The output impedance of IC1A is very low so you are effectively connecting R1 across the tuned circuit and making it's Q factor very low. Also ferrite is not a good material to use in a transmitting circuit, an air-cored inductor will work better.
Why?Instead of connecting R1 to the top of L1, try connecting it to a point maybe 10% of the turns from the bottom
Yes but I've chosen this one because I need also a line at 2 MHz, with a zero phase difference between the two lines, and a square wave it's the only way (in my opinion and knowledge) to do so..You would still find a conventional RF crystal oscillator works better.
Your post sugests, that you aren't understanding yet the behaviour of resonant circuits. The series circuit has a low impedance in resonance and nearly shorts the amplifier output, which results in maximum energy transfer.
And I didn't say connect R1 to the bottom of L, I said connect it to a point about 10% from the bottom of L. That means LC stays as it is but has a third connection from the 10% tap to R1.
On a wild guess, the parallel Rp of the ferrite tank will be in the range of 5k to 15k ohms. If you want to drive it with a ten ohm source then configure a matching circuit to take 10 ohms to 5k ohms. .................................................................
Ferrite and iron powder are different materials. Ferrite is ferrimagnetic oxide. Antenna rods are mostly using RF ferrites, but may be also iron powder in some cases.Ferrite is not used for antenna loop. It is actually powered iron and permability needs to be selected based on operating frequency.
I wasn't aware of a strong effect (magnetic remanence affecting Q or small signal permeability) with RF ferrites. Considering the fact, that most classical AM radios are using the ferrite rod inductor in it's tuned input tank, it sounds unlikely. I would need to check, if I can achieve a similar effect with ferrite rods from my parts stock.An RF ferrite tank is very susceptable to any magnetizing fields. You can measure the unload Q, wave a magnet near ferrite and Q will be destroyed. Only way to restore ferrite is to take it back up above its Curie temperature.
do you mean in this way?You can get an ideal of the ferrite tank Rp (or Rs if you prefer) by measuring the unloaded 3 db bandwidth. Resonate the coil and very lightly couple into the tank with small coupling caps that you applied an RF source and RF detector (could be spectrum analyzer and tracking gen or network analyzer).
Sounds very unlikely related to your application. You'll hardly achieve considerable ferrite magnetization in an open magnetic path, particularly with mW power. The problems are exclusively caused by inappropriate matching, as discussed before.I've concluded that maybe ferrite antenna for transmitting a sine wave with an amplitude of 2 V (peak to peak) isn't so good. The ferrite permeability seems to become very low with "strong" signals, and so it's impossibile to reach distances higher than 1 meter or so..
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