Tuesday, March 5, 2019

The Z-match antenna coupler

Most HF antenna couplers have a couple of variable capacitors and a tapped inductor that is switched for various inductances.  That means there are three controls to fiddle with. And, if building  your own, you need to find a rotary switch. That needs to be heavy duty if your coupler is going to handle more than QRP power levels.

This is where the Z-match comes into its own. It covers a wide frequency range with just two variable capacitors to adjust. At least one and preferably both of the variable capacitors need to be dual gang. The inductor can either be air-wound or on a toroid. It normally has only two taps, carefully selected to afford gapless frequency coverage. Although there is a secondary winding for the antenna.

Antenna couplers often operate as filters. For example the pi network is a low pass filter and the T-match is a high pass filter. The first is good for suppressing harmonics while the latter may help if you suffer break-through from a strong AM broadcast station below the HF bands. The Z-match is a bandpass filter, attenuating signals both well below and well above the operating frequency. This makes it suitable for use with simple homebrew receivers with weak or unselective front-ends.

What type of antennas do Z-matches worth with? A wide variety. Including tuned feeder doublets. A good Z-match with a ladder-line fed dipole at least 3/8 wavelength long on its lowest frequency band can provide an efficient antenna system for almost all the HF spectrum.   So find some variable capacitors and start assembling some coils. Plenty of Z-match ideas in the links below.

* AD5Z Compact 100 watt Z-match (pdf)
* KC8AON 50 watt Z-match
* Modified Fri-match by VE2DPE
* PA0FRI Fri-match
* VK5BR single coil Z-match
* WB3GCK Z-match

PS: The items below may assist your experiments.  They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.


No comments:

Post a Comment

Upgraded vk3ye.com website

Enjoy reading about diverse facets of amateur radio? Like building projects? Sometimes find my videos hard to find? If any of these applies ...