Re: Topband: 8 circle: DXE vs Hi-Z
The HI-Z was erected quite aways from anything else which involved bushwhacking and clearing the entire circle, trenching almost 1200 feet of feedline etc so there was a lot of sweat work done on that project. But on 160 and 80 where I have the tx antennas to use as a comparison, the specialized rx stuff just doesn't hear the weaker stuff. And it's not that I have a pristine can hear a pin drop low noise qth, esp on 160 - plenty of flare stack ingitors plus the usual powerline and smps junk. It's especially frustrating to hear all the glowing success stories of these rx arrays and how they make the dx just jump out of the noise and into your log... The proper test is, during the quietest time, to replace the antenna system elements with loads of the same impedance and see if the noise floor drops significantly. If the noise does not drop significantly (at least 8-10 dB), you will lose weak signals. Another test that *sometimes* works on lower bands is to measure and observe the noise floor from midday to night. If you observe a significant noise increase in the hissing background noise, your site and antennas are limited by propagated noise. This does not work with local or power line noise dominated systems. The difference here between day and night on quiet winter nights is about 20 dB or more on 40 meters, and sometimes almost the same on 160. If the ionosphere is sucking up signals, the increase can be less. That noise level is different for different directions. That ratio tells me what sidelobe levels are acceptable. I can have antennas with higher directivity that work consistently worse because side lobes don't adequately attenuate noise from unwanted directions. I'm sure the ideal case for a station looking out over the cold ocean without thunderstorms is much different than the case of a system looking out over thousands of miles of noise generators. My NE direction, because the path is over densely populated land for several hundred miles, is noticeably noisier with background hiss than the more easterly paths or southeast paths that reach the ocean in a few hundred miles. I don't necessarily assign the same pattern priorities (like side lobe levels) to NE as I do other directions. NW here is actually pretty quiet because population is so low on that path, which means I have to be fussier about different things. I'm sure this is the case for everyone, and why we can't really use calculated RDF (directivity) for everything. It was just intended as a better guideline than other things being used, not as a perfect answer. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Hi David and Don I understand your point. Gain is cheap and quite easy to get with a good low noise amplifier, but to keep the common mode noise out of it is very expensive, and could be very complicated. The beverages are very forgiveness and does not requires much amplification. It is an ideal antenna. The noise measured at 500Hz BW on my TX antenna, varies from average -90 dB, when I do not have power line noise to -100 dB few mornings during winter. The noise floor from my HWF is - 120dB (500Hz BW) after a 43db gain preamp (.5dB NF). I have no space for beverages and my station with all antennas uses only 150ft x 100ft. Using 100 Hz BW the noise floor drops to -145dB during the day. Connecting the HWF on the 43db gain increase the noise only 0.2db , you can't hear the increase of noise, I measured it with QS1R SDR, basically the noise is below the sensitivity of the receiver. I can hear very well on 160m. not bragging but just for reference, 4W6, 9M0, 9M4,9M2, HS, DU, XU, and other very weak signals logged in 160 since 2006. Doug worked 292 and I worked 275 on 160m from city lot. The new stuff works. But as I said, it is very expensive. Also the implementation was not possible without the information shared by K9YC, W8JI, and others how to control common mode noise, grounding, shielding and best practices. The list of MUST do things to implement the new stuff is very long The signal above noise is there at the RX array, to bring it at the station and amplify only the signal coming from the RX array without adding common mode noise is very touch. Here is a sort list of must do things 1- Detune all resonant antenna, feed line, rotor cable tower, any metal thing over 90 ft. long . 2- Ground everything at the tower, outside the shack, and in the shack 3- Choke every single cable that enter your radio system, including the preamp. 100's of toroid's is quite common, and few toxoids does not get the job done. 4-All electronics' must be shielded with steel boxes, aluminum does not cut magnetic field and does not help below -120dB noise floor. If possible run all cables inside galvanized grounded water pipes or hot deep galvanized conduit. 5- All cable inside the tower and grounded at the top and at the bottom 6- NO ground loop with the AC lines, isolation transformer and one point ground for the system, your house wires is an effective way to drive noise into the RX system. A good RDF RX antenna does not fix the issues above. There is no allowance here, all points above can deteriorate your RX signal to noise ratio. Using Horizontal antenna does help a lot with interaction with TX antennas but do not eliminate the common mode nose or ground loops problems. Even a single flag is complicated because the feed line can introduce common mode noise, and turn the flag into a loaded vertical. There is only two solution, choke the line overkilling the common mode noise , or use unshielded 100 ohms twisted pair cable. See T6LG results on his web page, only after replacing the coax with twisted pair he was able to work 100's of DX from a military base in YA on 160m. The results using the new RX system varies form excellent to a perfect disaster depending on the points above. 73's N4IS JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of David Raymond Sent: Thursday, December 18, 2014 1:01 AM To: Don Moman VE6JY; Topband@Contesting. Com Subject: Re: Topband: 8 circle: DXE vs Hi-Z My experience is similar to Don's outlined below. Both gain and noise figure are important in very low noise environments. In my own case, I have a noise floor from my TX array in the high -120s or -130s assuming a quiet atmosphere. A high RDF performance RX array often brings virtually no improvement. In my case, since the RX arrays lack gain, they often don't have the horsepower (gain) to reach down and hear the super low level signals picked up by the TX array. Switching from the TX antenna to the high RDF receive array not only fails to make the signal jump out of the noise (what noise?) but fails to hear the signal at all. In these circumstance both gain and noise figure become very important factors. 73. . .Dave, W0FLS - Original Message - From: Don Moman VE6JY ve6j...@gmail.com To: Topband@Contesting. Com topband@contesting.com Sent: Wednesday, December 17, 2014 10:53 PM Subject: Re: Topband: 8 circle: DXE vs Hi-Z Well I disagree that gain isn't important. Maybe you topbanders in the better areas of propagation can afford to throw away many db to get a better rdf, but that sure isn't the case up here in mid-northern VE6 land. I have numerous receive antennas including many beverages and Wellbrook loops (large area) and the Hi-Z 4-8PRO 8 element circle. They all work more or less as expected on the easy stuff and show reasonable directivity but when I need help for the weaker dx, there just isn't any signal there to work
Re: Topband: 8 circle: DXE vs Hi-Z
Bravo, John! Well stated on all points. No disparaging comments noted. I especially appreciate your discussion of RDF and what it actually means in practice. As you commented, in practice, RDF is calculated (EZNEC, etc.) assuming equal amplitude distribution of noise over all 3D free space. On 160m, in North Florida, I am sure that the assumed equal distribution of noise is never the real case. It is actually possible to calculate RDF for any arbitrary spatial distribution of noise, but to do so you must mathematically characterize the noise distribution in 3D - obviously a formidable task at 1.8 MHz. Usually everyone just takes the simplifying leap and assumes that all the bad noise is coming from off the back and the sides of the antenna, in some well-behaved average way. Noise sourced from the front of the antenna pattern is largely ignored. Antenna patterns are often optimized? to reduced side lobes to near zero levels. The main lobe is generally broadened as a result of such side lobe optimizations. Now consider the case of non-uniform noise distribution, with a high noise level broadly sourced at the front of the antenna pattern and lower noise levels sourced on the sides and back of the antenna pattern. By minimizing noise reception in the side lobes, the main lobe is now broadened and thus is exposed to a greater solid angle of high noise source. Furthermore, the increased exposure to high noise takes place in the main lobe, which has the highest pattern field gain. The actual antenna RDF would be substantially degraded as a result of additional received noise power. For this example, optimizing the antenna pattern for minimum side lobes would actually degrade the antenna's environmental SNR. RDF is a very useful metric for comparing receiving antennas. But, we must use the concept in its entirety - we cannot ignore the system aspects that are hard to measure, calculate, or characterize. Perhaps W7EL will incorporate an arbitrary 3D noise model in his next EZNEC update? 73, Terry K4RX John wrote in part: ...RDF as a receiving metric: RDF is indeed a very useful metric for comparing receiving antennas. However, we need to be aware that it assumes the ambient background (atmospheric) noise is uniformly distributed in 3-dimensional space, which is not always true in specific instances. For this reason, RDF may not exactly predict the differences between two arrays in any given situation. It is possible for a system with a lower RDF to equal or even outperform another system with higher RDF under certain noise conditions. If the noise were always uniformly distributed, then RDF would perfectly predict relative receiving performance (actually SNR). The next point about RDF is that it is calculated for a specific signal arrival direction in three dimensional space. In terms of azimuth, it is the peak direction of the forward lobe. In elevation, it is common practice to use 20 degrees, which can be considered appropriate for DX reception. If the signal arrives from a different azimuth or elevation angle, the SNR advantage predicted by RDF may not actually be realized. I have seen a simple low dipole with a lousy RDF occasionally outperform my 8-circle system by a large amount when the elevation angle of arriving signals is very high and the RDF advantage of the array cannot be realized. As RDF gets higher, the beamwidth of the antenna system generally gets narrower. You can see this if you look at chart #2 in K7TJR's Dayton presentation (http://www.kkn.net/dayton2014/HiZ_DAYTON_2014_7n2.pdf). This brings up another point. By making the RDF very high, you are necessarily restricting the angular sector over which the antenna delivers its best performance. This is fine as long as the angular sector coincides with a direction that is important to you. The flip side is you give up some of that performance outside that sector. For switched arrays with a finite number of selectable directions, that could be a disadvantage when a direction of interest falls halfway between contiguous switching directions. Looking at the pattern of the array will tell you what you give up in the in between directions. These comments with respect to RDF are not intended to be disparaging. On the contrary I do believe RDF is an excellent tool for comparing receiving antennas. You just have to aware of what it actually means in practice... 73, John W1FV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Excellent discussion John and Terry. Interestingly enough if you take the 8 elements in a 200 foot circle you can optimize the peak RDF to nearly 15dB. M.T. Ma in his book outlines his math to optimize feeds for the specific purpose of maximizing directivity. Using his mathematics produces 15 dB of peak RDF in this circle with horrible side lobes and a narrow beam. If you set the 8 elements for crossfire phasing you can get an RDF of 14 dB or so. However using either of these phasing and amplitude schemes requires a circuitry system accuracy that is presently unobtainable for backyard installations. Relaxing the RDF to 13.45 and playing with the phasings allows an array to be realized using the technology at hand. Lowering the available RDF of these 8 elements to 13.45 causes the close in side lobes to decrease and the 90 degree side lobes to increase. Interestingly enough these 90 degree side lobes are at a very low elevation angle. Further lowering of the RDF allows a very clean pattern as John and Terry have pointed out. At my location the side lobes generated by keeping the RDF at 13.45 cause none or little harm to the real SNR at my location Just as Terry has pointed out. My goal for designing the all active 8 element array was the very same as Joel has mentioned and that was to build the best performing array that I could for myself in my environment. After all the tests I have made at this location comparing receiving antennas, I wait with great anticipation the tests Joel is making. It will be most interesting to me if one can tell the difference between systems with an RDF within a dB or so on very weak signals. I have successfully measured 1 dB difference in S+N to N ratios between antennas using Spectran. There are things to be learned here. Lee K7TJR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Terry Posey Sent: Wednesday, December 17, 2014 7:57 AM To: 'John Kaufmann'; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z Bravo, John! Well stated on all points. No disparaging comments noted. I especially appreciate your discussion of RDF and what it actually means in practice. As you commented, in practice, RDF is calculated (EZNEC, etc.) assuming equal amplitude distribution of noise over all 3D free space. On 160m, in North Florida, I am sure that the assumed equal distribution of noise is never the real case. It is actually possible to calculate RDF for any arbitrary spatial distribution of noise, but to do so you must mathematically characterize the noise distribution in 3D - obviously a formidable task at 1.8 MHz. Usually everyone just takes the simplifying leap and assumes that all the bad noise is coming from off the back and the sides of the antenna, in some well-behaved average way. Noise sourced from the front of the antenna pattern is largely ignored. Antenna patterns are often optimized? to reduced side lobes to near zero levels. The main lobe is generally broadened as a result of such side lobe optimizations. Now consider the case of non-uniform noise distribution, with a high noise level broadly sourced at the front of the antenna pattern and lower noise levels sourced on the sides and back of the antenna pattern. By minimizing noise reception in the side lobes, the main lobe is now broadened and thus is exposed to a greater solid angle of high noise source. Furthermore, the increased exposure to high noise takes place in the main lobe, which has the highest pattern field gain. The actual antenna RDF would be substantially degraded as a result of additional received noise power. For this example, optimizing the antenna pattern for minimum side lobes would actually degrade the antenna's environmental SNR. RDF is a very useful metric for comparing receiving antennas. But, we must use the concept in its entirety - we cannot ignore the system aspects that are hard to measure, calculate, or characterize. Perhaps W7EL will incorporate an arbitrary 3D noise model in his next EZNEC update? 73, Terry K4RX John wrote in part: ...RDF as a receiving metric: RDF is indeed a very useful metric for comparing receiving antennas. However, we need to be aware that it assumes the ambient background (atmospheric) noise is uniformly distributed in 3-dimensional space, which is not always true in specific instances. For this reason, RDF may not exactly predict the differences between two arrays in any given situation. It is possible for a system with a lower RDF to equal or even outperform another system with higher RDF under certain noise conditions. If the noise were always uniformly distributed, then RDF would perfectly predict relative receiving performance (actually SNR). The next point about RDF is that it is calculated for a specific signal arrival direction in three dimensional space. In terms of azimuth, it is the peak direction of the forward lobe. In elevation, it is common
Re: Topband: 8 circle: DXE vs Hi-Z
All this discussion about RDF overlooks the issue of polarization. If you make an array of verticals with a certain RDF (assuming noise comes from all directions uniformly), the array will be better than an individual vertical by the RDF factor. However, what I have found is that a horizontally polarized antenna, such as a low dipole frequently receives considerably better than a vertical. In that case, you would be better off using an array of low dipoles. The reason why horizontal polarization can be better is that the horizontal component of terrestrial based noise is highly attenuated over distance as a ground wave. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Good points about polarization. If the signals and/or noise are polarized predominantly in one state, then RDF may not be a good predictor of SNR performance, particularly if the antenna receives predominantly in an orthogonal polarization. On the other hand, if the polarization state of the signals and noise evolve randomly with no preference for any one state, which is often assumed for skywave signals, then RDF will be--on average--a good receiving metric, subject to the previous stated qualifications about the spatial distribution of the received noise. However, some of the past discussions on this reflector about preferential polarization of skywave signals on 160 may call into question the assumption of randomly polarized signals. 73, John W1FV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard (Rick) Karlquist Sent: Wednesday, December 17, 2014 3:19 PM To: Lee K7TJR; 'Terry Posey'; 'John Kaufmann'; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z All this discussion about RDF overlooks the issue of polarization. If you make an array of verticals with a certain RDF (assuming noise comes from all directions uniformly), the array will be better than an individual vertical by the RDF factor. However, what I have found is that a horizontally polarized antenna, such as a low dipole frequently receives considerably better than a vertical. In that case, you would be better off using an array of low dipoles. The reason why horizontal polarization can be better is that the horizontal component of terrestrial based noise is highly attenuated over distance as a ground wave. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Hi guys Polarization does play a lot on 160m for two reasons. I can say that because I am using my HWF (two horizontal flags end fire) since 2009. The first one is local man made noise that propagate only vertical due the attenuation on the horizontal component near the ground. And Second the DX signal always come in both polarization. The result form the two reasons is an optimized signal to noise ration using horizontal polarization. I have both WF with the same RDF, during SR or SS there is almost no sky noise coming from the back because of the darkness, however local man made noise comes from any direction, especially if you live in a city lot like I do. Most of the time the noise is coming at the same direction you want to hear the DX, and if you add power line noise the situation deteriorates a lot for the VWF due vertical polarization. Using my HWF I normally get 10 dB better SNR than my VWF that has the same RDF and same aperture of 74 degree measures, I can turn the antenna and measure it, they are not optimized for best F/B, I optimized them for maximum rejection of local man made noise. The HWF is not a dipole. The two phased loops take of angle us 40 degree and there is a huge attenuation for signals above 60 degree. Low dipole is a huge issue if the dipole is resonant, it will interact with all other receiver antennas and will destroy directivity of all of them, if you want to use a low dipole make it not resonant. Gain in not important so it can be short as a 30 m dipole and still will hear the same way. Another issue with low dipoles is the amount of energy absorbed from the TX antenna. If you connect a power meter and a 50 ohms load o the low dipole and transmit KW on the TX antenna, you can measure several WATTS at the low dipole . You can burn you front end with a low resonant dipole. Adding to all that there is another very interesting observation from my last 5 year using a high RDF horizontal RX antenna, when the TX signal refract on the ionosphere the signal split in two waves, that was very well explained by K9LA. What I observed is that these two waves does propagate in different directions. I normally receive VK6 near my SR with better SNR horizontal from 210 degree SSW and with better SNR from 280 degree vertical. Sometimes the horizontal peak is 20 minutes before the vertical peak that is most of the time at my SR. 73's N4IS JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of John Kaufmann Sent: Wednesday, December 17, 2014 8:59 PM To: topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z Good points about polarization. If the signals and/or noise are polarized predominantly in one state, then RDF may not be a good predictor of SNR performance, particularly if the antenna receives predominantly in an orthogonal polarization. On the other hand, if the polarization state of the signals and noise evolve randomly with no preference for any one state, which is often assumed for skywave signals, then RDF will be--on average--a good receiving metric, subject to the previous stated qualifications about the spatial distribution of the received noise. However, some of the past discussions on this reflector about preferential polarization of skywave signals on 160 may call into question the assumption of randomly polarized signals. 73, John W1FV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard (Rick) Karlquist Sent: Wednesday, December 17, 2014 3:19 PM To: Lee K7TJR; 'Terry Posey'; 'John Kaufmann'; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z All this discussion about RDF overlooks the issue of polarization. If you make an array of verticals with a certain RDF (assuming noise comes from all directions uniformly), the array will be better than an individual vertical by the RDF factor. However, what I have found is that a horizontally polarized antenna, such as a low dipole frequently receives considerably better than a vertical. In that case, you would be better off using an array of low dipoles. The reason why horizontal polarization can be better is that the horizontal component of terrestrial based noise is highly attenuated over distance as a ground wave. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
I forgot to mention another very important development. My friend N8PR is experiencing with the WF in another level, Peter is using a rotator to turn the WF vertical to horizontal. He worked FT4TA on 160m with the WF at 45 degree polarization, (not elevation, the rotor turns axial) and only 45 degree at the right side, turning the WF 45 degree on the left side the signal was below noise and any other polarization was not good that day. Peter has a lot of noise from a AM BC station 1 mile from his QTH and he is working to improve the common node noise. However the experiment with polarization rotation is providing return in new countries for him. Regards JC N4IS -Original Message- From: JC [mailto:n...@comcast.net] Sent: Tuesday, December 16, 2014 1:02 PM To: 'Tom W8JI'; 'Lee K7TJR'; 'Bob Tabke'; 'topband@contesting.com' Subject: RE: Topband: 8 circle: DXE vs Hi-Z Hi guys I would like to commented on the subject of RX comparison Tom when you introduced the RDF methodology to measure directivity, you really hit the nail in the head. I'm working on RX antennas only since 2005, after hundreds of tests, I am sure that just 1db RDF matters a lot. When you compare RX antennas you really want to know how much you can improve from your TX antenna Signal to Noise Ratio. Better RDF means better SNR, similar RX antennas performance have similar RDF. 1 RDF does help a lot when the signal is just 2 db above noise and you can't pull it out, adding just 1 db you can change from 339 to 449 and log a QSO, or new country. 3db SNR is just what you need on cw. The implementation of the RX is different from EZNEC , you need to consider all elements neat resonance that will be part of the RX system and deteriorate RDF, it means deteriorating SNR. Common mode noise is not well understood for most of DXer's including grounding, these are factors to consider as well. My recommendation is to kook in the space you have and select the best RDF Rx antenna for your available space. Nothing beats the 13.8db RDF from 8 circle array, but you need 300ft radius to achieve that directivity. If you are able to broadside some good RX antennas and get over 14 dB RDF you shall expect better SNR than the 8 cycle/300ft. Remember to detune your TX antenna during RX, It is hard to measure that and sometimes the only way is to compare the SNR from the TX antenna with the RX antenna, is you are using a 11db RDF system you should see more than 10db SNR over the TX antenna. It means you can hear Q5 signals not even detected by the TX antenna, it is not about move comfortable e copy , it is about to hear what is not there in the RX antenna. Detuning he tower won't fix other common mode noise, like cables not grounded, bad grounding, rotor cable 120 ft long working like a vertical, etc, It is necessary detune them all. Regards JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Tuesday, December 16, 2014 7:52 AM To: Lee K7TJR; 'Bob Tabke'; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z Lee, We probably will just have to disagree about this. From my viewpoint, the behavior isn't too much different than a big yagi stack or other antennas we are used to. The size of the array generally sets the directivity limits. We can add more elements that are closer-in than optimum, and that can certainly help if the size is smaller than optimum, but the trade is gain or pattern cleanliness and sharpness for size. The forward two elements and back two elements are too close to contribute broadside pattern, which is what provides the clean pattern absent major side lobes in the full size 8 circle. As a matter of fact, adding them in destroys some of the broadside directivity. If, however, we make the array so small that it loses broadside pattern multiplication, then we can see an increase in directivity through the small endfire length increase. A .327wl radius array gives about .25 wl endfire spacing in the primary cells (the center elements), and is not improved in pattern quality by adding the forward and rearward cells. The two forward pairs and rearward pairs are not only too close to have broadside pattern contribution, they are closer endfire. They are about 75% of the endfire spacing in the central quad, and nearly 40% of the broadside width. They certainly can contribute endfire, but they actually remove broadside directivity in the process! In an optimum size array the amplitude ratio from the primary quad has to be 4:1 or 5:1 or more to prevent some pretty significant pattern null area deterioration when the additional 4 elements are added, because they deteriorate broadside pattern multiplication faster than they contribute endfire gain (at ~.187 spacing when the primary endfire cell has .25 wl spacing). If the array is made so small that there is little broadside contribution from array width, then the addition of the four will improve
Re: Topband: 8 circle: DXE vs Hi-Z
Well I disagree that gain isn't important. Maybe you topbanders in the better areas of propagation can afford to throw away many db to get a better rdf, but that sure isn't the case up here in mid-northern VE6 land. I have numerous receive antennas including many beverages and Wellbrook loops (large area) and the Hi-Z 4-8PRO 8 element circle. They all work more or less as expected on the easy stuff and show reasonable directivity but when I need help for the weaker dx, there just isn't any signal there to work with. The beverages do the best of the bunch, they aren't anything special - typically in the 700-1100 foot range. With the many vertical structures I have there is no doubt their patterns are somewhat affected but they seem to work fine for Eu and JA bcb dx vs the loops and the 8 verticals. Not that this has been a good year for much of anything on the low bands in this area. The HI-Z was erected quite aways from anything else which involved bushwhacking and clearing the entire circle, trenching almost 1200 feet of feedline etc so there was a lot of sweat work done on that project. But on 160 and 80 where I have the tx antennas to use as a comparison, the specialized rx stuff just doesn't hear the weaker stuff. And it's not that I have a pristine can hear a pin drop low noise qth, esp on 160 - plenty of flare stack ingitors plus the usual powerline and smps junk. It's especially frustrating to hear all the glowing success stories of these rx arrays and how they make the dx just jump out of the noise and into your log... 73 Don VE6JY On Thu, Dec 18, 2014 at 4:11 AM, JC n...@comcast.net wrote: Hi guys Polarization does play a lot on 160m for two reasons. I can say that because I am using my HWF (two horizontal flags end fire) since 2009. The first one is local man made noise that propagate only vertical due the attenuation on the horizontal component near the ground. And Second the DX signal always come in both polarization. The result form the two reasons is an optimized signal to noise ration using horizontal polarization. I have both WF with the same RDF, during SR or SS there is almost no sky noise coming from the back because of the darkness, however local man made noise comes from any direction, especially if you live in a city lot like I do. Most of the time the noise is coming at the same direction you want to hear the DX, and if you add power line noise the situation deteriorates a lot for the VWF due vertical polarization. Using my HWF I normally get 10 dB better SNR than my VWF that has the same RDF and same aperture of 74 degree measures, I can turn the antenna and measure it, they are not optimized for best F/B, I optimized them for maximum rejection of local man made noise. The HWF is not a dipole. The two phased loops take of angle us 40 degree and there is a huge attenuation for signals above 60 degree. Low dipole is a huge issue if the dipole is resonant, it will interact with all other receiver antennas and will destroy directivity of all of them, if you want to use a low dipole make it not resonant. Gain in not important so it can be short as a 30 m dipole and still will hear the same way. Another issue with low dipoles is the amount of energy absorbed from the TX antenna. If you connect a power meter and a 50 ohms load o the low dipole and transmit KW on the TX antenna, you can measure several WATTS at the low dipole . You can burn you front end with a low resonant dipole. Adding to all that there is another very interesting observation from my last 5 year using a high RDF horizontal RX antenna, when the TX signal refract on the ionosphere the signal split in two waves, that was very well explained by K9LA. What I observed is that these two waves does propagate in different directions. I normally receive VK6 near my SR with better SNR horizontal from 210 degree SSW and with better SNR from 280 degree vertical. Sometimes the horizontal peak is 20 minutes before the vertical peak that is most of the time at my SR. 73's N4IS JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of John Kaufmann Sent: Wednesday, December 17, 2014 8:59 PM To: topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z Good points about polarization. If the signals and/or noise are polarized predominantly in one state, then RDF may not be a good predictor of SNR performance, particularly if the antenna receives predominantly in an orthogonal polarization. On the other hand, if the polarization state of the signals and noise evolve randomly with no preference for any one state, which is often assumed for skywave signals, then RDF will be--on average--a good receiving metric, subject to the previous stated qualifications about the spatial distribution of the received noise. However, some of the past discussions on this reflector about preferential polarization
Re: Topband: 8 circle: DXE vs Hi-Z
My experience is similar to Don's outlined below. Both gain and noise figure are important in very low noise environments. In my own case, I have a noise floor from my TX array in the high -120s or -130s assuming a quiet atmosphere. A high RDF performance RX array often brings virtually no improvement. In my case, since the RX arrays lack gain, they often don't have the horsepower (gain) to reach down and hear the super low level signals picked up by the TX array. Switching from the TX antenna to the high RDF receive array not only fails to make the signal jump out of the noise (what noise?) but fails to hear the signal at all. In these circumstance both gain and noise figure become very important factors. 73. . .Dave, W0FLS - Original Message - From: Don Moman VE6JY ve6j...@gmail.com To: Topband@Contesting. Com topband@contesting.com Sent: Wednesday, December 17, 2014 10:53 PM Subject: Re: Topband: 8 circle: DXE vs Hi-Z Well I disagree that gain isn't important. Maybe you topbanders in the better areas of propagation can afford to throw away many db to get a better rdf, but that sure isn't the case up here in mid-northern VE6 land. I have numerous receive antennas including many beverages and Wellbrook loops (large area) and the Hi-Z 4-8PRO 8 element circle. They all work more or less as expected on the easy stuff and show reasonable directivity but when I need help for the weaker dx, there just isn't any signal there to work with. The beverages do the best of the bunch, they aren't anything special - typically in the 700-1100 foot range. With the many vertical structures I have there is no doubt their patterns are somewhat affected but they seem to work fine for Eu and JA bcb dx vs the loops and the 8 verticals. Not that this has been a good year for much of anything on the low bands in this area. The HI-Z was erected quite aways from anything else which involved bushwhacking and clearing the entire circle, trenching almost 1200 feet of feedline etc so there was a lot of sweat work done on that project. But on 160 and 80 where I have the tx antennas to use as a comparison, the specialized rx stuff just doesn't hear the weaker stuff. And it's not that I have a pristine can hear a pin drop low noise qth, esp on 160 - plenty of flare stack ingitors plus the usual powerline and smps junk. It's especially frustrating to hear all the glowing success stories of these rx arrays and how they make the dx just jump out of the noise and into your log... _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Their meaning with respect to gain as unimportant is due to the fact that the RX antenna is all about SNR maximization. A low noise preamp can fix overall signal weakness, if your rig's preamps are insufficient. 73/jeff/ac0c www.ac0c.com alpha-charlie-zero-charlie -Original Message- From: David Raymond Sent: Thursday, December 18, 2014 12:00 AM To: Don Moman VE6JY ; Topband@Contesting. Com Subject: Re: Topband: 8 circle: DXE vs Hi-Z My experience is similar to Don's outlined below. Both gain and noise figure are important in very low noise environments. In my own case, I have a noise floor from my TX array in the high -120s or -130s assuming a quiet atmosphere. A high RDF performance RX array often brings virtually no improvement. In my case, since the RX arrays lack gain, they often don't have the horsepower (gain) to reach down and hear the super low level signals picked up by the TX array. Switching from the TX antenna to the high RDF receive array not only fails to make the signal jump out of the noise (what noise?) but fails to hear the signal at all. In these circumstance both gain and noise figure become very important factors. 73. . .Dave, W0FLS - Original Message - From: Don Moman VE6JY ve6j...@gmail.com To: Topband@Contesting. Com topband@contesting.com Sent: Wednesday, December 17, 2014 10:53 PM Subject: Re: Topband: 8 circle: DXE vs Hi-Z Well I disagree that gain isn't important. Maybe you topbanders in the better areas of propagation can afford to throw away many db to get a better rdf, but that sure isn't the case up here in mid-northern VE6 land. I have numerous receive antennas including many beverages and Wellbrook loops (large area) and the Hi-Z 4-8PRO 8 element circle. They all work more or less as expected on the easy stuff and show reasonable directivity but when I need help for the weaker dx, there just isn't any signal there to work with. The beverages do the best of the bunch, they aren't anything special - typically in the 700-1100 foot range. With the many vertical structures I have there is no doubt their patterns are somewhat affected but they seem to work fine for Eu and JA bcb dx vs the loops and the 8 verticals. Not that this has been a good year for much of anything on the low bands in this area. The HI-Z was erected quite aways from anything else which involved bushwhacking and clearing the entire circle, trenching almost 1200 feet of feedline etc so there was a lot of sweat work done on that project. But on 160 and 80 where I have the tx antennas to use as a comparison, the specialized rx stuff just doesn't hear the weaker stuff. And it's not that I have a pristine can hear a pin drop low noise qth, esp on 160 - plenty of flare stack ingitors plus the usual powerline and smps junk. It's especially frustrating to hear all the glowing success stories of these rx arrays and how they make the dx just jump out of the noise and into your log... _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Lee, We probably will just have to disagree about this. From my viewpoint, the behavior isn't too much different than a big yagi stack or other antennas we are used to. The size of the array generally sets the directivity limits. We can add more elements that are closer-in than optimum, and that can certainly help if the size is smaller than optimum, but the trade is gain or pattern cleanliness and sharpness for size. The forward two elements and back two elements are too close to contribute broadside pattern, which is what provides the clean pattern absent major side lobes in the full size 8 circle. As a matter of fact, adding them in destroys some of the broadside directivity. If, however, we make the array so small that it loses broadside pattern multiplication, then we can see an increase in directivity through the small endfire length increase. A .327wl radius array gives about .25 wl endfire spacing in the primary cells (the center elements), and is not improved in pattern quality by adding the forward and rearward cells. The two forward pairs and rearward pairs are not only too close to have broadside pattern contribution, they are closer endfire. They are about 75% of the endfire spacing in the central quad, and nearly 40% of the broadside width. They certainly can contribute endfire, but they actually remove broadside directivity in the process! In an optimum size array the amplitude ratio from the primary quad has to be 4:1 or 5:1 or more to prevent some pretty significant pattern null area deterioration when the additional 4 elements are added, because they deteriorate broadside pattern multiplication faster than they contribute endfire gain (at ~.187 spacing when the primary endfire cell has .25 wl spacing). If the array is made so small that there is little broadside contribution from array width, then the addition of the four will improve things. There isn't any broadside pattern to hurt. That isn't the same as a broad general statement that using more of the elements allows the array to be made smaller, unless we want to compromise pattern to have the same directivity. I go through similar things with Yagi arrays. All of my Hygain 5 element Yagis have been changed to four elements, and my KLM six elements have become 5's. :) It isn't so much they work better, they just work different in a way that is a better compromise for pattern, bandwidth, complexity, and gain. Everything is a compromise. If the target is maximum directivity and a clean pattern (more like a flashlight), the array has to be large. It can never be the same if small, or we all be running multi-element short boom antennas in close-spaced stacks. I do agree, however, if space is so limited the array can't use broadside multiplication (which is the same as stacking gain in a Yagi array) then all active elements with more elements is better. 73 Tom - Original Message - From: Lee K7TJR k7...@msn.com To: 'Tom W8JI' w...@w8ji.com; 'Bob Tabke' b...@onehorsecreek.com; topband@contesting.com Sent: Monday, December 15, 2014 11:09 PM Subject: Re: Topband: 8 circle: DXE vs Hi-Z The primary difference between DXE and Hi-Z 8 circle arrays is the fact that Hi-Z uses ALL 8 verticals actively at the same time where DXE uses only 4 at a direction. Using all 8 verticals allows the use of a smaller diameter and a performance edge on Directivity over the larger 4 active array. All 8 element arrays do NOT work the same way. Lee K7TJR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Monday, December 15, 2014 7:24 PM To: Bob Tabke; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z - DXE wants a 320' diameter and Hi-Z wants 200' for optimum performance. It's hard to tell what DXE performance is because it does not disclose RDF, beam width or F/B. And neither vendor supplies EZNEC files so I can see the effect of varying the layout. So I'm not sure how to decide what array size is best for me. It would be wonderful if someone has a model for these two systems. Bob, The ideal spacing of arrays like this is entirely dependent on the frequency range and goal you have for pattern or directivity. It is NOT dependent on the design or manufacturer, there are no magical space saving tricks. The circle diameter determines both endfire and broadside spacing, and spacing determines the beamwidth. Something in the 330-350 foot range across the element pairs is near optimum for 160 directivity. You can use it down to spacings where the element-to-element spacing is about 35-40 feet on 160, but it might as well be a four element vertical or some other array at that spacing. You can narrow the 160 pattern by going larger than 350 feet, but the array can develop unwanted lobes. If element-to-element goes over 135 feet or so, you will start to have F/R issues. This is the way every single
Re: Topband: 8 circle: DXE vs Hi-Z
Greetings Bob Reflector folks, Please allow me to provide a bit of my experience since I run both a broad side/end fire passive 8 vertical array (350 ft diameter) with a DXE controller AND a HiZ 8 vertical array spaced for 160 meters (220 ft diameter). To your specific question about controllers both will perform very well but there are differences in the arrays that need to be considered, so please allow me a bit of bandwidth here to explain. I installed my BSEF array about five years ago when there was practically no avalable information about the array and no commercially available controllers. I built the array and a controller and published my work in a paper on my website that later was published in QEX. Since that time, I have gained a great deal of experience with the array both mechanically and eletrically and as a result of my published work others have built arrays (w3LPL for one) had have shared their valuable experience publically as well. As a result, I rebuilt my BSEF 8 vertical array this year with a different mounting scheme like W3LPL uses and also moved to a better controller that Mike, W9RE first made boards available for and now that DX Engineering sells, which I now use for control of the BSEF array. Over this time Lee's HiZ arrays have become quite popular and are excellent performers. What I have noticed is there is considerable confusion among the masses about the differences in these arrays and to be quite blunt many folks equate living in an excellent geographical location for 160 meters propagation to amazing performance of a specific RX array which is an error. I am obsessed with 160 meter RX antennas and achieving peak performance from my rural location in central Arkansas, an area that is not enhanced by coastal propagation, etc. So I set out last year with a personal mission to evaluate both 8 vertical array systems, the passive BSEF array an the HiZ. I am not in the amateur radio business, I'm just a ham with a desire to have the best 160 meter RX system possible for my geographical area. So, both systems are operational here. There is significant sepeation between the two arrays (800 ft) and both are a significant distance from the transmit antenna. Both have their own level of complexity with installation and from personal experience I can tell you they each take about the same amount of time to construct and install. I have already recorded several real on the air comparisons of patterns, noise floors (taking in to account one is active and one is passive)and several signal comparisons of DX stations (actual signal level about noise floor, not S meter readings). I plan to publish these results in early spring at the end of the 160 meter DX season for north america. I would be more than pleased to discuss any specific questions you may have about these arrays off line a bit more in detail if you would like but again the short answer to your question is both will be excellent arrays. 73 Joel W5ZN I'm new to 160 and am planning to add an 8-circle. I would like to buy commercial preamps and the controller. I would greatly appreciate any advice on the choice of preamp/controller vendor. I live in a rural area and have a 4-direction 3-ele vertical array for 160 with a 20+ dB f/b. So I'm looking for a beamwidth improvement on receive. Here are a couple questions: - Are the functions of the control network the same or similar between DXE and Hi-Z? (so I could use either one?) - DXE wants a 320' diameter and Hi-Z wants 200' for optimum performance. It's hard to tell what DXE performance is because it does not disclose RDF, beam width or F/B. And neither vendor supplies EZNEC files so I can see the effect of varying the layout. So I'm not sure how to decide what array size is best for me. It would be wonderful if someone has a model for these two systems. - If I use DXE, is it a no-brainer to use 24' verticals instead of the shorter supplied whips? - are there any best practices for weatherproofing the Hi-Z components? - are there any build-quality differences between the two that I should consider? I live in MT, so it is a harsh environment. Thanks! Bob, N7IP _ Topband Reflector Archives - http://www.contesting.com/_topband www.w5zn.org _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
This thread comes at a good time for me, as I am planning an 8 circle array as we speak. My installation will be an 84' diameter circle as I intend to us it on both 160 and 80m. My installation will be in the woods on a rocky hill (New England glacial moraine). I have found a plateau near the top of the hill where I can install the elements with all feed points at the same height. There is no area where I could put a larger spaced array at this location, and I am willing to trade-off some performance on 160 for coverage of 80m as well. I plan to go with the DXE kit, as i have been impressed with DXE products in the past. While reviewing the manual for the active receive antennas, I found that DXE recommends four to twelve radials at least 15 feet long, but no longer than 20 ft. I plan to deploy radials around each element due to the rocky area this array will be installed over, so I know radials will be required. My question is why the cutoff at 20'? Another question is would I benefit from a taller vertical element than the 8.5' whip included with the kit? 73 Greg N2GZ On Tue, Dec 16, 2014 at 9:35 AM, Joel Harrison w...@w5zn.org wrote: Greetings Bob Reflector folks, Please allow me to provide a bit of my experience since I run both a broad side/end fire passive 8 vertical array (350 ft diameter) with a DXE controller AND a HiZ 8 vertical array spaced for 160 meters (220 ft diameter). To your specific question about controllers both will perform very well but there are differences in the arrays that need to be considered, so please allow me a bit of bandwidth here to explain. I installed my BSEF array about five years ago when there was practically no avalable information about the array and no commercially available controllers. I built the array and a controller and published my work in a paper on my website that later was published in QEX. Since that time, I have gained a great deal of experience with the array both mechanically and eletrically and as a result of my published work others have built arrays (w3LPL for one) had have shared their valuable experience publically as well. As a result, I rebuilt my BSEF 8 vertical array this year with a different mounting scheme like W3LPL uses and also moved to a better controller that Mike, W9RE first made boards available for and now that DX Engineering sells, which I now use for control of the BSEF array. Over this time Lee's HiZ arrays have become quite popular and are excellent performers. What I have noticed is there is considerable confusion among the masses about the differences in these arrays and to be quite blunt many folks equate living in an excellent geographical location for 160 meters propagation to amazing performance of a specific RX array which is an error. I am obsessed with 160 meter RX antennas and achieving peak performance from my rural location in central Arkansas, an area that is not enhanced by coastal propagation, etc. So I set out last year with a personal mission to evaluate both 8 vertical array systems, the passive BSEF array an the HiZ. I am not in the amateur radio business, I'm just a ham with a desire to have the best 160 meter RX system possible for my geographical area. So, both systems are operational here. There is significant sepeation between the two arrays (800 ft) and both are a significant distance from the transmit antenna. Both have their own level of complexity with installation and from personal experience I can tell you they each take about the same amount of time to construct and install. I have already recorded several real on the air comparisons of patterns, noise floors (taking in to account one is active and one is passive)and several signal comparisons of DX stations (actual signal level about noise floor, not S meter readings). I plan to publish these results in early spring at the end of the 160 meter DX season for north america. I would be more than pleased to discuss any specific questions you may have about these arrays off line a bit more in detail if you would like but again the short answer to your question is both will be excellent arrays. 73 Joel W5ZN I'm new to 160 and am planning to add an 8-circle. I would like to buy commercial preamps and the controller. I would greatly appreciate any advice on the choice of preamp/controller vendor. I live in a rural area and have a 4-direction 3-ele vertical array for 160 with a 20+ dB f/b. So I'm looking for a beamwidth improvement on receive. Here are a couple questions: - Are the functions of the control network the same or similar between DXE and Hi-Z? (so I could use either one?) - DXE wants a 320' diameter and Hi-Z wants 200' for optimum performance. It's hard to tell what DXE performance is because it does not disclose RDF, beam width or F/B. And neither vendor supplies EZNEC files so I can see the effect of varying the layout. So I'm not sure
Re: Topband: 8 circle: DXE vs Hi-Z
On Tue,12/16/2014 6:35 AM, Joel Harrison wrote: Please allow me to provide a bit of my experience since I run both a broad side/end fire passive 8 vertical array (350 ft diameter) with a DXE controller AND a HiZ 8 vertical array spaced for 160 meters (220 ft diameter). Thanks for a great post, Joel. I'll look forward to your publication. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Hi guys I would like to commented on the subject of RX comparison Tom when you introduced the RDF methodology to measure directivity, you really hit the nail in the head. I'm working on RX antennas only since 2005, after hundreds of tests, I am sure that just 1db RDF matters a lot. When you compare RX antennas you really want to know how much you can improve from your TX antenna Signal to Noise Ratio. Better RDF means better SNR, similar RX antennas performance have similar RDF. 1 RDF does help a lot when the signal is just 2 db above noise and you can't pull it out, adding just 1 db you can change from 339 to 449 and log a QSO, or new country. 3db SNR is just what you need on cw. The implementation of the RX is different from EZNEC , you need to consider all elements neat resonance that will be part of the RX system and deteriorate RDF, it means deteriorating SNR. Common mode noise is not well understood for most of DXer's including grounding, these are factors to consider as well. My recommendation is to kook in the space you have and select the best RDF Rx antenna for your available space. Nothing beats the 13.8db RDF from 8 circle array, but you need 300ft radius to achieve that directivity. If you are able to broadside some good RX antennas and get over 14 dB RDF you shall expect better SNR than the 8 cycle/300ft. Remember to detune your TX antenna during RX, It is hard to measure that and sometimes the only way is to compare the SNR from the TX antenna with the RX antenna, is you are using a 11db RDF system you should see more than 10db SNR over the TX antenna. It means you can hear Q5 signals not even detected by the TX antenna, it is not about move comfortable e copy , it is about to hear what is not there in the RX antenna. Detuning he tower won't fix other common mode noise, like cables not grounded, bad grounding, rotor cable 120 ft long working like a vertical, etc, It is necessary detune them all. Regards JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Tuesday, December 16, 2014 7:52 AM To: Lee K7TJR; 'Bob Tabke'; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z Lee, We probably will just have to disagree about this. From my viewpoint, the behavior isn't too much different than a big yagi stack or other antennas we are used to. The size of the array generally sets the directivity limits. We can add more elements that are closer-in than optimum, and that can certainly help if the size is smaller than optimum, but the trade is gain or pattern cleanliness and sharpness for size. The forward two elements and back two elements are too close to contribute broadside pattern, which is what provides the clean pattern absent major side lobes in the full size 8 circle. As a matter of fact, adding them in destroys some of the broadside directivity. If, however, we make the array so small that it loses broadside pattern multiplication, then we can see an increase in directivity through the small endfire length increase. A .327wl radius array gives about .25 wl endfire spacing in the primary cells (the center elements), and is not improved in pattern quality by adding the forward and rearward cells. The two forward pairs and rearward pairs are not only too close to have broadside pattern contribution, they are closer endfire. They are about 75% of the endfire spacing in the central quad, and nearly 40% of the broadside width. They certainly can contribute endfire, but they actually remove broadside directivity in the process! In an optimum size array the amplitude ratio from the primary quad has to be 4:1 or 5:1 or more to prevent some pretty significant pattern null area deterioration when the additional 4 elements are added, because they deteriorate broadside pattern multiplication faster than they contribute endfire gain (at ~.187 spacing when the primary endfire cell has .25 wl spacing). If the array is made so small that there is little broadside contribution from array width, then the addition of the four will improve things. There isn't any broadside pattern to hurt. That isn't the same as a broad general statement that using more of the elements allows the array to be made smaller, unless we want to compromise pattern to have the same directivity. I go through similar things with Yagi arrays. All of my Hygain 5 element Yagis have been changed to four elements, and my KLM six elements have become 5's. :) It isn't so much they work better, they just work different in a way that is a better compromise for pattern, bandwidth, complexity, and gain. Everything is a compromise. If the target is maximum directivity and a clean pattern (more like a flashlight), the array has to be large. It can never be the same if small, or we all be running multi-element short boom antennas in close-spaced stacks. I do agree, however, if space is so limited the array can't use broadside multiplication (which
Re: Topband: 8 circle: DXE vs Hi-Z
Hi Guys, Excellent point Tom as we will have to disagree on this. I have built both types of arrays here and like the smaller circle with active elements. I believe it has a cleaner pattern. You can see a 3D picture comparison of several arrays at http://www.kkn.net/dayton2014/dayton-2014-antenna-forum.html; starting at page 11 There are some real differences between 8 element passive BSEF and the Hi-Z 8A npatterns. Receiving antennas are all about hearing what you want and getting rid of what you don't want. I think the 3D pictures show this pretty well. We almost never design RX antennas for gain, only how it receives which is mostly about pattern or directivity. The observations by Joel will indeed be interesting, These two antennas are VERY close in performance and I think the differences will be interesting, who knows, it may spur the development of something new. Go Joel! Lee K7TJR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Tuesday, December 16, 2014 4:52 AM To: Lee K7TJR; 'Bob Tabke'; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z Lee, We probably will just have to disagree about this. From my viewpoint, the behavior isn't too much different than a big yagi stack or other antennas we are used to. The size of the array generally sets the directivity limits. We can add more elements that are closer-in than optimum, and that can certainly help if the size is smaller than optimum, but the trade is gain or pattern cleanliness and sharpness for size. The forward two elements and back two elements are too close to contribute broadside pattern, which is what provides the clean pattern absent major side lobes in the full size 8 circle. As a matter of fact, adding them in destroys some of the broadside directivity. If, however, we make the array so small that it loses broadside pattern multiplication, then we can see an increase in directivity through the small endfire length increase. A .327wl radius array gives about .25 wl endfire spacing in the primary cells (the center elements), and is not improved in pattern quality by adding the forward and rearward cells. The two forward pairs and rearward pairs are not only too close to have broadside pattern contribution, they are closer endfire. They are about 75% of the endfire spacing in the central quad, and nearly 40% of the broadside width. They certainly can contribute endfire, but they actually remove broadside directivity in the process! In an optimum size array the amplitude ratio from the primary quad has to be 4:1 or 5:1 or more to prevent some pretty significant pattern null area deterioration when the additional 4 elements are added, because they deteriorate broadside pattern multiplication faster than they contribute endfire gain (at ~.187 spacing when the primary endfire cell has .25 wl spacing). If the array is made so small that there is little broadside contribution from array width, then the addition of the four will improve things. There isn't any broadside pattern to hurt. That isn't the same as a broad general statement that using more of the elements allows the array to be made smaller, unless we want to compromise pattern to have the same directivity. I go through similar things with Yagi arrays. All of my Hygain 5 element Yagis have been changed to four elements, and my KLM six elements have become 5's. :) It isn't so much they work better, they just work different in a way that is a better compromise for pattern, bandwidth, complexity, and gain. Everything is a compromise. If the target is maximum directivity and a clean pattern (more like a flashlight), the array has to be large. It can never be the same if small, or we all be running multi-element short boom antennas in close-spaced stacks. I do agree, however, if space is so limited the array can't use broadside multiplication (which is the same as stacking gain in a Yagi array) then all active elements with more elements is better. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
Joel, This will be very interesting when you can report some comparative results on both these good receiving antennas. I am building - what I believe to be a somewhat novel antenna to try this season and hope to get it finished in early January. Maybe someone considering a new receiving array might be interested? The 4NEC2 models indicate that it will have a F/B on 160M of better than 50 dB and an RDF (thanks Tom for this measure) of about 11.9 dB. Its gain is calculated to be in the - 16 dB range. The modeling seems to be pretty robust - meaning that playing with the physical parameters does not dramatically change the calculated performance. In other words, I would be very suspect if a slight change in some input parameter totally destroyed the calculated performance results. I comes by way of some further development of the SAL-30 Array (from Array Solutions) invented by Mark Bauman KB7GF. Larry Gauthier K8UT optimized the dimensions for the 160m band only. I think Mark calls it the High RDF CC-SAL (optimized for 160m) array. It is 25 feet high and about 50 feet in diameter. The complete model showing all the algebra for the optimization (and dimensions) is readily available to all on the 'shared apex loop' reflector. I'll let you know what I can about the performance - as soon as I can generate some numbers with my Kay attenuator pads. 73, Bruce W8RA From: Joel Harrison w...@w5zn.org To: topband@contesting.com Sent: Tuesday, December 16, 2014 9:42 AM Subject: Re: Topband: 8 circle: DXE vs Hi-Z Just to correct a typo, my HiZ 8 vertical array is spaced 200 ft, no 220 ft. Greetings Bob Reflector folks, Please allow me to provide a bit of my experience since I run both a broad side/end fire passive 8 vertical array (350 ft diameter) with a DXE controller AND a HiZ 8 vertical array spaced for 160 meters (220 ft diameter). To your specific question about controllers both will perform very well but there are differences in the arrays that need to be considered, so please allow me a bit of bandwidth here to explain. I installed my BSEF array about five years ago when there was practically no avalable information about the array and no commercially available controllers. I built the array and a controller and published my work in a paper on my website that later was published in QEX. Since that time, I have gained a great deal of experience with the array both mechanically and eletrically and as a result of my published work others have built arrays (w3LPL for one) had have shared their valuable experience publically as well. As a result, I rebuilt my BSEF 8 vertical array this year with a different mounting scheme like W3LPL uses and also moved to a better controller that Mike, W9RE first made boards available for and now that DX Engineering sells, which I now use for control of the BSEF array. Over this time Lee's HiZ arrays have become quite popular and are excellent performers. What I have noticed is there is considerable confusion among the masses about the differences in these arrays and to be quite blunt many folks equate living in an excellent geographical location for 160 meters propagation to amazing performance of a specific RX array which is an error. I am obsessed with 160 meter RX antennas and achieving peak performance from my rural location in central Arkansas, an area that is not enhanced by coastal propagation, etc. So I set out last year with a personal mission to evaluate both 8 vertical array systems, the passive BSEF array an the HiZ. I am not in the amateur radio business, I'm just a ham with a desire to have the best 160 meter RX system possible for my geographical area. So, both systems are operational here. There is significant sepeation between the two arrays (800 ft) and both are a significant distance from the transmit antenna. Both have their own level of complexity with installation and from personal experience I can tell you they each take about the same amount of time to construct and install. I have already recorded several real on the air comparisons of patterns, noise floors (taking in to account one is active and one is passive)and several signal comparisons of DX stations (actual signal level about noise floor, not S meter readings). I plan to publish these results in early spring at the end of the 160 meter DX season for north america. I would be more than pleased to discuss any specific questions you may have about these arrays off line a bit more in detail if you would like but again the short answer to your question is both will be excellent arrays. 73 Joel W5ZN I'm new to 160 and am planning to add an 8-circle. I would like to buy commercial preamps and the controller. I would greatly appreciate any advice on the choice of preamp/controller vendor. I live in a rural area and have a 4-direction 3-ele vertical array for 160
Re: Topband: 8 circle: DXE vs Hi-Z
A few comments based on my own experience with various receiving arrays: Circle diameter of the Hi-Z array: A circle diameter of 200 feet is specified for the Hi-Z 8-circle array on 160m. In fact, I have found that there is nothing magic about 200 feet. It happens to be a good compromise between maximizing RDF and minimizing sidelobe levels. You can use smaller circle diameters and still get very good performance. For example, with a circle diameter of 140 feet and the exact same phasing you would use for 200 feet, you still get a very clean, highly directional pattern with all lobes to sides and back down by more than 20 dB relative to the peak of the forward lobe. The RDF is 12.6 dB at a 20 degree elevation angle for the 140 foot circle vs. 13.45 dB for the 200 foot circle, so you do give up a small amount of RDF. Considering the 140 foot circle uses half the real estate area of the 200 foot circle, that is a fair compromise for many people (like me). To prove that smaller circle works in practice, I installed exactly that system and have observed directivity that is totally consistent with the results I modeled in EZNEC. Rejection off the sides and back are excellent. One caveat is that the smaller array is probably less tolerant of amplitude and phase errors, although I have not done any analysis to quantify that. I just built everything very carefully and made the installation as clean as possible. I also took care to switch in detuning of my transmit antenna when receiving on the array. RDF as a receiving metric: RDF is indeed a very useful metric for comparing receiving antennas. However, we need to be aware that it assumes the ambient background (atmospheric) noise is uniformly distributed in 3-dimensional space, which is not always true in specific instances. For this reason, RDF may not exactly predict the differences between two arrays in any given situation. It is possible for a system with a lower RDF to equal or even outperform another system with higher RDF under certain noise conditions. If the noise were always uniformly distributed, then RDF would perfectly predict relative receiving performance (actually SNR). The next point about RDF is that it is calculated for a specific signal arrival direction in three dimensional space. In terms of azimuth, it is the peak direction of the forward lobe. In elevation, it is common practice to use 20 degrees, which can be considered appropriate for DX reception. If the signal arrives from a different azimuth or elevation angle, the SNR advantage predicted by RDF may not actually be realized. I have seen a simple low dipole with a lousy RDF occasionally outperform my 8-circle system by a large amount when the elevation angle of arriving signals is very high and the RDF advantage of the array cannot be realized. As RDF gets higher, the beamwidth of the antenna system generally gets narrower. You can see this if you look at chart #2 in K7TJR's Dayton presentation (http://www.kkn.net/dayton2014/HiZ_DAYTON_2014_7n2.pdf). This brings up another point. By making the RDF very high, you are necessarily restricting the angular sector over which the antenna delivers its best performance. This is fine as long as the angular sector coincides with a direction that is important to you. The flip side is you give up some of that performance outside that sector. For switched arrays with a finite number of selectable directions, that could be a disadvantage when a direction of interest falls halfway between contiguous switching directions. Looking at the pattern of the array will tell you what you give up in the in between directions. These comments with respect to RDF are not intended to be disparaging. On the contrary I do believe RDF is an excellent tool for comparing receiving antennas. You just have to aware of what it actually means in practice. 73, John W1FV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
- DXE wants a 320' diameter and Hi-Z wants 200' for optimum performance. It's hard to tell what DXE performance is because it does not disclose RDF, beam width or F/B. And neither vendor supplies EZNEC files so I can see the effect of varying the layout. So I'm not sure how to decide what array size is best for me. It would be wonderful if someone has a model for these two systems. Bob, The ideal spacing of arrays like this is entirely dependent on the frequency range and goal you have for pattern or directivity. It is NOT dependent on the design or manufacturer, there are no magical space saving tricks. The circle diameter determines both endfire and broadside spacing, and spacing determines the beamwidth. Something in the 330-350 foot range across the element pairs is near optimum for 160 directivity. You can use it down to spacings where the element-to-element spacing is about 35-40 feet on 160, but it might as well be a four element vertical or some other array at that spacing. You can narrow the 160 pattern by going larger than 350 feet, but the array can develop unwanted lobes. If element-to-element goes over 135 feet or so, you will start to have F/R issues. This is the way every single eight element circle will work. The primary difference between the DXE and Hi-Z is construction quality, and that determines cost. The DXE unit is a metal case that serves as a groundplane for the connectors, and a much better PC layout. How much that translates into better performance depends on how pure the rest of the installation is. If the installation is sloppy or compromised, that will set the limit more than construction. The DXE is a nearly direct copy of what I use here, which is a very clean layout with PC mounted connectors and a super good groundplane between connectors to prevent ground loops that affect performance and minimize chances of lightning damage. One reason I especially worry about connector grounding is my eight verticals are spread in around a 350ft circle, and each has several 70 ft buried radials. The large physical size of a system like this sets the system up for large common mode currents in storms, it is actually a yearly event here to melt the shields off at least one cable with a nearby lighting hit (within a few thousand feet) because of ground loop currents, and yet I almost never have box troubles. I use a 20ft vertical with a small loading coil and series load resistor in my elements, and a three wire hat. Mine is single band 160 (although I'm very slowly working on a 16-element circle for 160-80). People who operate here just love the 8 circle. I can send you an EZNEC file that would roughly approximate the array. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 8 circle: DXE vs Hi-Z
The primary difference between DXE and Hi-Z 8 circle arrays is the fact that Hi-Z uses ALL 8 verticals actively at the same time where DXE uses only 4 at a direction. Using all 8 verticals allows the use of a smaller diameter and a performance edge on Directivity over the larger 4 active array. All 8 element arrays do NOT work the same way. Lee K7TJR -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Monday, December 15, 2014 7:24 PM To: Bob Tabke; topband@contesting.com Subject: Re: Topband: 8 circle: DXE vs Hi-Z - DXE wants a 320' diameter and Hi-Z wants 200' for optimum performance. It's hard to tell what DXE performance is because it does not disclose RDF, beam width or F/B. And neither vendor supplies EZNEC files so I can see the effect of varying the layout. So I'm not sure how to decide what array size is best for me. It would be wonderful if someone has a model for these two systems. Bob, The ideal spacing of arrays like this is entirely dependent on the frequency range and goal you have for pattern or directivity. It is NOT dependent on the design or manufacturer, there are no magical space saving tricks. The circle diameter determines both endfire and broadside spacing, and spacing determines the beamwidth. Something in the 330-350 foot range across the element pairs is near optimum for 160 directivity. You can use it down to spacings where the element-to-element spacing is about 35-40 feet on 160, but it might as well be a four element vertical or some other array at that spacing. You can narrow the 160 pattern by going larger than 350 feet, but the array can develop unwanted lobes. If element-to-element goes over 135 feet or so, you will start to have F/R issues. This is the way every single eight element circle will work. The primary difference between the DXE and Hi-Z is construction quality, and that determines cost. The DXE unit is a metal case that serves as a groundplane for the connectors, and a much better PC layout. How much that translates into better performance depends on how pure the rest of the installation is. If the installation is sloppy or compromised, that will set the limit more than construction. The DXE is a nearly direct copy of what I use here, which is a very clean layout with PC mounted connectors and a super good groundplane between connectors to prevent ground loops that affect performance and minimize chances of lightning damage. One reason I especially worry about connector grounding is my eight verticals are spread in around a 350ft circle, and each has several 70 ft buried radials. The large physical size of a system like this sets the system up for large common mode currents in storms, it is actually a yearly event here to melt the shields off at least one cable with a nearby lighting hit (within a few thousand feet) because of ground loop currents, and yet I almost never have box troubles. I use a 20ft vertical with a small loading coil and series load resistor in my elements, and a three wire hat. Mine is single band 160 (although I'm very slowly working on a 16-element circle for 160-80). People who operate here just love the 8 circle. I can send you an EZNEC file that would roughly approximate the array. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
