yashsingh1/xdaforums huggingface dataset:
[Android Head-Units] TorstenH:
The USB DAB+ adapters

The adapters come in different housings, in shape of a box or as stick.

View attachment 6104624

The box adapters have a MCX antenna connector, a micro USB or USB-C socket and are shipped with an USB lead.

The stick adapters have a SMA antenna connector. The one on the bottom left is special because it has a metal housing.

All the adapters are shipped with a windshield antenna.

All the adapters use the same dark main circuit board:

View attachment 6104625

Due to the same board it seems to make absolutely no difference which one gets used. Only a metal housing might be beneficial.

The adapters provide a 5V phantom power supply for the active windshield antenna:

View attachment 6104778
[Android Head-Units] TorstenH:
General hints

USB car chargers can have massive negative impact on DAB+ receiption.

View attachment 6104786

This is not only valid for cheap chargers, even chargers from known brands can be the root cause for bad DAB signal quality.

Such chargers can even disturb DAB+ receiption in cars equipped with DAB by the car manufacturer.

Also power supply adapters for dashcams or other in-car accessories should be disconnected if DAB+ signal isn't as good as expected. Influence might be different depending on the frequency of the station you're listening and on the strength of the DAB signal.
[Android Head-Units] TorstenH:
Experiment I - Wrap the adapter (and the USB lead) in aluminium foil

I often read that this hack significantly improves receiption quality. But not in my case. Moving the position of the adapter / USB lead has much more impact. Even several layers of aluminum with and without contact to the antenna connector have no effect. I would even think that people saying that this hack helps only moved the adapter accidentally to a better position.
[Android Head-Units] TorstenH:
Experiment II - Add an additional ground connection

Quick and dirty I assembled this lead...

View attachment 6105131

... to ground the outer mesh of the antenna wire (shield). Since I had already split the ground cable of the radio wiring harness for the rear view camera, it was easy to test with such a professional Y-adapter.

Nope, no improvement at all. But don't panic as more experiments are left.
[Android Head-Units] TorstenH:
Experiment III - Disable 5V phantom power supply

I've read that the 5V phantom power supplied by the USB DAB+ adapter influences active DAB splitters. As I use an active 16V antenna, disabling the power supply seemed to be worth a try.

This can be done by desoldering a coil:

View attachment 6105440

Source: https://www.android-hilfe.de/forum/...ab-splitter-im-kfz.1006027.html#post-13221232

This shouldn't be done if you use a windshield antenna or another antenna which needs a 5V phantom power supply. It would be hard to re-solder the coil without the right soldering equipment and the required experience.

The reception quality has not changed by removing the coil and ATTB (Antennentechnik Bad Blankenburg) has already confirmed that the 5V have no negative influence.
[Android Head-Units] TorstenH:
Experiment IV - Audio isolators

In meantime I tested two USB audio isolators.

The adapter gets detected and is working fine with one of the isolators in between.

View attachment 6108128

Unfortunately, I can't see (or better hear) an impovement. The position of the USB lead has still massive impact on the receiption quality.
[Android Head-Units] TorstenH:
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[Android Head-Units] TorstenH:
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[Android Head-Units] TorstenH:
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[Android Head-Units] TorstenH:
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[Android Head-Units] TorstenH:
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[Android Head-Units] TorstenH:
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[Android Head-Units] FMode:
Do you have a datasheet of the wradio c100? Does it have an analog output for the signal quality? Idea: TEA6101 and multiple antennas...
[Android Head-Units] PrinceLc:
Position of the USB DAB dongle for better reception is away from near the Radio also not behind the radio better in the glove box. Other tests I had was to attach the dongle on an usb hub better reception. What can cause a bad reception is a usb car charger most of them don't have a filter due to less costs some have an filter and are good to go.
[Android Head-Units] FMode:
So the next thing we should do is disconnect the VUSB line and powering the dongle from a battery/powerbank. If this solves our problems then we should have a look at filters? https://andybrown.me.uk/2015/07/24/usb-filtering/
[Android Head-Units] surfer63:
In my current car I have terrible reception. By occasion the transmitter tower/mast is 1 km away from my home, which gives of course excellent reception. More than 10 km away drops the reception.

Alu foil: I tried that as well but as long as the USB-feed is bad, you still have no good reception.

Edit: dashcam and reverse cams can also create noise and interference. Using ferrite cores around those dashcam/reverse cam cables might help as well.

Question: anyone knows what more or less "sun shielding coating" in the car windows does? I have searched far and wide using several search engines and chat-gpt and apart from the "the coating can contain metal or ceramic particles and might have a negative influence on reception", I can't find anything substantial (and yes: I know the OP has an external Calearo antenna).

My previous car had "lighter" sun shielding in the car windows than my current car. In my previous car reception with a simple windshield antenna was good. By now I tried already 3 types of antennas and have hardly any reception.
[Android Head-Units] surfer63:
What kind of USB-hub? A (cheapo) non-powered USB-hub does not filter anything. It is just a 1-x splitter.
[Android Head-Units] Jetblack31:
Hi @TorstenH,

Thank you for this thread that will be, I'm sure, very useful.

In my case, I have the same observations as yours.

I have a question: from the data you collect from the USB DAB stick, you obtain the signal strength. I am wondering if other properties are available, e.g. signal to noise ration (SNR), bit error rate (BER) or anything that could be linked to noise or errors ?

Regards,

Bernard

PS : in my case, I'm using a stick with the car stock antenna that is integrated in the rear shield (Renault Megane 3). Thus antenna is supposed to receive FM + 433 MHz. There is a stock amplifier close to the antenna. Currently it is supplied with +5V phantom coming from the DAB stick, whereas it is designed to be supplied with +12V from the stock radio.
[Android Head-Units] PrinceLc:
Normal usb hub
[Android Head-Units] surfer63:
So unpowered? Did you use ferrite cores?

I also tried to use a 12V -> 5V usb-hub which I bought on aliExpress. To use the 12V from the car. That didn't help either.
[Android Head-Units] PrinceLc:
I have this
[Android Head-Units] brodzik:
I can confirm that I have the same issue, once usb lead or the usb adapter moves the signal can drop from excellent to poor instantly, really weird...

Forgot to add: I'm using 12V Roof mounted aerial
[Android Head-Units] surfer63:
On my unit, the USB-female/male connection is rather loose. Moving the DAB dongle sometimes means that the USB male/female connection "wiggles" sometimes, even if it is less than 1 mm, but that gives immediate signal loss.

So I always tape my USB connections to make sure they keep connected. I did not yet use conducting tape around the male connector as it is then immediately too thick for the female connector, and I don't want to use conductive glue.

Next to that: even touching the SMA connection sometimes also results in signal loss even while the SMA connector is tightly connected. This is for all my 3 DAB-dongles.

So for me the weak connection between USB-female/male and the SMA-connector can also cause a big signal loss. And that is then a result from moving it. Not the location itself.
[Android Head-Units] TorstenH:
Arrived today...
[Android Head-Units] TorstenH:
Unfortunately the DAB+ adapter gets not detected with the filter circuit board in between.

I re-soldered all soldering points but it still not works:

Nevertheless, I ordered two alternatives... unfortunately it's again time to wait.
[Android Head-Units] TorstenH:
I think it's important to use an USB 2.0 hub. I have already tested with a 3.0 hub but this has no effect.

However I will try to find a cheap filter board that works.
[Android Head-Units] surfer63:
I did use a 12V 2.0 hub. I did not measure how clean the car 12V was.

I just ordered 12 ferrite cores. I read somewhere else that dashcams and reverse cams can cause a lot of interference on those unshielded USB cables. I have both cams. I will test tomorrow with the ferrite cores around the cam cables and around the usb lead to the dab dongle and around the antenna cable.
[Android Head-Units] sukimdennis:
If you are thinking about these ferrite cores, unfortunately they didn't do anything for me and I stuck them everywhere.

I also have a retrofitted camera, but it's only on when reverse gear is engaged and the cable is only a short distance next to the antenna and next to the head unit and otherwise in the footwell. I shortened the antenna cable and re-soldered it, DAB on the right under the headliner, VHF and power supply on the left under the headliner, of course everything meets somehow behind the head unit.

I once shielded the display with aluminum foil and used a clear film for insulation between the circuit board and display and again on the display. This was the best result for me.

I removed it again and then tried copper tape but only on the back of the display. It was a bit worse but much better than without it on a 720p display. After that I bought a 2k display, which has advantages but also disadvantages in general. With the 2k display, copper tape was less effective but I also had the feeling that it was less of an issue, so it wasn't that bad. But it could also have been because the cables were moved. Nevertheless, the display is still an issue.

My DAB reception reacts most when I move the main wiring harness behind the radio, and that also has an additional Canbus adapter for the PDCs.

I plan to replace the antenna tomorrow with an ATTB, fix the cables firmly, and experiment with two more or less identical DAB adapters. One with an active 5V supply and one without, without changing positions, and I plan to shorten the main wiring harness, because the longer it got over time, the worse the interference, so I'm shortening it.

I'll see how far I get tomorrow and what I can report.
[Android Head-Units] sukimdennis:
One more information, the connector on this DAB adapter is either just pressed onto the circuit board or very little solder was used, so I soldered or resoldered all the connection points from both sides to rule out connection problems.
[Android Head-Units] surfer63:
Thanks for your extensive report.

And thanks for destroying my hopes on a better reception when using ferrite cores ;)

You did exactly what I also planned to do: first the ferrite corres and if not working well enough, also put alu-foil around.

Your remark about the display is a good one. I had almost forgotten that one. In the 1.x version of @TorstenH's "competitor" with the other DAB app, it was discussed widely that these displays generate a lot of interference, not only for DAB but also to other audio as well.

In my previous car (Skoda Octavia 2010 with Joying Sogfia-3GR, PX5 and sc9853i DAB worked fine with just a window antenna.I started using DAB in 2017 on that Sofia-3GR.

In my current car (Skoda Ocativa 2015 with Mekede 7862) DAB doesn't work farther than ~10 km for the transmission mast. The windows of these newer car are (of factory) much darker than my previous car. I still don't know whether this "extra" window sun coating (metal and ceramic particles) indeed cause a worse reception as is generally assumed.
[Android Head-Units] sukimdennis:
One possibility, however, would be to use the ferrite cores only around + and -. Experimenting with different resistances between shield and vehicle ground might help, but I haven't tested it yet.

I've got a few window antennas lying around now. Have you ever attached one to the outside just for fun? Duct tape always worked for MacGyver too.😅

And of course the environment plays a role too. I drive past a 3 by 3 meter LED advertising board almost every day. My reception is bad or I can't receive anything. There is a hair salon 30 meters from the LED advertising board. When it's open I have no reception, when it's closed everything is great. That's because of their LED lighting. I have no idea how these jammers got approval. I had this interference there in the past too with a simple Sony DAB radio but with more or less the same antenna as now.
[Android Head-Units] TorstenH:
With one of my next experiments I will use a step-down converter to power the DAB adapter so negative power supply of the adapter would be GROUND. Then it could make sense to solder the cover plate to the antenna connector to GROUND the whole adapter housing.

This could avoid external interferences by LEDs and chargers... hopefully.
[Android Head-Units] surfer63:
I have two window antennas and this one. To me it looks exactly the same as the 4G antennas you get with your head unit. I tried with the window antenna, the amazon one and the 4G antenna and all improve reception, but none good enough.

I have read on the Skoda brisk forum that some users have the standard skoda FM/AM/GPS sharkfin on the roof and don't want to fiddle with that one or put a new one there. Some use an aerial antenna and put it horizontally inside the front or back bumper as that is made of plastic. As you have to put it horizontally inside the bumper, it will not work as good as when installing it vertical as the polarization is optimized for vertical position. Never the less, they report much better reception than with a windscreen antenna.

And no: so far I did not put a windscreen antenna on the outside. It certainly has crossed my mind, but I could not find a good way yet on how to do that.
[Android Head-Units] sukimdennis:
First, a bit more information. The roof liner has been removed, the antenna replaced and connected somehow for testing purposes. The reception is now, as I expected, terrible because the cables are all over the place, so I'm looking for the right places. But I have results for the DAB adapters regarding the power consumption of the roof antenna, regardless of whether it is active with a coil or passive without a coil, it has no influence on the power consumption of the roof antenna, it is identical.

The power consumption of the adapter itself is different when the roof antenna is not powered. Adapter active, 5V, 7mA. Adapter passive 0V, 0mA.

If the roof antenna is powered, the active adapter 5V has almost no power consumption, the passive adapter has 0V, 0mA.

The window antenna showed a similar result. Adapter active, 5V, 26mA. Adapter passive 0V, 0mA.

Only power consumption pictures.

Blue led ON/OFF.

Whether and how this will cause problems later or not remains to be seen.

Then I'll carry on. Hopefully these were the right pictures and no neighbor comes by with a beer. Oh, and I found some built-in ferrites when I removed the antenna😅...
[Android Head-Units] surfer63:
Well. I tested it this afternoon. As @sukimdennis already mentioned: No difference at all. Reception is still terribly bad. About 8 ferrite cores around the several wires.

So far the only result is now a bulky set of wires.
[Android Head-Units] sukimdennis:
Thanks, I almost forgot to reconnect the reversing camera👍🏻. I tested it and also the "USB dashcam" (complete junk) before I started to take everything apart, so the roof lining was down and I could simply disconnect it. No difference for me with the reversing camera, the front one reacts but I think that's because the main wiring harness is being moved. But I've also just seen that I can disconnect it directly under the roof lining, I'll test that later.

Rear

Front
[Android Head-Units] sukimdennis:
Put everything back together, tried various cable routings for DAB...it worked best when I threw everything in the middle under the roof liner.

So it was completely pointless. Now I have more loss at certain frequencies when the display is bright.

But I noticed one thing when I was putting it back together. The cable harness for the reversing camera is really long, so I tied it together. When I moved it, the reception strength changed.

So I'll continue tomorrow. I think I overdid it today😅
[Android Head-Units] Bettman66:
I don't want to destroy hope, but I tried these things years ago without success.

Only when I used the original DAB preparation from the car manufacturer did I get the same reception quality with the cheap dongle as the standard radio from the manufacturer. I think the manufacturers know what they are doing and carry out tests themselves to find the optimal antenna position and hardware.

If the original DAB preparation is available and the dongle has poorer reception than the factory radio, these tests could be of some use, as there is most likely an error.
[Android Head-Units] sukimdennis:
Damn...and I thought I was close to the solution.

🤣😅🤣

What's really annoying is that moving one or more cables leads to such big differences in reception. I don't think it's the antennas, more the USB thing. I'll hook up a cell phone tomorrow and compare it with the head unit.

But unfortunately it really feels like that. I retrofitted an original DAB module in the original radio to a Dacia Sandero 2 radio media nav and the reception with the 1 meter antenna and an active DAB splitter is excellent.

Unfortunately we don't have a run out of the box system, but we do have cool free apps and system improvements from people who sacrifice their time, hopefully enjoy it, and simply cool and detailed support.

I don't think I need to name any users, just thank you for that. Without you, these things would just be Chinese paperweights.
[Android Head-Units] surfer63:
Thanks for testing. I do see that you did not ground the wire antenna.

However, I tested that separately some months earlier. I did not connect the grouding copper "flap" to the metal of the A-bar, but by connecting a copper wire to that grounding "flap" and lead it back to a good grounding piece of metal in the bodywork. That didn't help either.

I also tested a DAB/FM-splitter on my FM-cable, together with an SMB-2-SMA adapter. I was already afraid that that wouldn't work but at some point you get desperate. I have an active antenna with 5V (or 12V?) on the central pin, which means that with such a splitter I also put 5V (or 12V?) on the central pin of the DAB receiver. My DAB receiver doesn't work at all due to this. Both DAB apps that I (try to) use can't find a DAB dongle anymore.
[Android Head-Units] Bettman66:
For cars from the Volkswagen world (VW, Skoda, Seat) without DAB preparation.

DAB-Splitter

Replace the existing FM amplifier with this part.
[Android Head-Units] Mr.TT_NZ:
Don't overlook the car's own systems as a cause of interference!

I saw a case of a Hyundai car which my company (before I retired) installed a two-way radio into, the reception on the comms radio was very bad and we used a spectrum analyzer to find that it was the car's own dash display that was radiating a huge amount of interference over a wide range of frequencies. The comms radio was using the 150 MHz band which is very close to the frequencies that DAB+ uses in the countries that have it (we don't). We were unable to do anything to help that poor customer, he had only just purchased the car brand new and the dealer could not even understand what we were talking about.

Some of those ferrite clamp around cores may be of some use but quite likely not.

Edit: I see the ferrites have already been tried.
[Android Head-Units] surfer63:
Thanks.

I am afraid this is going off-topic for the DAB reception itself. Still, I would like to know.

It mentions: Power Supply DAB 8.5 - 12V phantom.

But that would mean that again power is put on the signal pin of the DAB dongle, causing the same issues as I had with the antenna splitter. Or is that incorrect?

In the slightly newer units as of 2016, the DAB fakra is black and is expecting 12V.

So again: Wouldn't this put 12 phantom power again on the DAB dongle signal pin?

(please note: I am (or used to be) a technical software guy, not a technical hardware guy)
[Android Head-Units] Bettman66:
@surfer63 ,

I didn't read the text on the linked splitter completely and missed phantom power for both antennas.

I have this Kufatec DAB Splitter

The DAB dongle is connected directly without phantom power and FM is connected with a 12V phantom power adapter.
[Android Head-Units] Scale&Hardwarebox:
Hello everyone,

I've been dealing with the topic of DAB reception in my car since last year. When I bought an Android radio back then, I naturally wanted to have DAB as well, since my car only offers FM radio. Unfortunately, my reception has been getting worse over the years because I have a shark antenna (these generally have worse reception than regular rod antennas). I suspect that it is corroding from the inside, which is why the reception is no longer good.

When I then bought a USB DAB adapter, I attached it to the windshield as recommended. The result was very disappointing, with very poor reception of just 16 radio stations. What I didn't know is that my car has a heated windshield, and this interferes with the DAB signal. So, attaching it to the windshield was not an option.

Then I considered placing the antenna on the rear window. After gathering more information on the topic of DAB, I came across something in another forum about the antennas that come with the receivers. These have a much too short length and are not able to properly receive the signal. Moreover, they can only be operated with a 5V phantom power supply, whereas 12V would be better. Nevertheless, I have currently installed the following solution:

I replaced the DAB antenna with a copper tape of 35 cm length. I then installed it in the tailgate. The 2m SMA cable was a bit too short, so I bought an extension to route the cable behind the glove compartment. The DAB USB dongle is also housed there.

The reception has significantly improved as a result, and I found about 80 stations in the scan. I can listen to about half of them; the rest have poor or no reception. Wi-Fi signals, in particular, interfere with the reception. When I drive through streets and pass by houses, the reception fluctuates. On open roads with trees, the reception is almost entirely uninterrupted. However, it’s still not as good as it should be.

I started a new experiment and got an active 12V rod antenna with integrated FM and DAB reception. I scientifically connected it to my car:

The antenna is, of course, on the roof, where it belongs. The blue cable coming from the antenna is the ground cable. The FM connector is plugged into the radio, and the DAB cable into the USB dongle.

The red light indicates that the antenna is powered.

The first test with the FM radio worked; the reception is there. What about DAB now? I ran a scan and found over 80 stations again! And here it is: the reception is fantastic! Many stations that I couldn't get or received very poorly now work perfectly!

For example, Beats Radio. Radio2NL couldn't be heard before due to poor reception.

I assume most problems are due to poor antennas, like those on the USB dongles, and the fact that they can only be operated with 5V instead of 12V.

My next project is then to install a rod antenna (replacing the shark antenna) to achieve full DAB reception.

I hope this information has been helpful to you.

Regards, Roland