RF transmitter with external 8-12v power not working properly So I have this pair of transmitter and receiver


RPI is powered by USB from laptop
Transmitter is connected to Attiny85 being interfaced from RPI at 3v3
Receiver is connected to Arduino at 5v

If I have transmitter VCC connected to RPI 5v, data pin to Attiny85 running at 3.3v and all of them having same ground - all works fine, but obviously range is not great.
At this point same ground connects: transmitter, Attiny, RPI.

So I've tried using external power supply for transmitter. 

I have power brick with DC output running at 12v

DC output positive goes to VCC, negative to common ground.
At this point same ground connects: transmitter, Attiny, RPI, power brick.
This doesn't work at all, receive nothing.

I have YwRobot breadboard power, which is broken and now supplies 8v on 5v pins


I've connected same power brick DC output to YwRobot DC in, positive 5v from board (actually pushing 8v) goes to VCC, negative from board goes to common ground.
At this point same ground connects: transmitter, Attiny, RPI, YwRobot.
This setup transmits data some times, still worse results than connecting VCC to RPI 5v.

Am I missing something? Does external power supply has to be something specific? I've thought as long as grounds are connected any power supply can be used on transmitter.

Update:
This 433MHz transmitter with PCB integrated antenna from my thermostat (powered by 2xAA) has no problem penetrating 3 walls and floor in my house. Sorry for my ignorance, but I need to achieve similar form factor and performance. 2.4GHz modules also require a lot of pins limiting what else can be done with Attiny85.


Update:
Attiny is using manchester and software serial (part of Arduino IDE) on attiny core.
RPI is using serial, not sure which version, installed using sudo apt-get install python-serial
Those 433MHz modules are tricky. I got the best results with 3V3 on the receiver, and 5V on transmitter. You should add an external antenna. 

While it would be prudent to remove the little loop antenna, you don’t need to. I got an okay signal at 25 meters with line-of-sight. Metal, or brick will block the signal even at a meter or so - there’s no penetration. Consider a 2.4GHz module for high penetration at low range, or a LoRa module for high range (up to 10km).

A 433MHz antenna I’ve used with good results (can be cut for any frequency really)


Use the same material for both antenna and radials - copper is good - and optionally stiffen the radials with bicycle spokes on the inside ... make sure there is no electrical contact between the radials and the spokes; tape or heatshrink tube. I found coax cable to suck hard for this application, so I recommend using shielded headphone wire or something similar... just connect the shield to 0V/GND.

As for your breakout power module, I’ve had the same issue. Those modules are dangerous, avoid them. Use 7805 and LM1117 instead. Or just one 5V source (your powerbank?) and a TO-92 LM317 set to 3V3 output (max 100mA). Tiny 3V step-down converters like this can supply 800mA.
https://m.banggood.com/5V-To-3_3V-DC-DC-Step-Down-Power-Supply-Buck-Module-AMS1117-800MA-p-933674.html
( you can find them a lot cheaper )