Re: Topband: Skimmer calibration
We were talking about validating or debunking people's RX experience at the shore in various relationships to the edge of salt water. And the anecdota included just about any signal around, on whatever path and whatever TX takeoff angle, not just the signals of a few specific TX stations. Contests would create a maximum number of stations, where signals on a pair or trio of identical RX antennas get reported by a pair or trio of skimmer RX. A test grouping could consist of one antenna were over salt water or at edge, another 500 meters off shore, and another well inland but within 50 km. This would assess the same situations as anecdotal reports, and create enough paired or tripled data to identify differences greater than 2 or 3 dB. It is possible that a single contest might generate 10,000 groupings of over a thousand stations, from the very weak to the quite strong. What will be missing in a recent contest's worth of data apparently is the over salt water data, perhaps a few within 500 meters, and the rest. I don't know of current RBN nodes in the first two categories. They serve the spotting network's users well by not reporting signals at water's edge that a lot of people might not be able to hear. It is one thing to RX at exotic sites with short vertical antennas, and quite another to transmit there, with transmit grade antennas. An RX setup, would use a common vertical, include a power source, RX and CPU and blue tooth or 811g to connect, in a sealed box. The base of each vertical would be 8 feet and use for each box a technology chosen from the RX short vertical techniques. Each setup would be calibrated with a milliwatt source to a very short standard antenna at 100 meters distance to calibrate the band-is-dead background noise. These could be transmitting during during the contest as a beacon. Then we would have the ability to mark ambient noise with an absolute value, thus deriving an absolute signal value for any skimmer s/n reading. Then it's up to program analysis of all the signals that came in during a contest. The basic reference points become certain functions against all the data or complete categories of data. Everything is very large sample analysis. It would be yet to be determined what degree of dB accuracy could be proven. It would be useful to operate these skimmers to a separate server just used for the signal trio, and keep ALL the data readings, instead of using the [necessary for general spotting use] reducing a single skimmer's data release to a skimmer's reading of a given station on a given frequency to once every ten or fifteen minutes. Then it would be simple to remove fades, or measure fade depth, etc in the data analysis math. 73, Guy. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: A35LT
Dear friends, congratulations on the expedition, it will be a success, but your schedule is a bit late for us in South America. Please can you try from your SS. Have fun. Dick PY2RO 2014-08-18 16:30 GMT-03:00 Brian Sarkisian : > A35LT was on 160 during the North American morning grey line. We plan on > being on the air again the next North American morning grey line. > > > 73 de Brian, KG8CO >A35CO > _ > Topband Reflector Archives - http://www.contesting.com/_topband > -- Dick Rodrigues PY2RO _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: A35LT
A35LT was on 160 during the North American morning grey line. We plan on being on the air again the next North American morning grey line. 73 de Brian, KG8CO A35CO _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Skimmer calibration
Hi Guys, Thank goodness the QRP-types amongst us all don't seem to be so fixated & obsessed with such intricate & minute details... If they were, most would probably never even get on the air with their peanut-powered rigs...and why would they? There'd most likely be assaulted by dozens of gurus lurking in the sidelines, ready to advise them that what they are attempting to do goes beyond the realm of possibility. ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Skimmer calibration
Since no one likely knows the gain of a reference antenna within a dB or so, splitting hairs doesn't matter. Ten dB would jump right out, while 3 dB might get lost in the QSB. When I was comparing high dipoles to verticals on 160, I collected reports for about a year. It was thousands of reports. I probably could have done it in a week or two with skimmer, but then I would have had to repeat it for seasonal changes. I'm sure a good test protocol using skimmer could be worked out. - Original Message - From: "Jim Brown" To: Sent: Monday, August 18, 2014 12:47 PM Subject: Re: Topband: Skimmer calibration On Mon,8/18/2014 4:53 AM, Tom W8JI wrote: A live comparison of S/N ratio or relative level over time is with very few exceptions an excellent comparative test. It is much more accurate than S meters or absolute levels without a comparison reference. As such, the RBN is a great tool for evaluating systems. Yes. BUT -- my experience has been that I must average hundreds of data points to get meaningful data. The reasons are simple -- we must contend with QSB, and as Tom noted in another post, nulls in the patterns of antennas at both ends. A few years ago, I tried to compare two 160M antennas using JT65 and W6CQZ's JT65 RBN. On a good night, I would see reports from 3-4 stations east of the Mississippi. I alternated between the two antennas for hours, putting the reports in a spreadsheet, and studying the data. Modelling predicted differences of a few dB, and I never found that the data was good enough to confirm the models. The antennas are passive arrays of fairly tall verticals of a quarter wave or less, so there are no vertical nulls in their pattern. I can clearly hear their directivity on RX, but their gain is what I was trying to confirm. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4745 / Virus Database: 4007/8057 - Release Date: 08/18/14 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Skimmer calibration
On Mon,8/18/2014 4:53 AM, Tom W8JI wrote: A live comparison of S/N ratio or relative level over time is with very few exceptions an excellent comparative test. It is much more accurate than S meters or absolute levels without a comparison reference. As such, the RBN is a great tool for evaluating systems. Yes. BUT -- my experience has been that I must average hundreds of data points to get meaningful data. The reasons are simple -- we must contend with QSB, and as Tom noted in another post, nulls in the patterns of antennas at both ends. A few years ago, I tried to compare two 160M antennas using JT65 and W6CQZ's JT65 RBN. On a good night, I would see reports from 3-4 stations east of the Mississippi. I alternated between the two antennas for hours, putting the reports in a spreadsheet, and studying the data. Modelling predicted differences of a few dB, and I never found that the data was good enough to confirm the models. The antennas are passive arrays of fairly tall verticals of a quarter wave or less, so there are no vertical nulls in their pattern. I can clearly hear their directivity on RX, but their gain is what I was trying to confirm. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Skimmer calibration
It's also worth mentioning that you can evade the Skimmer's "wait 10 minutes before re-spotting" limitation simply by QSYing 500 Hz or sobefore re-sending - that way you can get a lot of data points in a relatively short period. So long as you use TEST as your keyword rather than CQ, and stay out of other people's way, nobody should be upset. 73, Pete N4ZR Check out the Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com. For spots, please go to your favorite ARC V6 or VE7CC DX cluster node. On 8/18/2014 12:16 PM, Tom W8JI wrote: This is why some time and multiple skimmers must be involved in the statisticsotherwise data doesn't mean much. Without skimmer I never settled on antennas until many dozens of blind AB test reports. I think skimmer is a more accurate way, because the human at the RX end is out of the picture. There's a lot of scatter in the dB measurements from skimmers. If I see dozens of spots graphed on the reversebeacon "spots comparison tool" then I can believe systemic differences like 3-5dB. But I could never draw that conclusion over a single pair of spots. Any given skimmer will spot a given station on a given frequency at most once every ten minutes. But when the geographic density of skimmers is large enough (e.g. East coast US or Western Europe) just raw quantities or breadth of spots starts being more interesting than exact dB level. Even with the paucity of skimmers on west coast of US, I can still see who has a 4-square for transmit and how they steer it during the contest. Tim N3QE On Mon, Aug 18, 2014 at 7:53 AM, Tom W8JI wrote: I am not a Skimmer expert, and am just asking. Question: Are all the Skimmers individually(and collectively) calibrated in concert? Can one rely on them for comparing scientific data and conclusion to prove or ascertain a point?Val Val, A live comparison of S/N ratio or relative level over time is with very few exceptions an excellent comparative test. It is much more accurate than S meters or absolute levels without a comparison reference. As such, the RBN is a great tool for evaluating systems. The problems are: 1.) For determining small differences, less than around 5 dB, you have to know the performance level of the reference antenna or station. (For that reason, I use a simple dipole reference.) 2.) The reference and AUT (antenna under test) have to be reasonably close together to eliminate propagation variances, but not so close as to interact, and they have to be in the clear. For example, it would be foolish for me to plant a dipole in the middle of a bunch of Yagi antennas and call it a reference, or put the antenna being evaluated in an obstructed area. 3.) On skywave, there has to be some time involved with readings averaged over time. This is somewhat true if there is more than a few wavelengths distance between antennas, and especially true (almost critical) when comparing different polarization antennas. 4.) Ideally the reference and AUT should be the same polarization, unless we simply want to know which is louder overall. 5.) Antennas have sweet and sour heights for a given set of conditions. We have to be very careful of this. This is especially true when antennas are more than a half wavelength high above ground, because the antenna pattern will be a series of deep nulls that selectively "notch out" a given wave angle. The RBN is an excellent tool. It does not need to be calibrated in absolute level, only in dB, and dB to noise is just fine provided the noise level of the receive site is steady. One thing I hope we all can do is stop acting so "American" (we are now what, 30th or 40th in math and science?) and get back to constructive exchanges of information. If we stop learning and just pick a position and fight, which is our trend today, this becomes a useless hobby and there is no reason to communicate. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4745 / Virus Database: 4007/8057 - Release Date: 08/18/14 _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Skimmer calibration
This is why some time and multiple skimmers must be involved in the statisticsotherwise data doesn't mean much. Without skimmer I never settled on antennas until many dozens of blind AB test reports. I think skimmer is a more accurate way, because the human at the RX end is out of the picture. There's a lot of scatter in the dB measurements from skimmers. If I see dozens of spots graphed on the reversebeacon "spots comparison tool" then I can believe systemic differences like 3-5dB. But I could never draw that conclusion over a single pair of spots. Any given skimmer will spot a given station on a given frequency at most once every ten minutes. But when the geographic density of skimmers is large enough (e.g. East coast US or Western Europe) just raw quantities or breadth of spots starts being more interesting than exact dB level. Even with the paucity of skimmers on west coast of US, I can still see who has a 4-square for transmit and how they steer it during the contest. Tim N3QE On Mon, Aug 18, 2014 at 7:53 AM, Tom W8JI wrote: I am not a Skimmer expert, and am just asking. Question: Are all the Skimmers individually(and collectively) calibrated in concert? Can one rely on them for comparing scientific data and conclusion to prove or ascertain a point?Val Val, A live comparison of S/N ratio or relative level over time is with very few exceptions an excellent comparative test. It is much more accurate than S meters or absolute levels without a comparison reference. As such, the RBN is a great tool for evaluating systems. The problems are: 1.) For determining small differences, less than around 5 dB, you have to know the performance level of the reference antenna or station. (For that reason, I use a simple dipole reference.) 2.) The reference and AUT (antenna under test) have to be reasonably close together to eliminate propagation variances, but not so close as to interact, and they have to be in the clear. For example, it would be foolish for me to plant a dipole in the middle of a bunch of Yagi antennas and call it a reference, or put the antenna being evaluated in an obstructed area. 3.) On skywave, there has to be some time involved with readings averaged over time. This is somewhat true if there is more than a few wavelengths distance between antennas, and especially true (almost critical) when comparing different polarization antennas. 4.) Ideally the reference and AUT should be the same polarization, unless we simply want to know which is louder overall. 5.) Antennas have sweet and sour heights for a given set of conditions. We have to be very careful of this. This is especially true when antennas are more than a half wavelength high above ground, because the antenna pattern will be a series of deep nulls that selectively "notch out" a given wave angle. The RBN is an excellent tool. It does not need to be calibrated in absolute level, only in dB, and dB to noise is just fine provided the noise level of the receive site is steady. One thing I hope we all can do is stop acting so "American" (we are now what, 30th or 40th in math and science?) and get back to constructive exchanges of information. If we stop learning and just pick a position and fight, which is our trend today, this becomes a useless hobby and there is no reason to communicate. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband - No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4745 / Virus Database: 4007/8057 - Release Date: 08/18/14 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Modeling the proverbial "vertical on a beach"
On 2014-08-18, at 11:58 AM, Guy Olinger K2AV wrote: > You clearly have not been subject to "Finding True North" and its > endless reincarnations on TopBand reflector, or you would not be > complaining about such a minor thread as this. :>) > > 73, Guy. Hi Guy, Thankfully & mercifully, I seem to have been spared that particular episode of fun & frolics...! ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Modeling the proverbial "vertical on a beach"
You clearly have not been subject to "Finding True North" and its endless reincarnations on TopBand reflector, or you would not be complaining about such a minor thread as this. :>) 73, Guy. On Sun, Aug 17, 2014 at 7:03 PM, Eddy Swynar wrote: > Hi Guys, > > ENOUGH of the "...modeling the proverbial 'vertical on the beach'" already...! > > My "delete" button is beginning to wear out. > > Just "...Build it, and they will come." Period. > > ~73~ de Eddy VE3CUI - VE3XZ > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Skimmer calibration
There's a lot of scatter in the dB measurements from skimmers. If I see dozens of spots graphed on the reversebeacon "spots comparison tool" then I can believe systemic differences like 3-5dB. But I could never draw that conclusion over a single pair of spots. Any given skimmer will spot a given station on a given frequency at most once every ten minutes. But when the geographic density of skimmers is large enough (e.g. East coast US or Western Europe) just raw quantities or breadth of spots starts being more interesting than exact dB level. Even with the paucity of skimmers on west coast of US, I can still see who has a 4-square for transmit and how they steer it during the contest. Tim N3QE On Mon, Aug 18, 2014 at 7:53 AM, Tom W8JI wrote: > > > I am not a Skimmer expert, and am just asking. Question: Are all the > Skimmers individually(and collectively) calibrated in concert? Can one rely > on them for comparing scientific data and conclusion to prove or ascertain > a point?Val > > Val, > > A live comparison of S/N ratio or relative level over time is with very > few exceptions an excellent comparative test. It is much more accurate than > S meters or absolute levels without a comparison reference. As such, the > RBN is a great tool for evaluating systems. > > The problems are: > > 1.) For determining small differences, less than around 5 dB, you have to > know the performance level of the reference antenna or station. (For that > reason, I use a simple dipole reference.) > > 2.) The reference and AUT (antenna under test) have to be reasonably close > together to eliminate propagation variances, but not so close as to > interact, and they have to be in the clear. For example, it would be > foolish for me to plant a dipole in the middle of a bunch of Yagi antennas > and call it a reference, or put the antenna being evaluated in an > obstructed area. > > 3.) On skywave, there has to be some time involved with readings averaged > over time. This is somewhat true if there is more than a few wavelengths > distance between antennas, and especially true (almost critical) when > comparing different polarization antennas. > > 4.) Ideally the reference and AUT should be the same polarization, unless > we simply want to know which is louder overall. > > 5.) Antennas have sweet and sour heights for a given set of conditions. We > have to be very careful of this. This is especially true when antennas are > more than a half wavelength high above ground, because the antenna pattern > will be a series of deep nulls that selectively "notch out" a given wave > angle. > > The RBN is an excellent tool. It does not need to be calibrated in > absolute level, only in dB, and dB to noise is just fine provided the noise > level of the receive site is steady. > > One thing I hope we all can do is stop acting so "American" (we are now > what, 30th or 40th in math and science?) and get back to constructive > exchanges of information. If we stop learning and just pick a position and > fight, which is our trend today, this becomes a useless hobby and there is > no reason to communicate. > > 73 Tom > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Skimmer calibration
I am not a Skimmer expert, and am just asking. Question: Are all the Skimmers individually(and collectively) calibrated in concert? Can one rely on them for comparing scientific data and conclusion to prove or ascertain a point?Val Val, A live comparison of S/N ratio or relative level over time is with very few exceptions an excellent comparative test. It is much more accurate than S meters or absolute levels without a comparison reference. As such, the RBN is a great tool for evaluating systems. The problems are: 1.) For determining small differences, less than around 5 dB, you have to know the performance level of the reference antenna or station. (For that reason, I use a simple dipole reference.) 2.) The reference and AUT (antenna under test) have to be reasonably close together to eliminate propagation variances, but not so close as to interact, and they have to be in the clear. For example, it would be foolish for me to plant a dipole in the middle of a bunch of Yagi antennas and call it a reference, or put the antenna being evaluated in an obstructed area. 3.) On skywave, there has to be some time involved with readings averaged over time. This is somewhat true if there is more than a few wavelengths distance between antennas, and especially true (almost critical) when comparing different polarization antennas. 4.) Ideally the reference and AUT should be the same polarization, unless we simply want to know which is louder overall. 5.) Antennas have sweet and sour heights for a given set of conditions. We have to be very careful of this. This is especially true when antennas are more than a half wavelength high above ground, because the antenna pattern will be a series of deep nulls that selectively "notch out" a given wave angle. The RBN is an excellent tool. It does not need to be calibrated in absolute level, only in dB, and dB to noise is just fine provided the noise level of the receive site is steady. One thing I hope we all can do is stop acting so "American" (we are now what, 30th or 40th in math and science?) and get back to constructive exchanges of information. If we stop learning and just pick a position and fight, which is our trend today, this becomes a useless hobby and there is no reason to communicate. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
