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That is not the best way to make an antenna. You should have a monopole, that is a straight wire perpendicular to the ground. In your case "ground" is not very well defined - but think of it as most of the pcb!  It will radiate (and receive) least along a line in the direction that the wire points, therefore the transmitting and receiving antennas should be roughly parallel.

You are working at 433 MHz?

Very interesting!

Yessir: 433 Mhz.

So I have to change my wire with a larger one and not turn it?

The wire diameter will make very little difference. It is the length that must be correct, and if you have 165 mm - NOT cm (clearly from your picture you do not have 165 cm = 1.65 m) all you need to do is make it straight and point away from the PCB.

Ehm lol you're right :D

I will try to make both antennas straight tomorrow and let you know...

Since I would like to keep the dht22 in a small box is there any kind of compact alternative to a 165mm antenna?

Thanks a lot: keep you posted :)

You can "shorten" the antenna with a loading coil at the base, but RF is not my area of expertise, so beyond suggesting you turn to your favourite search engine with "antenna loading coil", I can't help you there.

Hello,

The compact antenna you're asking about is commonly referred to as a "rubber duck" Here's a link to a picture of a few of them:

  www.alibaba.com/showroom/rubber-duck-433mhz-antenna.html

If you decide to use one, you'll need a short length of coaxial cable with the appropriate connector on one end. (often referred to as a pig-tail, and usually sold by the vendor you buy the antenna from)

The overall length is of the first one listed on the page is 50 mm.

The picture is just for reference, (chinese website) but hopefully, a google search will turn up a local seller.

One thing to keep in mind, as this type of antenna is a compromise, the range may not be as good as with a wire monopole.

Hi everyone and thanks for great suggestions...

I think I'll go for the "rubber duck", after checking better how to solder it to my TinyTX: I just need it to work 5 meters away from the pi :)

I'll come back and write news as soon as I've done

Have a great day!

Here's a link to a pigtail similar to the one you'll need. Again, for reference...

http://www.alibaba.com/product-detail/solder-pigtail-cable-with-sma-female_1372840210.html?s=p

With the short distance between your transmitter and receiver, the rubber duck will work fine.

Hi there!

Appreciate all the suggestions...

This model looks easier to solder, ultra cheap and compact:

http://www.ebay.it/itm/251172074951?ssPageName=STRK:MEWAX:IT&_trksid=p39...

Anybody tried anything similar?

I think it'll do the job...