J
@Jaco-Pretorius In RC1, there is a duty cycle limit at 1%, measured per hour.
This means you can send at most 6 messages per hour (6 messages taking 6 seconds of airtime each = 36 seconds per hour = 1%, so one message every 5 minutes is not possible.
Not sure how or why you then only get 2, but it may be related to how the duty cycle limit is implemented.
Regarding the antenna, a larger antenna is not necessarily better, what makes a difference is antenna gain (a bit, but watch out for EIRP limits!) and line-of-sight.
You can try to test outside, in an area with no obstacles around (buildings, trees, hills), on a high point, to see if that makes a difference.
But change your interval first, set it to 10 minutes or more to see the result.