8

If I searched right, the unit has a maximum output frequency of 1MHz. A 1MHz wave has 300m wavelength in free space. It will be slightly longer in a cable. So the cable you will use, will be electrically short for sure, and only the capacitive loading of the cable and thus the bandwidth is to be assessed. Such a coaxial cable should have roughly 100pF/m ...


4

At the frequencies your using there is little effect in using a lower impedance cable. However you will want to terminate it with a 600 ohm load so the source can still drive it at full voltage. Frequencies at or above 50MHZ are very fussy about impedance matching and standing waves and you are nowhere near that high in frequency. 600 ohms is typical for ...


3

Look into the MT8870 DTMF (Dual tone multi frequency) decoder IC. DTMF is sometimes called Touch-Tone, and every digital phone uses these frequencies. In each case 2 frequencies are mixed together. They have no mathmatical relationship to avoid harmonic resonance. Example: The dial-tone is a mix of 350 and 440 Hz sinewaves. Link to PDF The MT8870 outputs a 4 ...


3

RG59 Coax is 75 Ohms and as I recall 30pF/ft. Twisted pair impedance and pF/ft depend on twists /ft. The fewer twists, the higher the impedance and inductance must be considered as well. It becomes a matter of tradeoffs whether you have rounded edges or ringing or attenuation with properly matched RC impedance divider like an 8:1 to 75 Ohms or unshielded ...


2

600 ohm is unrealistic; needs center conductor about the size of an atom, shield with diameter of the universe, from what I heard. Use the 75 ohm; you are not expecting standing waves, so don't worry. Regarding achieving 600 ohm COAX is not the same as achieving 600 ohm TWINLEAD. Pole/crossbar mounted telephone cables are twinlead.


2

Just look in the respective data sheets: - I do not know how the capacitor into the diode and the MOSFET evolve in function of the frequency You can rely on the capacitance values above for up to 1 MHz but gradually, as frequency rises you will get inductive properties of the devices coming into play and the data sheets are pretty lean in this respect. As ...


2

Don't you just hate when we say, "well, it depends"? Your 30mH coil might have been designed for an application at a much lower frequency. Its inductance in the 30-40 kHz range may be much different, requiring less capacitance than 800 pf for resonance. Having a handful of 100pf capacitors to apply in parallel may be a good plan. If you are adding ...


2

The MV2201 has a nominal capacitance of 6.8 pF at 4 volt DC and can span a range of 1.9 to one when the DC control voltage changes from 1 volt to 10 volt. So, the range might be from 8 pF (@1 volt) to about 4 pF (@10 volts). Now ask yourself how much that is going to change the main frequency of the oscillator given that the varactor diode is, in effect, in ...


2

The NE602A from Philips has differential RF inputs and differential IF outputs, with a single-ended (use a series DC_block capacitor) Local Oscillator pin. 8 pin package. The NE602A onchip function is a double-balanced mixer (which nulls out the LO injection and the RF injection, as much as silicon_layout_symmetry can achieve) with response down to DC. Oh, ...


2

The tolerances are listed in the datasheet, pages 40 and 41.


1

you can find mica compression trimmers, with a dozen layers of mica, on that 2cm by 3cm ceramic_base, providing 5:1 or 10:1 change in capacitance, with well over 100pF final capacitance.


1

At your frequency, the 8 parallel capacitors will be the same as 800 pf. Lead inductance won't be relevant. However, the tolerance of your original capacitor and the 100pf capacitors may come in to play. You could measure the capacitance if your multimeter can measure capacitance.


1

The problem is that when I try using the general formula for inverse Fourier transform I get stuck by the infinities. The reason for this is that a cosine function has infinite energy, and therefore its Fourier transform is not a well defined function. Instead, one usually uses the Fourier series for periodic functions, since that integral will converge. ...


1

The relevant physics here is the LC tank formed by the secondary coil, where the capacitor is the 'stray' or 'parasitic' capacitance. The feedback from the secondary coil provides feedback to the remainder of the circuit, which only exists to drive the tank resonantly. To fully understand this, we must note that the other side of the secondary 'capacitor' is ...


1

This answer is actually @glen_geek's who commented on Jun 21 at 1:23: That upper right knob "VARIABLE" looks rotated counter-clockwise. Should be turned clockwise to the "CAL" position. and it is true. I have no idea why I didn't notice the discrepancy, I should have heard that 440 Hz is nothing like the tune fork and the 1 kHz of which ...


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