An introduction to the InnovAntennas OP-DES Yagi

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:

• Opposing Phase Driven Element System
  • Reduces side lobes and helps provide a much wider band antenna with constant performance characteristics
• 50Ω Direct Feed - No Matching Loss
  • The OP-DES Yagi has been carefully Computer Optimised with the 'bent' Driven element in place to ensure a 50Ω feed-point. This ensures no matching loss and minimal resistive (Ohmic) loss
• High F/B ratio
  • as with the LFA and OWL, the OP-DES Yagi has an exceptional Front to Back ratio for a direct-feed, 50Ω Yagi. Get rid of unwanted signals from behind your antenna!
• Super Wide Bandwidth
  • The broadest bandwidth of all our antennas, the OP-DES is best suited to HF applications where performance and bandwidth is needed in a single package.
• Constant Impedance & 'All-Weather' Stability
  • Following the LFA and OWL, the OP-DES Yagi is able to maintain impedance in wet weather and therefore will not de-tune like other antennas can

• Class-Leading Direct Feed Yagi Performance
  • For a given boom length, we believe the OP-DES Yagi provides superior all-round performance than any other HF direct feed Yagi.
• Simple SWR Fine-Tuning Feature
  • No two locations for an antenna are the same. With this in mind the requirements of the perfectionist as well as the every day user in our sights, the driven element of the OP-DES has adjustable end sections to allow for very simple SWR fine-tuning
• The Most Important Part of your Receiver has to be The Best
  • Your antenna is a part of your receiver and arguably the most important part of your station. You have spent thousands on radio equipment, make sure you don't short-change your set-up by choosing anything else other than the InnovAntennas OP-DES Yagi for HF
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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.

 There is a Patent Pending on the OP-DES Yagi - all enquiries to InnovAntennas Limited