>
> Leaving GPS running on a smartphone tends to rapidly run down the
> battery. A dedicated GPS mapping device has fewer tasks and less
> hardware running, and therefore will have a longer battery life.
> Garmin 800 spec says battery life can be up to 15 hrs. My guess is
> your LG Nexus 5x can do about 6 hrs with average use and maybe 8 to 10
> hrs if you turn off the un-needed hardware and services.
>

Phone GPS is on permanently. It isn't that draining. Using the phone as
a Sat Nat would be.

My point was more that I have only used the bike computer as a Sat Nav
on very few occasions, it just isn't much good. Pre smart phone era I
had become lost on bike adventures so thought a bike computer with GPS
would be a good idea.

In reality I use the bike computer for performance stats, speed,
elevation, cadence, time, heart rate. A bike computer giving these
stats, without the mapping is about 50% the price. If I do get lost I
have the smart phone maps.