And now you know "the rest of the story".

You should try working in the GHz range sometimes. It seems more like magic than science, until you really start understanding things.

Luckily I rarely have to deal with it, except occasionally with custom designs for antennas.

Another thing we haven't brought up here is how you can sometimes have a circuit working perfectly until you mount it in the case.

Luckily what he's working on is a fairly forgiving project.

 

I got my fill of GHz working with Radar/Firecontrol in the Navy. RF plumbing indeed!

 

After you have the inductors placed AND set as you want them. I would suggest putting a small, very small piece of paper(Tissue), rolled into a pin shape inside the inductor and then using a candle drop some hot wax onto the coil and paper form. This will hold them securely and still allow you to further tweak them if needed.

(once things are set and ready to be enclosed, wires and other 'stuff' can intrude on the circuit components(coil) and bend or deform them. You won't see it either as the enclosure prevents it.)

Just a hack from lessons learned the hard way. Good luck with the project.
Kermit

Thanks, I've heard that wax inside the coils can protect them, with some of my FM transmitters I've found that they worked until I put them in an enclosure, hehe!

 

Another thing we haven't brought up here is how you can sometimes have a circuit working perfectly until you mount it in the case.

Luckily what he's working on is a fairly forgiving project.

I have had that happen to me! I've also seen that the proximity of the 9V battery is not too good for the transmitters.

I'm learning the lessons as I go along, I really love this hobby and wish I had loads more time to spend on it.

 

My FM transmitter is built on stripboard with every track cut as short as possible and the parts are close together. Its board is 5cm x 3cm including space for two mounting bolts.
It works perfectly.

 

My FM transmitter is built on stripboard with every track cut as short as possible and the parts are close together. Its board is 5cm x 3cm including space for two mounting bolts.
It works perfectly.

Great to hear, I like working on stripboard - although creating a good layout seems to be an art

Thanks!

 

Audioguru,

I have a few more questions about your FM transmitter.

1. I see you specify a different value for C4 - one for Europe and one for North America - why is that?
2. You have 3 monoblock capacitors on the stripboard - which ones are they on the diagram?
3. I see 2 variable capacitors on the diagram - C6 (5-35pF) and C13 (5-35pF) but I don't see any on the stripboard?

Thanks in advance, I am trying to learn from how you produced your stripboard layout from the circuit diagram.

 

Audioguru,

I have a few more questions about your FM transmitter.

1. I see you specify a different value for C4 - one for Europe and one for North America - why is that?

i just finished answering these same questions on your personal message.
They use different amounts of pre-emphasis (treble boost) because America began broadcasting FM radio first and used more. Microphones and recorders were better when Europe began broadcasting later whiuch overloaded the transmitter so they reduced their amount of boost.

2. You have 3 monoblock capacitors on the stripboard - which ones are they on the diagram?
3. I see 2 variable capacitors on the diagram - C6 (5-35pF) and C13 (5-35pF) but I don't see any on the stripboard?

See my marked-up photo.

 

Thanks Audioguru,

My browser crashed while sending the PM, then I did not see it in my sent items, so I posted rather.

RF electronics really is fascinating, I am learning so much.

 

"Dead-bug" aka free-form style works very well for RF prototyping. This method gives you a big ground plane to work with. You can "dead bug" with a double-sided board, and have both power and ground planes for best performance.
Keep your wiring as short as reasonably possible. I'm talking very short.

I've been experimenting with dead-bug style and it works well. I have to admit I struggle to keep my soldering as neat as I'd like.

Does it have any effect on an RF circuit built dead-bug style if your soldering joins where multiple leads come together is a bit "blobby" (for lack of a better term?