1.5 Volt Tracking Transmitter

[Nigel Goodwin]

As I presumed, you haven't cut the unused tracks on the board, so you have lot's of extra capacitance sending the frequency way off - assuming it will even oscillate like that.

 

[audioguru]

AG, I don't understand how you build your boards. This one has no solder showing, no cut tracks, and apparently bare jumpers across tracks. How does that work? What's on the back side?

The photo of my stripboard shows the component and jumpers side. The other side has the horizontal copper strips that I cut and all the solder joints.
The white strips on the component side is just a paint pattern of the copper strips on the other side.

 

[yuanong]

i have already cut those that is connecting. And i have already confirm with a multimeter that its not linked.

 

[Roff]

The photo of my stripboard shows the component and jumpers side. The other side has the horizontal copper strips that I cut and all the solder joints.
The white strips on the component side is just a paint pattern of the copper strips on the other side.

Oh.
I didn't realize that was white. As you guessed, I thought I was looking at tin or solder plating.

 

[Nigel Goodwin]

i have already cut those that is connecting. And i have already confirm with a multimeter that its not linked.

You need to cut, or (and) remove all unused strips as well.

 

[1oskar]

Only for digital circuits and audio frequency usually I was use such this PCB,
for high frequency only PCB or I was made or buy. RF circuits are not good on experimental PCB
The experimental PCB not good for such this, and make own PCB is really cheap and easy and more fun.

Frequency are measure using Frequencies meter.
Anny will be work good.

 

[duffy]

Yuanong, it looks like you are missing a capacitor (should be 3 on the transistor oscillator), and I don't see the emitter resistor.

 

[yuanong]

this image shows my component value compare to audioguru circuit.
Did i miss any component? If yes please tell me. Thank you
**broken link removed**
https://www.electro-tech-online.com/attachments/tracking-transmitter-again-png.25911/

 

[duffy]

Where's R1?

 

[yuanong]

R1 is block by the LED
**broken link removed**

 

[Roff]

You need to cut, or (and) remove all unused strips as well.

Yuanong, did you do this?

 

[yuanong]

yup, i have already done. its small now.

 

[audioguru]

You must slowly tune the transmitter with a plastic bladed screwdriver because a metal screwdriver blade will mess up the capacitance.

It does not transmit a tone, it transmits silence. You will hear the FM background noise in an FM radio go quiet each time the LED lights. The radio must not have muting.

 

[colin55]

You are doing a wonderful job.
The first piece of test equipment you need is a "power meter." It simply detects if you have RF present.
**broken link removed**
Once you know you have RF. you can work on getting the frequency somewhere on the 88-108MHz band.

 

[colin55]

Here is a Tracking Transmitter that uses easy-to-obtain components:
**broken link removed**

 

[Bogidar]

That transmitter looks more feasible. No need to locate an LM3909. Does the blinking LED provide an audible pulse in the same way that the IC would? Is there any more information available, recommended tolerances and the like?

 

[colin55]

The flash-rate is 1Hz.

<snip: spam link deleted?

 

[Bogidar]

Thanks. Does this design have a trimmer capacitor? Where can I expect to fing it on the FM dial?

 

[audioguru]

Thanks. Does this design have a trimmer capacitor? Where can I expect to fing it on the FM dial?

The one at Talking Electronics has a 47pF fixed capacitor that could be a trimmer capacitor for variable tuning frequency.
It should tune over most of the FM dial.

 

[colin55]

Use 39p ceramic and 4-11p air trimmer and adjust the spacing of the turns of the coil to set the approx frequency.