I made the experience that many radio amateurs give up, if the first mathematical equation cropping.
But that does not have to be.
On this webpage I offer the calculation of simple circuits and other things from the range of radio amateurs as forms.
Their use is easy, so each one can use it.

If you want to know, how looks the equations used into the scripts, then see the mathematical background at the end of each webpage.

**Parallel and series connections of resistors**

In the meantime are resistors avaiable of the series E24 and E96 with tolerance of 1 % relativ inexpensive.
So the usuable 24 or 96 values in each decade, which have at one's disposal, shold be sufficient for homebrewer.
But if one need resistors with higher power dissipation, one can fall back only on resistors of the serie E12.
You can use the calculation to determine the nonexistent values, calculation of parallel connections of up to 5 resistors and calculation of series connections of up to 5 resistors are possible with small javascripts.

**Attenuators**

If the output level of a stage is too high, in order to be led directly to the input of another, one scolded attenuators between them.
The calculation of attenuators is possible with a small javascript.

But only rarely resistances are available in the computed values.
Change on the specified page the calculated resistances against from you used and see, which deviations with it to arise.

If larger power must be processed, you can use the calculation of power attenuators to determine additionally the necessary power dissipations for individual resistors.

At the attenuators were used so far, the input and output impedances are equal.
However if different impedances must be adapted somehow, it can be also used resistors for it.
The calculation of the loss arising inevitably with it determine the calculation of attenuators with minimum loss.

Since no coils or capacitors are used in the 3 circuit above, the matching takes place frequency-independently.
Attenuators are suitable therby for the wide-band matching.

**Signal splitters with resistors**

Sometimes it is necessary to divide an output signal on several building groups. Also this is realizable with resistors.
The calculation of the loss arising inevitably with it determine the calculation of signal splitters.
Since no coils or capacitors are used, the matching takes place frequency-independently.
Attenuators are suitable therby for the wide-band matching.

**Color code of resistors**

Especially mechanical small resistors are provided with a code in the form of color bands.
For resistors with 3 or 4 color bands, the first two color bands denotes the value.
The third color band denotes the multiplier and the fourth color band denotes the tolerance.
For resistors with 5 color bands, the first three color bands denotes the value.
The fourth color band denotes the multiplier and the fifth color band denotes the tolerance.
There is a color code calculator for resistors, which used a small ajavscript.

**Band spreads with variable capacitors**

A variable capacitor is rather rarely directly applicable in a circuit.
If the tuning range is too largely and/or the initial capacity is too small, the desired values can be reached nevertheless by two additional capacitors.
Frequently this is used as so called band spread in a VFO.
You can use the calculator of the band spread.

But only rarely capacitors are available in the calculated values.
Change on the specified page the calculated capacitors against from you used and see, which deviations with it to arise.

**Parallel connection of reactances**

Every now and then resistors must be connected in parallel.
With ohmic resistors the calculation is simple.
The calculation of parallel connection of reactances is a little more difficult, but possible under the same rules.

On this webpage you can calculate reactances with two coils, two capacitors and a capacitor and a coil.
The components can thereby also contain resistive components.

**Reactances in series and parallel connections**

Each reactance consists an ohmic resistor.
Capacitive reactances additionally include a capacitor and inductive reactances include a coil.
Each series of complex resistances can be replaced by an electrically equivalent of a parallel reactances and vice versa.
The conversion of reactances in series and parallel connections is possible with a small javascript.

**Resonant circuits**

Two important elements are the coil and the capacitor, particularly if they appear together as resonant circuit.
The calculation of resonant circuits determine mutually the frequency, the inductivity and the capacity of a tank circuit.
By the way also the impedances of the circuits will be calculated.
That are equal to the inductive reactances of the coils and to the capacitive reactances of the capacitors.

**Fuchs network**

The Austrian radio amateur named Josef Fuchs, OE1JF, used for matching of λ/2-dipoles at its ends a resonant circuit (Fuchs network).
The calculation of Fuchs networks is possible with a small javascript, based on the finite impedance at the antenna ends an the used frequency.
Such networks with coils and capacitors are usable only for one frequency.

**Matches with LC networks**

Two circuit groups with different resistances can be connected with less loss over a coil and a capacitor.
The values of the LC networks determined with the calculation of match of resistances are valid always only for one frequency, since the used parts are frequency-dependent.

But it is not necessary, lest the output resistor is a resistance.
It can be also a reactance.
The script calculate only LC networks with low-pass characteristic.
Such LC networks are in use in antenna tuners.
The values of the LC networks determined with the calculation of match of reactances are valid always only for one frequency, since the used parts are frequency-dependent.

**Power levels**

The level indication at instruments with an output or input of 50 Ω takes place usually in decibels relative to 1 mW (dBm).
The indication in watts (W), milliwatts (mW) or microwatts (µW) is often important for amateur radio operators.
A conversion of power levels into each other are possible with a small javascipt.
In addition you can convers power levels and voltage levels at 50 Ω hear.

**Spherical geometry**

It's possible to calculate the distance between 2 places on earth is possible, if you know the geographical latitude and longitude of both.
In addition, it is possible to determine the direction.
Besides, the conversion of a locator in the geographical latitude and longitude is possible.

**Heatsink**

All electronic components generate heat which must be dissipated in order do not to destroy it.
The calculation of the thermal resistance of a heatsink determined the maximal required thermal resistance of the heatsink.