300MHz RF module

[Hero999]

It looks like a good IC, it's easier to use than the MAX7030 and the configureation software is another bonus.

You'll still need to use SMT componants (just less of them) and build it as small as possible.

 

[audioguru]

The modern IC is tiny, has many pins close together and its recommended parts are surface-mount and you said you can't get them.
They say it is for short range.
The IC needs to be programmed.

 

[Hero999]

Yes it does need to be programmed, but not how you would a PIC. A microcontroller is required to load the configureation data into RAM when it's powered up.

 

[bananasiong]

Yes, I got where to buy the smt components. But I have to order for certain value of components and I have to buy 10 items for each type. Is there any smt crystal?
I think I will use the MAX7030 since I have already order the components. But I don't see any hand made coil or trimmer capacitor, can the receiver receive signal from the transmitter without tuning?

 

[audioguru]

If you can't make them exactly like the manufactured ones then they need to be tuned to the same frequency or the range will be next to nothing.

 

[bananasiong]

then i have to use a trimmer cap for the tank circuit? 2.7 pF trimmer cap is too small, don't know whether can get it or not...

EDIT: Does the amount of the solder affect the stray capacitance or the frequency?

Thanks

 

[audioguru]

then i have to use a trimmer cap for the tank circuit?

It has only a couple of tuned circuits and the values of the capacitors and inductors are specified. They will have a very wide bandwidth and the accurate frequency is determined by the quartz crystal.

EDIT: Does the amount of the solder affect the stray capacitance or the frequency?

This is UHF isn't it? It is nearly microwaves. Everything affects a tuned circuit at such a high frequency.

 

[bananasiong]

Oh.. then i have to make sure both the transmitter and receiver to be the same. So difficult..

 

[Nigel Goodwin]

Oh.. then i have to make sure both the transmitter and receiver to be the same. So difficult..

Any decent quality of soldering won't be a problem, any changes will be too little to make any difference - however, if your soldering is really poor, it could have an effect?.

 

[bananasiong]

I think my skill is not that poor, but I haven't involved in smt. I think I will cover a layer of solder on the PCB before putting the parts, any good idea?

Thanks

 

[Nigel Goodwin]

Tinning it first is perhaps a good idea (as thin as possible), but in any case, using liquid flux will help greatly!.

 

[bananasiong]

Why should it be as thin as possible?

I always use soldering paste/flux. But what's the purpose of using it? Easier to remove the solder?

When soldering, I'm always facing this problem: some oil (or whatever that I don't know) left on the PCB after soldering and removing the components for a few times that makes the solder not to stick on the PCB.

If I use UV PCB, should I remove the film after etching?

Thanks

 

[Nigel Goodwin]

Why should it be as thin as possible?

Because the components are supposed to be flat on the board!

I always use soldering paste/flux. But what's the purpose of using it? Easier to remove the solder?

It makes the solder flow and 'stick' - please notice I said LIQUID flux, not paste - it's really important for SM work.

When soldering, I'm always facing this problem: some oil (or whatever that I don't know) left on the PCB after soldering and removing the components for a few times that makes the solder not to stick on the PCB.

The PCB needs to be PERFECTLY clean and dry, don't even touch the surface with your fingers (the grease stops the solder taking properly).

If I use UV PCB, should I remove the film after etching?

Don't know, I don't make PCB's.

 

[Sceadwian]

Flux does several things, it conducts heat to the joint, insulates it (compared to air) and cleans the joint as well. Without flux a lot of thermal oxidation takes place with air and can ruin the joint completly. You should always use a minimum of a denatured alcohol cleaning of the board. Drug store alcohol is a waste of your time as even the best of it (90% isopropyl even if you can find it) is still 10% water. Denatured alcohol is a pure solvent, and usually available at a local hardware store. It disolves particulates well, is cheap enough to use as a flushing liquid to remove small debris, and given even moderatly dry air conditions will completly evaporate.

 

[bananasiong]

How to use liquid flux? Soak the tip into it like soldering paste?

 

[Sceadwian]

Flux is usually applied to the joint to be formed just before heat is applied. The only reason nigel recommends liquid flux is because the flux will wick via capilary action inbetween the leads all by itself where paste flux will just kind of glob in bad places unless you're careful with it. Mind you there is always a flux residue afterwards that needs to be dealt with, sometimes acidic and VERY bad if left in place.

 

[bananasiong]

How should I apply to the joint? By using cotton tips??

Thanks

 

[Nigel Goodwin]

With the little brush that comes in the top of the bottle - rather like a nail varnish bottle (if you do your nails?).

 

[Sceadwian]

You only need enough to 'wet' the surface, whatever method you chose to apply it is your own buisness. Cotton would be a HORRIBLE idea. I've tried to clean leads with cotton swabs before, and they always catch the threads and tear it to shreds right on the board leaving cotton mess behind. If it doesn't come with a brush like Nigel says use a generic nylon paintbrush from a hobby store.

 

[audioguru]

Don't use plumber's flux that has acid in it.

I haven't used liquid or paste electronic flux for about 40 years. Instead I have been using solder with electronic flux as its core.

I never had to clean a pcb, I just solder and it works. My soldering iron is temperature-controlled so it never gets too hot and never burns the flux like cheap soldering irons.

Maybe you are using the horrible new solder without lead in it. I haven't tried it but others say it sticks poorly.