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Sporster 4 FM transmitter

2826 Views 12 Replies 6 Participants Last post by  BCScott
The transmitter on the Sportster 4 is terrible, tons of static. Much worse then the Starmate. I have looked around it seems that I will need wired fm modulator to plug into my radio's antenna. Has anyone used one of these things? Do they work ok? Where can I get one?
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Well, I went and got the FM modulator and it works like a charm.
I've had lots of success boosting the signal using the little wire and the FM out jack in the base of the cradle. That worked wonders in my car with the Sportster Replay. I've posted on this site before about using a $5.99 ear-bud from the source to do the trick.

Today though I decided to be a bit more "do-it-yourself" so I followed these instructions without a hitch:

Worked like a charm and boots the signal immensely. Using that for the FM transmitter on my other car with my S100.

So while there's no doubt that the FM direct (aka FM modulator) is a great way to go, it's also $25 plus you have to pull out your car radio. With very little effort there is the $2.99 method that I did today and worked very well for me. Or if you don't even want to do that much, there is the $5.99 ear-bud solution discussed in other threads on this topic.

Just some suggestions for anyone who may want to try other solutions that have a fairly good chance of working for a minimal cost and effort.
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Thanks for the link, North of Calgary! Works like a charm and gives a decent signal around the house. Great $3 investment.
Yes, the boost is nothing short of remarkable. First I tried it with my car dock hooked up in the house. I tested with my regular audio receiver (which is primarily for TV/DVD). It received the Calgary radio stations anywhere from somewhat static-y to somewhat decent depending on the channel. With the Stiletto car dock about 3ft away, my audio receiver got nothing - absolutely zero. Then plugged in the wire I built as per the link and it went from nothing to perfectly clear.

So in my car where I was getting a so-so signal already, the new wire made it completely clear. Plus I tucked with wire in behind the plastic molding on the dash making it almost completely out of site.

An awesome solution for me for only $3.00!
This little mod just gave me reach to a cabin 350 ft from the house! I have a JVC system in that cabin so it must have stronger reception than the Panasonic units in my other 3 cabins as reception wasn't as good in them even though they're closer. Even in the JVC cabin, the reception isn't stellar, but it beats the crap out of listening to a crystal clear CJ92 from Calgary. Now to figure out a way to boost it a bit.
The wave length of an 88.1 signal is 3.4 metres, and my fm out wire is 170cm, do you think if I made one 6.8 metres and strung it outside, I'd get much better broadcast strength? Since 2 phono plugs came with the $3 package, I guess I'll just have to try it out.
Failing this, are there boosters available?
If anyone's's the formula for calculating the required length of antenna.

Even easier, there's a chart at the bottom that does the calculation for you.

A question, though, does the measurement start with the wire, or with the tip of the plug?
Do both methods work equally as well (the earbud and the wired one that you made yourself)?
same here it worked fine in my car pre hardwire, post wire tonnes of static, bougth an FM modulator and all better. I got it at the stereo install place
I finally got around to trying to boost the fm broadcast strength. I ran a 17 metre (5x3.4 metre) antenna outside. It made a small gain in the signal, but not much. Any ideas on how to boost it a bit more?
I don't quite know what you mean by 5 X 3.4 meter... Did you connect five 3.4 meter wires together to make a 17 meter long wire?

If so, it's WAY too long.. It won't work properly with the transmitter in your Sirius unit. Antennas have to be cut to a length that resonates with the radio frequency you're using.

Go to this link:

Then fill in the frequency in Mhz that your transmitter is tuned to.. (EG 88.1 or 97.5). That will tell you how many inches the antenna has to be. Use the 1/4 wave value.....
The chart I used said that for 88.1 frequency, the wavelength should be 3.4 metres. I wanted the run to go outside to see if the broadcast would reach farther. When comparing the 3 antennas I made, 85cm, 170cm, and 17 metres, the longest one does work marginally the best, giving me the strongest signal in my farthest cabin. The 85cm one works fine in the car. I was hoping for a bigger improvement with the longer run, but can live with it for now. I see that Sat. Radio Source is now selling a short fm out antenna that looks good for $12.99. All told, my 3 antenna experiment cost me $14.00.
I'd still like to find a way to boost it a bit more though.
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