Dunno if this helps, but having worked with some RF stuff before, the first try is to remove the antennas from whatever transmitter/receiver you are using so the working range often down to the length of your bench.
You can then move them apart to find the range where they get 'iffy'.
A slightly more scientific approach is to fit RF attenuators to one or both communicating units. If you are working on one end, the 'other end' is fitted with an attenuator (or has it's antenna removed) so your unit is still 'sensitive'. Then, if you don't have any specific test gear, use something like an active WiFi router and put it right next to your unit.
There are "rf noise generator" (google) circuits out there and you can buy RF noise generator boards - even cheap ones:
https://www.ebay.co.uk/itm/SMA-noise-source-Simple-spectrum-external-tracking-source-DC-12V-R3O4-B1O7/263270616777
which you can use to force a level of noise into a receiver (you really need a bunch of attenuators and a spec. analyser to mess about like this).
Just a few thoughts there... good luck 
Yours,
TonyWilk