we cross posted
With antennas like rubber duck, whip, things like that are called horizontal or vertical plane. idea being if the transmitter has an antenna sticking up, you want the receivers to do the same, and if it's horizontal, make em both horizontal. most important is to match the angles of them through a flight, which is what makes em not so good for multi rotors or helis for that matter cause we tilt to move. In uhf radio control your holding the transmitter and as you get further out moving the antennas angle around increases rssi signal strentgth when the angle match up, falls off alot when there not.
When you get bad signal underway, try moving the ground stations antennas around to match the craft. on mine got diversity with one antenna straight up hovering, one 45 degrees back so it is straight up and down underway.
On my video am using circular polarized antennas and they don't have those multipathing issues like you have there for the fact the angle the antenna is doesn't matter because the waves are coming off it in a circular pattern instead of a horizontal or vertical pattern.
So the real lawmate antennas are suppose to have a crazy high swr out of the box, but the plane thing negates the good of that. You want something like a bluebeam 3 lobe with a mast to get it up and away from the craft so get the right plug that makes that happen, as of now you'd want a 90 degree end with it the way it is now
on the ground station side your not gonna beat a helical. 3 turn is plenty for your goals. 4.5 would be a touch narrower and reach a little further but won't cast off to the sides as well. a crosshair is a little more convienant cause the size is small, but the don't cast off to the sides at all and behind it doesn't have much signal at all at this frequency. Strangley i've seen better sides and behind signal from the 5.8 crosshairs than the 1.2/1.3 stuff.
only downside to all this is there massive, 1.3 bluebeams are 5 inch across
if there wiggling down, need to be tighter or the antennas connector is failing
126 more grams aint bad if you stripped off 150