[werk_ag]

Interesting test!

How many walls between outside and the RX unit?
Is the RX unit at ground level?

[meteoestarreja]

For even better results I guess one could try RG-58 cable and say half the lenght (20 cm).

Nice initiative! You should definitely try with RG-58, although you will probably find it harder to work (more thicker than RG-174), it have less signal loss.

[hvalentim]

Interesting test!

How many walls between outside and the RX unit?
Is the RX unit at ground level?

Direct line of sight (see attached pic.) should include three to five walls and a number of trees. RX unit placed at ground level, in a desk, yes.

Once I have the TX up in the roof I will do another round. This time with the RX in the vehicle.

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try with RG-58, although you will probably find it harder to work (more thicker than RG-174)

That was the main reason why I chose RG-174. It is lighter, easier to bend and thus less prone to force/break the solder while moving the unit during the installation.

[hvalentim]

Just to tie a couple of loose ends:

1) I did test the TX without antenna with the device placed in the roof and it seemed to work well enough.

2) I redid the mobile RX test once I had the TX+antenna placed in the roof and I got a range increase to around 100 meters, most notoriously with a couple of houses as an obstacle.

[werk_ag]

Thanks for those well documented tests in a real situation.
The best I had achieved until now is around 150m to 180m. TX unit in the roof (my house is in a high place), RX in line of sign, but without any obstacles between.

[Shred]

I've been doing some tweaking to get my system reliable. The transmitter is 30m from the receiver and there are two brick walls, one with foil insulation between the two units. Every now and again the connection drops out - sometimes for hours, but Cumulus MX is blissfully unaware (the Last Station Update time continues to update), so I just see all the external readings flatline in the charts.

I found SDR# ( http://airspy.com/download/ ) as mentioned earlier in the thread quite handy, because it meant I could make changes and compare the signal strength in the house before and after the modification. If you do use SDR#, note that the frequency will not be exactly 433.92MHz and it will drift a bit over time. The transmitters only use a resonator, so the frequency is approximate and drifts with temperature. This is kind of useful, since you will see your transmitter(s) and the Rx board transmitting on slightly different frequencies.

At the moment, I am evaluating a "coaxial sleeve dipole" antenna (Google it for more info). I've connected some RG-58 coax to the Tx module (via an SMA to BNC adapter and a BNC plug). The "antenna" was made by carefully stripping back about 17.3 cm of the outer sheath from the coax, then combing out the braid. The braid was then folded down over the outer sheath of the cable, leaving the inner conductor and its dielectric exposed. My Tx is in an unused childrens' cubby house, so water ingress isn't a problem. If it was exposed to the elements, I'd encase the aerial in a plastic pipe or at least heat shrink tubing. The signal strength is markedly better with the dipole than with the various rubber ducky aerials bought from eBay.

[Palmyweather]

My work has just started selling 433MHz antennas, I was shocked at the size however. In the photo attached you can see the size difference. The top antenna is 100mm long, and is what I am currently using however what my business is selling is only 40mm in length with an apparent 13dbm of gain. I can not seem to find the gain information for my origonal larger antenna, but it was sold as a 433MHz.

[attachment=608]

It suppresses me how different sizes can be used for the same frequency, but I guess results on distance will vary.

I will give this little guy a go and see what happens with my weather station, if it works, it would be a nice little addition and fit well inside my housing. My only concirn is maybe the size is too small for the power the transmitter module is putting out and could burn something out.

[werk_ag]

If you remove the plastic on both of them, I'm almost sure you find the same thing inside, just a very small coil.
if you gonna change your antenna, and you are planning attaching it directly on the RX board, try a model with a right angle connector. For a unit placed on the roof, I always get better results with the antenna in horizontal than in vertical position, and don't forget that 433mhz is very directional, the better you position your antenna regarding the position of your RX unit, the better the results.

[hornychz]

Hello,

in the last two days I measured the antenna gain in the band of 433MHz. The results are quite interesting and maybe answer a range of questions:



What is certain and substantial:

1) As already stated Werk AG, arguably the best antenna is a small 5 cm antenna with a gain of 2 dBi dictated.
2) The ideal supply voltage is around 9V.
3) Critically important is the quality of the supply voltage - its publication.
4) Critically important is the same polarization of both antennas - the transmitter and receiver and their proper orientation to each other.
5) And very important is the environment in which the RF signal propagates.

The photo of this antenna and measurement:


And the others photos:
   

Another photos in the next contribution ...
Regards

[hornychz]

The last tree photos:

16cm
20cm - unusable
1.5m - unusable

... the last two antennas are not applicable at all, even I bought them for 433MHz band!

Regards