jwt873

This post will hopefully clear up some confusion that exists about a Sirius acessory known as the FM Direct Adapter, (Also known as a Wired FM Modulator Relay).

Despite being called a Modulator Relay, the device doesn't modulate anything. This accessory takes the FM signal produced by the FM transmitter that is built inside your Sirius receiver and connects it DIRECTLY to the antenna input of your car FM radio. At the same time, it disconnects your car's FM/AM antenna. The adapter is nothing more than a simple switch.

It works like this:

When your Sirius radio is OFF, the FM Direct adapter switch is set so your car antenna is connected directly to the antenna input of your car radio. In this position you can listen to local AM and FM stations as you always have.




When your Sirius radio is ON, 5 volts is sent down the cable to the Direct FM adapter. When this happens, the switch changes positions. Your car antenna is disconnected from your radio and the FM-OUT from the modulator built into your Sirius receiver is connected directly to the antenna input of your car radio.




The adapter provides two big advantages.

- First: When you disconnect your car antenna from your radio, signals from local radio stations are either eliminated or greatly reduced. This prevents local FM stations from interfering with the FM signal put out by the transmitter built into your Sirius receiver.

- Second: FM radio signals travel much better through wire than they do through the air. Connecting the transmitter built inside your Sirius unit directly to your FM radio antenna plug by wire will deliver a far more powerful signal to your FM radio. This will make sure the signal is loud and free from hiss.

The image below shows pictorially how the FM direct adapter connects between your Sirius Receiver and your car FM radio.



Further reading...

The PDF version of the FM Direct Adapter installation manual

ProperModulation

This should have "static" added to the title and be made into a sticky! Great info! It should be a big help to all the new people here who are asking about static.

TSS Taylor

That's so helpful. Thank you for putting that together.

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DRC

PhillyPhan

I agree. This very useful thread should be made a "sticky."

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Gone to DRC!!!

Chad49

Since this link has outstanding detailed info on how the FM direct works I ask the following:

Is there a way to boost the signal for a FM station to stock radio?

I have FM direct for my Sportster replay in my Dodge Truck. but I want to take the radio out with me to the company cars. I use different cars all the time and can't use the FM Direct. I live and work the LA and Orange county areas of California and there are only two stations really that are free 88.3 and 106.9. But my sportster replay has less than zero output. I can barely hear the sirius broadcast through the static. I need something that will increase the power to the car's FM antenna. Thank you for any help.

gman88

You may need a cigarette lighter splitter to power it and your radio. CCrane works great but cost about 100. Other FM transmitters may work for you.

jwt873

You might want to try the FM Antenna Extender. These are now being included as standard kit with some Sirius units.

You plug the extender into your FM-OUT and it causes the signal to be radiated at the other end. You put the other end of the extender near your car antenna. Here are the instructions on how to install one

Of course, a powerful external transmitter is the best way. I have an old 12 Volt Pyle PLMD-1 transmitter (long out of production).. It has a solid range of 1/4 mile. The only hitch is that it only works on 88.7 and 89.1, so if you have a local station on those freqs, then you can't use it.

Joe C

I don't have a cradle for my Brix Streamer that has FM out, just the regular aux out jack. Would this still work, or do I need a cradle with the FM settings on it ?

jwt873

I'm not familiar with the Brix Streamer, but you must have an FM transmitter for the adapter to work. If the Brix has the FM transmitter built into the dock, then you need the dock with the FM transmitter.

PhillyPhan

The car cradle for the Original Brix Streamer has the FM transmitter built into the cradle.

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Gone to DRC!!!

Joe C

Thanks for the responses guy, my existing cradle does not have the fm frequency transmitter settings so I ordered one from TSS-Radio.

LakersFan

So will this completely eliminate the static, being that's it's directly plugged into the antenna? I, too live in So Cal and am having static problems.

jydawg

I just purchased a Sportster4 and had awful static....installed the direct FM module and yep...no static.

Think they should put this with the car kit, cause without it...nadda

Michigan Made

I made this a sticky. Great write up jwt873!

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SentraStyleEMW

It won't completely get rid of static, but it is 100% than the wireless option. You still might have to go into the menu of your unit from time to time to adjust the frequency it transmits on, but that's only if you travel a lot. If you tend to drive in the same area all the time, you shouldn't have to change the frequency very often.