RF Module

[dhouston]

Melanie,

As much as I hate to disagree with you, I'm afraid I must. X-10 has used that same basic transmitter design for about 25 years in all of their RF remotes sold in North America and they have passed FCC certification tests. You're right about the low data rate but it's fairly easy to get >100m range by using an efficient receiving antenna along with an MMIC wide-band preamp which costs less than $2. Out-of-the-box range is usually in the 10-15m zone.

In Europe, X-10 uses the same basic circuit (with exactly the same RF daughterboard) but with a SAW resonator and higher power since your regulations allow for much higher power but also have tighter frequency tolerances. I have no idea what the regulations may be in Pakistan.

I would have referred shahidali55 to some of X-10's designs on the FCC's online site but, a few years ago, they asked the FCC to block access to all their schematics. But I have attached the schematic to one of their universal remotes which I downloaded before they blocked access. I should also note that the North American versions like the attached use 310MHz.

[Melanie]

shahidali55 was talking about 433MHz... if you build that LC Oscillator circuit as shown, it'll move by several MHz if you approached it with your hand or finger (or even if it's damp or dry weather!!). Also, you're keying the Oscillator on/off with a square-wave (rich in harmonics), that alone would guarantee out-of-band radiation. Unless it's professionally built to extremely high tollerances with a lot of consideration to board layout, I'll stand by the comment it's unsuitable. A SAW resonator is a completely different ball game - but this isn't - it's a crude one-transistor LC Oscillator...