Viofo A139 pro // router plus sim-card instead of external Wifi-antennas

[Müller]

Hello.

I scratched my head regarding the following, but cannot tell if there´s actually any merits to it:

1.) Place a router with a simcard nearby the A139 (or several A139s) in station-mode. Connect the A139 to the router. Transmit the live-stream(s) over cellular-network and watch it/record it/store it (them) anywhere (?).

2.) To even get around ANY antennas and thus ANY hf-struggles: Assumed an A139 is modified like this, then there is a hf-output on the cam which is waiting for a 50Ohm hf-device to be connected to, usually a 50Ohm-WLAN-/Wifi-antenna. This (sending) antenna would transmit to a second, receiving antenna, which is also a 50Ohm device that is plugged in the corresponding connector on, for example, a router.

So the electrical-/hf-connection basically/simply consists of: two hf-connectors, one on the cam and one on the router and a 50Ohm connection-line between them (the two antennas) AND a more or less high-loss air-gap between the antennas.

But, and this is where the expertise of actual hf-knowledgeable people might be required: Shouldn´t it be possible to eliminate both antennas and the high-loss air-gap between them (the modified A139 and the router) and replace that by a short 50Ohm hf-/coax-cable, connected on one side to the modified A139´s hf-output and on the other side directly to the hf-input of the router? That would basically be nothing else like transmitting via ideal, quasi lossless 50Ohm-antennas AND without an air-gap between them, means: the hf-circuit from cam to router is working with the correct 50Ohm resistance but with nearly no losses which would then, in whole, behave like an (yes, bulky) A139 with an "integrated" sim-module ...

 

[SPL15]

The issue w/ connecting the A139 Pro’s antenna circuit to the router’s antenna jack via a 50 ohm coax cable will be massively overloading the receiver front end on each radio, causing severely corrupted signals. It could also potentially damage the receiver front end circuits (not likely with the low power that WiFi operates at)

It could theoretically work, but you’d need to attenuate the transmit signal both directions by several orders of magnitude. The radio front end circuits are looking for femto watt level signals, where the transmitter is producing milliwatt or larger signals. The 50 ohm coax cable will only attenuate several decibels (3-6 db) w/ reasonable lengths, even w/ cheap thin cable. You need more around 80 - 120 db of attenuation (depending on transmit power of the WiFi radios, where the router will have much higher transmit power than the A139 Pro)

There are easily made circuits to attenuate RF down to what you need, the issue w/ ghz RF is that spacing of parts & component selection is critical to get the desired impedance & level of attenuation. Resistor, inductor, & capacitor AC specs don’t often translate well when you get into the GHz RF range, datasheets only show specs for MHz range typically. Details such as PCB trace width, clearance, & length, as well as ground plane impedance can make a big difference & isn’t intuitive unless you have access to competent EDA simulation software. At ghz range, everything is an antenna, where there will be both e & I field coupling between traces, conductors, & components that will impact end results.

Fortunately, for the low power that WiFi produces, being slightly mismatched w/ impedance with an attenuator won’t likely blow up the transmit circuits, so it’s not the end of the world if the two antenna circuits aren’t perfectly impedance matched, in fact, the mismatch will further attenuate the signal (which is actually desired in your application)

 

[Müller]

Hello SPL15,

Thank You for taking the time to share your knowledge and educate. HF really is a special kind of electromagnetism and way not that plug-and-playable or (more or less) easy to understand like our common "boring" mains- down to battery-type low voltages. Alone already the various often headscratches inducing geometries of antennas and the different functional elements in/on them and how the electromagnetic field propagates in/through/on them, then finally "just" stepping out into free space like Jesus jogging straight off the shoreline out onto open waters. HF-guys sometimes seem like real world magicians ...

But thinking about this "ethernet-for-the-poors-concept" twice, it finally comes along as an unflexible and more expensive one in comparison to the standard device(s) > antenna(s) > air > antenna > router-one because for every each device (cam) one would need a router and a sim. And with what real world advantage over a connection of the same amount of devices via good matched quality antennas to one piece of router with one sim? I think some small transmisson-glitches during the time of flight of the signals can be forgiven compared to the wireless flexibility and connectivity of a multi-devices to one (long-range-) transmission-device-scenario and which is why it´s done as it´s done in today´s world ... ^^

So i think, concept #2 is somewhat dead on arrival and it´s case should be quietly closed ...

 

[acters]

It is possible to read from the SD card for high quality videos to store on a separate larger capacity device that can allow to streaming the contents to the cloud or home server. This can either be done by using wifi station mode to connect to the hub device, which allows low bitrate live streams, or by using an SD card multiplexer. Introducing LTE/cellular integration will increase complexity and time required to allow reading and viewing the live stream. I have not tested the A139 pro if it is capable of Live stream and sending data from SD card.
A SD card multiplexer will be more reliable and allows periodic backups, if there is a desire to save every single recorded data. You may be able to setup an automated script to sense when parked and vehicle is off to do this backup. Also allows you to format the SD card periodically and thereby increasing the lifespan marginally, formatting does not damage or limit lifespan of an SD Card, theoretically.(Increase of lifespan comes from the storage being completely erased and reset) Does not have live stream capabilities and will require the Camera to be turned off before reading the contents from the SD card. There are already devices created for this purpose and custom software made to do this. custom hardware is needed to be purchased and hooked up, and a hub device to store all the content to another storage medium. Also a method to stop recording or turning off/on camera while keeping parking mode capabilities. Adding LTE/Cellular for remote viewing of files is possible but will increase complexity.

For the wifi station mode device, the device will need a wifi router capable connection, storage capabilities and custom software to read data from the camera. If the custom device is made with the intention of backing up all data from the SD card, the custom software may need to be able to stop reading data off the SD card and send the live stream to the connected user.(I have not tested if it is possible to do live stream and copying from SD card) no one has made this custom software yet. Adding LTE/Cellular for remote file access will increase complexity, adding ability to view live stream over LTE/cellular will increase complexity immensely. may take months-years to do this cloud like solution properly.

Both methods are considerable more complex than manually doing the procedure of taking the SD card, copying contents and replacing SD card. Having multiple SD cards will allow you to move files to a cloud/local storage medium at a later time. This is not automated and will take time from your life.

 

[acters]

I also forgot about the 3.5 mm AV out port that can be used for live streaming instead of Wifi station mode and can be captured for cloud viewing. I do not know if the AV out is either: full resolution and high bitrate, or limited resolution and low bitrate. Would be nice if Viofo responds with what the AV out is capable of.

 

[Dashmellow]

I do not know if the AV out is either: full resolution and high bitrate, or limited resolution and low bitrate.

AV out on dash cams will never be full resolution, especially on a 4K camera like the A139 Pro. It is also neither high bit rate or low bit rate because it is not digital. AV out is an analogue composite output which plugs into a standard video monitor or TV usually via a 3.5mm plug or an RCA type plug.

 

[acters]

AV out on dash cams will never be full resolution, especially on a 4K camera like the A139 Pro. It is also neither high bit rate or low bit rate because it is not digital. AV out is an analogue composite output which plugs into a standard video monitor usually via a 3.5mm plug or an RCA type plug.

Completely understand, I do not know if the recording is being converted from digital to analogue. I suspected that the AV out will be low resolution. this may still be the best way to allow remote live stream viewing from an LTE/Cellular connection instead of doing Wifi station mode.

 

[Dashmellow]

Completely understand, I do not know if the recording is being converted from digital to analogue. I suspected that the AV out will be low resolution. this may still be the best way to allow remote live stream viewing from an LTE/Cellular connection instead of doing Wifi station mode.

The lower resolution would be ok but you would need a method to port the composite analogue AV output from the camera into the LTE/Cellular device.

 

[acters]

The lower resolution would be ok but you would need a method to port the composite analogue AV output from the camera into the LTE/Cellular device.

I am guessing the implementation will vary wildly. I do see devices that are used for live streaming video that have AV input with LTE connectivity.
It is also possible to setup a device to host a VPN server(so you can tunnel from remote location) and be connected with the wifi station mode and be reachable by LTE, this device could also do long term storage on the go. This would require a lot of custom software and may take a long time to get setup proper. Doable though, I don't have a need for it and not willing to make it happen.

 

[Müller]

Hello acters.

acters: "[...] the AV out [...] may [...] be the best way to allow remote live stream viewing from an LTE/Cellular connection instead of doing Wifi station mode."

The AV-out functionality is only active in station-mode.

 

[EdSM]

I scratched my head regarding the following, but cannot tell if there´s actually any merits to it:

Well, I think it does have merit. If someone breaks into your car and steals your dash camera you lose all the recordings that are stored on the camera, but if you record its video stream somewhere else, you get to keep the video footage to sort things out. It would be interesting to see how your antenna experiment plays out.
At the moment i use my A139 in station mode and record its video stream straight to my phone with this app: https://play.google.com/store/apps/details?id=com.unicordia.dc_free. It also does person detection in the recorded video

 

[acters]

Well, I think it does have merit. If someone breaks into your car and steals your dash camera you lose all the recordings that are stored on the camera, but if you record its video stream somewhere else, you get to keep the video footage to sort things out. It would be interesting to see how your antenna experiment plays out.
At the moment i use my A139 in station mode and record its video stream straight to my phone with this app: https://play.google.com/store/apps/details?id=com.unicordia.dc_free. It also does person detection in the recorded video

Interesting, it would not help if the break in occurred outside your Wifi's range, such as away from your property/public location. How do you plan on dealing with a break in and stealing of camera outside your property/you are not close to record with your phone?

 

[EdSM]

It does help if you set it up right. When I go traveling off-grid i use my retired phone as hotspot, even if I don't have cell signal reception or internet access. The phone also behaves as a cheap DVR. I keep it hidden so if they steal the dash cam I still have the recordings on my phone.

 

[acters]

It does help if you set it up right. When I go traveling off-grid i use my retired phone as hotspot, even if I don't have cell signal reception or internet access. The phone also behaves as a cheap DVR. I keep it hidden so if they steal the dash cam I still have the recordings on my phone.

I notice the A139 Pro has 2 screw holes for mounting the protection bracket. Would that be a possible consideration instead?
How do you deal with running out of storage space? Do you save everything or only for one day's worth of recordings?

 

[EdSM]

If you think of protecting the dash cam from vandalism, im not sure. I don't think the camera is made to take shocks.
My phone has a SD card of 256 GB. The app does loop recording and I have more than a day of recording space. I do not record in 4K. My newer phone does support a larger SD card but so far I did not need more space.

 

[acters]

If you think of protecting the dash cam from vandalism, im not sure. I don't think the camera is made to take shocks.
My phone has an SD card of 256 GB plus its internal storage. The app does loop recording and I have more than a day of recording space. I do not record in 4K. The newer phones do support a lot larger SD cards

very true, it will make it more inconvenient for an attacker to take the dash cam, After all we paid 300 bucks for this model. there is aftermarket parts insurance you can get through some auto insurance companies, Dash cams are considered aftermarket accessories. It depends on your cost to savings ratio. after a year or two, the aftermarket insurance coverage would cost more than the dash cam.
I guess you could hook up a large drive via USB C to the phone for larger storage capacity. would last longer for the amount of writing the loop recording will do.

 

[LateralNW]

I guess you could hook up a large drive via USB C to the

or the dashcam designers could lift their game add a feature like this Mirror Dashcam - SSD storage.
This is a very interesting Mirror dashcam.

Rydeen Tombo 360X Mirror Dash Cam 360° VIEW​

 

[EdSM]

That's neat! I love the "360" coverage and the backup camera function. The only problem with the setup is the cable trail that gives you the location of the secret hiding spot of the hard drive (for data transmission the cable cannot be verry long). And maybe the fact that no camera has the dynamic range or our eyes so when the sun or a headlight is behind the car it is likely that the rear-view mirror is not showing much.

 

[LateralNW]

That's neat! the only problem with that is the cable that gives you the location of the secret hiding spot

I'd like to see new options like this and others like the SIM card.
A couple of dashcam companies do this with the SIM but I believe you have to subscribe to their cloud service and other got you terms and conditions.

His example is just for demonstration. I'm sure it can be secured and/or hidden.

 

[EdSM]

The app I use does not require cloud subscription or internet access.