Factory Fitted antenna

[Father Ted]

Hi All.
As I've noted on other threads, I've replaced the factory fitted stereo with a touch screen double DIN unit as my original failed and it was only a little more expensive to upgrade rather than repair.
However, I now need a permanent solution for an antenna. I currently have a cheap windscreen antenna, but this is very much a stop gap.
I want to use the roof antenna. I can probably run a coax to this unit and solder onto the terminals straight off the antenna. But! I understand that the factory unit has an amplifier. Does anyone know if there is an RF take off on this before it goes into the tuner, or is it all one package?

Thanks to this bleeding virus I've been "furloughed" from work for at least a month, so I'll have a bit of time to play with this (if the Mrs lets me! ) but I figured I'd ask before re-inventing the wheel.

[Clan]

Originally Posted by Father Ted

Hi All.
As I've noted on other threads, I've replaced the factory fitted stereo with a touch screen double DIN unit as my original failed and it was only a little more expensive to upgrade rather than repair.
However, I now need a permanent solution for an antenna. I currently have a cheap windscreen antenna, but this is very much a stop gap.
I want to use the roof antenna. I can probably run a coax to this unit and solder onto the terminals straight off the antenna. But! I understand that the factory unit has an amplifier. Does anyone know if there is an RF take off on this before it goes into the tuner, or is it all one package?

Thanks to this bleeding virus I've been "furloughed" from work for at least a month, so I'll have a bit of time to play with this (if the Mrs lets me! ) but I figured I'd ask before re-inventing the wheel.

the aerial tuning unit is in the rear roof under the outside plastic panel,
I have never ever had any problems with these so not looked myself , the tuner sends the audio down to the front via fibre optic cable so no good to you .

[SwissXC90]

The rear roof antenna is for pre-facelift models. You don't have much option here, you will need to fit an external antenna somewhere.

For facelift models, from about 2007, the FM antenna is an on-glass antenna.
Actually 2: one on the left hand, and one on the right hand rear side windows. For these cars the antenna runs to the dash board over normal coax cable. Each antenna contains an amplifier powered separately.
You can use one or the other of the two antennas with a corresponding adapter.
PS the left hand is also AM - it's the one with the more complex on-glass design.

[john langrick]

Just a suggestion, but how about mounting the aerial on the panel where your existing aerial is fitted in the roof? Something like this

https://www.incarconnections.co.uk/c...l-antenna.html

It could be that this very position may be beneficial.

You could also sell your old aerial assembly on the bay?

In any case thanks for the conundrum to give me something else to think about in these lockdown days!

John l

[Father Ted]

Originally Posted by john langrick

Just a suggestion, but how about mounting the aerial on the panel where your existing aerial is fitted in the roof? Something like this

https://www.incarconnections.co.uk/c...l-antenna.html

It could be that this very position may be beneficial.

You could also sell your old aerial assembly on the bay?

In any case thanks for the conundrum to give me something else to think about in these lockdown days!

John l

That's such a simple solution, I should have thought of it myself!

I have a windscreen antenna, currently mounted on my windscreen. I can easily extend this through to the rear and mount it to the roof panel. If the location proves a good one (and why wouldn't it?) then I will look to invest in a better quality one.
And, as I've got not work for a month or two, I'll have time to do it!

[Father Ted]

So. I have the roof lining out and the aerial removed. Then I had a thought.
Could I use the antenna part, disconnect the Antenna Module and fit my own amplifier (https://www.ebay.co.uk/itm/12V-Car-T...cAAOSwqB5cz~w- )
I presume Volvo would have put a bit of thought into the pattern of tracks.
This leads to my next question.
What are the different patterns for? There seems to be 7 different patterns, with 3 connections going into the Antenna Module. One of these connections is ground, but the other two must be associated with FM / AM reception.

I'm thinking of linking these two, connecting them to my amplifier and running the output to my radio.
But! It's a long time since I've done much with radio (other than listen). If, as I think, one is FM and one is AM, would wiring them in together compromise their effectiveness?

[SwissXC90]

Originally Posted by Father Ted

So. I have the roof lining out and the aerial removed. Then I had a thought.
Could I use the antenna part, disconnect the Antenna Module and fit my own amplifier (https://www.ebay.co.uk/itm/12V-Car-T...cAAOSwqB5cz~w- )
I presume Volvo would have put a bit of thought into the pattern of tracks.
This leads to my next question.
What are the different patterns for? There seems to be 7 different patterns, with 3 connections going into the Antenna Module. One of these connections is ground, but the other two must be associated with FM / AM reception.

I'm thinking of linking these two, connecting them to my amplifier and running the output to my radio.
But! It's a long time since I've done much with radio (other than listen). If, as I think, one is FM and one is AM, would wiring them in together compromise their effectiveness?

Yes, BUT

The many different traces on the antenna circuit board are for AM, FM, and maybe even LW. I cannot remember if the older Volvo radio uses LW.
For FM there will be 2 antennas, as FM needs diversity reception to be reliable with such circuit board antennas.

Each antenna goes to an antenna amplifier to match the very specific impedance and tuning of the antenna, and amplify the signal to feed to the radio.

You can try and connect your coax cable direct to the antenna part, but you have to make an educated guess, or use trial and error, to see which part of the antenna will work best for you on FM. Make sure the antenna board is disconnected from the Volvo electronics board.

The circuit board antenna will never work as well for you as a dedicated FM antenna, because of the lack of an antenna amplifier and the impedance mismatch.

But it will work to some extent - and if you primarily drive in a strong FM signal area, then the "some extent" may well be sufficient for you.

So try and see - you have nothing to lose.

PS when I was working in car audio, we'd use a 1m length of insulated wire as an antenna stuck into the antenna socket for a jury rigged antenna for testing purposes. In the city where I lived at the time, it was more than sufficient for decent FM reception. But the main FM transmitter tower was only 10km away

PPS: I am a qualified radio electronics engineer, and RF stuff was my love and passion when I was working in this field.

[Father Ted]

Originally Posted by SwissXC90

So try and see - you have nothing to lose.

PPS: I am a qualified radio electronics engineer, and RF stuff was my love and passion when I was working in this field.

Originally Posted by john langrick

Just a suggestion, but how about mounting the aerial on the panel where your existing aerial is fitted in the roof?

Thanks for your input both.
As Swiss says, I have nothing to lose, so I tried. And it works!

For others, here is what I did:
I removed the roof antenna and unbolted the amplifier/tuner board.
I noticed on the connector that there were two connections (and a ground). So I soldered a piece of wire and inserted it into the first slot on the plug. I soldered a second piece, inserted that into slot 3 (2 isn't used), then crossed this over the first and soldered them together. This means that I have both available as receivers. (Pic 1)
I had bought a £4 windscreen antenna from Halfords as a temporary fix. So I removed the amplifier from this and soldered the other end of my wire to the input on this. (Pic 2)
It needs power, so I used the 12v feed to the old tuner and picked up a ground on the antenna assembly. NB! You can't connect directly to the screw as this is insulated. You will need to connect under the small PCB to ground it on the chassis.(Pic 3 &4)

Then I put it all back together. I stuck the amplifier on the underside so that I could access it easily in future.(Pic5)

I routed the coax down through the rear post to the fusebox, then, with the aid of a coax extension lead, routed this through the bottom of the door opening (plastic trim is a pig to get off!!!!) to avoid the airbags.

The amplifier is very basic, but it does the job. I've not travelled anywhere since carrying out the work (lockdown!) but outside the house I have better reception to the stations I had and have more stations available to me.

[SwissXC90]

Well done!

If you look at the antenna circuit board, you can see 6 different antennas
These will be, at the least:
1 x LW, maybe 2
1 x AM, maybe 2
2 x FM, maybe 3

You can see the antennas clearly here:
https://www.ebay.com/itm/03-06-VOLVO...sAAOSw8t1eaP2c

I believe the 2 x triangle- shaped antennas in the middle are the FM antennas

Now here's the method to determine which antenna is the best.


1. Park the car in a known spot, ie: outside your garage
2. Tune the radio to the weakest radio station you can find on FM, one that is down in the noise and the hiss
3. Turn the stereo up load so you can hear it in the back
4. Go to the back and try one antenna connection after the other to find the one that brings in the signal as clearly as possible. The lower the noise and hiss on FM, the stronger the signal. So focus on the antenna which reduces the noise the most. You will find that touching the antenna or the connections with your fingers will change the tuning and may decrease or increase the signal. So try to compare without touching the wires.
5. If more than one antenna brings in a stronger signal and you cannot determine the difference, then try to find an even weaker station down in the noise where the difference is more obvious.

Make sure that the outside of the antenna coax (the shield) is connected to the ground of the antenna system via as short a connection as possible.
Only the center core of the coax is the live antenna wire, and only the center core should connect to the antenna element on the antenna circuit board. Via the amplifier, if you are using the antenna amplifier.

[SwissXC90]

Found this amazing gem of data. I understand this

5.6 Volvo XC90 aperture antenna
Swedish manufacturer Volvo fitted a unique antenna to their XC90 SUV, launched in 2003.The system an alternative to glass mounted wire antennas which may be adversely affected by heated windscreen elements and window tinting films containing conductive metallic layers. The XC90 is fitted with a traditional metallic skinned “turret top” roof, but an aperture is created at the rear of the vehicle. This opening is covered with a polymeric panel, and forms an ideal location for some hidden antennas (Low et al., 2006). Fig. 15(a) shows the XC90 from above and Fig. 15(b) shows some simulation results of the vehicle’s metallic structure for different antenna configurations. The aperture in the vehicle body is clearly shown. The portion of roof which contains the antennas is the black unpainted section at the rear of the vehicle in Fig. 15(a) which at first glance may look like a sunroof.
Seven antenna components (Fig. 16) are formed by printing wire shapes onto a large polyester film using conductive ink. The antennas act as monopole probes, exciting the aperture in which they are placed. For some services, multiple antennas are used in different locations to achieve radiation and polarisation differences between elements allowing diversity reception. The film bearing the printed antennas is attached to a plastic carrier which contains the necessary amplifiers, and the whole unit is located in the aperture and covered with a black polymeric composite material. Examination of Fig. 16 reveals that these antennas are for low frequency services, with Table 1 revealing each service is centred well below 1 GHz. This low frequency implies a long wavelength which requires physically long antenna elements. Note that the services targeted in this design are different from
those commonly used in the smaller shark-fin style antennas.



Performance of the roof aperture antenna for the FM band was compared in both simulation and measurement against a roof mounted monopole with a length of 80 cm and a side window antenna as used in an estate car Fig. 15(b). Unsurprisingly, the authors report that the roof mounted monopole provided exceptional performance for vertically polarised signals, but performed poorly for horizontally polarised signals. On average, the roof mounted aperture antenna performed approximately 2 dB better than the side window antenna, but was unable to trump the roof mounted monopole for vertical polarisation gain.