Using dirtybird posting to comment for all readiers.
My Spectrim DX7 receivers R7000 have antenna lengths of 1 /1/8 inch sticking out of their case.
Some of the antenna lengths are partly inside the case.
I believe those antennas are half wave long end to end which would include any lenth inside the case.
I measure end to end _ _ _
Main Rcvr ............ 3 1/16 inch ( 77.7875 milimeters)
Satellite Rcvr ,,,,,, 3 1/16 inch ( 77.7875 milimeters)
I did not do any mathematics.
Perhaps these dimensions can be useful.