The OP-DES (Opposing Phase - Driven Element System) Yagi is another development of Justin Johnson, G0KSC. The OP-DES Yagi has been specifically developed for HF applications where bandwidth and performance within one package is difficult to come by.
The OP-DES Yagi has one characteristic of all G0KSC developed Yagis, it has a 50 Ohm feed-point impedance and all impedance transformation is done within the driven element itself and therefore, the antenna is not susceptible to matching losses in the same way traditional Yagis are (more on this subject can be found here).
For the wider of the HF bands many hams opt for the OWA (Optimised Wideband Array) style Yagi to give all-band performance. However, the OWA does not provide the levels of performance lower impedance antennas can albeit the OWA has the prefer split-dipole, 50Ohm feed-point.
The OP-DES has the ends of a split-dipole bent back towards the reflector element. This provides 2 functions. First of all, the current phase in each end section is in opposing phase and therefore cancel one another out, this helps to reduce/remove side lobes. Additionally, these end sections act as impedance controllers, taking this job away from D1 (first director) and thus making the adjustment of the antenna (while in computer optimisation much easier resulting in better levels of performance. As with all of our antennas the OP-DES driven element has adjustable end sections in order that SWR fine-tuning is possible.
All band performance on bands from 40m to 12m is possible with 1MHz coverage on 10m too. When we say all band performance, we do not simply mean the SWR is at an acceptable level, the OP-DES provides excellent levels of gain and F/B throughout each band too. If you are looking for the ultimate in mono-band HF performance, look no further than the OP-DES Yagi !!
Some of the key OP-DES Yagi benefits are listed below:
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The Unique U shaped driven element of the OP-DES can be clearly seen in the Illustration below (pink lines denote current distribution) and it is the bends at the ends of the OP-DES driven element that enhance the performance of the OWA 50Ω split dipole Yagi in order to achieve never-seen-before performance. The OP-DES is highly suited for applications requiring very wide bandwidth and consistent performance throughout. It is extremely easy to fine-tune with the OP-DES supporting adjustable end tips and to complete the package, a simple 1:1 choke balun (a few turns of coax) at the feed-point is all that is needed for the antenna to be good to go.
The bandwidth flexibility of the OP-DES means it can provide excellent solutions for HF to microwave and having a direct 50Ω feed-point means no matching devices are needed for connection to 50Ω coax and therefore losses are kept to an absolute minimum.
For both commercial and ham use the OP-DES will prove to be an excellent replacement for the age old (and rather weathered!) OWA Yagi showing superior F/B, gain and bandwidth too. For ultra-wideband applications, there is only one antenna to choose, the OP-DES !!
InnovAntennas have a Patent Pending on the OP-DES style Yagi.
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All InnovAntennas Yagis are designed with the very latest PSO (Particle Swarm Optimisation) computer optimisation techniques. It is for this reason our VHF/UHF antennas are among the lowest noise Yagis ever produced!
If I say a 15m is phenomenal, that would simply be an understatement. I've worked a tone of NA,they where calling and calling ... :-) The pile up was really huge.Sam, 9A3OS
...The LFA worked a treat and I followed your advice from the web site which worked perfectly..Andy, M0CTR
The drop in noise when the antenna is pointed away from a noise source or elevated is incredible, thanks for a great design! Ray, WA4NJP
... so I moved the antenna out to the eastern paddock today, still only at 6 meters high but SWR still flat from 27.9 to 29.1'Bob, ZL1RS
Had the 6el LFA measured and swr is perfect, the reflection co-efficient measured here an incredible 39 dB.Never found such figures on a antenna in real life. - '73's de Paul PA3GND
There is a Patent Pending on the OP-DES Yagi - all enquiries to InnovAntennas Limited