I recently purchased a 4 element quad for 10 m from Lightning Antennas in USA. The antenna is designed to be mounted so the elements are diamond shaped. Notice in the picture how nice and straight the element wires are.
The driven element of this antenna is a closed loop with no breaks, and it has two matching stubs which are lengths of wire permanently connected to one side point for vertical polarization and the bottom point for horizontal polarization. These are hard to see in the picture but you can see the horizontal polarization stub at the bottom of the driven element second from the left.
The stubs have an adjustable coax connection point at the ends to allow the SWR to be set, and the idea is to use an antenna switch to switch between the two so you can choose the polarization you want.
So the driven element has two approx 9 foot pieces of wire permanently connected, one at the side and one at the bottom, with the center of a piece of coax hanging off the end of each, all the time. The shield of the two pieces of coax are supposed to connect to the boom.
I can't see how this arrangement won't mess up everything about the quad driven element, including the interaction with the other elements and also the radiation pattern of the entire antenna, does anyone have any thoughts on this ?
Also, for transmit, won't the current on the inside of the coax split up between the boom and the outside of the coax and cause the familiar common-mode-current-on-the-outside-of-the-coax problem ?
So far the antenna has been an expensive disappointment as the spreaders aren't strong enough to support the copper quad wires supplied, so the wires can't be pulled tight to make them straight, and the wires hang loose and the antenna elements wave around in the slightest breeze all over the place. My understanding is that the dimensions for a quad are fairly critical and the large amount of movement will cause the radiation pattern, gain and other antenna properties to change all over the place also. When mounted on a mast the antenna looks like a 5 year has assembled it.
This picture above reminds me of McDonalds TV adds which show a luscious quarter pounder brimming with healthy goodness, when the thing you actually get looks like something that got run over by a truck and was then left in the sun for a few hours after which it died.
So far i'm very unimpressed, looks like i am sticking to my home made 3 element vertical yagi antennas mounted from the back in front of a metal pole for now.