FM Transmitter Problems

[mybuickskill6979]

can i ask a question? what would happen in this situation if you screwed the antenna wire to the metal body? would the metal body then become an antenna? or would it not work at all?

 

[the dude of dudes]

The point of all this information is to show that you have these choices:

- find a way to move the transmitter that you have closer to where you are working (some sort of audio relay from the truck). How about running an audio cable from the trailer up to within the work area? Cheap and relatively easy and fairly foolproof. Just annoying. This is legal and cheap.
- go illegal with more transmitter power (either buy something new or modify your unit)
- give up and get some sort of Sirius receiver that you carry with you.
- wear an antenna on your head (I could suggest a design) to extend range another 50 foot or so, but look like a dork.

Personally I think you should consider running an audio cable and putting your transmitter close to where you are working. And don't fall for the scam of brand name audio cables like "Monst--". They are vastly overpriced and unnecessary. It shouldn't cost you more than about $35 for a couple of hundred feet of audio patch cable.

I'd like to go with modifying my existing unit. I might try using AudioGuru's amp from another thread. Do I run the risk of burning out my transmitter by connecting the antenna to this circuit?

 

[audioguru]

My RF amplifier has a 33pF input capacitor which protects the transmitter from damage. This one uses a 4.5V battery for a fairly high power output. Another one uses a 1.5V battery for hardly any output power (like the BA1404 IC). My FM transmitter is designed for a 9V battery for plenty of output powetr.

 

[the dude of dudes]

Could I just strip the insulation off the end of the 55" antenna coming out my transmitter and connect it to your RF amp? Or would I have better results (less interference I would think) if I cut the existing antenna off and connected it directly to the transmitter?

 

[audioguru]

Connect the output of your transmitter directly to the input of the RF amplifier circuit with the shortest wires (output and ground) you can.

 

[audioguru]

Horray!
The feds in Canada changed the law so the RF cops can't shoot you and chop off your head anymore.

Now you get to tell a judge why the interference from your FM transmitter caused an airplane to crash and caused TV interference to thousands of couch potatoes. Maybe the judge will chop off your head.

 

[Jerry_yuan]

I think this transmitter is very likely be made out of a BH1417, and since the RF output of it is weak, a single stage amp made of a transistor might be already added, then about 10-20mW can be produced. to reduce the size, the ant is just the audio line (an inductor isolates the audio and RF signal). so, if you wanna improve the range, it is better to isolate the ant from the audio line, let your metal house be the ground, and set up an ant above the house and be sure it is isolated with the metal house.