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Vertical vs Horizontal shootout part one
Based on another thread a few weeks back in which Horizontal dipoles
were being compared to Vertical antennas, and from a little chiding from Roy, W7EL, I decided to do some testing on my own personal versions of the two. My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Part one of this experiment is to calibrate the S-meter. I found that trying to calibrate the thing with on-air signals was a nuisance, and probably wouldn't be as accurate, so I used a signal generator. I started out with a +20 signal, then worked my way down. +20 start S9 -18 db S8 -23 db S7 -26 db S6 -29 db S5 -32 db S4 -35 db S3 -37 db S2 -39 db S1 -41 db All in all, I would have to say that the meter tracks very well from S8 to S4, and the only place that wasn't that great was from S9 to S8. But considering the transient nature of the signals we are receiving, I would have to day that the S-meter is of reasonably close accuracy. With my newly calibrated S-meter I am ready to start looking at what the two different antennas are doing for me. I have a coaxial switch to jump back and forth between the two. My initial impressions are that there are some surprises. The difference in noise levels varies by antenna by band. On some bands the vertical is noisier, and on others it is the OCF dipole. Especially intriguing is that on PSK mode, where I can see several signals at one time, switching between antennas will attenuate some signals, while other signals increase in strength. I think that my vertical works better than I gave it credit for, but If I definitely want *both* antennas. Next installment will be the band to band comparison of the two antennas with some numbers. Installment three will be an investigation of that PSK signal strength business. - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
On Sun, 05 Mar 2006 19:29:12 -0500, Mike Coslo
wrote: Based on another thread a few weeks back in which Horizontal dipoles were being compared to Vertical antennas, and from a little chiding from Roy, W7EL, I decided to do some testing on my own personal versions of the two. Mike, this sounds interesting. My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? Another, are the antennas coupled significantly, eg is one within the near field zone of the other? It is pretty hard to avoid in a residential block on the low bands, and it will confuse the results somewhat. Part one of this experiment is to calibrate the S-meter. I found that trying to calibrate the thing with on-air signals was a nuisance, and probably wouldn't be as accurate, so I used a signal generator. I started out with a +20 signal, then worked my way down. +20 start S9 -18 db S8 -23 db S7 -26 db S6 -29 db S5 -32 db S4 -35 db S3 -37 db S2 -39 db S1 -41 db Not only is the shape of the scale an issue, but the granularity or resolution, especially with LCD meters, or any meter where there are discrete steps in the meter current (such as where a D/A converter drives the meter movement). If you want to move beyond S meters, you could try FSM (www.vk1od.net/fsm) and organise some constant carriers at known distances / radiation angles that you could make a series of measurements of and produce summary statistics (median and inter quartile range) for each antenna type. All in all, I would have to say that the meter tracks very well from S8 to S4, and the only place that wasn't that great was from S9 to S8. But considering the transient nature of the signals we are receiving, I would have to day that the S-meter is of reasonably close accuracy. With my newly calibrated S-meter I am ready to start looking at what the two different antennas are doing for me. I have a coaxial switch to jump back and forth between the two. My initial impressions are that there are some surprises. The difference in noise levels varies by antenna by band. On some bands the vertical is noisier, and on others it is the OCF dipole. Especially intriguing is that on PSK mode, where I can see several signals at one time, switching between antennas will attenuate some signals, while other signals increase in strength. I think that my vertical works better than I gave it credit for, but If I definitely want *both* antennas. I described a technique for assessing the relative performance of mobile stations by having them transmit known constant carrier, each station space about 200Hz and turning circles in a carpark near each other, and to observe them at typical propagation distances with an audio spectrum analyser, watching the relative strength of the carriers. Your PSK setup is affording you the same type of comparison, and provides a ready (and recordable) assessment of the relative strength of the stations under the two antenna scenarios. Be great if you could orchestrate stations at known distances as part of an organised test. Owen Next installment will be the band to band comparison of the two antennas with some numbers. Installment three will be an investigation of that PSK signal strength business. - 73 de Mike KB3EIA - -- |
Vertical vs Horizontal shootout part one
I'm glad to see that my chiding has had a positive result.
Be sure you calibrate your S-meter on each band you'll be using it on, and that the RF gain control and any preamplifier and input attenuator settings are the same as they are when making measurements. Especially when comparing horizontal and vertical antennas, you'll likely have to make several measurements over a period of time. I've seen many cases where one antenna is a good 20 dB stronger than the other, then over the next minute or so their relative strengths reverse. This is due to polarization rotation of the received signal. On 40 and 80 meters at least, this is common and often has a period of around a minute or more. Really makes me chuckle when I hear "Ok, this is antenna 1. Now this is antenna 2. Which is stronger?" If neither antenna is consistently stronger than the other, you can put a fixed attenuator is line with one of the antennas and the step attenuator in line with the other to make comparison easier. People who blindly assume the marks on their S-meters are 6 dB apart should take a good look at your calibration results. Roy Lewallen, W7EL Mike Coslo wrote: Based on another thread a few weeks back in which Horizontal dipoles were being compared to Vertical antennas, and from a little chiding from Roy, W7EL, I decided to do some testing on my own personal versions of the two. My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Part one of this experiment is to calibrate the S-meter. I found that trying to calibrate the thing with on-air signals was a nuisance, and probably wouldn't be as accurate, so I used a signal generator. I started out with a +20 signal, then worked my way down. +20 start S9 -18 db S8 -23 db S7 -26 db S6 -29 db S5 -32 db S4 -35 db S3 -37 db S2 -39 db S1 -41 db All in all, I would have to say that the meter tracks very well from S8 to S4, and the only place that wasn't that great was from S9 to S8. But considering the transient nature of the signals we are receiving, I would have to day that the S-meter is of reasonably close accuracy. With my newly calibrated S-meter I am ready to start looking at what the two different antennas are doing for me. I have a coaxial switch to jump back and forth between the two. My initial impressions are that there are some surprises. The difference in noise levels varies by antenna by band. On some bands the vertical is noisier, and on others it is the OCF dipole. Especially intriguing is that on PSK mode, where I can see several signals at one time, switching between antennas will attenuate some signals, while other signals increase in strength. I think that my vertical works better than I gave it credit for, but If I definitely want *both* antennas. Next installment will be the band to band comparison of the two antennas with some numbers. Installment three will be an investigation of that PSK signal strength business. - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
"Roy Lewallen" wrote in message ... I'm glad to see that my chiding has had a positive result. Be sure you calibrate your S-meter on each band you'll be using it on, and that the RF gain control and any preamplifier and input attenuator settings are the same as they are when making measurements. Especially when comparing horizontal and vertical antennas, you'll likely have to make several measurements over a period of time. I've seen many cases where one antenna is a good 20 dB stronger than the other, then over the next minute or so their relative strengths reverse. This is due to polarization rotation of the received signal. On 40 and 80 meters at least, this is common and often has a period of around a minute or more. Really makes me chuckle when I hear "Ok, this is antenna 1. Now this is antenna 2. Which is stronger?" If neither antenna is consistently stronger than the other, you can put a fixed attenuator is line with one of the antennas and the step attenuator in line with the other to make comparison easier. People who blindly assume the marks on their S-meters are 6 dB apart should take a good look at your calibration results. Roy Lewallen, W7EL Mike Coslo wrote: Based on another thread a few weeks back in which Horizontal dipoles were being compared to Vertical antennas, and from a little chiding from Roy, W7EL, I decided to do some testing on my own personal versions of the two. My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Part one of this experiment is to calibrate the S-meter. I found that trying to calibrate the thing with on-air signals was a nuisance, and probably wouldn't be as accurate, so I used a signal generator. I started out with a +20 signal, then worked my way down. +20 start S9 -18 db S8 -23 db S7 -26 db S6 -29 db S5 -32 db S4 -35 db S3 -37 db S2 -39 db S1 -41 db All in all, I would have to say that the meter tracks very well from S8 to S4, and the only place that wasn't that great was from S9 to S8. But considering the transient nature of the signals we are receiving, I would have to day that the S-meter is of reasonably close accuracy. With my newly calibrated S-meter I am ready to start looking at what the two different antennas are doing for me. I have a coaxial switch to jump back and forth between the two. My initial impressions are that there are some surprises. The difference in noise levels varies by antenna by band. On some bands the vertical is noisier, and on others it is the OCF dipole. Especially intriguing is that on PSK mode, where I can see several signals at one time, switching between antennas will attenuate some signals, while other signals increase in strength. I think that my vertical works better than I gave it credit for, but If I definitely want *both* antennas. Next installment will be the band to band comparison of the two antennas with some numbers. Installment three will be an investigation of that PSK signal strength business. - 73 de Mike KB3EIA - Man, this is Ham Radio at its best! west AF4GC |
Vertical vs Horizontal shootout part one
Roy says,
People who blindly assume the marks on their S-meters are 6 dB apart should take a good look at your calibration results. ======================================= The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do with which antenna produces the stronger received signal. It is purely a comparison. Just use the same meter throughout the tests. Roy, you must be still be using that ancient receiver. No doubt it is working fine. But you still refer, quite arbitraliry, to your personal S-meter as the North American Calibration Standard. Must everybody else fall into line? Not me! ---- Reg. |
Vertical vs Horizontal shootout part one
Reg Edwards wrote:
Roy says, People who blindly assume the marks on their S-meters are 6 dB apart should take a good look at your calibration results. ======================================= The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do with which antenna produces the stronger received signal. It is purely a comparison. Just use the same meter throughout the tests. Roy, you must be still be using that ancient receiver. No doubt it is working fine. But you still refer, quite arbitraliry, to your personal S-meter as the North American Calibration Standard. Must everybody else fall into line? Not me! ---- Reg. I hate to call a liar a liar, but sometimes it's hard to take. You're lying again, Reg. I've never referred to my rig's meter as a calibration standard. I've used it as an example many times of a meter whose response is far from the 6 dB per S unit many people assume. It's my argument that any S-Unit "standard" at all is of no use, except by misleading people into thinking that it has some relation to the markings on their S meters. Mike's measurements serve the same purpose. And you've claimed your rig has an adjustment allowing calibration of its S-meter to 6 dB per unit, but have never been willing to share the type of rig or what the adjustment control designation is. Frankly, I believe you're fabricating that, also. It's sad -- you have a lot to offer, but somehow feel compelled to come up with pure fabrications from time to time. It makes some of us view everything else you say with some skepticism. Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
And you've claimed your rig has an adjustment allowing calibration of its S-meter to 6 dB per unit, but have never been willing to share the type of rig or what the adjustment control designation is. Frankly, I believe you're fabricating that, also. This thread raises a possible marketing opportunity for someone. Yes, it is quite unlikely, due to their non-linear construction, that an analog meter would properly display S units in 6dB increments. So..... someone ought to design a nice little digital unit that could somewhat easily be hooked up to most radio Rx circuits, and be capable of displaying S units or microvolts (selected at push of a button) and also have a fully adjustable means to calibrate the S unit readings so that they would, in fact, display in linear 6dB increments, and actual microvolts at Rx input, too. Probably wouldn't sell cheap, but there would be those hams who'd love to have such a device. I suppose just a display for microvolts would suffice, though, and that isn't hard to do at all. or just calibrate and re-paint the S meter face to match... Ed K7AAT |
Vertical vs Horizontal shootout part one
"Ed" wrote:
I suppose just a display for microvolts would suffice, though, and that isn't hard to do at all. or just calibrate and re-paint the S meter face to match... ________________ Just don't expect that the S-meter so "calibrated" is reading the real value of the incident field arriving at the rx antenna. It won't be, unless that calibration includes (exactly) the real-world performance of the receiving antenna system at each frequency, including line loss, local reflections, and other factors. Otherwise the reading still will be given in fairly meaningless, relative terms -- the same as S-units. RF |
Vertical vs Horizontal shootout part one
Just don't expect that the S-meter so "calibrated" is reading the real value of the incident field arriving at the rx antenna. It won't be, unless that calibration includes (exactly) the real-world performance of the receiving antenna system at each frequency, including line loss, local reflections, and other factors. Otherwise the reading still will be given in fairly meaningless, relative terms -- the same as S-units. The bottom line for the Rx, all it cares about since it doesn't know what kind of antenna is feeding it, is the signal strength at the input.... so I'd say a calibrated microvolt reading reflecting that strength is not very meaningless at all. Any changes in the antenna system will of course change that, but the whole point of any antenna work is to maximize the signal voltage to that rx input, so I'd think a calibrated reading would be extremely useful over an S meter alone. Ed K7AAT |
Vertical vs Horizontal shootout part one
Ed wrote:
The bottom line for the Rx, all it cares about since it doesn't know what kind of antenna is feeding it, is the signal strength at the input.... so I'd say a calibrated microvolt reading reflecting that strength is not very meaningless at all. Any changes in the antenna system will of course change that, but the whole point of any antenna work is to maximize the signal voltage to that rx input, so I'd think a calibrated reading would be extremely useful over an S meter alone. I'm afraid it might require more than simple calibration. The S-meter typically just shows the AGC voltage. The AGC response is only approximately logarithmic, and depends on the gain characteristics of the various stages being controlled. Gain characteristics are commonly very temperature sensitive, so any calibration scheme would have to take that into account, as well as the common deviation from true logarithmic response of the various stages. Calibration would also be different on different bands, with and without preamplifier or attenuators, etc. Of course, you could make a receiver with very nearly true logarithmic response, by use of one of the excellent, wide dynamic range log amps which are available these days. But however much you or I might like one, the vast majority of amateurs couldn't care less about what their S meter is really indicating, so they wouldn't pay the added cost for it. On top of that, most amateurs would consider a 6dB-per-S-unit meter to be "dead", and would rather have it wiggle more. Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
K7ITM wrote:
I fully agree with Roy's comment about the AGC-derived S-meter output. As he says, the AGC characteristics are temperature dependent, and they are also dependent on the particular set of active devices (and to some extent the passives too) in the signal path. If you have access to a spectrum analyzer, chances are decent that it will have a well-calibrated amplitude readout. The one I use is accurate in a relative sense to a fraction of a dB over more than an 80dB range, and would certainly be sensitive enough for antenna comparisons. I suppose both those would be true of most modern spectrum analyzers. In addition, some are quite good at determining the total power in a specified frequency range, and if you can find such a range with no signals, you can get a better reading on noise than you're likely able to do with an S meter, or even a narrow band spectral measurement. One of the most complex and difficult parts of a spectrum analyzer to design is the log amp which provides this stable and precisely logarithmic response over a wide dynamic range. There's an incredible amount of really ingenious work on the part of some extremely talented engineers in those circuits. In relatively recent times, Barrie Gilbert and his folks at Analog Devices have done some equally clever work in the design of IC log amps. It's not a trivial task by any means. Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
Of course, you could make a receiver with very nearly true logarithmic
response, by use of one of the excellent, wide dynamic range log amps which are available these days. But however much you or I might like one, the vast majority of amateurs couldn't care less about what their S meter is really indicating, so they wouldn't pay the added cost for it. On top of that, most amateurs would consider a 6dB-per-S-unit meter to be "dead", and would rather have it wiggle more. Roy Lewallen, W7EL So true, that last part! Well, I certainly understand the non- linearity of the RX when comparing gain accross the entire HF spectrum. I tend to limit my operations to top band and 75, so I hadn't considered changes in Rx gain when moving down the band (or up, as some would have it). Currently, when I do an Rx calibration, I just take some readings on my "S" meter when injecting a signal in the bands of my concern. A "list" of these readings for each band suffices, although I agree with you that that is far more than most hams would bother with. Ed , K7AAT |
Vertical vs Horizontal shootout part one
On Mon, 06 Mar 2006 13:47:04 -0800, Roy Lewallen
wrote: [snip] Of course, you could make a receiver with very nearly true logarithmic response, by use of one of the excellent, wide dynamic range log amps which are available these days. But however much you or I might like one, the vast majority of amateurs couldn't care less about what their S meter is really indicating, so they wouldn't pay the added cost for it. Bill Carver, W7AAZ, designed such a beast. "A High-Performance AGC/IF Subsystem", QST, May 1996. I actually have one of his boards about half constructed... one I started in 1996. Gotta get back to that someday. |
Vertical vs Horizontal shootout part one
"Ed" wrote:
The bottom line for the Rx, all it cares about since it doesn't know what kind of antenna is feeding it, is the signal strength at the input.... so I'd say a calibrated microvolt reading reflecting that strength is not very meaningless at all. ___________ Received signal strength, whether in terms of relative S-units or the measure of real incident fields, is at least as much the result of local conditions as of the ERP of the transmission source on the path toward the receiver, the frequency, and propagation conditions. So the received signal strength indication, whether relative or "real," isn't a hugely significant indicator of any of these parameters. RF |
Vertical vs Horizontal shootout part one
On Mon, 06 Mar 2006 13:47:04 -0800, Roy Lewallen
wrote: Ed wrote: The bottom line for the Rx, all it cares about since it doesn't know what kind of antenna is feeding it, is the signal strength at the input.... so I'd say a calibrated microvolt reading reflecting that strength is not very meaningless at all. Any changes in the antenna system will of course change that, but the whole point of any antenna work is to maximize the signal voltage to that rx input, so I'd think a calibrated reading would be extremely useful over an S meter alone. I'm afraid it might require more than simple calibration. The S-meter typically just shows the AGC voltage. The AGC response is only approximately logarithmic, and depends on the gain characteristics of the various stages being controlled. Gain characteristics are commonly very temperature sensitive, so any calibration scheme would have to take that into account, as well as the common deviation from true logarithmic response of the various stages. Calibration would also be different on different bands, with and without preamplifier or attenuators, etc. Of course, you could make a receiver with very nearly true logarithmic response, by use of one of the excellent, wide dynamic range log amps which are available these days. But however much you or I might like one, the vast majority of amateurs couldn't care less about what their S meter is really indicating, so they wouldn't pay the added cost for it. On top of that, most amateurs would consider a 6dB-per-S-unit meter to be "dead", and would rather have it wiggle more. Roy Lewallen, W7EL Back many years ago, and probably still today, many hams would turn away from a receiver that had what they called a "scotch" S meter. To them a receiver that read S 6 while another receiver only read S 4 on the same signal "had to be much better". Manufacturers started making receivers with more lively S meters. Looking at some of the older receivers such as the Collins had much more realistic S meters than most today. The calibration points that Mike did on his receiver should be valid for any band for his antenna comparisons. An actual signal strength measurement is not required nor would it be valid between bands. All that is really needed is the difference measurements between the two antennas so his calibration between points on the meter scale will be valid on any band. A really nice instrument that would be good for signal strength measurements is an old HP 3586C selective level meter. It covers from around 100 hz to 32 Mhz and has a digital readout to 2 decimal places in dbm signal strength. Hard to use with other than a steady signal though. 73 Gary K4FMX |
Vertical vs Horizontal shootout part one
Gary Schafer wrote:
. . . The calibration points that Mike did on his receiver should be valid for any band for his antenna comparisons. An actual signal strength measurement is not required nor would it be valid between bands. All that is really needed is the difference measurements between the two antennas so his calibration between points on the meter scale will be valid on any band. I'm not sure I fully understand this. The difference from one S meter division to another *is* likely to be different on different bands, since it depends on the gain-vs-voltage characteristics of the controlled stages which can vary with frequency. But I do agree that he can make good comparative antenna measurements without good S meter calibration, because he has a step attenuator. By simply setting the attenuator so he gets the same S-meter reading on both antennas, S-meter calibration is completely irrelevant -- the antenna gain difference is the attenuator setting. I find it useful, however, to be able to see the difference with reasonable accuracy just by looking at my S meter. But that does require calibration for the band in use. . . . Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
Roy, you appear to have mislaid your sense of humor. Hope you recover
it soon. ;o) ---- Reg. |
Vertical vs Horizontal shootout part one
Owen Duffy wrote:
On Sun, 05 Mar 2006 19:29:12 -0500, Mike Coslo wrote: Based on another thread a few weeks back in which Horizontal dipoles were being compared to Vertical antennas, and from a little chiding from Roy, W7EL, I decided to do some testing on my own personal versions of the two. Mike, this sounds interesting. Sorry for the delay getting back on-line... My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Another, are the antennas coupled significantly, eg is one within the near field zone of the other? It is pretty hard to avoid in a residential block on the low bands, and it will confuse the results somewhat. Almost certainly there is some interaction. It isn't a very big yard. Part one of this experiment is to calibrate the S-meter. I found that trying to calibrate the thing with on-air signals was a nuisance, and probably wouldn't be as accurate, so I used a signal generator. I started out with a +20 signal, then worked my way down. +20 start S9 -18 db S8 -23 db S7 -26 db S6 -29 db S5 -32 db S4 -35 db S3 -37 db S2 -39 db S1 -41 db Not only is the shape of the scale an issue, but the granularity or resolution, especially with LCD meters, or any meter where there are discrete steps in the meter current (such as where a D/A converter drives the meter movement). If you want to move beyond S meters, you could try FSM (www.vk1od.net/fsm) and organise some constant carriers at known distances / radiation angles that you could make a series of measurements of and produce summary statistics (median and inter quartile range) for each antenna type. All in all, I would have to say that the meter tracks very well from S8 to S4, and the only place that wasn't that great was from S9 to S8. But considering the transient nature of the signals we are receiving, I would have to day that the S-meter is of reasonably close accuracy. With my newly calibrated S-meter I am ready to start looking at what the two different antennas are doing for me. I have a coaxial switch to jump back and forth between the two. My initial impressions are that there are some surprises. The difference in noise levels varies by antenna by band. On some bands the vertical is noisier, and on others it is the OCF dipole. Especially intriguing is that on PSK mode, where I can see several signals at one time, switching between antennas will attenuate some signals, while other signals increase in strength. I think that my vertical works better than I gave it credit for, but If I definitely want *both* antennas. I described a technique for assessing the relative performance of mobile stations by having them transmit known constant carrier, each station space about 200Hz and turning circles in a carpark near each other, and to observe them at typical propagation distances with an audio spectrum analyser, watching the relative strength of the carriers. Your PSK setup is affording you the same type of comparison, and provides a ready (and recordable) assessment of the relative strength of the stations under the two antenna scenarios. Be great if you could orchestrate stations at known distances as part of an organised test. I'll probably be doing the next best thing, which is to do a lookup of the various callsigns as I see them. The more I see of waterfall displays, the more I like them. I would love to see one as standard on an HF rig. - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
Reg Edwards wrote:
Roy says, People who blindly assume the marks on their S-meters are 6 dB apart should take a good look at your calibration results. ======================================= The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do with which antenna produces the stronger received signal. It is purely a comparison. Just use the same meter throughout the tests. It does allow me to make a stab at comparing those two antennas. As I continue on this test, it would be nice to have something that has some sort of calibration. Otherwise we might as well just go to say "works great" or "doesn't work well for all measurements. - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
Roy Lewallen wrote:
K7ITM wrote: I fully agree with Roy's comment about the AGC-derived S-meter output. As he says, the AGC characteristics are temperature dependent, and they are also dependent on the particular set of active devices (and to some extent the passives too) in the signal path. If you have access to a spectrum analyzer, chances are decent that it will have a well-calibrated amplitude readout. The one I use is accurate in a relative sense to a fraction of a dB over more than an 80dB range, and would certainly be sensitive enough for antenna comparisons. I suppose both those would be true of most modern spectrum analyzers. In addition, some are quite good at determining the total power in a specified frequency range, and if you can find such a range with no signals, you can get a better reading on noise than you're likely able to do with an S meter, or even a narrow band spectral measurement. One of the most complex and difficult parts of a spectrum analyzer to design is the log amp which provides this stable and precisely logarithmic response over a wide dynamic range. There's an incredible amount of really ingenious work on the part of some extremely talented engineers in those circuits. In relatively recent times, Barrie Gilbert and his folks at Analog Devices have done some equally clever work in the design of IC log amps. It's not a trivial task by any means. And in this case, it really isn't necessary. I simply need some baseline to start my readings from. Already I have noticed that different stations come in at different strengths - presumably on the basis of propagation differences. There may be some differences over time scales of minutes also. All I need is a meter that allows me to derive a signal strength difference from two different antennas. There was a need to calibrate that. Of course, I would *love* to have a decent analyzer!! - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo
wrote: .... My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Mike, I understand that feedline radiation is an un-escapable characteristic of an OCF dipole, caused by the asymmetric feed. Some even claim it as a major advantage (eg Caroline Windom). Whilst no dipole is perfect in that respect, the OCF dipole is less perfect, and it may be worth modelling the thing to comment in your findings on the probably magnitude of the contribution by the feedline. Great project, look forward to follow-ups. Owen -- |
Vertical vs Horizontal shootout part one
On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo
wrote: Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Hi Mike, Not all 4:1 BalUns exhibit enough (or sometimes any) common mode Z. 73's Richard Clark, KB7QHC |
Vertical vs Horizontal shootout part one
Hmmm... Gee, I could connect a spectrum analyzer channel to each of
two different antennas and get a continuous real-time comparison of the signals and noise them. Cheers, Tom |
Vertical vs Horizontal shootout part one
Richard Clark wrote:
On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo wrote: Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Hi Mike, Not all 4:1 BalUns exhibit enough (or sometimes any) common mode Z. Okay. Perhaps I might better characterize my experiment as a comparison of a vertical and an OCF dipole of indeterminate vertical vs horizontal performance. I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". In that case you would feed the antenna with balanced line. Certainly the antenna doesn't seem to be radiating RF from anywhere but the antenna bits. p.s. forgive the spelling, I am using a beta of Thunderbird for my newsgroups, and it seems to have a few quirks that make it hard to see what I have written!! - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
On Wed, 08 Mar 2006 09:47:18 -0500, Michael Coslo
wrote: I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". It is pretty well known that an OCFD is a bear when it comes to common mode current on the feedline. Usally requiring more than one common mode choke to tame the sucker. Danny, K6MHE |
Vertical vs Horizontal shootout part one
On Wed, 08 Mar 2006 09:47:18 -0500, Michael Coslo
wrote: I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". Hi Mike, This is not outside the realm of possibility. Whose antenna is it? 73's Richard Clark, KB7QHC |
Vertical vs Horizontal shootout part one
Michael Coslo wrote:
Okay. Perhaps I might better characterize my experiment as a comparison of a vertical and an OCF dipole of indeterminate vertical vs horizontal performance. I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". Unfortunately, even if the designers don't intend the feedline to radiate, it's very difficult to avoid. A single balun at the feedpoint is very likely not enough to prevent it. In that case you would feed the antenna with balanced line. That would make no difference at all in determining whether or not the line would radiate. Certainly the antenna doesn't seem to be radiating RF from anywhere but the antenna bits. The amount of feedline common mode current and therefore radiation will vary from band to band, probably a great deal. It's easy enough to make up a simple current probe with a clamp-on core and make quantitative measurements if you're interested. They've been described on this newsgroup several times. Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
Radiation from feedlines is grossly exaggerated.
For many purposes, practically it does not occur. When discussing the importance of such radiation one should always crudely estimate its level relative to transmitter or radiated power. If you don't know what its level is then you don't know what you are waffling about. ---- Reg. |
Vertical vs Horizontal shootout part one
On Wed, 8 Mar 2006 21:55:42 +0000 (UTC), "Reg Edwards"
wrote: If you don't know what its level is then you don't know what you are waffling about. Hi Reggie, Seeing you lack any quantifiables, are you offering belgian waffles? 73's Richard Clark, KB7QHC |
Vertical vs Horizontal shootout part one
On Wed, 08 Mar 2006 13:58:19 -0800, Richard Clark
wrote: On Wed, 8 Mar 2006 21:55:42 +0000 (UTC), "Reg Edwards" wrote: If you don't know what its level is then you don't know what you are waffling about. Hi Reggie, Seeing you lack any quantifiables, are you offering belgian waffles? 73's Richard Clark, KB7QHC Richard, Just anouther one of Reg's factoids (e pluribus unum). Danny |
Vertical vs Horizontal shootout part one
Richard Clark wrote:
On Wed, 08 Mar 2006 09:47:18 -0500, Michael Coslo wrote: I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". Hi Mike, This is not outside the realm of possibility. Whose antenna is it? It's a homebrew antenna. I'm operating from memory here.... Total length is around 134 feet Short end is around 26 feet. - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
Reg Edwards wrote:
Radiation from feedlines is grossly exaggerated. Hi Reg, I can't see who you are replying to - a line of quote would be wunnerful. 8^) For many purposes, practically it does not occur. When discussing the importance of such radiation one should always crudely estimate its level relative to transmitter or radiated power. Is there any way of doing that? Guessing? I've looked around a bit, and mostly seen "Yes it does", or "no it doesn't". I suppose I could make a current probe,(too) but can see this exercise edging toward me buying some large tract of land somewhere and putting up an antenna range! ;^) If you don't know what its level is then you don't know what you are waffling about. - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
"Mike Coslo" wrote Reg Edwards wrote: Radiation from feedlines is grossly exaggerated. Hi Reg, I can't see who you are replying to - a line of quote would be wunnerful. 8^) ========================================= I'm not replying to anyone in particular. Just to anybody who discusses power radiated from feedlines. ========================================= For many purposes, practically it does not occur. When discussing the importance of such radiation one should always crudely estimate its level relative to transmitter or radiated power. Is there any way of doing that? ========================================== Mike, you'd better ask that from people who discuss power radiated from feedlines. They ought to know! ---- Reg. |
Vertical vs Horizontal shootout part one
Danny,
Since I am not fluent in Latin, could you please tell me what is a "Factoid"? ---- Reg. |
Vertical vs Horizontal shootout part one
Reg Edwards wrote:
Danny, Since I am not fluent in Latin, could you please tell me what is a "Factoid"? Danny should be able to translate that. He lives at the coast, where they get lots of touroids from points inland. Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
On Thu, 9 Mar 2006 10:15:23 +0000 (UTC), "Reg Edwards"
wrote: Danny, Since I am not fluent in Latin, could you please tell me what is a "Factoid"? ---- Reg. How about English? Surely your English dictionary has it listed? http://encarta.msn.com/dictionary_/factoid.html\\ (definition #1) "e pluribus unum" at one time was our national motto and still appears on our coins. http://en.wikipedia.org/wiki/E_pluribus_unum Danny |
Vertical vs Horizontal shootout part one
"Dan Richardson adelphia net" k6mheatdot wrote in message ... On Thu, 9 Mar 2006 10:15:23 +0000 (UTC), "Reg Edwards" wrote: Danny, Since I am not fluent in Latin, could you please tell me what is a "Factoid"? ---- Reg. How about English? Surely your English dictionary has it listed? http://encarta.msn.com/dictionary_/factoid.html\\ (definition #1) ========================================= It's not in MY dictionary. I have the Concise Oxford English Dictionary, 1951 edition. But you've got it wrong. "Factoid" doesn't apply to me anyway. ---- Reg. |
Vertical vs Horizontal shootout part one
On Thu, 9 Mar 2006 13:50:07 +0000 (UTC), "Reg Edwards"
wrote: It's not in MY dictionary. I have the Concise Oxford English Dictionary, 1951 edition. From the Oxford English Dictionary: http://www.askoxford.com/results/?vi...r=score%2Cname Danny |
Vertical vs Horizontal shootout part one
FACTOID:
"A small granule of truth." A factoid is to insight, as a small hard turd is to a bowel movement. Bob Brunius, AC7PN Dan Richardson wrote: On Wed, 08 Mar 2006 13:58:19 -0800, Richard Clark wrote: On Wed, 8 Mar 2006 21:55:42 +0000 (UTC), "Reg Edwards" wrote: If you don't know what its level is then you don't know what you are waffling about. Hi Reggie, Seeing you lack any quantifiables, are you offering belgian waffles? 73's Richard Clark, KB7QHC Richard, Just anouther one of Reg's factoids (e pluribus unum). Danny |
Vertical vs Horizontal shootout part 1.5
Okay, all. I rand a multi-band check on my s-meter. The results a (with the previous 80 meter test included. 80 meter +20 start S9 -18 db S8 -23 db S7 -26 db S6 -29 db S5 -32 db S4 -35 db S3 -37 db S2 -39 db S1 -41 db 40 meter +20 start S9 -18 db S8 -22 db S7 -25 db S6 -28 db S5 -31 db S4 -34 db S3 -36.5 db S2 -38.5 db S1 -41 db 30 meter +20 start S9 -19 db S8 -23 db S7 -27 db S6 -31 db S5 -34 db S4 -36 db S3 -39 db S2 -41 db S1 -43 db 20 meter +20 start S9 -19 db S8 -22 db S7 -26 db S6 -30 db S5 -34 db S3 -38 db S2 -41 db S1 -50 db There is no doubt that the readings are different, and significantly in some cases. I will give a calibration of the meter for each band that I do. Lesson learned here is that the meter should be calibrated to do this test, IMO. Yes, it is true that on any given band the readings are going to be relative to each other. But it is inevitable that questions will arise about the relative efficiency of my antennas by band, as both are multi-band antennas. Part 2 to follow soon....... -73 de Mike KB3EIA - |
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