DNS series head unit (new generation dual core RNS-510 alternative)

[Kakourgos]

Hi all,

The rather big writing below has nothing to do with you if your car has a single external antenna. Read at your own risk.

As I have already mentioned in a previous post one of my big issues was that the DNS reception is worst that the factory RCD510 unit.
I need to point here that my “finding” is affecting cars with two FM antennas like my 2010 Passat.
The two antennas are used in a receiver implementer hardware function known as “diversity” reception.
In that function the receiver sort of continuously selects (switches to) the antenna that provides the best signal.
That switching is very fast and is not noticed by the listener. The two antennas are located at distances of usually half or quarter of the wavelength ( λ) of the reception frequency.
Say, for an FM band of 88-108 ( in Europe) they select a frequency in the middle of the band (99Mhz) where the λ/4 is about 75cm.
In my car the FM antennas are the two vertical lines in the rear windscreen that are combined with the heated windows lines.
I haven’t measured them but I think they should be distanced in half of the above 75cm. There is no need to get too technical but the reason is that due to the “wavy” propagation of the radio signals it is very probable that when one of the antennas is at the low of the signal the other will be at the height of it so the Radio will switch to that antenna and so on.
Especially when the car is moving that improves the reception a lot improved the fading reception in a noticeable degree.

Now, why my receiver is not as good as it is supposed to be provided that it is equipped with a good FM receiver chip (Philips NXP 6646)?
I didn’t found enough documentation with a reference design about how diversity is implemented but what I sure found is that the people made the DNS have NOT implement that function.
So, is that really bad?
Yes, my other cars have a single –thus no diversity reception- antenna but they are still have a better reception than my Passat has now.

Why? Because as you can see in the photo below, both antenna feeds are internally connected to the same pcb trace!!



So what? Shouldn’t I have a better reception with two antennas than with just one?
No, because of two reasons:
1) The two antenna outputs of the car harness feed the car radio with signals that are in phase difference (because of the antennas spacing) that causes the signal of one antenna to cancel signal of the other antenna.
Somehow imagine it like when you have two woofers/speaker where the wires of one speaker are connected in reverse causing the bass to disappear (sort of..)
2) The impedance matching of the antenna feeds is not designed for paralleling the antennas also worsening the reception.

I’m no RF expert but the above are somehow should explain the situation

I was thinking about what I can do to improve the reception, so as I bought a dual Fakra to two single Fakra (or maybe the opposite?) adaptor.




I removed the plastic securing clips from the single Fakras side in order to be able to remove the connector from the plastic holder as you can see above.

Then while I was parked at home I tested the reception of 6 of my stored stations, the reception was bad so it was very easy to see if there is improvement or not in the reception.

What I realize is that:
1) Of course it doesn’t matter which antenna input you are using in the DNS as they are internally connected just behind the connectors.
2) For me, using a specific antenna feed has a slight better reception than the other and this is valid for both FM and AM stations.
3) The difference between using both antennas and using just one antenna is big, one specific stored station I cannot receive it with two antennas connected but I can listed quite well with just one antenna.
4) The antennas have built-in amplifiers so the DNS is supplying them with power. The voltage at the DNS antenna connector with no antenna connected was (engine stopped) about 12.6V
With one antenna connected it was about 12V and with both antennas connected about 11.3V. I didn’t note the voltages so the above are approximate values.
I also have no idea what is the minimum operation voltage of the antenna amplifiers but with the engine running and both antennas connected at least 12V should reach the antenna amplifier including the cabling losses so I see no issue there.

5) The antenna I decided to use is the one the normally goes to the corner of the unit.



If you think that you have reception problems you could try my approach to mitigate the problem or if you are brave you could also scrap off and interrupt the pcb trace of one antenna inside the unit.



This has no cost and can be undone if you are good with a soldering iron but don’t blame me if you mess up your unit.


It’s been a couple of days since I’m using just one antenna and I can confirm that my reception is indeed better as I’m driving at least 50km per day and I know where I’m losing signal of specific stations.
I live in the city with lots of multipath distortion as the signals are reaching the receiver directly and also delayed after reflected on big buildings.
I didn’t had the chance yet to check the improvement in the open country side so if you try something of the above please let us know.

[antoineschaller]

Can someone point me to the latest firmware for a DNS 810 please? I have what I think is called the Old CANBUS version. I have tried Sandy but no response.

This is my current firmware.

Attachment 21376

Sme question here...

Plus does anyone know if these instructions are still up to date?
https://www.dropbox.com/s/x1atq79s5k...ANBUS.doc?dl=0

Else do you know here to find up to date firmware update informations?

Thanks

[moda]

Can someone point me to the latest firmware for a DNS 810 please? I have what I think is called the Old CANBUS version. I have tried Sandy but no response.

This is my current firmware.

Attachment 21376

Sme question here...

Plus does anyone know if these instructions are still up to date?
https://www.dropbox.com/s/x1atq79s5k...ANBUS.doc?dl=0

Else do you know here to find up to date firmware update informations?

Thanks

So looking at my archives of firmwares and photos, I think that was the last version that I was using for the old cpu, old canbus version. It might pay to shoot Audiosources an email and see if they have any later versions for you. Try Fiona or Raylene at audiosources@audiosources.net, marketing@audiosources.net or sales9@audiosources.net.

I believe those instructions are still valid, yes?

Hi all,

The rather big writing below has nothing to do with you if your car has a single external antenna. Read at your own risk.

Excellent post, thanks mate Interesting, as I never had any reception issues with both the DNS and DS units, even with driving in some pretty rural/country/mine site areas. So it's obviously a case of YMMV. Good to know anyways.

[Spuddo]

Moda,

Thanks so much for your quick response. I will contact Audiosources and see what they have. If I get anything I will post back here.

Kind Regards

[jimmej]

Awesome write up! I cannot believe they are combining the antennas directly. No wonder the reception sucks. A interesting test here would to build a simple resistor based combiner. Or even get something off the shelf like a TV antenna splitter - installed backwards ofcouse.

I also have had issues with reception. What I noticed was that I got a great improvement when I changed my dash cam. It's still not great but so much better than it was.

[DSGVW]

Sorry if been asked before, but I bought a DS811 and it came with Sygic and I'd love to run iGO. But it's 1024x600 resolution and that doesn't exist for iGO.. any suggestions?

[551704]

Hello. I have been looking for the first DNS firmware versions (16 bit). It is desirable from 2014 (if there were such). Thank you. Yes - can anyone interested in connecting to the Internet DNS610? I did it. I can tell you how to do it through 3g modem.

[rainbows222]

Hi,

have anybody the newest Firmware for the DS811. It is possible to get Internet on the Unit. Thanks for help.

[551704]

Hi,

have anybody the newest Firmware for the DS811. It is possible to get Internet on the Unit. Thanks for help.

Here it will not work?
AudioSources DS611 - Firmware Update

[rainbows222]

Thank`s

I have that one, I search for a newer one. That one has no internetaccess. I need Internet for TMC, because it should be not possible to get a GNS-TMC-Port installed on the unit.

Can you tell me how to get internet on your unit.