My 94 Miata is transmitting an extremely powerful unknown signal that is snuffing the WiFi signal on my GoPro Hero3.
Tinfoil hat time?
Normally I link the GoPro to a Nexus 7 via WiFi to set up and remote control the camera. This morning I was setting up the camera and the WiFi connection would drop out every time I got close to the Miata.
There is an antenna on the windshield of the Miata just behind the rear view mirror. I always assumed the antenna was not connected to anything because my Miata doesn't have a radio or any other entertainment device.
This antenna thingy is glued to the windshield and appears to continue broadcasting when the ignition is off. I disconnected some wires going the the antenna thingy and it appears to continue broadcasting.
Anyone recognize this type of antenna and is it a Miata part? Could it be a LoJack antenna? WTF????
Sorry for the crappy photo.
Some used car lots install a GPS locator on the car in case the loan is not kept current. That looks similar to one that we installed at LaFontaine.
Looks like an amplified antenna to me.
GoPros run at 2.4 GHz
Wikipedia says:Certain car manufacturers use the 2.4 GHz frequency for their car alarm internal movement sensors. These devices transmit on 2.45 GHz (between channels 8 and 9) at a strength of 500 mW. Because of channel overlap, this will cause problems for channels 6 and 11, which are commonly used default channels for Wi-Fi connections. Because the signal is transmitted as a continuous tone, it causes particular problems for Wi-Fi traffic. This can be clearly seen with spectrum analysers. These devices, due to their short range and high power, are typically not susceptible to interference from other devices on the 2.4 GHz band.
Of course, this does not mean the antenna IS 2.4 GHz, but it probably is.
Update!
The sun heated the windshield enough to soften the adhesive on the antenna, I yanked it off the windshield. The label on the antenna says "directed". Apparently this is part of the key-less entry/alarm system. I think Sperio nailed it with the alarm link.
Anyway, this is not what is broadcasting the powerful signal. Something else is going on.
In the past I have had most of the interior out of the car and never saw anything out of the ordinary.
What else should I look for?
RossD
PowerDork
4/11/14 9:48 a.m.
What's near your Miata? Does the non-WiFi-ness follow your Miata if you were to move it?
Follow the antenna leads. Disable whatever is connected. It MAY still be broadcasting and if it is grounding to your chassis it can still be interfering. A small box under the dash, maybe? Hope you have better luck than Malaysia. Also, move your car like RossD says.
For the 2nd time while reading this thread, I'm wondering if there's some tracking device secretly stuck to your car. That's the only thing (other than certain alarm systems, as I just learned) that should transmit when the car is off. If you pull the battery and the transmission stops, you can be pretty sure it's nothing malevolent.
I'm at the office right now and I left the camera at home since it wasn't working. I'm limited to observations from this morning.
When I was fighting with the camera this morning I noticed the camera would go offline whenever I approached the Miata.
The Nexus 7 showed various Wifi Signals including the GoPro when standing within ten feet of the Miata. As soon as I walked up to the Miata with the nexus 7 and the GoPro the GoPro wifi signal would disappear from the nexus 7 screen.
Its only the GoPro signal that drops out, all the other known WiFi signals are still displayed on the Nexus 7.
The Miata was parked near my new camper so I moved the Miata into the driveway in case the camper was broadcasting something I wasn't aware of.
Moving the car didn't help. The Non Wifi follows the Miata.
When I get home this evening I'll disconnect the battery on the Miata and see if the problem goes away.
Apparently the car has some sort of transmitter that is not associated with the alarm.... interesting.
fujioko wrote:
Apparently the car has some sort of transmitter that is not associated with the alarm.... interesting.
You only disconnected the antenna. Transmitters will use whatever they can to transmit. That means wires as well. You need to find the module and remove it.
Whatever is TXing is doing so at a very similar wavelength as the camera. The camera has a weaker signal than a router or computer, so other devices may be detected around it, but the camera will be interrupted.
I really doubt it is anything different. Get under that dash and dig around. Its down there and if the antenna was live, this thing still is. 
N Sperlo wrote:
GoPros run at 2.4 GHz
Wikipedia says:Certain car manufacturers use the 2.4 GHz frequency for their car alarm internal movement sensors. These devices transmit on 2.45 GHz (between channels 8 and 9) at a strength of 500 mW. Because of channel overlap, this will cause problems for channels 6 and 11, which are commonly used default channels for Wi-Fi connections. Because the signal is transmitted as a continuous tone, it causes particular problems for Wi-Fi traffic. This can be clearly seen with spectrum analysers. These devices, due to their short range and high power, are typically not susceptible to interference from other devices on the 2.4 GHz band.
Of course, this does not mean the antenna IS 2.4 GHz, but it probably is.
Change channels on the wi-fi?
In reply to MrJoshua:
I don't think the GoPro has that capability.
The mystery continues...
I got home a short while ago and tried to duplicate the scenario from this morning. The GoPro is now working fine.
I reattached the alarm antenna thingy and played with the buttons on the key fob. Doors lock and unlock and the GoPro continues to work fine.
On a side note, I discovered the car has remote start. Who puts a remote start on a stick-shift?
I'm going to yank the alarm system out and toss it in the bin... but first I want to figure out why the camera absolutely would not work in the vicinity of the Miata.
to be continued...
fujioko wrote:
On a side note, I discovered the car has remote start. Who puts a remote start on a stick-shift?
probably the same people who wanted to put a remote start in my saab 900. (think about that for a moment)
I would definitely unhook the battery and go from there. You might even have to start removing fuses
I want to see it try walking down the street without you when you hit that button... 
Hopefully the problem just stays gone.
With the remote start the antenna is probably for a 2-way remote to indicate that the car did or didn't start. I wonder if you hit some combination of buttons that made the remote start try to work and it was trying to send a message to the remote?
In reply to oldopelguy:
That sounds plausible. Maybe the transmitter was channel hopping trying to say "hey, someone's stealing me!" or whatever and waiting for the remote to answer "ok got it." Somewhere along the line it barges into the gopro's channel and knocks it offline in a spew of messages that confuse the poor camera.
Perhaps if you wait long enough after hitting the magic combination of buttons it gives up and stops trying to transmit any more messages.
Arggg! berkeleying alarm system!
So .... about ten minuets after my last post I decided to do some video tests. Sure enough the camera zonked out when it got close to the Miata.
I disconnected the car battery and everything was cool again... The most likely suspect is of course the alarm.
Crawling under the dash of a Miata ain't fun but I located the "black box" without the aid of the US Navy.
The alarm system is intricately woven into the Miata harness and its going to take a bit of effort to surgically remove everything. Whomever installed the alarm did a nice job and I'm really impressed. I was figuring on a few wire nuts and duct tape.
Anyway I removed the black box and left the harness for another day. The car starts and runs fine without the head of the hydra spewing its blasphemous 2.4 GHZ signal to yet another unknown demon.
What impresses me the most is my question was effectively and correctly answered within five minuets of my original post.
Thanks a million!
