433 MHz Transmitter range

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I have the transmitter sold by pilight (looks like this: http://rely.sell.everychina.com/p-90880674-rf-transmitter-module-for-alarm-systems-tx1.html ), and made an antenna like this: https://www.elektor.nl/Uploads/Forum/Posts/How-to-make-a-Air-Cooled-433MHz-antenna.pdf

All was well with my outlet switches working every time (except a dimmer, which sometimes did not work correctly). Recently I had to place a switch close to the ceiling and it won’t work most of the times. I moved the homeduino to another place and I have now found that the simple 17.3cm wire works better than the coil antenna. When I made the coil antenna, it seemed to work better. Weird.

The transmitter is not far from the new ceiling receiver, something like 4 meters, but there’s a wall very close to the transmitter in the way to the receiver, and is placed near the ground (at knee height).

I would probably work better if it would be placed in a higher place, but I want it to be hidden.

I now tried bending the 17cm wire, making a 90 degree curve (not a cusp, but a smooth curve) and it seems to have improved it! Maybe now the RF wave is also sent vertically instead of going only horizontally?

Do you guys have any tips? I know I could increase the voltage up to 12V on the transmitter, but that would require another power supply.

Thanks.

My simple wire 17.3 cm works quite well and can cover my whole (relatively small) flat.

Important is that the 17.3 cm is measured directly from the receiver circuit-board as every part unshielded cable will become part of the antenna. Also what many people forget that basicly all of these antennas theoretically need a ground plane below them to work well.
Also the antennas are “polarized” so they work best if sender and receiver are in the same orientation.

So in your case I would do the following.

1. Check if there is any unshielded wire between the antenna and the receiver?
2. Provide a ground plane for the antenna (in your case maybe put the antenna upside down then as the ground plane will basically throw a RF shadow.
3. Check if the sender/receiver are oriented in the same way

For receiving i upgraded to a factory made antenna as I use some battery powered light-switches which have a very weak signal.
Something similar: http://www.ebay.de/itm/DeLock-ISM-433-MHz-Antenna-Antenne-3-dBi-ungerichtet-Schwarz-/351378459846?hash=item51cfc9ccc6:g:Y60AAOSwymxVN1zW (should be available cheaper elsewhere)

@thex Thanks for the tips!

My homeduino receiver is working well with the 17.3cm antenna.
The ceiling receiver is a Homeeasy RF relay, not made by me.

1. I actually have a small solder “path” to a pin socket where I insert the antenna, which should count for 5mm (path + socket). I should cut 5mm from the antenna then?
2. It is not easy to add a ground plane to my current setup since the antenna “socket” is in the middle of the board where the arduino+receiver+sender are soldered. Would adding an SMA and external antenna help? Also, since the receiver relay is on the ceiling, putting the antenna upside down (with the ground plane above it) would not make it worse?
3. I don’t really know the orientation of the relay receiver antenna.

I thought the sender was on the ceiling, if not it doesn’t need to be upside down.

1. Hm 5mm are not much should not have a huge impact especially as you only have 4m to cover.
2. A ground plane would already be som sheet of metal you rest the box with your transmitter on.
3. You can simply try if one orientation of the transmitter works better than an other.

I also have one socket which only sometimes works but the distance doesn’t matter there, seems more like it simply is faulty and sometimes can’t correctly decode the signals. What sometimes helps here is fine tuning the pulse timings in the protocol. (compare to raw receive data from the original remote)

@thex the ground plane needs to be connected to the circuit’s ground, right?

Ideally but should already improve a bit without being connected to ground. I’m also not an expert, just digging up what I remember from studying

@thex Thanks. For now I just bent it in a half “U” shape, with the upper part pointing horizontally, and it seems to be back in the business! (as in: working 100% of the times).

If I need to add a new receiver and it won’t work I’ll try the ground plane.

Can you post some image of your ground plane @thex ?

As I understand you just put a piece of metal underneath the breadboard with your transmitter?

Would aluminium work as well? Sorry I’m not an expert…

Aluminum should work fine.
I’m currently NOT using a ground-plane as my range is fine without one. You could for example try one of these inexpensive aluminum bowls for grilling
https://www.amazon.de/Schalen-Alu-eckig-218-Menüschalen/dp/B00F0L1IEQ

(or you order some takeout )