I would like to put out a shameless plug for Don and his antennas.
On top of being a super nice person, Don knows his stuff and as you can see, he has the equipment needed to design his antennas.
See Don for your antenna needs is the recommendation!
Been using two of his Com antennas for a couple years now and they work great on the belly of the RV. He designs them with some unique features that provide top performance for a reasonable cost.
Some antenna designs have issues with static buildup but Don has addressed this with his units.
Several of the certified antennas claim super wide frequency response with low VSWR across the entire range. The way they do this is by embedding passive components into the antenna base to fake the impedance match. The power is not radiated but instead is wasted as heat. Don has addressed this with his designs.