I tried encapsulating the ferrite rod transformer using aluminum foil but the outcome was pathetic. Instead of improving the reception, I got very poor signal. So, my conclusion is that the ferrite rod is not working as a transformer here, but it's working like a supporting loop antenna along with the main loop. that's why covering the ferrite loop stick reduces signal. BTW, there is no point of caring about signal interferences because even if I use a toroid or won't use anything at all, the main loop will still pick up the noise. So, keeping the ferrite loop stick along with the main loop would only improve the signal strength.
Signal improvement using a ferrite rod with a small loop antenna
I think you’re making wrong assumptions here. Ferrite, iron and some other materials will increase inductance of a coil. Aluminum, brass and some other non ferrous metals will reduce inductance when placed near a coil. Wrapping a ferrite rod transformer with aluminum foil will certainly reduce its inductance and cause other problems. Placing the same ferrite rod transformer inside an aluminum box where the aluminum is not touching the transformer will have little operational effect on it and will shield it somewhat.
Your ferrite transformer may be acting like an antenna but since it’s not tuned it will be a very poor performing antenna and probably not add anything to reception from an antenna standpoint. If I take my tuned 16” ferrite rod antenna and remove the capacitor making it more of a transformer, reception goes to zero, probably loosing 40dB of signal. So basically a bunch of random wire for the primary and secondary on a ferrite rode does not make an antenna that is useful.
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As I said, you can't make a transformer using a ferrite rod. I was wrong and now I came to know that a ferrite rod will only act as an antenna only. So, even you keep it in a aluminum box, it's not going to work as a transformer. I tried that too and that doesn't work. However, if you connect another loop antenna with it then it works as a booster antenna in combination.
It's not required to be tuned because I am using a variable cap and it can be adjusted to match with any radio receiver. I have tried on an AM receiver and a SDR RTL and it works. So, I don't think that my innovation is a crap.
Ferrite rods have been pretty standard for making RF transformers and baluns for probably 70yrs. I have some from Hy-Gain, W2AU and others using a ferrite rod. And you’re making wrong assumptions on how your setup is working.
Maybe ferrite rods are used as a balun but still they will pickup signal like an antenna and I believe that using a toroid will be a perfect transformer. BTW, the ones shown by you are not using any conductive espousers at all. So, I think you don't need any encloser for a transformer.
The reason why 4:1 ferrite stick would be a best choice (not as a transformer) for using with a loop antenna to match with any AM radio because the impedance ratio of 16:1 will give maximum outcome on most impedance mismatches. It's like using a maximum amps of charger available in the market for charging any type of a phone.
Maximum signal transfer happens when impedances are matched, not when you have the highest impedance and is in no way related to the available current from a cell phone charger. From your statements we can see you’re just guessing how things work and that’s not a good place to be when building antenna stuff.
The primary coil of a ferrite rod antenna along with the tuning capacitor determines the resonant frequency and the secondary coil both couples signal to the radio and also affects impedance matching. If you built the antenna right it should not require any transformer between the antenna and radio input.
