• G0KSC designed 3el, 40M & 6el 20M (Force 12)

    This antenna uses the G0KSC OP-DES design on both 40m and 20m to provide full-band coverage on each.

  • 6 x 7el WOS 50MHz LFA Yagi

    175' fully rotating tower and 6 x 7el 50MHz WOS LFA Yagis at W7EW

  • 3 el 24MHz LFA Yagi by InnovAntennas

    Serious low-noise performance for the HF bands too!

  • 4 x 6el 50MHz LFA Yagis @ DL5WP

    Those that do their research and want low noise Yagis choose G0KSC designs!

  • 4 x 11el 144MHz LFA's @ F3EGA

    Excellent G/T figure antenna array ensuring F3EGA can hear and be heard!

  • G0KSC Monoband 14MHz Log Periodic

    With a boom of just 2m and F/B in excess of 20dB including full-band coverage, this is a super-compact Field day antenna!

  • 4 x 24el 432MHz LFA @ PA2V

    PA2V selected G0KSC LFAs (built by InnovAntennas) when he wanted the very best in EME performance!

  • 4el 27MHz LFA Yagi by InnovAntennas

    A 4 element 27MHz LFA by InnovAntennas. The LFA can handle 20KW plus and does for many radio stations, commerical and hobby!

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There are quite a number of 'new design' Yagis out there to self-build that claim to be great but how good are they?

The easiest way to establish what you should build is looks at those serious hams, those that are investing thousands of Euros/Dollars/Pounds into their multi-Yagi systems. These people have done their research and now what makes a good Yagi good. Sure, anyone can talk up their own designs and appear to be neutral in their overview of 'competative' designs but what really makes a good yagi good and why?

There is far more to a modern Yagi that just gain or bandwidth. More than just F/B or F/R. You see there are many things to get wrong when selecting your Yagi as their maybe requirements you need that you are not aware of.

Yagis are not the same form one band to another (or should not be). Simply scalling a good Yagi from HF to VHF will not make a good VHF Yagi, there is so much more in play.

The 432Mhz EME array built by InnovAntennas @ EI8JF


Regardless of how quiet you beleive your location to be, a quiet Yagi will improve your signal to noise ratio and allow you to receive weak signals that you would not otherwise be able to hear. If you antenna is receiving (of sorts) form all directions, your noise floor will be higher. Reducing this noise floor to a minimum (by increasing F/B and minimising side lobes will lead to a much more preferable signal to noise ratio (S/N). This signal to noise ratio is more important at upper VHF and as we move into UHF.

Take a look at services and systems outside of Ham radio and the importance of S/N and minimum unwanted noise. One reason observatories are generally located away from towns and cities is to avoid light polution. This same is the case for radio observatories, absolute minimum noise is required but often, the location for the receive array is more limited and has to be in-town.

W2PU, the radio astronomy site of the Princeton University, New Jersey USA and the home of Joe Taylor, K1JT (the developer behind weak signal programs such as WSJT, JT65, MAP 65 etc.). Joe asked me if it were possible to produce a crossed LFA Yagi for 432Mhz (Radio astronomy is normally carried out on 406Mhz but Joe chose 432Mhz in order that the array could be used for EME (Earth Moon Earth) communication too. I agrred to the task but only on the basis the final antennas would have no compromise electromagnetically as the importance of alignment and external influences (even the coax cable feeding the antenna is an issue on 432Mhz) help decide how well (or not) and array on this band will perform, especially when it is crossed.

A close-up of one of the 432Mhz X-pol LFA Yagis at W2PU - K1JT


While Joe and I will prepare a paper on the extent of the design and how it works so well, some give-aways can be seen in the aboved close-up shot of one of the 432Mhz X-pol LFAs. First is the fact the antennas are all rear mounted (30 elements, 2 x 15el), the square boom supporting the elements is fibreglass to avoid interaction and the drive loops are made from brass which once adjusted, has been solded. Even the coax cable (ultra-thin, low-loss) is soldered directly to the feed point to avoid dismilar metal issues.

Watch out for next year for our joint paper on this subject which will most likely appear first in DUBUS magazine. Keep tunes to these pages as new, latest design antennas will be appearing over the coming weeks, ready for your over-winter projects! These will include a Quad-style LFA-Q antenna for 50Mhx with 3 elements on a 1.9m long boom which produces over 9.1dBi, WOW !!

73 Justin G0KSC

 
 
 
 

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