Total posts : 45366
“The 50-ohm standard is designed around tall 1/4-wavelength antennas, but does not agree well with short antennas.”
True..for far field radiators. However look down there in the basement..ie the CC system, which has a 50 ohm standard input impedance coupling to a much different impedance on the output of the coupler while maintaining the 50 ohm input impedance standard.
Now with short radiators to produce far field, the short radiator CAN be matched up with a 50 ohm impedance standard with the right matching circuitry. The TCU-8/30 and CP-15 couplers would do that very nicely btw.
The Isotron manual reference to needing a ground is not a definition of needing a ground for antenna performance or functionality whatsoever. It is for lightning protection and nothing more. The Isotron in of itself to operate (resonate) and emit a signal requires no additional ground attached to the lower plate. In most cases the reason for using an Isotron is because of limited access to Earth dirt for a grounding system. Though they can be used outdoors and elevated, they still do not need that ground line to Earth dirt below to operate or shoot a signal. That ground line going below only serves for a lightning or static charge dump..ie pathway to Earth dirt.
The 15.219 Isotron does it’s best sitting on it’s own in situations where access to that Earth dirt is hindered, such as apartments or hi-rise buildings, and excellent for indoor uses, ground level or elevated. But when outdoors in the open, on top of roofs or up on a mast, to meet NEC safety requirements you need that ground line no doubt. But the Isotron does not require that ground line to function as an antenna or require it to bring it to resonance.
What happens at that point is the long ground lead issue and the radiating ground lead issue..to which that round and round merry go round circus needs no further spinning or discussion. And I say it again, no matter if it’s an elevated Isotron or elevated 3 meter monopole, the ground lead length/radiating/lighting protection argument applies to both.
The only difference, elevated or not, is that the Isotron does not need any help with a ground to function, whereas the 3 meter monopole does.