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PacMang
11-06-2008, 12:13 PM
Some people on the Other Hardware forum wanted pics and a guild for the 200mW FM transmitter so here it is.

http://www.tallahasseelights.com/tech/fm_transmitter/index.htm

electr0n
11-06-2008, 05:48 PM
PacMang - thank you for the how-to, it's exactly what I need. I haven't gotten my board(s) yet but when I do now I'll be ready.

WWNF911
11-06-2008, 10:36 PM
PacMang,

I'm curious. Why do you short out green to black on the power supply?

Thanks

Leon

PacMang
11-06-2008, 11:58 PM
PacMang,

I'm curious. Why do you short out green to black on the power supply?

Thanks

Leon

That connector is normally connected to the motherboard and ends up being connected to the push button (on/off) for the case. So if you want it to be on you have to short it out.

electr0n
11-07-2008, 10:31 AM
Are you going to mount your transmitter in a case? If so I'd be interested in what you went with.

PacMang
11-07-2008, 11:54 AM
yes i actually mounted it in a case last night (used a clear tupperware container) ill post pics tonight.

Aurbo99
12-05-2008, 10:12 PM
I have a few questions regarding this Transmitter PacMang,

How is this working for you?

Did you post the pics for your case?

Is there anything not covered in this thread that might be useful to know.

I received a similar unit to yours, short 8" antenna wire soldered to the board, and NO power supply came with it. otherwise its identicle to your posted pics.

I've build a Dipole using RG-58 50ohm cable and my connection is a Chassis mount BNC connector instead of the SO239.

All my 12vdc wall warts range from 150 to 850mA.

Checking reach of them with a voltmeter they indicate 17-18.6 VDC and I'm leary of plugging them into this unit at this point.

Right now I have a variable radio shack power supply at 500mA but set to 7.5vdc as the Voltmeter reads 11.97 on the 7.5 setting.

I think the power readings so far are read without a load, so they would be higher than expected, but I'm still not willing to try them yet.

Did the ATX power supply work ok with this unit?

gmijackso
12-06-2008, 10:47 PM
Power supplies need to have a load before you can measure them with a multimeter/voltmeter and get an accurate reading. Your power supplies will put out a much higher voltage with no current draw, which a voltmeter only will draw no current, and will produce the rated voltage when a load is applied.

A voltmeter is intended to measure voltage across a load. Your power supplies are behaving as they should without a load, use the 12V supply, not the 7.5V one.

Aurbo99
12-07-2008, 10:24 AM
Thanks for the info, I suspected that much and I really should have remembered that too.
Too much crap to do, so little time.. I think I'm starting to forget basis stuff. =)

I went with the ATX power supply, Looking at what I am using I had too many wall-warts plugged in everywhere.

I also tested my Ground plane antenna vs the di-pole. to be honest, I could NOT really detect a difference between them.

Since my dipole was leaning in the corner INSIDE my garage and the GP was mounted to a 8 foot pole outside, I think I'll go with the Di-pole as it can sit where it is and its one less thing to worry about setting up outside.

One thing I did notice was with either antenna I have a very slight hum in the audio.

I'll try a few Ferrite chokes and see if I can clean it up.

Aurbo99
12-17-2008, 12:16 PM
I seem to have picked up a high pitched hum or tone in my transmission.

Any suggestions what might cause this and perhaps a cure?

It disappears mainly when songs are playing and becomes very noticable in the a few seconds of dead air between songs.

WWNF911
12-17-2008, 02:03 PM
I seem to have picked up a high pitched hum or tone in my transmission.

Any suggestions what might cause this and perhaps a cure?

It disappears mainly when songs are playing and becomes very noticable in the a few seconds of dead air between songs.

For T/S purposes, try switching frequencies and see if the problem goes away. I noticed by accident that I can produce a high pitch hum/squeal if I leave my sirius radio on. It uses the same freq. as my show trasmitter. :rolleyes:

Perhaps someone nearby has a personal transmitter using your freq.