So say you got a common loop active antenna like the ones that you use in compliance testing good for like 30MHz.
And you got a efield present.
Naturally even a unshielded loop antenna will reject the efield to some amount.
How many db of rejection could i expect from adding a shield to this antenna? I think i unsderstand that you cant have the existance of a varying hfield without a efield but you can change impedances to make it small with the so called shield.
This is because fabricating a nice shielded loop is a bit of a pain. Currently i just use bent aluminum bar. I suppose to make a nice balanced shielded loop i would need some monster sized hardline.. The idea of a loose bent wire in a nicely formed shield just kind of irritates me and i dont want to do that. But if a shield basically does fuck all i dont want to go through the hassle of finding 1 inch hardline etc. This thing will psychologically irritate me unless the dimensiions/balance is good. I am not gonna put a fucking loose wire into a hoola hoop wrapped in copper tape. Just NO!!
Also other then reducing efield pickup, does a shield cause any other effects like bandwidth, distortion, etc. Keep in mind i am basically connecting this to a impedance transforming differential amplifier, if it makes a difference.
Why do i care? Because these are rather fun to make and if i could justify owning both shielded and unshielded varients of the same size i will, otherwise i am inclined to take the amplifier in the unshielded one i built and eventually transfer it over to a shielded one, when i am able to fabricate it.
To me, from a standpoint of measurement, it seems best to seperate e and h field pickup as much as possible, so building a hybrid unshielded one is kind of useless unless it has some kind of improved parameter that neither varient can provide.
However, is there some kind of communications reason to use an unshielded loop (not from an emi measurement prospective), like for signal hunting or getting a quick intuitive feel (so i guess this could be considered practical/tool use). An analogy that comes to mind is how people still like to use analog vom because its filtering effect and mechanical time constants are handy for gaining quick intuition. I would consider this to be a benefit due to a well known parameter which would in this case be partial efieldbpickup and major h field pickup.
Also like, something that would be handy would be to assume you got a monopole, unshielded loop and shielded loop in a e field and signal power of efield in each of the antennas.. And i guess the same for the same three antennas in a hfield (helmholtz coil?)