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I am using nRF24L01+ 2.4 GHz transceiver.

When I connect them directly (with SPI pins 10..13 from Arduino) to the adapter board for the nRF24L01 I get occasionally errors (meaning the receiver does not get the sent message).

However, I want to use one nRF24L01 purely for transmitting, and one for receiving. So each Arduino will have 2 nRFs, one for receiving, one for transmitting.

Since they both use SPI, I need to take the pins 10..13 to a breadboard and forward them from there to both nRFs. However, I did a test with only the transmitter, and found out I get more errors than direct wiring.

The only difference is that I now use extra jumper wires (4" / 10 cm). Can the extra cable length cause problems? Would it help if I use less long M/F dupont cables? (so the total length still is 8"/20cm)? ... I don't have such short ones, so I cannot try.

I use for the breadboard to the nRFs 8"/20cm M/F dupont cables.

See picture below. The white/grey/red/blue 20cm/8" dupont cable directly wired to pins 10..13 Arduino gives less errors than the situation on the photo where the white/orange/red/blue 4"/10cm cables are added.

enter image description here

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    More likely to be the breadboard itself. Try rotating the module 180 degrees so the antenna trace is outside the footprint of the breadboard. – Majenko Aug 3 '17 at 5:19
  • @Majenko see the comment in the answer of Code Gorilla ... it cannot be the rotation or breadboard. Unless the connection of the wires to the breadboard might cause it. – Michel Keijzers Aug 3 '17 at 8:12
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the Antenna is interfering with the signals because of its proximity to the point on the bread board where you are connecting the wires, as Majenko said.

If you rotate the nRF24L01 board 180 degrees you will increase the distance between the wires and the antenna and this will reduce the interference, but because of the way radio waves propagate there is also a chance that it may make it worse. The radio wave propagate from the antenna in a share particular to the antenna. I don't know what shape this antenna puts out, I'd expect it to be omnidirectional (all ways) because of its purpose. However all directions are not equal because of reflections, the shape of the antenna, defects in the shape of the antenna, etc and if the pattern of the propagation can be mapped you can identify the make of board and if the mapping is accurate enough even the instance of the board itself.

So, to cure interference:

  1. Increase the distance this reduces the power of the interference by the square of the distance.
  2. Change the orientation, usually by something other than 90 or 180 degrees.
  3. Shield the wires.

In short move the antenna further away from the wires, can you use MF DuPont wires to remove the radio from the breadboard all together. The fact it won't sit still and is sliding all over you desk will probably help with reflections.

  • Maybe it was not fully clear from my question, however the 2 radios you see do not communicate with each other. One is only for transmitting, one only for sending. In my case only the upper one is used (the other is not even connected). The only change between better and worse communication is that in the better case pins 10-13 for SPI are directly connected from the Uno to the (upper) RF and in the worse case wires are first lead through the breadboard and than to the RF. In both cases the upper (and lower unused) radio were on the breadboard – Michel Keijzers Aug 3 '17 at 8:06
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    The junction of your wires is directly under the antenna. That is what you need to move the module away from. – Majenko Aug 3 '17 at 8:30
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    The large chunks of metal under the antenna (breadboard strips) won't be helping your signal quality much. In general it's best to not have any metal around the antenna area - hence the suggestion to rotate 180 degrees and have the antenna sticking out of the breadboard footprint. – Majenko Aug 3 '17 at 10:20
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    Sticking the board vertically may be the best solution, because that antenna design is going to output least of its signal out the thin edge of the PCB. Therefore least signal goes to the metal in the breadboard. – Code Gorilla Aug 3 '17 at 12:21
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    @CodeGorilla ... my intention is indeed to put a 1 byte serial number (sequence) ... if more is needed than the communication is a mess anyway :-) – Michel Keijzers Aug 5 '17 at 16:59

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