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Hi Guys!

I just recently finished a tx/rx project using vwire. Problem is that the range of my tx module is lame. I need it to reach a downstairs outlet from my room. Can I just add something like a signal amplifier? Please send me some recommendations smiley

A
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I'm going to guess I'm not the only one who doesn't know what vwire is.  So you should probably add more context...
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Try adding a 17cm antenna wire both ends, will help a lot.

vwire=virtualwire
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Also see previous thread on this:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1293118735/all

And yes, any RF link without at least a quarter-wave antenna will have pants performance!
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Thanks for your replies! I'll put antenna onto it, but first a few more questions..

1. what kind of wire should i use?
2. do i need to solder it, or can i just stick it into the bread board?
3. can i bend the antenna to save space, or should i just keep it straight?

Thanks so much!
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Quarter wave antenna is 1/4 wavelength long, sticking out into space, hopefully from a ground plane 1/2 wavelength across or more.

Alas 433MHz a quarter wavelength is 17.3cm or so, which will be unwieldy (and that ground plane is an issue too).  You can run a 1/4 wave ground wire in the opposite direction to make a 1/2 wave dipole.  Without the proper test equipment its guesswork partly, but a proper aerial at each end should really boost the range considerably!

Avoid having the antennas pointing along the line-of-sight between RX and TX, and they should work best if parallel to each other and right-angles to line-of-sight (although this is really only true in free space).
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I found wire was not so critical. 17cm piece of 26 guage wire sticking in the protoboard worked across my house just fine.

When I built my project  I used 17 cm piece of 30 guage wirewrap wire, just dangles loose in the plastic box holding my card.  That works fine also.
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As for the kind of wire, copper wire!  There's nothing special about an aerial, its a piece of wire sticking out into space.  To radiate effectively it needs to reach out into as much space as possible, but also be resonant at the right frequency.  A standing wave builds up on the antenna till the losses (radiation and heating) match the incoming power.  A good (resonant) antenna radiates far more than it wastes as heat (hence copper being a good choice!).  A good transmitting antenna is automatically a good receiving antenna at the same frequency and impedance (because the same resonance allows it to pull power out of the air).

One way to measure the quality of an antenna is its equivalent cross-section.  This is the notional area is has, assuming it perfectly captures all the radio energy crossing that area.  Clearly the lower the frequency (the longer the wavelength) then the greater the antenna's cross-section - this is why 2.4GHz typically has much shorter range than 433MHz (at the same power with 1/4 wave or dipole antennas).

I love the fact that when antenna is on an insect the plural is antennae, but on a radio the plural is antennas, despite being the same word.  [Or 'aerials' if you're British!!]
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