Yagi Performance Directives - Why ours are different
For many years, commercial Yagi performance directives have been driven by the needs of the mass-market and the general limited knowledge of the end-user as to what makes a good Yagi good. Most manufacturers know the answers to these questions. Questions perhaps their customers do not know they need to ask. However, being able to articulate the reasons why a Yagi needs to be designed in a specific way with performance parameters being balanced rather than biased in one direction or another extends to more than can be presented in a magazine advert or a few minutes worth of phone call.
At InnovAntennas we intend to change that. Through our extensive website and knowledge base which will grow as time goes by, we aim to re-educate the market and present all the facts and reasons why a Yagi needs to look and perform like an InnovAntennas Yagi in order to be the best of the best in all-round performance.
There is not one way to design a Yagi which suits all bands and yet there are many designers and commercial entities that present antennas with similar performance profiles whether they are HF, VHF, UHF (or other bands) and this the tell-tale way of establishing if design considerations have been given to the frequency in use and if indeed an antenna range has been designed correctly and for best performance for a given band.
When looking for a small HF Yagi, pretty much anything goes. There is not a lot that can be done with a 3 or 4 elements per band to enhance performance one way or another. Additionally, modelling for lower noise patterns on larger arrays would be lost due to the larger levels noise both natural and man-made. Sure, certain considerations for noise reduction can be made as we do with our antennas but it is limited.
Maintaining gain and F/B over as wide a bandwidth as possible (hopefully the whole of the band in question) is about as good as it gets for most. For InnovAntennas, we have looked at the market needs and requirements and designed the OP-DES Yagi to suit HF. The OP-DES provide very wideband, stable performance for HF as the traditional OWA (Optimised Wideband Array) does. However, the OP-DES combines OWA bandwidth with lower impedance antenna (lower impedance antennas generally give more gain but are narrow in bandwidth, mostly only covering a part of a given band) performance in one package.
Although very new, we are quite sure the OP-DES will become THE Yagi to have for all HF applications.
Turning now to VHF and the very different requirements for a Yagi there. Sky and sun noise are starting to become an issue here so if you are in a very quiet location and seek to hear very weak signals such as EME (Earth Moon Earth) you need to look towards an antenna with a good G/T figure. The G/T figure is a mean opinion score between an antennas gain and its sky temperature. The more positive this figure, the better the antennas ability is to receive signals and it is the overall G/T figure which is the most important measurement figure for an antenna centered around the 2m band.
Within Internet lists (such as those published by VE7BQH) the G0KSC Yagi styles stand head and shoulders above almost anything else in respect of G/T and it is for this reason, the LFA Yagi has quickly become a favourite within EME circles. This is due to the superior performance it offers partly due to the LFA loop arrangement and the flexibility this provides the antenna while being optimised and secondly, because the LFAs are optimised with directives focused on the requirements of a good antenna upon VHF.
Looking towards UHF frequencies and beyond, Sky temperature becomes much more important and as a result, attention to maximum suppression of the 'rear' bubble of the antenna is far more important than on VHF or HF frequencies. This is ultimately at the sacrifice of forward gain. However, a much more capable antenna for UHF frequencies is a result.
Below is an elevation plot for a 16 element 432MHz LFA Yagi. Note the very high suppression of all lobes in every direction other than the main, single forward lobe.
In a recent DUBUS article (2010) a test was conducted and compared a single 432MHz Yagi designed for low sky temperature with 4 similar sized 432MHz Yagis renowned for their 'HF' style design characteristics. Within EME (Earth Moon Earth reflected signals) better reception was seen on the single low noise antenna than on the 4 phased/stacked antennas.
This was quite a compelling result and further proof of the need to design antennas as we do for these frequencies. After all, many times you hear of stations that are 'deaf' and just cannot hear all those that call them. Often this is because they are using antennas not designed for the frequency they are being used upon and with QRO (high power) too. As a result, anyone with less power has no chance.
With InnovAntennas Yagis that have been specifically designed for the individual bands they are in use on (not simply scaled up or down from other bands) the station using them has the ability to hear not just be heard.
If you to want to be able to hear or have a specific requirement you would like an antenna designed for, drop us a line or give us a call. We would be more than happy to call you and discuss the requirement and even present you with some ideas and examples too.
InnovAntennas really is the only choice you have when it comes to modern-day directional low-noise antennas.
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