Re: Topband: HIZ 8 Circel Diameter.....
On 3/3/2018 11:29 AM, dl8yhrfrank--- via Topband wrote: Hi everyone... Did annyone has experience in using more wide spacing the 8 circel rx arrya? Im running the hiz 8a lv2 160-2 arrya in a 200 foot spacing in the fields on a litel hilltop away from A very simple analysis is as follows: Imagine a 4 element rectangular array: end-fire/broadside. In the broadside case, the beam width decreases as the spacing increases. However, once you go past 5/8 wavelength, sidelobes appear. Thus in some sense 5/8 wavelength is the optimum for the broadside dimension. For end fire, the beam width is nearly constant up to 1/8 wavelength, but the gain increases with increasing spacing. Beyond 1/8 wavelength, the beam width gets considerably wider. Thus in some sense 1/8 wavelength is the optimum for the end fire dimension. If we now take our optimum 1/8 by 5/8 wavelength 4 element rectangular array and fit it to a circle, we find that it is almost a perfect fit to a circle of 16 elements. IOW, you drive four elements at a time, but have 16 directions to select from. The size of the 16 sided polygon is 5/8 wavelength across the flats. The diameter is 2% larger than 5/8 wavelength. This results in a 0.637 wavelength diameter circle, which works out to 342.6 feet or 104.4 meters for 1830 kHz. Now if you only have 8 elements in a circle, you have a compromise. If you want to optimize the broadside component of the pattern, you need 5/8 wavelengths across the flats, which results in a diameter of 0.676 wavelengths which works out to 363 feet or 111 meters. This will result in excessive end fire spacing. Smaller diameter circles with 8 elements would have better end fire patterns in exchange for a suboptimal broadband pattern component. Thus it may be the case for 8 elements, four driven, that 200 feet is just as good as 300+ feet. You would have to model it. Another issue is it is entirely possible to get beam widths that are sufficiently narrow that 8 directions are not enough to avoid directions that are several dB down. This is another reason why a large circular array really needs 16 elements. And why an 8 element array should not be made too large. The Hi-Z array drives all elements, not just 4, so it is a more complicated analysis. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: HIZ 8 Circel Diameter.....
Hello Frank and All, First you must tell us what you are expecting to make better with a Hi-Z array. Do you want Better front to back? Do you want Front to side? Do you want better signal to noise ratio? You want narrower beam width? Not ALL things get better at once with size. To my knowledge, with this phasing scheme Just changing the spacing on your current 8A array will do more harm than good to the overall performance. The front to back will remain about the same. The front to side lobe will get severely worse to where the side lobes are only down about 8 dB. The RDF or signal to noise improvement of the 8A is the highest commercially available anywhere. It only changes 0.2 dB better theoretically going to 300 feet diameter. There is NO conventional wisdom that I am aware of that tells us the array should be better with a larger footprint. This array has ALL elements active all the time. Raising the foot print to 300 feet and going to 4 elements active per direction will only improve the front to side rejection but suffer from a 0.5 dB or so less signal to noise improvement. I could change the phasing on the 200 foot diameter array and lower the side lobes easily. I choose to stay with the higher RDF. Theoretically it is possible to model 8 elements like this and get over 16 dB of RDF ( I have the Eznec model) or signal to noise improvement. Unfortunately theoretics and reality don't match. The current array from Hi-Z (8A) requires all of the transformers and components plus the cable lengths and element placement to be quite accurate (around 1% for each sub part) to even do the 13.5 dB of RDF. It is at this time likely NOT within a Ham budget to actually build an array accurate enough to even attempt getting more RDF or signal improvement out of 8 Elements with 8 directions. I even tried 12 elements in 12 directions all active. There are installations using two arrays phased together to get approximately 3 dB higher RDF. Even this is tricky but it is being done. At this time phasing two or more arrays has the best chance. First we know the smaller arrays work but can be affected by other antennas and power lines etc. A higher RDF array gets affected by the same things only worse. So phasing two arrays that are not affected as bad have a better chance of working in the environment than a single SUPER RDF array. Now, If it seems your 8A only array just simply does not have enough gain or the noise level from it remains extremely low because of your low noise area contact me directly as we have a pilot program going on right now that reduces the Noise figure of this array by nearly 9 dB. Its not really simple but it works. This does NOT change the lobes or front to back or anything about the patterns only the VERY VERY weak signal performance. I get questions all the time about; can I make it better if I make it bigger. NO: if changing size would have been better I would have provided it a long time ago. I have 100's of acres here to try things like that. I even looked at a 4-square of 8 element arrays. The beam gets so narrow you have deep gaps between the main lobe. Ahhh so many antennas so little time. Thanks for the question Frank, I hope this has been helpful. 73, Lee K7TJR Hi-Z Antennas. -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of dl8yhrfrank--- via Topband Sent: Saturday, March 03, 2018 11:30 AM To: topband@contesting.com Subject: Topband: HIZ 8 Circel Diameter. Hi everyone... Did annyone has experience in using more wide spacing the 8 circel rx arrya? Im running the hiz 8a lv2 160-2 arrya in a 200 foot spacing in the fields on a litel hilltop away from man made noise and have lots off space their so i think about to get it up to 300 foot spacing to optimize it for 160 Annyone tryed it ore can model it maybe if that will give more performace on 160? Anny comments vy welcome Best wishes Frank DL8YHR _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: HIZ 8 Circel Diameter.....
If you will use your circle array strictly for 160m band, then go for 300 foot spacing (which is optimal for top band). No personal experience here, just some common sense. 73 Mirko, S57AD 2018-03-03 20:29 GMT+01:00 dl8yhrfrank--- via Topband < topband@contesting.com>: > Hi everyone... > Did annyone has experience in using more wide spacing the 8 circel rx > arrya? > Im running the hiz 8a lv2 160-2 arrya in a 200 foot spacing in the fields > on a litel hilltop away from > man made noise and have lots off space their so i think about to get it up > to 300 foot spacing > to optimize it for 160 > Annyone tryed it ore can model it maybe if that will give more performace > on 160? > Anny comments vy welcome > Best wishes > Frank > DL8YHR > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > -- Mirko S57AD _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: HIZ 8 Circel Diameter.....
Hi everyone... Did annyone has experience in using more wide spacing the 8 circel rx arrya? Im running the hiz 8a lv2 160-2 arrya in a 200 foot spacing in the fields on a litel hilltop away from man made noise and have lots off space their so i think about to get it up to 300 foot spacing to optimize it for 160 Annyone tryed it ore can model it maybe if that will give more performace on 160? Anny comments vy welcome Best wishes Frank DL8YHR _ Topband Reflector Archives - http://www.contesting.com/_topband
