I want to ask sir. I have an AM radio. The ferrid antenna looks a bit short. And that's already factory default. How about I add or connect a few ferrid rods to make it look longer. and without changing the coil position. Will it increase sensitivity in signal capture? Or does it actually make signal reception worse...? please explain!!
Making ferrite rod longer by adding or connecting one or a few ferrite rods together doesn't improve signal reception, but may get it worse. AM radio wave propagating in air is comprised of two components: electric field component (the vertical component which is also the same orientation of the broadcast antenna) and magnetic field (the horizontal component). The ferrite rod antenna is designed to receive only the magnetic field (the horizontal component) component of the radio wave. That's why the ferrite rod is placed in horizontal orientation. The more magnetic field lines go through the coil of the antenna the higher voltage is induced on the coil, and therefore better signal reception. So the coil with bigger cross section area captures more magnetic field lines, and therefore stronger signal received. The ferrite core help to gather more and concentrate magnetic field line, and conduct magnetic flux through the coil. Placing one or more ferrite rods on the magnetic line paths, may block the magnetic lines and therefore reduce signal reception. Before the ferrite core antennas were used, the old tube radio antennas had big cross section areas placed on the back of the radios. Since the ferrite core were used, the cross section area of the coil in later AM radio has much smaller cross section than the old air core radio. To improve AM radio signal reception, people use antenna boosters. You can look online for many AM radio antenna booster videos Basically, the antenna booster is a secondary AM antenna, which include a coil and a variable capacity, the core can be air or ferrite. To improve the signal reception for a radio station, both the main antenna radio and the booster antenna must be tuned to the same radio station. The resonance of the secondary antenna adding more magnetic field strength to the antenna of the main radio, that boosts receive signal on the radio. So back to your question, if you just add ferrite rod only to the radio antenna, it doesn't help. But if on the adding ferrite rod, you add a coil and a capacitor forming a resonant tuned circuit, you can improve the signal reception significantly of the radio. It's an antenna booster. Here is a little bit more about the ferrite rod. The ferrite material can conduct magnetic flux (or magnetic current) but cannot conduct electric current. This prevents the forming of eddy current occurs in the core. If the core is made of iron, the oscillation of the magnetic flux generates eddy current in the core, and since the iron conduct electric current, the iron causes the short circuits, and that kill of the magnetic flux in the core, and therefore less voltage is induced on the coil of the antenna. Hope it helps!
Great Video simple effective explanation. I suggest putting a simple amp or high impedance headset and detector diode, like a crystal set. It amazes everyone I show it to at a museum.
yes that oscilloscope shows that the signal , gets to the second coil with physically touching it. hard to see the second coil except on the schematic. nice demo with math to back it up
You have to calibrate that meter before taking measurements but imagine it's close. It's a great meter for it's price. I have compared it with my more expensive meter and it's very accurate (once calibrated 😁).
Very good presentation and radio(s) (especialy older 1s and antennas). You have earned a least.. 1 New Subscriber... *also iLike Camera(s) but being doh! The Economy. Just Α too poor fool, and a Way Too Much of : "just a weird-wiggly Tripod Man".: to be able jump back into film cameras, or filming 📹😫 if you know what iMean 📻📻☕🦫📱 εh
You can get the antenna from "Elenco Two IC AM Radio Kit" on Amazon. I tried to get some measure of the antenna and here what I get: . Ferrite core dimension: 80mm long, 10mm diameter . Big coil # of turns: 106 turns, inductance: 740uH, resistance: 9.34 ohm . Small coil # of turn: 7 turns, inductance 7.2uH, resistance: 1.11 ohm I'm not sure with the copper wire gauge. It's multi-strand yarn wire. If you can not find them, I think you can use any copper wire with size from 32AWG to 26AWG. You can also find other similar AM ferrite antenna on Amazon, ebay, or Aliexpress or from old AM radios. Good luck.
