Calculators, tools

Tools to calculate the following:

• frequency to wavelength for radio waves
• conversion of metric to Imperial (meters to feet and inches) lengths
• conversion of VSWR losses to dB losses
• conversion of impedance values to VSWR, return loss and mismatch loss
• conversion of reactance value to inductance or capacitance value
• addition or subtraction of two decibel (dB) values
• quarter-wave line matching transformer

Frequency / wavelength calculator

 

Metric to Imperial units calculator

• Convert decimal meters to feet and inches, or
• Convert decimal feet to meters

Simply type a meters or feet length into the appropriate field, and the corresponding value will be calculated as you type:

Convert VSWR value to power loss

Any value of VSWR higher than 1:1 can cause power loss due to reflected RF being dissipated in the feeder line. Use this to calculate how much power loss is due to VSWR:

 

Convert impedance values to VSWR, return loss and mismatch loss

Choose a system or coax cable impedance, input a complex load impedance, and calculate the following:

• Reflection coefficient
• VSWR
• Return loss
• Mismatch loss

 

Convert reactance value to inductance or capacitance value

 

Decibel calculator

Add or subtract two decibel (dB) values

 

Quarter-wave line matching transformer

The 1/4-wave line matching transformer, also known as a Q-section, is a section of feed-line having a specific impedance designed to transform an input impedance to a different output impedance.

This can be useful when connecting feedlines of different impedances: say, a length of 50Ω coaxial line to a length of 75Ω coaxial line.

The matching 1/4-wave section is connected in series between the input line and the output line, or load.

Wire cutting/adjustment table

When creating a new wire antenna, it is always advisable to add extra length - a couple of percent extra - to the calculated length. In this way, you ensure that the wire you cut for the antenna is, from the outset, not too short for its' intended purpose.

It's handy to know just how much wire to cut off, in order to arrive at the correct length - i.e. the length at which the antenna resonates at the intended frequency, or frequencies. The table presented here can help you to determine just that.

Use the controls to choose your wire core diameter, and insulation thickness and type if needed: the table will be updated to reflect your choice.

To use the values listed, it will be necessary to first erect the antenna in its' intended configuration.  Attach a length of coax, and measure the VSWR on the band of interest with whatever you have available - an analog VSWR meter, or a VNA / digital VSWR device.  Note the frequency at the VSWR minimum, and estimate how far this deviates from the design frequency: this deviation we will call delta.

Find, in the table headers, the closest frequency discrepancy to this delta (you may wish to interpolate between two columns) and, in the row for the band of interest, read off the required adjustment in millimeters.  Given your choice of wire and insulation, this adjustment amount should be close to what you will need to cut from the wire, in order that the VSWR minimum frequency will be close to the design frequency.  Make your adjustment to the antenna, and measure the VSWR again.

Please note that the values listed in the table are intended only as an approximate guide to adjusting the length of your antenna - as with all things, caution is advised when cutting antenna wire to length.   If in doubt, take less off than the value derived from the table, and measure the VSWR again.