Topband: THeory
A common quip running around the system engineering department I ran for years: Sure it works in practice...but what about in theory? Happy Thanksgiving everyone... N4GG ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: no response to query: feeding phased verticals at half wave spacing
On 11/22/2011 08:06 PM, Gerry Treas, K8GT wrote: Hi Dale, I'm no antenna expert, but certainly read as much of the experts publications as I can get my hands on, but having a Teflon brain, it doesn't stick very well. That said, the ARRL Antenna Book has a page that shows the patterns of various spacings and phasings of vertical antennas, which I found very enlightening. Enlightening, but also somewhat misleading... The patterns in the ARRL Antenna Book are correct if the current in both elements is the same. However, if you feed an array of antennas with delay lines, those delay lines will act as impedance transformers for the antenna impedance of each element (like all feedlines do). This can result in each element getting different currents, and the pattern no longer being what it was. This makes feeding a phased array with delay lines much trickier than one would imagine at first glance. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: no response to query: feeding phased verticals at half wave spacing
- Original Message - From: Rik van Riel r...@surriel.com To: topband@contesting.com Sent: Thursday, November 24, 2011 10:59 AM Subject: Re: Topband: no response to query: feeding phased verticals at half wave spacing On 11/22/2011 08:06 PM, Gerry Treas, K8GT wrote: Hi Dale, I'm no antenna expert, but certainly read as much of the experts publications as I can get my hands on, but having a Teflon brain, it doesn't stick very well. That said, the ARRL Antenna Book has a page that shows the patterns of various spacings and phasings of vertical antennas, which I found very enlightening. Enlightening, but also somewhat misleading... The patterns in the ARRL Antenna Book are correct if the current in both elements is the same. However, if you feed an array of antennas with delay lines, those delay lines will act as impedance transformers for the antenna impedance of each element (like all feedlines do). This can result in each element getting different currents, and the pattern no longer being what it was. This makes feeding a phased array with delay lines much trickier than one would imagine at first glance. For 2 elements coax phasing is sufficient if 15dB or a bit better F/B is acceptable especially when using low noise receiving antennas. I was more than satisfied with a pair of sloping wires on 160 (NE/SW cardiod, NW/SE figure 8) and was happy to not be wasting power in a dummy load. I used a noise bridge and the rig to cut the lines to exact lengths and about 18dB FB was the norm, sometimes a bit better or worse but I could also load it up to about 1950 in a contest without wasting more RF in a tuner. Carl KM1H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: slow speed contester
Great advice Rick. In my post I should have added something about eradicating every nonessential dit from the exchange. 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. On 11/24/2011 9:35 AM, Richard (Rick) Karlquist wrote: The biggest problem with working slow speed stations in the ARRL 160 is that I leave the frequency unattended for too long, and risk having an east coast station fire up his CQ machine. To mitigate this, the slow speed station should send the minimum number of characters: 5NN SV. Please don't send QSL, 73, BK, etc. Please don't wait several seconds before coming back to me. Be prepared for me to send TU as soon as I hear your section. If you can't copy my call at my CQ speed, send CALL?. Otherwise, I will send your exchange slow but assume you managed to copy my call despite the high speed. If sending with a straight key, please err on the high side of the 3:1 dash to dot ratio, and please leave appropriate spaces between characters and between RST and section. Conditions for QRS stations tend to be friendlier higher in the band and later in the contest. CU on the air next weekend when we Occupy 160 meters, hi. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: no response to query: feeding phased verticals at half wave spacing
This is quite true although some patterns will be closer to theory than others. In a commercial phasor as is used for broadcast there are several elements that must be taken into account. The first is the matching at each vertical element. It must take the actual drive impedance of the elements and match to the transmission line (usually 50 ohms). These networks all have phase shift which must be taken into account as a part of the total system design. The next important element is the power divider. There are various designs but in the end they all permit the adjustment of power to each element so the currents are correct. The ARRL patterns are idealized examples where the current in both elements are equal but in the real world this is not often the case. A power divider also has phase shift. The final element is the means of making the phases of each tower the desired value while taking into account the fixed phase shift of the matching network and the power divider. There are two common methods used. The first is a lumped constant network which adds or subtracts phase to achieve the correct values after transmission line phase delay is added into the system. The other method is to use the transmission line to achieve the proper phase relationships. Even when transmission lines are used it is necessary to have a small lumped constant network to trim for minor variations in phase. It is apparent that such a system is very sensitive to a change in frequency. Adjusting a typical phased array requires a means of measuring impedance and typically there is a phase monitor which shows the phase and current ratio of each tower. This is all verified by field measurements that require a calibrated field intensity meter and a lot of paperwork to plot the pattern or a more complex (and expensive) GPS based measurement system. It should be obvious at this point that no amateur phased arrays are built as described above and do not have the same requirements. Commercial arrays are usually designed to provide protection to other stations on the same or adjacent frequencies. Amateur arrays are generally intended for gain in a desired direction and must have at least a small amount frequency agility. While the ARRL patterns are very much theoretical a few can be implemented for practical amateur use. The broadside two tower array spaced 180 degrees is probably the best if space is available. One drawback is the figure 8 pattern has zero db front to back ratio. This could be handled with a parasitic reflector but at the expense of more complexity and space. The bottom line is that practical amateur arrays will not achieve performance close to theoretical. On 11/24/11 10:59 AM, Rik van Riel wrote: On 11/22/2011 08:06 PM, Gerry Treas, K8GT wrote: Hi Dale, I'm no antenna expert, but certainly read as much of the experts publications as I can get my hands on, but having a Teflon brain, it doesn't stick very well. That said, the ARRL Antenna Book has a page that shows the patterns of various spacings and phasings of vertical antennas, which I found very enlightening. Enlightening, but also somewhat misleading... The patterns in the ARRL Antenna Book are correct if the current in both elements is the same. However, if you feed an array of antennas with delay lines, those delay lines will act as impedance transformers for the antenna impedance of each element (like all feedlines do). This can result in each element getting different currents, and the pattern no longer being what it was. This makes feeding a phased array with delay lines much trickier than one would imagine at first glance. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: slow speed contester
Great reply Rick I fondly remember my novice days at 6-7 wpm in my first contest. I had a XTal as close to the bottem of the 15 Mtr. novice band I dared to go and my slow CQ was answered by a lot of contest stations. and my speed slowly began to pick up. I worked most of the major contests mostly on 15 meters with my 5 el Gothem beam I added 10 ft to the 20 ft boom 30 Ft and made the spacing better. I hung on to my novice ticket with the goal of DXCC but when my 2 years were almost I had only 85 worked and abt. 78 confirmed, But I had WAS, WAC, and WPNX #56 They are my proudest Awards!! I then went to Detroit and came back with My Advanced. My old beat up pickup never got below 5 ft all the way back to BirchRun, ED K8OT In a message dated 11/24/2011 12:05:08 P.M. Eastern Standard Time, k...@k6xt.com writes: Great advice Rick. In my post I should have added something about eradicating every nonessential dit from the exchange. 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. On 11/24/2011 9:35 AM, Richard (Rick) Karlquist wrote: The biggest problem with working slow speed stations in the ARRL 160 is that I leave the frequency unattended for too long, and risk having an east coast station fire up his CQ machine. To mitigate this, the slow speed station should send the minimum number of characters: 5NN SV. Please don't send QSL, 73, BK, etc. Please don't wait several seconds before coming back to me. Be prepared for me to send TU as soon as I hear your section. If you can't copy my call at my CQ speed, send CALL?. Otherwise, I will send your exchange slow but assume you managed to copy my call despite the high speed. If sending with a straight key, please err on the high side of the 3:1 dash to dot ratio, and please leave appropriate spaces between characters and between RST and section. Conditions for QRS stations tend to be friendlier higher in the band and later in the contest. CU on the air next weekend when we Occupy 160 meters, hi. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: slow speed contester
would that have been around birch and little birch?? braxton county wv john wej On 11/24/2011 5:47 PM, gedk...@aol.com wrote: Great reply Rick I fondly remember my novice days at 6-7 wpm in my first contest. I had a XTal as close to the bottem of the 15 Mtr. novice band I dared to go and my slow CQ was answered by a lot of contest stations. and my speed slowly began to pick up. I worked most of the major contests mostly on 15 meters with my 5 el Gothem beam I added 10 ft to the 20 ft boom 30 Ft and made the spacing better. I hung on to my novice ticket with the goal of DXCC but when my 2 years were almost I had only 85 worked and abt. 78 confirmed, But I had WAS, WAC, and WPNX #56 They are my proudest Awards!! I then went to Detroit and came back with My Advanced. My old beat up pickup never got below 5 ft all the way back to BirchRun, ED K8OT In a message dated 11/24/2011 12:05:08 P.M. Eastern Standard Time, k...@k6xt.com writes: Great advice Rick. In my post I should have added something about eradicating every nonessential dit from the exchange. 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. On 11/24/2011 9:35 AM, Richard (Rick) Karlquist wrote: The biggest problem with working slow speed stations in the ARRL 160 is that I leave the frequency unattended for too long, and risk having an east coast station fire up his CQ machine. To mitigate this, the slow speed station should send the minimum number of characters: 5NN SV. Please don't send QSL, 73, BK, etc. Please don't wait several seconds before coming back to me. Be prepared for me to send TU as soon as I hear your section. If you can't copy my call at my CQ speed, send CALL?. Otherwise, I will send your exchange slow but assume you managed to copy my call despite the high speed. If sending with a straight key, please err on the high side of the 3:1 dash to dot ratio, and please leave appropriate spaces between characters and between RST and section. Conditions for QRS stations tend to be friendlier higher in the band and later in the contest. CU on the air next weekend when we Occupy 160 meters, hi. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.920 / Virus Database: 271.1.1/4032 - Release Date: 11/22/11 07:55:00 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Counterpoise very interresting
Models are very good in relative comparisons, with some very important caveats. 1) Hold everything possible constant between the two models, EXCEPT the singular issue(s) you are trying to trend. Don't try to vary dirt. If you don't already have burn scars and embarrassing gaffes about dirt, you likely won't have the experience or the burn scar gut motivation to guide you through this mine field. 2) Dirt is not handled well by any model, and each model has techniques for getting reasonable results in spite of dirt. If the comparison between two models is distance from dirt, or varying the kind of dirt, then other than just noting a general trend, one must take any absolute result with a fair measure of suspicion. The way to avoid dirt as an issue is to pick dirt characteristics and technique for representing dirt, and then hold those CONSTANT everywhere in the suite of comparisons. The comparisons will be good, but the absolute values are suspect. EZNEC, in particular, has help sections on how to deal with dirt, which are required reading if you are trying to do something serious that will cost you time and money. 3) Every model has combinations of model input that will cause the model to compute incorrectly. Even the mighty NEC-4 has these. If you have one of these gotcha's in your data, it can queer the outcome, even between two models with very little difference between them. You need to know these for your modeling program and rigorously avoid them. 4) Get a measured actual data point from a test case for low band wire antenna stuff. Account for the difference between reality and your model of that reality before you venture on. If you can't reconcile the two, it's time to bulk up your understanding of what is going on and get some experienced help to go forward. In my last design for immediate construction and contest use, the data points vs. modeled proved that height and droop angle of the elements were critical, and the antenna would fail if height and droop angle were not maintained to design specs for the life of the antenna. More important, seeing the results the owner was convinced as well. This resulted in some on the spot adjustments to design so those height and droop specs COULD be maintained reasonably on his property. 5) If you are serious about an antenna in a certain place, be sure to model ALL the conductors literally. Especially on 80 and 160. Particularly if the antenna is supported by a tower. Everything within a wavelength is in play to some degree. Comparing two antennas where the real ones are on different sites with different sets of miscellaneous conductors and dirt, probably can't be done adequately with models. The best thing to do with modeling is to get started and stick with it. Personally I can't imagine doing antennas without the programs. Like trying to drive a car blind. People have their favorite logical simplification devices to describe what is going on in antennas. Most of these break down if you use those mental devices to actually design something. The models simply show you what is going on between wires due to the physics. Even if you are right when reality and a model differ, you need to know why and how. Some here advocate the throw it up and be happy school of antenna design, and it IS a hobby. Your money and your time, hope you enjoy yourself, honestly. But if you've gotten beyond that, and want to COMPETE with other hams, so pieces of dB's here and there add up to your advantage, or you're just not working anyone and don't get it, running blind without the model won't cut it. And there is lots of help available, if you want it. 73, Guy. On Thu, Nov 24, 2011 at 11:44 AM, Rik van Riel r...@surriel.com wrote: On 11/23/2011 05:49 PM, Gene Smar wrote: Gents: A man much wiser than I once told me, The difference between theory and practice in theory is less than the difference between theory and practice in practice. I suspect that while models may be somewhat inaccurate sometimes (especially due to lack of things like trees and houses in the models), the modeling software will still give a good picture of the relative quality between two antennas in the same installation. For example, the performance of antennas in my yard is likely to be off due to the presence of things like trees, my house, and the neighbors' houses. This could cause the model to be off by several dB. However, I suspect that the models of various antennas are likely to each be off by similar amounts in the same direction. In other words, if NEC tells me that one antenna has a few more dB gain than another, this is likely to be true, even if it gets the gain for both antennas slightly wrong. Am I wrong in my thinking? Has anyone observed something contrary? ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB -
Re: Topband: Counterpoise very interresting
Hi Guy, I am chasing down the modeling software to try and get the best results I can on my small lot and sandy soil. I am not really competing against other hams but against my own past performance and experiences. What other hams are doing gives some idea of what might be possible. Meanwhile I am going to toss as much wire into the trees as I can get up there along with low or on-the-ground counterpoise and hope for the best. I'll get some QSOs for sure but more will be better. An end fed wire and a bazooka were two of the best (multiband) antennas I used before. The bazooka is directly proportional to the wavelength and I did mention my small lot. I'm trying to get my wire up before we run out of operating events for the year. 73, Bill KU8H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: THeory
Message: 1 Date: Thu, 24 Nov 2011 08:14:07 -0500 From: Hal Kennedy hal...@comcast.net Subject: Topband: THeory To: topband@contesting.com Message-ID: 57EC67C786854307B664F3BE15B88CB0@N4GG4 Content-Type: text/plain; charset=us-ascii THeory. Theory is the application of science to the real world observation. When we observe an incident in the real world, we try to apply theory to explain our observations. We call this forensic science. There is always a scientific explanation for what we observe in this universe. The challenge is applying the known science to the observation. Sometimes the observation does not match our known science at the time, and thus requires us to further our scientific understanding to explain our observation. Just because our observation does not match our science, does not mean the science is wrong. It just means that our understanding of our science to the observation is not entirely correct. Engineering is the study of observation and the application of observation in the proliferation in the advancement of understanding. Everything we observe has justification. The challenge is applying science to the observation. Chet Latawiec, P.E., P. EngVE3CFK / W2NHA A common quip running around the system engineering department I ran for years: Sure it works in practice...but what about in theory? Happy Thanksgiving everyone... N4GG *** ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Erroneous info on ARRL web site about ARRL 160 contest
There is an advertisement on the ARRL web site for the 160 meter contest at: http://www.arrl.org/news/reach-for-the-top-in-the-arrl-160-meter-contest Unfortunately, it states the KL7, KH6, etc count as DX. They actually count as ARRL sections. KV4FZ has been campaigning for years to educate DX stations who think they can't work him. Elsewhere, the site says DX to DX qsos don't count, and KL7 is DX, but KL7 can still work DX stations. Very confusing. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Erroneous info on ARRL web site about ARRL 160 contest
This would be a welcome change if true, however I think Rick is right. This is primarily a domestic contest, and KH2 counts the same as a KH6 - Pacific Section - even though Guam is 3,800 miles west of Hawaii (greater than the distance between NYC and LAX). This really makes it pointless to participate from my standpoint, unless I get on to hand out an easy QSO to the 20-some JAs who are active in this contest. ARRL 160 is really a great contest - from North America. Elsewhere, CQ160 and the SP are king. 73, Dave KH2/N2NL aka NH2T On 11/25/2011 11:26 AM, Richard (Rick) Karlquist wrote: There is an advertisement on the ARRL web site for the 160 meter contest at: http://www.arrl.org/news/reach-for-the-top-in-the-arrl-160-meter-contest Unfortunately, it states the KL7, KH6, etc count as DX. They actually count as ARRL sections. KV4FZ has been campaigning for years to educate DX stations who think they can't work him. Elsewhere, the site says DX to DX qsos don't count, and KL7 is DX, but KL7 can still work DX stations. Very confusing. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
