Benefits of the LFA-R 'Reflectorless' Yagi.

The InnovAntennas LFA-R 'Reflectorless' Yagi

A dual-band LFA-R for 40m and 30m is raised ready for use

What is the LFA-R?

The G0KSC designed LFA-R is a convertional style Yagi with a rectangular (grounded) loop driven element (laid flat on the antennas boom) which consists of driven and director elements only, unlike conventional Yagis which have a reflector element also.

What benefits does it over?

Within smaller desgins, there is a great deal of benefit in terms and gain and Front to Back ratio (F/B) over traditional Yagis. A 2el direct fed (no impedance matching device) Yagi with reflector and driven element will have relatively lower gain and little F/B whislt the LFA-R in the same format shows impressive numbers (example polar plot below). There is a comparision document HERE which conpares this.

Impressive - 1/16 wl long (0.51 metres @40MHz) and delivering 6.6dBi and 26dB Front to Back (F/B)

Direct 50Ω feed point

As with many of the G0KSC/InnovAntennas designs, there is no need to use an impedance matching device as the antenna has a direct 50Ω impedance without.

Why is the removal of a matching device important, particularly at VHF/UHF?

There is no method of transforming anything known to science that is 100% efficient. Inefficiencies will present thereselves in a number of ways. In this case the important attributes are the production of heat (resulting in input power limitations) and most importantly, noise which will reduce the receivers ability to hear weak signals.

What are the disadvantages?

The LFA-R typically has a much narrower bandwidth than LFA Yagis so maybe less stable in wet weather.