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Hardwired FM Modulator- Not

17K views 40 replies 14 participants last post by  ukinne 
#1 ·
Well today I planned to hardwire a FM Modulator into the HU-803 so I could have an Auxiliary Audio Input. Task one, was to get to the antenna connector on back of the HU-803 to insert the Adapter cables for the FM Modulator.



To get to the back of the radio you first have to remove the pen holder by carefully prying up the edges. I used a plastic knife so I would not scratch any thing.



You then remove the gear selector panel and remove the two screws behind the pencil holder at the base of the environmental control panel.



Now comes the tricky part. To remove the environmental control panel, you have to lift out from the bottom while you are pulling down and out from the top with a rocking motion simultaneously! It took me an hour to figure that out. Move the unit off to the driver side.



You then remove the two screws at the base of the radio



You then lift out on the bottom of the radio to clear the lip on top of the radio. Slide the radio and car phone out once you clear the lip.



Now for the bad news. You will notice the antenna input on back of the HU-803 has two antenna inputs. One for the left rear antenna and one for the rear bumper antenna. The adapter cables fit fine but only utilize one of the antenna inputs. If I used these adapters I would lose the diverse antenna signal capability. So I put everything back together and will have to look elsewhere to connect the FM modulator. I would bet if anyone had a FM modulator hardwired by a car stereo shop they are operating their radio with one of the antenna disconnected.



Doug H
 
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#3 ·
Re: (23109VC)

Quote, originally posted by 23109VC »
what is this thing you were trying to install anyway..what does an FM modulator do?

It's for installing a satellite radio for one.
JRL
 
#4 ·
Re: (23109VC)

Quote, originally posted by 23109VC »
what is this thing you were trying to install anyway..what does an FM modulator do?

A FM Modulator enables you to broadcast your MP3 player, Satellite receiver, tape player, etc. to a specific FM station on your car radio. The Quality will be about the same as a high power FM radio station in your area. Normally you wound use an Auxiliary input, but Volvo in their wisdom they decided we did not need one.


The modulator connects to the antenna input of your head unit. Your antenna then plugs into the fm modulator. It has several settings to choose a non- interference radio station for the modulator to broadcast

Doug H
 
#5 ·
Re: Hardwired FM Modulator- Not (defgh1)

Nice work on the how-to-(try) Doug.... I am quoting the following as it is significant and no one should overlook it.

Quote, originally posted by defgh1 »
I would bet if anyone had a FM modulator hardwired by a car stereo shop they are operating their radio with one of the antenna disconnected.
 
#6 ·
Re: Hardwired FM Modulator- Not (JimLill)

I operated my Sirius receiver over FM Modulation for about five months without a lot of degredation in the signal by having only one of the diversity antennas plugged in. Granted, I rarely listened to normal radio but when I did, the reception and RDS information came through just fine. Though not optimal, the difference was negligable.
 
#7 ·
Re: Hardwired FM Modulator- Not (RobS60R)

Quote, originally posted by RobS60R »
I operated my Sirius receiver over FM Modulation for about five months without a lot of degredation in the signal by having only one of the diversity antennas plugged in. Granted, I rarely listened to normal radio but when I did, the reception and RDS information came through just fine. Though not optimal, the difference was negligable.

I am sure the impact of loosing one antenna input will vary by location and strength of local radio stations. Since Volvo does not make a habit of adding extraneous components, they would not have incorporated a diverse antenna capability without a good reason.

Doug H
 
#8 ·
Re: Hardwired FM Modulator- Not (defgh1)

how would the fm modulator work if you had only one antenna input? who makes, and what are the model numbers of, the two pieces you have a picture of?

john
 
#10 ·
Re: Hardwired FM Modulator- Not (JimLill)

Quote, originally posted by JimLill »

Nice work on the how-to-(try) Doug.... I am quoting the following as it is significant and no one should overlook it.

Trust me, I installed hardwired modulators in both my S60AWD and now my V70R and there has been ZERO change in FM reception clearity or range...

You may well be right about losing diversity, but, in my experience, there is no significant functional effect..
 
#11 ·
Re: Hardwired FM Modulator- Not (defgh1)

i don't think you need to worry about "losing" the signal from either antenna, as the fm modulator works this way: when the radio is tuned to a pre-selected frequency, the modulator blocks the incoming signal from the antenna and inserts its own. Thus, when you're listening to any frequency but the frequency set on the modulator itself, the radio is still able to select the antenna with the strong signal. when you tune the radio to, say, 88.9, the radio selects the 'antenna' with what it believes is the strong signal, but it actually gets whatever is wired to the fm modulator. you would only have a problem if there was an fm station on 88.9 with a stronger signal than the one being supplied by the modulator.

so go ahead, put it in and try it out. i bet you could test the signal strength by removing the other antenna from the radio to see if station reception is affected by the modulator. there might be a 3 or 6 db dip in power due to the connections, but the actual radio reception would likely be relatively unaffected by that.
 
#12 ·
Re: Hardwired FM Modulator- Not (s60r05)

Quote, originally posted by s60r05 »
how would the fm modulator work if you had only one antenna input? who makes, and what are the model numbers of, the two pieces you have a picture of?

john

I got the adapters from http://www.Circuitcity.com:

1 MET 40VL10 Metra Volvo Antenna Adapter-Aftermarket Radio to Factory Antenna
1 MET 40VL20 Metra Volvo Antenna Adapter-Factory Radio to Aftermarket Antenna

There are numerous FM Modulators. The one I purchased was from http://www.partsexpress.com:

205-687 FM MODULATOR / TRANSMITTER 7 CHAN $37.25

Doug H
 
#13 ·
Re: Hardwired FM Modulator- Not (defgh1)

My first post!
anyway, i just did this install
if you look at the factory connector, you'll see a darker grey clip. same on the adapters. if you remove it, you can pull the antenna lead that gets disconnected by the adapters, and plug it into the adapter connector that gets plugged into the HU.

I have both antenna leads hooked in, with one of them being interrupted by the fm modulator... works great... although, in theory, that second antenna could allow a signal over the same channel to overpower the modulator's signal. not likely, since the signal power of the modulator should be enough to completely overpower the incoming on the other lead. the diversity system SHOULD pick the stronger of the two signals and lock on, stronger being the modulator.

now if i could only get rid of the ground loop noise i'm hearing...
 
#15 ·
Re: Hardwired FM Modulator- Not (defgh1)

if you have a small flat blade screwdriver, its pretty easy. the darker grey retention piece is held in by a clip molded into the connector. if you gently pry up the part that latches the retention piece, it slides right out. a light tug will get the antenna cable loose. remove the retention clip on the adapter that plugs into the HU and socket the cable in. just replace the retention piece, done!.
 
#18 ·
Re: Hardwired FM Modulator- Not (defgh1)

UPDATE!

Based on a suggestion, I ventured back into my Dash to retry the FM Modulator hook up. You can release the Antenna cable from the connector by using a small screwdriver and releasing the dark-grey locking tab on back of the connector. You then have to lift a small plastic catch to allow you to completely remove the cable from the connector



I removed the second diverse antenna cable from the original Volvo connector on back of the HU-803 and inserted it into the adapter cable for the FM modulator and plugged it into the radio. I now have both diverse antenna leads still going into the back of the radio.



To route the wiring for the FM Modulator I removed the lower side panel on the passenger side. To remove rotate the rear screw head, by the seat, a 1/4 turn, pull the back of the panel slightly out and slide the whole panel back to remove.



This is a photo of the FM Modulator



The FM Modulator antenna leads connect into the adapter antenna cables and for the 12v source I used the wire for the cigaret/12v connector. The ground was connecter to the console bracket.



I routed the signal input cable through the consol and out the consol storage compartment. I then just tucked the FM Modulator and wiring behind the front carpet and reinstalled the plastic side panel.



The FM Modulator and HU-803 were tuned to a clear FM station and I tried various inputs: MP3 player, Portable CD player, and Portable Tape player. Everything played fine, but I was NOT impressed with the sound quality. It was not as good as a regular FM station. I would give it a 6/10 rating. Maybe the $40 FM modulator I purchased sucks, but at this point it was not worth all the effort. However, I learned a lot and now can get the radio out in about 10 minutes and know you CAN retain the diverse antenna even with the Adapter Cables. I hope you also got some good info out of it.

Doug H
 
#19 ·
Re: Hardwired FM Modulator- Not (defgh1)

one thing that i found is that grounding the modulator to the cig lighter ground causes a low level alternator hum to be present (ground loop)
I'm going to try grounding it to the radio chassis.

glad to see you were able to get the antenna hook up working!


Edit: oops, you did ground it to the chassis.
what frequency are you using?
at 88.1, my JVC modulator completely knocks out 88.1 broadcast here in NY.
supposedly, the lower the frequency, the better the sound quality (no idea if this is true though.)
 
#20 ·
Re: Hardwired FM Modulator- Not (SilverS60RNYC)

Quote, originally posted by SilverS60RNYC »

what frequency are you using?
at 88.1, my JVC modulator completely knocks out 88.1 broadcast here in NY.
supposedly, the lower the frequency, the better the sound quality (no idea if this is true though.)

88.3 works good in my area, but I was still not happy with the quality. The unit does not have the dynamic range needed to play all music types without some distortion being introduced at extreme high and lows.

Doug H

Modified by defgh1 at 8:55 AM 5-30-2004
 
#21 ·
Re: Hardwired FM Modulator- Not (defgh1)

Dynamic range is best in the middle of the FM band, hence the desire of most stations to be in 94-101 range. Theoretically, the best sound should come from 97.9.
 
#22 ·
Re: Hardwired FM Modulator- Not (defgh1)

Quote, originally posted by defgh1 »
The FM Modulator and HU-803 were tuned to a clear FM station and I tried various inputs: MP3 player, Portable CD player, and Portable Tape player. Everything played fine, but I was NOT impressed with the sound quality. It was not as good as a regular FM station. I would give it a 6/10 rating. Maybe the $40 FM modulator I purchased sucks, but at this point it was not worth all the effort. However, I learned a lot and now can get the radio out in about 10 minutes and know you CAN retain the diverse antenna even with the Adapter Cables. I hope you also got some good info out of it.

I might try this model of FM Modulator. Thanks for the detailed install documentation.

http://shop.store.yahoo.com/sa....html
(there are many places to buy it for $35)

Doug, how do you select from the 7 available frequencies on your FM Modulator?
 
#23 ·
Re: Hardwired FM Modulator- Not (rqc)

Quote, originally posted by rqc »


Doug, how do you select from the 7 available frequencies on your FM Modulator?

There are a set of 4 Dip Switches on the side of the unit which allow you to pick one of 7 frequencies from 87.7Mhz to 88.9Mhz.

Doug H
 
#24 ·
Re: Hardwired FM Modulator- Not (rqc)

Quote, originally posted by rqc »
Dynamic range is best in the middle of the FM band, hence the desire of most stations to be in 94-101 range. Theoretically, the best sound should come from 97.9.

Explain why the Dynamic Range is better in band center... are you speaking RF or AF?
 
#26 ·
Re: Hardwired FM Modulator- Not (defgh1)

And how does it know how to kick in and take over? Does it look for a signal or is there an on/off switch? If it uses auto on/off, how does it do with quiet songs?
 
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