One might think that to measure ripple noise of $2 Chinese power supply ~$70 unit is an overkill :-)

What are the benefits of software controlled PSU versus turn-knob style?

@Oitzu DSO138 scope is like $25 from aliexpress

Some ppl suggest - DIY.
The problem with DIY is that you need to know well what are you doing and you also need tools to debug your power supply when it does not work. Non of that applies to a typical novice.
I suggest getting one of the low-end bench grade power supplies ~$100 on amazon.
Example: http://www.amazon.com/gp/product/B00FPU6G4E

Make sure you don't try to save $20 and buy the cheapest possible with low precision pots.
Hi precision pots a re like $10+ a piece alone so you are likely to save nothing if decided to upgrade yourself. I did that and I regret it.

One bench power supply is not enough so you can DIY your second one.

@Oitzu
I though antenna ground and MCU ground is the same thing

Typically you point it up. It gives you vertical polarization.
You point both transmitter and received wire antennas same directions.
It's possible that your chips are at fault, if non of other tricks worked (capacitors, clear power, enough current, short wires, lo-noise rf spectrum channel) try other transceivers.

It must be something very dumb. Check that you have a solid galvanic connection to nrf modules on all lines.

I think @carlierd means that resistor '102' (1kOmh) is serially connected with led. It's also on the side so removing it much easier - you just heat one side and push then another side and push away. In the reference design I think this 102 is actually R11.
Correct me if I'm wrong.

@hek Speech recognition is a fantastic idea, I've added it to my list of may be projects!

Is there any use for all this CPU power in home automation scope?
I struggle to find any use for them.

With regard to 5V periphery I ordered
[1] http://www.aliexpress.com/snapshot/7243167912.html
[2] http://www.aliexpress.com/snapshot/7248371073.html

Both have quite high cut off voltage i.e. they will not boost if voltage drops below certain value, I believe i's like 2.4V :-(
#2 refused to work with my servo motor at all, so I don't recommend it. #1 is sort of OK but you need 3 AA cells to make a good use of it unfortunately.

Two AA gives you 3.2V when fresh and decline rapidly

I've read that DH22 gives wrong reading with lower voltages, so to properly power DH22 you need to maintain 3.3V from the day one.
After some research I found these step up regulators

https://www.pololu.com/product/2563

[Update for future generation]
I think I found my issue. It was the large transceiver see image below, with power amplifier and external antenna.
Once I replaced both receiver and transmitter with identical units, range got significantly better.
60m clear sight and almost whole house through multiple walls.

For whatever reason small unit can't hear ACK from the PA unit. I tried to reduce power on the PA end to

 radio.setPALevel(RF24_PA_MIN); 

but it did not seem to have any effect. My best guess now is that oscillator on the PA unit is slightly off. PCB antenna unit is battery powered.
Power source to arduino UNO that drives PA unit is good, 5V less that 2mV ripple. The transceiver is powered via 3V3 output (onboard regulator) of UNO though, could it be the problem?

Would you care to share schematics?

OK, so I tried with AA cells, no regulators.
Plain and simple. TMRh20 lib.
Not any better.
I then tried with a chunk of bare copper wire 83mm long, soldered to the end of that curly PCB antenna - not any better either.
Not sure what might I've done wrong. Layout is pretty simple

Voltage with load is 3.1V, current never goes above 19.2mA

I tried with direct line of sight, range has doubled to say 20m, but again - nothing to write home about.

I was/am trying to make a battery powered wireless sensor so there would be no AC if I can avoid it.

I intended to use the step up regulator to 3v3 to extend sensor life on a pair of AA batteries. I think voltage would drop fairly quickly below nrf24 lower limit.

It appears that I was quite foolish expecting FTDI adapter board to power my nrf24 :-(
datasheet says it can provide at most 50mA.

I'll try 2AA batteries and a step up regulator

@mfalkvidd Yes, a few more meters with PA_MAX.
Here is my best performing code

  radio.setPALevel(RF24_PA_MAX);
  radio.setDataRate(RF24_250KBPS);
  radio.setPayloadSize(4);
  radio.setChannel(2);
  radio.setRetries(15, 15);

Full code https://gist.github.com/ikatkov/6df540838bd4d3ea8b57

I also have a poor range. With all the tricks:

• pairs of electrolytic+ceramic capacitors

• short leads

• max out emittance power

• lowered KBS to 250

• increased retries and delays

• free of wifi interference freq

• lowered payload to 4 bytes

• powered usb hub for gateway

• laptop USB powered arduino for sensor

• what I did not try - is separate step down regulator for radio

I got 10m at most through couple of walls. These are plain wood frame + drywall + insulation walls.
Even that was only possible with max power output on both sides and 250KB/s speed + 4bytes payload. I'm not sure if mysensor serial protocol allow to change payload size. I had to go down to roots of nrf24 programming to debug my poor reception.
Payload size was the greatest impactor by the way I had to make my own test hardware+software to do these range tests (simple echo server, sending time back, thus 4 bytes payload)

I've almost give up on nrf24 and ordered 4 hopeRF 483MHz transceivers for testing.

How did you produce that nice ripple charts? Oscilloscope connected to a computer? What is the model?