Back on topic (!), I keenly appreciate diverse 433 MHz ISM regs. & again point out that it's quite legal to add
receiving antenna. Simple roll your own types have been endlessly discussed on the Forum, especially
"Cotanga" Yagi and
"Slim JIM". Both are capable of ~6dB gain (= range doubling), with the squashed radiation pattern of the Slim JIM particularly handy for omnidirectional terrestrial use -forget them for satellites!
Aside from elevation & selecting a clear RF "take off", if local regs. ban TX antenna then consider enhancing transmissions with a decent ground plane- even a car rooftop can do. A suitably placed reflector (open wire mesh perhaps) behind the setup can also be effective. It's positioning should relate to the 433 MHz wavelength of ~700mm - experiment with ¼ & ½ wavelength spacings.
N.B. Parabolic reflectors need to be at least a couple of wavelengths across to be effective.At 433 MHz a dish will be golf umbrella sized & inconveniently bulky- see pix below. Hence forget parabolic approaches at low UHF! They're however dead easy to rustle up at 2.4GHz (for WiFi,BT,ZigBee etc) as a wavelength then is only ~125mm, and a
"wokfi" dish need only be used for gains of ~12-15dBi.
Stan. (ZL2APS, & antenna wrangler since 1961)