Canvey Island, Essex, England Justin@g0ksc.co.uk
Twin boom quad
144MHz LFA Yagis
144MHz LFA Yagis

Low Noise LFA Yagis designed by G0KSC free to build for personal use.

144MHz LFA Yagis
70cms LFA Yagis
70cms LFA Yagis
Twin-Boom G0KSC Quads
G0KSC Twin-Boom Quads
Twin-Boom G0KSC Quads
G0KSC Custom Dish feeds - Above installation @ HB9Q
Custom low-noise dish feeds
Custom low-noise dish feeds
G0KSC Custom Dish Feeds

Above installation @ HB9Q

G0KSC Custom Dish feeds - Above installation @ HB9Q
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Read Time: 3 - 5 minutes

6el 4.5m long 70MHz OWL Yagi

 

The 6el 70MHz OWL with 11.98dBi gain

 

This antenna has a bit of history as it was the first ever OWL Yagi. I built it to confirm the modle and it featured in this DUBUS article. The antenna has 11.98dBi Gain and over 21dB F/B but most impressive of all is the fact the SWR bandwidth, less than 1.1:1 from 70-70.5MHz. This is a 12.5Ohm antenna which is fitted with a G0KSC Hybred transformer balun and N type connector so all you need do is plug in your coax, no external balun required!

 

I have used this antenna for the past few months with excellent effect. Even in the last few weeks (25th August now) I have been hearing 70MHz beacons. on 10th of August, I was the only UK station to spot OH2FOUR which was up to S6 on the meter !! Check it out on

 

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The impressive SWR curve of this antenna as presented by the antenna analyser once installed

 

At only 4.5m long it is very compact and light too. The antenna will also fit on a roof rack complete if you don't mind a bit of forward over-hang, I have done it, I know!

 

SOLD !! will secure this antenna, pick up only please !!

 

 

11el 6.3m long G0KSC OWL Yagi

Full details of this antennas performance can be found here

As with all of my antennas, high quality insulators have been used on this antenna and all fittings are Stainless Steel (not boom to mast mount). The antenna is a 12.5Ohm antenna fitted with a G0KSC variant impedance transforming Pawsey stub balun which incorporates a fully symmetrical balun too, all you need do is plug in 50Ohm coax and go!

I have added fine-tuning capabilities at the dipole ends to enable perfectionists to get SWR absolutley spot on. I have also added a small stand-off on the boom in order it may support its own guy line too.

 

Not much more to say on this one but like my other projects, I have to make room for the next! The first £100.00 takes it, picutres below (Collection only or I can arrange to meet somewhere).

Completed antenna with Balun installed

 

 

 

A close-up shot of the feedpoint and balun arrangement

 

 

The antenna in the air. EME with just 100W output too!

 

 

The first 28/50MHz Dual band interlaced Yagi is available for sale for local pick up only!

This is a slightly longer, better performing antenna than the one I list on this site and was built by me and installed for test at G8FJG. SWR is as predicted along with excellent performance too. Ron commented that he could hear an A71 beacon at 579 which was not detectable on his cobwebb!

 

The antenna has a 5.2m boom and performance is as per the images below.

The antenna uses tapered elements, 5/8 to 1/2 inch for the 10m elements and 1/2 to 3/8 inch for the 10m sections.

It has 9 elements in total, 4 are used on 28mhz and 5 are used on 50MHz. It has one feedpoint and both bands are used through this one connection.

 

Local pick up only but I will drive up to 100miles (fuel cost covered by buyer) if need be.   NOW SOLD!!

The dualband 28/50MHz Yagi installed briefly at G8FJG for testing and now available for sale

 

The antenna feedpoint. Stauff high quality clamps and stainless steel fittings used throughout

 

 

 

 

The antennas I built for use this summer are now off of the tower and available for sale. Both are very well made and will give many more years of excellent performance.

Note: below the 6M antenna photos is the 4M antenna with another set of photos.

The first is my 6el LFA for 50MHz with its 7.3M boom and huge gain which is just short of 12.4dBi. F/B still well above 23dB and a flat SWR across the whole of 6M as you would expect. The spec of this is a little different from those published as the antenna uses 1.2 inch elements throughout. Also, I have built this antenna to last huge winds and weather conditions so this will be good in the  worst weather scenario.

It has been built from 1.5Inch square boom which is doubled for around 5M below the boom resulting in no boom sag and no boom guying being required. Even in high wind, the antenna does not 'fish tail'. Hand crafted clear UV grade perspex has been used (for the outside sign industry) to form the element insulators. The antenna will include the Pawsey stub 1:1 balun too which is made from Westflex 103 and terminates with a female Ntype.

 

The boom has been sectioned into 2.5M pieces and all stainless steel hardware is used. Only the boom to mast U bolts are not stainless steel. The Pawsey stub balun is included in the sale!

4M Antenna details below the 6M antenna photos

NOW SOLD!!

Some photos below:

 

 

 

 

 

 

 

 

5el 70MHz 4.4M long LFA Yagi - 11.4dBi 28dB F/B

This was one of the prototypes I designed for Vine antennas. It has tapered elements stepping down from 5/8 to 1/2 inch and the LFA Loop ends are 3/8 inch. All stainless steel hardware is used onec more with the same handmade perspex insulator as with the above 6M antenna. The boom is 1.25Inch square and again has been doulbe booms part way to ensure no flex at all. However, the longest section is in one piece so a roof rack will be required for collection.

Available at just NOW SOLD!!

 

 

 

 

 

 

Read Time: 3 - 5 minutes

The Yagi reborn for 2010 - OWL Yagi is here

Choosing a Yagi can be quite a dilemma for many hams, if an OWA (Optimised Wideband Array) 50 Ohm Yagi is chosen, good bandwidth is the result along with simple feeding arrangements too. Another added bonus is the pattern in any modelling software package you see, is pretty much what you get.

With Low impedance examples, gain and F/B is better, bandwidth suffers but in most cases, still provides sufficient coverage of the band(s) wanted so this is not too much of a problem. The issue is matching. First of all, exact losses for a matching arrangement are not easily measured so actual final (built) performance is not known. The next is the impact the matching arrangement has on the pattern and performance. While most optimisation (software) tools provide an adjustment in impedance equal to the effects a matching arrangement will have on the antenna, they do not model the effects on pattern or performance the matching arrangements physical presence has.

As the impedance of a Yagi drops further, performance increases more so but the antenna becomes very unstable, especially when we reach near optimum levels, around 12.5Ohm and lower. What if an antenna could be developed with an input impedance of 12.5Ohm which retained the performance capabilities of that impedance level but adopted the wideband characteristics of the OWA too? What if it maintained the pattern symmetry and cleanliness the OWA 50 Ohm Yagi was renowned for?  What if it had other performance enhancing characteristics not seen in a Yagi before to ensure the highest levels of forward gain while maintaining Front to Back Ratio (F/B) and a matching arrangement proven to have very limited impact on the final pattern?

Enter the Optimised Wideband Low Impedance (OWL) Yagi

 

 a 7el 50MHz G0KSC OWL Yagi with a boom length of just 7.85 metre producing 12.84dBi at 50.250MHz

 

The SWR curve of the OWL looks more like an OWA 50 Ohm Yagi than a 12.5Ohm Yagi

 

 

Another comparison (below) presents a DK7ZB 11el 144MHz 28Ohm Yagi, a YU7EF 12el 50Ohm Yagi, and the G0KSC 11el 12.5Ohm OWL Yagi.

Antenna             length          Gain               F/B             Worst Lobe         144-145MHz Bandwidth

DK7ZB 11el            7.075M        15.83dBi          23.6dB         13.32dB                1.23:1

YU7EF 12el            7.260M        15.92dBi          20.21dB       16.59dB                2.14:1

G0KSC 12el OWL   7.123M        15.84dBi          27.93dB        17.13dBi               1.1:1

Comparison notes:

  • All comparisions were conducted within EZNEC Pro/4 and the latest NEC4.1 R3 Calculation engine
  • Segmentation density used was 28 per half wave in each antenna
  • Test Frequency 144.300MHz
  • 'Worst Lobe' being the largest unwanted forward lobe in the Azimuth planebigger number is better
  • Dimensions for both YU7EF and DK7ZB model from the respective website (10mm element versions)
  • G0KSC OWL using 1/2inch dipole and 3/8 inch elements
While the plots below do not look like some of those published in the designers websites exactly, I beleive this goes part way to prove my belief that you can not simply change the diameter size of elements within an antenna  and expect to get the same antenna results (many element diameter options are presented for 'the same antenna' on each site). In my opinion, an antenna has to be optimised in both X and Y planes for each element diameter in order to achieve the best possible results each time. For each set of element diameters, a new gain, SWR and F/B figures will result. As stated above, these comparisons are based on 10mm diameter elements as the G0KSC 12el OWL uses 3.8 inch (9.525mm) elements and these versions of both the YU7EF 12el and DK7ZB 11el where similar in both boom length and element diameter.

All antennas have good gain and this gain follows the boom length of each respective antenna with the YU7EF being longest and having highest gain, then the G0KSC OWL with the shortest being the DK7ZB. However, it is not gain we are looking at here. I beleive if you focus (when optimising) on all other attributes, the gain will come. Afteral, anyone can produce an antenna with gain alone using a Yagi optimiser after only 5 minutes right? What takes time and patience is maintaining that gain while modeling a wideband antenna. Wide bandwidth is important as it results in a less critical (build dimensions) designs and a much more stable antenna when built, less susceptible to Rain, Snow and Ice. The G0KSC OWL maintains high levels of gain while producing the very wide bandwidth characterisctics of the LFA Yagi and at the same time, suppressing unwanted lobes and maintaining F/B. All in all a very stable, very quite antenna!

Next are the comparison plots. Note the symmetry within the OWL Antenna.

DK7ZB Azimuth plane at 144.300MHz

 

DK7ZB Elivation plane at 144.300MHz

 

DK7ZB SWR Plot (NEC4.1)

 

YU7EF Azimuth plane plot

 

YU7EF Elevation plot

 

YU7EF SWR (NEC4.1)
 
 
 
G0KSC OWL Azimuth Plot
 
 
 
G0KSC OWL Elevation plot
 
 
 
G0KSC OWL SWR plot (NEC4.1)

 

The above example hopefully give the reader an idea of the incredible performance capabilities if the OWL Yagi by G0KSC. A 25 page article explaining how this has been achieved and why it has never been achieved before will be published in DUBUS magazine in the first issue 2010.

If you are interested in building one ahead of their release, email me with your requirement.

 

Justin G0KSC