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Capacitors in FM transmittor

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craynerd

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Hi guys,

I`m a nooby, started out with a few 555 timer projects, velleman kits, etc and now i want to have a go at a 2 transistor FM transmittor.

I`ve been looking at the basic version shown on here:

**broken link removed**

I went to Maplin yesterday and got myself ever component except the two capacitors 6p8 and 1p8. They were the only thing they don`t do and its the only thing on Harrys website that he says is "critical"!!

Any ideas of what else i could pick these up, anything else i could use or better designs instead. I know there is an FM transmitter on the projects section of this forum...is that a better option?

If i am being totally honest, i have ebayed 6p8 and 1p8 on ebay to see if i could pick up the capcitors there...but with no luck. Could they be labeled as anything different?

Thanks

Chris
 
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A transmitter project without a tuning capacitor is absolutely useless! Use a circuit that has a tuning capacitor.
 
There are far better places to buy componants from other than Craplin.

Anyway you haven't looked hard enough, the order codes are: WX35Q and WX42V.

**broken link removed**
 
I've seen coaxial cable, in short lengths, used as a capacitor.

Sources I use are Jameco, Digikey, Dan's Small Parts, Debco, Ocean State Electronics. I do not know if there are any restrictions on exporting.

They do make some fairly low value adjustable capacitors though I'd be inclined to adjust inductor value for a bit higher capacitor.
 
I agree with Audioguru that you really need a variable capacitor in your oscillator tank circuit. With a variable, you can tune around the FM dial to find a quiet spot away from other stations.

It would be difficult to get 6.8 pF by twisting wires together and this wouldn't be very stable I think (could be quite microphonic too), so don't do that. It is much better to use ceramic capacitors (and a variable capacitor) for this.

You should be gathering old broken electronics equipment like clock radios, tvs, stereos, computers and anything else you can get for free and then scrounging parts out of them. That's what I used to do when I had no money. Radios and stereo units usually have quite a good variety of ceramic capacitors so they are my favorites. Computers have a poor selection of small value capacitors and other useful discrete parts and they tend to take up a lot of space in my junk box, so I don't keep many of those.
 
craynerd said:
Such as...?
RS Commponants, Farnell, Rapid and JPR Electronics are the ones that first spring to mind.
 
Hi
Nothing is cheaper than trying from scrap of faulty items in home --perhaps you can recover many spare parts.

In fact component is cheap but the mode of procurement makes the item prohibitively costly--
 
Keep in mind that with salvaged parts, there is a risk that the item you salvage might be faulty. Someone skilled in electronics might easily test the item. Of course new components can be faulty too. Often some quick checks with a DVM can reveal some failures.
 
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