If you only need more receiver...

OK

Easy to use, but you need to find your own documentation.

All RF modules worked fine and even without external antenna I got around75 yards.

These types of transmitters and receivers are short range by design. Anyone who expects really long range is expecting more than they should. I'm consistently getting 40 feet, which is about what I'd expect from this type of transmitter and receiver. They work well inside, so long as they're not going through many walls or metal. I haven't tested it, but it's likely that if you want greater range, a higher voltage supply on the transmitter may help. I've been using a 5V supply. Thankfully, they have a really wide voltage input range. Ensuring you use a properly tuned antenna on both the receiver and transmitter would also help. The transmitters are smaller than the photo shows them to be. Transmitters are 18.2 x 18.2mm (minus pins) and the receivers are 12.5 x 28mm (minus pins). The transmitters are where I have an issue. The issue is that the pins on the transmitters are all but useless for prototyping. They are 2.0mm spacing, not 2.5mm, which is the standard for breadboards and most cable connectors used for prototyping. They are also too short to engage with DuPont-style connectors or breadboards. They are 4.5mm from bend to point (longest distance), where standard 2.5mm header pins are 6.4mm from bend to point. This means that even if you let the pins splay out to connect to a breadboard, they don't go deep enough to engage with the connector strips on a breadboard or the terminals inside a DuPont connector. You can leave the terminals bare, but that leaves lots of opportunity for shorting the pins. These are not among the most friendly headers to desolder from the boards. It would be far better for us users if the manufacturer simply omitted the pins on the transmitters entirely. The little bit of creativity to work around the lack of pins would be less than the effort to try and figure out how to use non-standard headers, most specifically pins that are too short.

These modules look good, nice solder points, decent materials, etc. Unfortunately, the documentation with them is so poor that I can't test them further. If an item comes damaged, I do not review it because there is no way to know where or how the damage occurred. In this case though, the issue isn't that they don't work, it's that the info is too sparse to troubleshoot them.