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Marconi testing the Sigma4 vs. Gain Master
- Thread starter Marconi
- Start date
I'm just having fun. I didn't say anyone was making fun of anyone, just the bigger part of the fun was the challenges. I didn't realize Mack was genuinely miffed. Sorry, Mack. I'm harmless.
I am learning, too. And am just as interested in the truth.
I would ask a question in the interest of clarifying a thought in my head, "Why would FM not be better than AM?". It would seem on the surface of things that given AM is subject to signal fluctuation due to modulation, and given FM is not so influenced, the deduction that FM is better for testing signals seems logical. I see some merit to the idea of FM being a superior mode for testing. Why not?
I am not the scientist many of you are. I am an empiricist. My lack of knowledge is complimented and assisted by what you guys say, and do. I just see if i can duplicate what others have done. If it has been done, perhaps I can repeat it. If I fail, then why is that so. I learn with my hands on something best. For me the proof of what others have said is in whether I can duplicate it. The proof of the pudding is in replicable results.
Perhaps we can add to the list of things we've learned:
No two people express the same thing the same way.
I am learning, too. And am just as interested in the truth.
I would ask a question in the interest of clarifying a thought in my head, "Why would FM not be better than AM?". It would seem on the surface of things that given AM is subject to signal fluctuation due to modulation, and given FM is not so influenced, the deduction that FM is better for testing signals seems logical. I see some merit to the idea of FM being a superior mode for testing. Why not?
I am not the scientist many of you are. I am an empiricist. My lack of knowledge is complimented and assisted by what you guys say, and do. I just see if i can duplicate what others have done. If it has been done, perhaps I can repeat it. If I fail, then why is that so. I learn with my hands on something best. For me the proof of what others have said is in whether I can duplicate it. The proof of the pudding is in replicable results.
Perhaps we can add to the list of things we've learned:
No two people express the same thing the same way.
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The AM stations in my area are little 500 watt pip squeaks that run 1 KW daytime. Closest one is about 4 miles away. The strongest SW broadcast station I've been able to locate is over 600 miles away in North Carolina on the 39 meter band that has no propagation to me during the day. Needless to say neither one is making past the front end of my receiver (quad conversion IF with band pass filters on the front end).
My antenna is about 40 feet AGL and his is about 60 feet AGL, both 5/8 waves. This path should have a radio horizon of at least 90 miles considering the terrain before antenna elevation. He's also not the only distant station I've seen this with. I've seen it in other directions not over water and at my old QTH.
I've tried to envision the rapid fluctuations as perhaps an airplane traveling several hundred miles per hour. Then the real slow fluctuations as the barges I see being pulled through the local shipping lanes at like 15 MPH. I still find holes in my theory. From what I know about radar, moving objects reflecting RF should demonstrate certain characteristics.
There seems to be nothing consistent with these fluctuations. I can't identify them as increasing in frequency and then slowing down. It can do this and speed right back up again as though another reflection was right in the same path. Some days it's there and others I don't see it at all. I never hear phase distortion between the carrier and sidebands as with selective fade or what I'm familiar with as multipath distortion in FM stereo (although that could be the result of the narrower bandwidth here).
It almost resembles the effect of having the polarization shift. I say this because I've seen very similar characteristics when receiving a distant horizontal station while using the vertical mode. The only thing I see that is consistent, is I never see the effect closer then about 30 miles. We could have 10 guys on frequency and only the most distant or cross polarized gets it. I've seen it on every band above 15 meters so far and never below.
I think you also mentioned movement of the antennas in wind. While that's not what is going on in my case (happens on dead calm days too) this can be pronounced in any longer colinear antenna. Learned this working at the Marinas as a kid with the VHF equipment. Many of the commercial vessels would get two antennas. Partially for redundancy and the other reason was sea conditions.
Get offshore 30 miles or more in rough seas and you can't even copy the weather channel on the main 16 foot colinear. The pitch of the antenna as you roll through the waves kills the signal in the axis of the pitch. Flip over to the 17 inch 1/4 wave and the station is 100% copy. Sure the peak signal never reaches that of the 16 footer but the 1/4 wave never drops out in the pitch.
Almost the same thing happens with the Sigma design. Pitch this antenna over on an angle approximately 10 degrees and you're already down 3db in the axis of the lean on the distant horizon (not noticed locally). It's all about the compressed beamwidth of the primary lobe required to give the vertical gain. Funny when you think about how many of these antennas we see installed with the permanent lean to them. With respect to Groton, only thing I think I hear coming from them is well under AM BC.
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I would agree with all of this except:
#3 has not yet proven true at my QTH (in the Spring I will start all over again with the 5/8ƛ and V4k) and
#6 has only been driven as an idea hard enough to silence the opposing point of view, IMO, but in some cases completely ignores the intent in the design of some antennas.
I know that it is dangerously unpopular to think that out loud, but it doesn't change anything. Arguing that it skewers the results in favor of one antenna over the other to raise the height of the shorter antenna to equal upper elevation ignores the fact that not raising the shorter antenna up skewers the results in favor of the longer antenna.
If I buy a compact car to enable myself to get better fuel mileage and to be able to find more accommodating parking it is just unrealistic to not drive the car unless it consumes fuel at the same rate as an 18 wheeler, or to refuse to park it in a smaller space simply because a larger car can't fit in the space as well. The inherent design advantages of the compact car are the reason for its production.
The Astroplane was designed and manufactured for the very purpose of raising it to the maximum legal height with less bulk and weight to contend with. I realize it is virtually impossible to get that idea to register with today's radio enthusiast who will mount his/her antenna at the maximum height they can afford to purchase; we are in the era of bigger wattage, bigger antenna, bigger tower. . . A case in point of this fact is the disappointment many have expressed in the GainMaster because of it's limited power handling. There was an era that would have embraced the GM happily as a breakthrough and gladly mounted it in rivalry to any other 5/8ƛ antenna of the time. Superior performance of a 5/8ƛ antenna without radials and offsets the disadvantaged noisiness/flimsiness of fiberglass and provides additional gain is what is supposed to be the reason for the GM. Some testing so far indicates the GM suffers at lower heights due to more severe coupling to nearby objects including the earth. So, the advantage of no radials which serve to decouple the antenna from the earth are lost to the GM at a lower height. So now we are expected to ignore the characteristics of the GM that make it work? No, not in my opinion. We will raise it up to its optimum operating height, and use it within its power limits. That's how it was designed.
I realize that it has been said, and I quote, "What could be more simple than that?", with respect to the argument to put every antenna tested at the exact same lower elevation, or mounting point height. This statement implies the ignorance of those who disagree. So be it. I realize no one means any harm, yet, I'm really too old to be bothered by such implications, except where the whole truth is concerned.
In explanation of my point, I venture to another scenario where the same height argument is inconsistent with realizing the design potential of antenna types. Enter the Yagi vs Quad beam advantages/disadvantages debate. At lower elevations the Quad has been observed to have better TOA than the YAgi. And with fewer elements the Quad is believed to show more gain. However, the Quad falls behind the Yagi in terms of potential maintenance issues due to its shape, higher wind loading, and poorer performance in severely inclement weather. It breaks easier. The Yagi no longer trails the Quad once certain elevations above ground are reached, TOA is no longer an advantage of the Quad, and after a given number of elements the argument for more gain to the Quad losses its impetus. Now the real design beauty of the Yagi comes into play. It is lighter, offers less wind loading, endures ice and snow more readily, suffers less maintenance requirements, more readily permits a vertical to be mounted above it. At greater height the Yagi comes into its own.
Choosing a small beam because of elevation restrictions I choose a 2 element Quad. Without the height and turn radius restrictions I choose a Yagi.
They are not the same in more ways than one, and trying to force either of them into the same mold is a rather quaint idea that lacks consideration for the inherent design features of the antennas being compared. The similarities end with their directionality. Truthful comparisons of the two antenna designs requires their differences, and the advantages/disadvantages of those differences be compared against each other.
The truth is this, when the AP is mounted at the same feedpoint as the 5/8ƛ, the 5/8 is superior. When the AP is raised to within 1.5' of the tip height of the 5/8ƛ the AP trounces the 5/8 in my mountainous topography. When the 5/8ƛ is mounted as low as 10' above the earth, it performs so far below that of the V4k at that height that there is no comparison. When both the V4k and the 5/8ƛ are set as high as 35' to feedpoint there has been no perceivable performance advantage in evidence so far in my part of the country for either one.
#6 is the broader consensus of those who speak the loudest, but is only another theory, and the jury is still out on that one in NW Arkansas.
Verticals are the same because they are vertical. But between designs they are innumerably different.
There rests my unpopular logic. I want the truth of things, too. I believe to get to the truth does not require ignoring the parameters of design, and the options built into those designs. There is legitimacy to testing and comparing every antenna against the other where the one has the home town advantage, but that is not the whole story of either of those antennas. Awaiting the whole truth while awaiting a better argument.
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"and audio was about double the other antenna." Love to hear the physics explanation to this phenomenon. The photo of the two vertical radiators appear close enough to create parasitic interaction. That's one too many variables to accurately ascertain the real performance parameters of these antennas. So, another manufacturer trying to make a living and employ people, might be unduly ridiculed over bad science. Al Gore would be proud.
With Regards to #3
This is a basic common fact whether on cb band or any other band, A 1/4 wave Ground plane can show same gain in close, when compared to a 1/2 wave or 5/8 wave when testing in close. Your results will change as you start taking advantage of the lower angle of radiation this is where a properly fed 5/8 should have an advantage no matter what brand antenna it is.
#6 You are trying to take away the intent of the design of the longer antenna , I dont know how else to tell you but people can argue all they want, when testing antennas feed point has to be the same, again this has nothing to do with trying to favor any antenna.
It is common practice with testing any antenna whether it is a model or out in field. I dont know how else to explain it but your theory about making the tips the same is not how antennas are tested. I ask you to find anywhere other than a cb forum where these types of test are conducted like that .
For some reason you/other want to take away the design advantage of a longer antenna. Thats why a longer antenna will work better, because it is longer trying to raise antennas up to somehow equal them out is ludicrous. If that how you wanna test antennas you most certainly can but dont expect your results to mean much.
That is like putting stilts on a 6' basketball player so he is as tall as Shaq to make it more fair. It just dont work that way.
I know this analogy has already been made but it hasnt sunk in a mobile coil antenna doesnt work as good as a full lenght 1/4 wave, why? because it is shorter. Do you somehow try to mount the coil anternna higher to make it work as good as the 102" whip? I ask again please show a credible antenna test that raises antennas tip to tip and Ill eat my hat.
Wideband FM would be interesting. An experienced person would be able to see multipath instantly with a spectral display.
Narrowband FM has a poorer signal to noise ratio with weak signals than AM. AM will allow testing of weaker signals than FM. If weak isn't what is needed it probably makes little difference if the bandwidth is similar. Slimeband would allow testing of even weaker signals but the guess meter would be responding to R.F. output duty cycle.
Airplane flutter is very commonplace on 27 MHz when using horizontal pol. Vertical I'm not so sure aout.
For starters you dont do any antenna test with modulation thats what make Am and FM the same. Ever try to do a weak signal test with FM? It's not the point of people being scientist it is about those that have thousands of hours testing antennas the correct way with repeatable results. Whether you do the test or I or Marconi.
Shockwave said this perhaps his opinion makes it more true than me saying it.
"Any stable carrier in the distance (not your signal generator placed to where you get a weak signal) is ideal to compare antennas against. Could be AM, CW, FM, or a few others as long as no modulation or power fluctuation takes place."
Thanks, MrSurburban, for your patience in explaining things.
I get the FM, AM, CW, thing without modulation. That makes a lot of sense.
I understand everyone's position on #3. I have one of those situations where I am up against the lay of the land. With the Ozarks all around me I am working with a situation where compared to Marconi's flat land close in 40 mile stations are my distance stations, and given that limitation, I haven't been able to prove the advantage of the V4k, nor the 5/8. I did say I can not cash in on the problem with #3 until I go back through my antennas, make sure they're perfect, and start my testing again. I've had this #3 discussion with a neighbor with decades of Amateur, and CB experience, building and buying his own antennas, and he admits to the difficulty in getting good distant contacts from our location. My back fence abuts his backyard. Our antennas towers may be about one hundred feet apart. He is much higher than I am.
As for #6, I have no difficulty understanding the testing of antennas at the same mounting height. My difficulty is with the notion that utilizing the design features of a shorter antenna to the advantages it was designed for is somehow less right than utilizing the design features of a longer antenna. To argue for allowing the length, a feature of design, of a 3/4 or 5/8 antenna to play a part in the testing, but deny the purposeful design features of the Astroplane re its size to weight ratio to be taken advantage of is a bit self-contradictory. The size, shape, and weight of the AP is no accident. It was designed that way so it could compete with longer antennas because it is easier to raise to maximum legal height. Let's see if this is true or not. That's the true test of the AP. I suppose it is not ludicrous to stuff the shorter player into a barrel and expect him to compete against Shaq? Let both players stand on their own feet and compete.
I am about to venture into less familiar territory here:
I do not believe there is a height advantage in free space modeling. This is represented by the theoretical isotropic dipole. No up, down, over, under, only around. There is a length difference. However, if in modeling one introduces the the presence of earth, things do change. When Avanti made the Astroplane they modeled it for best performance at maximum height - the legal 60' at the top. This they modeled against the 5/8 antennas also set to 60' top height. This is understood due to the way it was presented, and marketed. I do not find the argument against raising such an antenna to it's designed potential to be valid when making comparisons to each other. The argument for keeping the height of the mast unchanged becomes even more incredulous when one considers the feedpoint of the Astroplane is a mere 4' from its top. We now find ourselves needing to argue about the electrical equivalents of the feed point in order to decide the Astroplane is actually being fed from nine feet below the ring and other ingenious ideas. We get into what length mast is proper for the antenna, and soon we have discovered our feedpoint argument more cluttered with theories than irrefutable realities. Our Astroplane is now 21' long, which means we should get to set it up to the same top height as the 5/8 wave. Okay, I am reaching . . . but am I? I've read every one of these things on this forum. Although very interesting, it can get exhausting. Let me add that I am not faulting any of these ideas, rather, I am utilizing them to make a point.
The example of the mobile antenna is less than perfect given the same antenna is not at the same advantage from automobile to automobile. My 102" whip may suffer disadvantages when mounted on a motorcycle while a no GP type mobile does better. It is sometimes a matter of advantages in design for a given application. Even the 102" SS whip fails in performance in some marine applications when mounted at the same height as the no GP marine antennas. Fiberglass bodied automobiles do not take advantage of the height of the 102" whip. Design must be considered when utilizing antennas. One may say there are exceptions to the rules of thumb. That is exactly what I am saying. Design Matters.
Multiple references to TOA as a influence upon antenna performance, as in near field, far field, close contacts, distant contacts, in my opinion also belies the notion of every antenna must be measured at only one mast height (never mind that the example of Yagi vs Quad being passed over). TOA, which does have an immediate bearing on on the ability of antennas to be better close in or far out, has been demonstrated to be influenced by height above the earth. There is a limit to how much height continues to improve TOA for given designs, as in 1/4ƛ, 1/2ƛ, 5/8ƛ on up to 3/4ƛ, which has demonstrated poorer TOA than others until someone discovered the Sigma/Avanti DESIGN which plays into it's abrogation of the rules. Now we have an antenna which when utilizing its design features competes with antennas where before a 3/4ƛ and 7/8ƛ could not.
It is not meaningless to compare the merits of antenna designs when those designs require differing installation parameters to reach their potentials. That is what is ludicrous. It's done all the time, ergo, the Quad v Yagi comparisons, and the Beam v Omni comparisons. It doesn't change the truth. It embraces the truth. Different antennas can compete with each other under differing installation requirements. In fact, some are designed to do so.
Test and compare antennas every way. There is validity.
My point has never been to say it is wrong to compare on the same mast (just a little reading back over the forum threads will show I have advocated for putting each antenna on the same mast, coax, and rig for adequate testing). My point has been that to get to a full review of every antenna requires that all the parameters of their designs be explored, expressed, and compared. We are required to tell the whole truth, and nothing but the whole truth.
Of course, there is the big fellow who tells me he can whip me with both of my hands tied behind my back.
Respectfully,
Homer/Charles
I get the FM, AM, CW, thing without modulation. That makes a lot of sense.
I understand everyone's position on #3. I have one of those situations where I am up against the lay of the land. With the Ozarks all around me I am working with a situation where compared to Marconi's flat land close in 40 mile stations are my distance stations, and given that limitation, I haven't been able to prove the advantage of the V4k, nor the 5/8. I did say I can not cash in on the problem with #3 until I go back through my antennas, make sure they're perfect, and start my testing again. I've had this #3 discussion with a neighbor with decades of Amateur, and CB experience, building and buying his own antennas, and he admits to the difficulty in getting good distant contacts from our location. My back fence abuts his backyard. Our antennas towers may be about one hundred feet apart. He is much higher than I am.
As for #6, I have no difficulty understanding the testing of antennas at the same mounting height. My difficulty is with the notion that utilizing the design features of a shorter antenna to the advantages it was designed for is somehow less right than utilizing the design features of a longer antenna. To argue for allowing the length, a feature of design, of a 3/4 or 5/8 antenna to play a part in the testing, but deny the purposeful design features of the Astroplane re its size to weight ratio to be taken advantage of is a bit self-contradictory. The size, shape, and weight of the AP is no accident. It was designed that way so it could compete with longer antennas because it is easier to raise to maximum legal height. Let's see if this is true or not. That's the true test of the AP. I suppose it is not ludicrous to stuff the shorter player into a barrel and expect him to compete against Shaq? Let both players stand on their own feet and compete.
I am about to venture into less familiar territory here:
I do not believe there is a height advantage in free space modeling. This is represented by the theoretical isotropic dipole. No up, down, over, under, only around. There is a length difference. However, if in modeling one introduces the the presence of earth, things do change. When Avanti made the Astroplane they modeled it for best performance at maximum height - the legal 60' at the top. This they modeled against the 5/8 antennas also set to 60' top height. This is understood due to the way it was presented, and marketed. I do not find the argument against raising such an antenna to it's designed potential to be valid when making comparisons to each other. The argument for keeping the height of the mast unchanged becomes even more incredulous when one considers the feedpoint of the Astroplane is a mere 4' from its top. We now find ourselves needing to argue about the electrical equivalents of the feed point in order to decide the Astroplane is actually being fed from nine feet below the ring and other ingenious ideas. We get into what length mast is proper for the antenna, and soon we have discovered our feedpoint argument more cluttered with theories than irrefutable realities. Our Astroplane is now 21' long, which means we should get to set it up to the same top height as the 5/8 wave. Okay, I am reaching . . . but am I? I've read every one of these things on this forum. Although very interesting, it can get exhausting. Let me add that I am not faulting any of these ideas, rather, I am utilizing them to make a point.
The example of the mobile antenna is less than perfect given the same antenna is not at the same advantage from automobile to automobile. My 102" whip may suffer disadvantages when mounted on a motorcycle while a no GP type mobile does better. It is sometimes a matter of advantages in design for a given application. Even the 102" SS whip fails in performance in some marine applications when mounted at the same height as the no GP marine antennas. Fiberglass bodied automobiles do not take advantage of the height of the 102" whip. Design must be considered when utilizing antennas. One may say there are exceptions to the rules of thumb. That is exactly what I am saying. Design Matters.
Multiple references to TOA as a influence upon antenna performance, as in near field, far field, close contacts, distant contacts, in my opinion also belies the notion of every antenna must be measured at only one mast height (never mind that the example of Yagi vs Quad being passed over). TOA, which does have an immediate bearing on on the ability of antennas to be better close in or far out, has been demonstrated to be influenced by height above the earth. There is a limit to how much height continues to improve TOA for given designs, as in 1/4ƛ, 1/2ƛ, 5/8ƛ on up to 3/4ƛ, which has demonstrated poorer TOA than others until someone discovered the Sigma/Avanti DESIGN which plays into it's abrogation of the rules. Now we have an antenna which when utilizing its design features competes with antennas where before a 3/4ƛ and 7/8ƛ could not.
It is not meaningless to compare the merits of antenna designs when those designs require differing installation parameters to reach their potentials. That is what is ludicrous. It's done all the time, ergo, the Quad v Yagi comparisons, and the Beam v Omni comparisons. It doesn't change the truth. It embraces the truth. Different antennas can compete with each other under differing installation requirements. In fact, some are designed to do so.
Test and compare antennas every way. There is validity.
My point has never been to say it is wrong to compare on the same mast (just a little reading back over the forum threads will show I have advocated for putting each antenna on the same mast, coax, and rig for adequate testing). My point has been that to get to a full review of every antenna requires that all the parameters of their designs be explored, expressed, and compared. We are required to tell the whole truth, and nothing but the whole truth.
Of course, there is the big fellow who tells me he can whip me with both of my hands tied behind my back.
Respectfully,
Homer/Charles
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Hopefully I've not made a mistake and posted some signals in db's. All of my reports should have shown signals in Sunits only, unless a signal was over S9.
I do have some limited understanding of the complicated issue regarding the conversion of Sunits into db's, but I don't presume there is a standard as you note above, so I avoid relating my results in those terms and I don't have sophisticated test equipment. My radios also do not display signals in db's, except for signals over S9, and I typically don't see signals over S9. Most of the guys on my list of regular contacts are out of Houston, the notations for such are listed along with the guys names or handles.
You suggest I should do something to make my efforts count and provide more meaningful data. I've explained before that my reports are purely random, and I report what happens during the period of testing. Sometimes the report covers a few moments when conditions are right and enough guys are on the air talking. Sometimes the data may come from reports over several days and sometimes I update the numbers if I see a difference later in time. Sometimes I miss good opportunities and sometimes I make mistakes.
It may surprise you, but I don't consider this to be scientific. If you or some of the guys you refer too, having spent 1000's of hours doing antenna range testing, then why are we wasting our time and space on this forum, looking at my idea of testing? Bring on the work of the pro's. I doubt I'll understand the results, because I have looked at some of that work and it is very complicated without being very descriptive of what is going on. Most of the work looks to be produced for people that fully understand the science. So, we'll look to you to (splain') it all to us pilgrims...if and when you get some time.
MrS, all I see from you is words. If you posted some of your results, maybe I might be persuaded to agree with more of your ideas and suggestions. Maybe you are locked in due to the weather as many are, but surely you have some field notes, Signal Reports, Bandwidth Curves, modeling files/output from modeling, antenna reports noting tuning iterations. Anything that will help us get better informed and up to speed. I do test, albeit not perfect...and I do try to provide something for the guys to look at, study, consider, argue and analyze if interested. I don't dummy stuff up trying to make some meaningful stuff that will satisfy everyone. I record what I see, I recap when possible, and I post the results, hoping to be clear and understandable in the process. When I hear constructive criticism I try to fix my thinking and my stuff and I'm constantly on the look out for that one response that might get a point across.
I have a thought for another thread, concerning an issue that came up in several posts by others. It has to do with my antennas being close together and when testing side-by-side having some ill-affect on results. I have even stated that I might agree that my antennas might be too close and affect each other somehow. I have tried to test in all configurations possible to see if the results showed anything obvious, but nothing has been noticed by me as yet. I admit however, that I've not yet added my captions and comments to my Signal Reports where I sit and analyze the results as best I can and then put my thoughts to pen.
The question I ask is simple: how can we tell or measure this affect if it happens that two antenna close can/will react to one another in a way that will obviously make any comparisons invalid? Would it affect the match so as we could tell?
I have already taken Signal Reports for most antennas from both mounts, and I did most side-by-side, and then alone on the two mounts. I didn't organize the effort very well, so it might turn out that I missed one or two. I have already done what I think is simple to do, that may or should give some indication for this reaction, but I'll wait a while before posting my report and see what ideas this question generates.
BTW, I'll try any reasonable suggestion if I'm able.
Ya'll have also complained about me changing heights of the antennas, but I only did that with the AstroPlane type antenna, and I am about to do that again with the New Top One, so I'll have several test for this relatively new antenna which also has a 4' foot tall radiator and is at a disadvantage in testing. I agree with Homer's point of view on this one even though the idea may be impractical for most CB operators. The information is simply to help provide an option with using a smaller antenna that performs very nicely and to give some review and opinion time to Sirio's New Top One antenna.
I haven't completed my work with the Sigma4 up by itself yet, but while it is up that will be a good test for the question above. I also think the Sigma4 deserves more comparisons, because I lost three of the guys I use for signals earlier, and I see how just one contact missing can make a Signal Report look skewed when trying to compare different reports. This is not to say the reports are arguably meaningful or meaningless, but there are differences to be noted in recapping.
MrS, the question again is: how can we tell or measure this affect if it happens that two antenna close can/will react to one another in a way that will obviously make any comparisons invalid? Would it affect the match so as we could tell?
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Hello Guys,
It is already a known fact that if antennas are too close to each other they will have influence. This is not always measurable with a SWR meter.
The "rules' for antenna measuring is you put several wavelengths between them.
Yes, i know that is "a wide figure" but 2..3 WL is known as sufficient.
The reason for that is that within the near field of a antenna the radiation pattern is building up. Now the guru's have got different opinions of what is happening within that near field. Im not speaking about guys like us, but the pro's.
Any measurement within that near field is also "useless" as neither the true radiation pattern has buildt up and we dont know what is happening.
Secondly, please dont forget about "ground reflections"
The receiving antenna should be say 10 to 20 wl away.
There should be a additional antenna in between to pick up those ground reflections.
The sugestion (on that other thread) about using one mast to test the antenna isnt good as you still have a variable wich is time (especially with disctance station).
(ofcourse all the futher normal things in regards to heigth coax length etc.)
The thing i dont know: why everyone keeps debating about how things are measured...
It is already a known fact.
Every other measurement is "certainly valuable" but cant be used in "court".
In regards to the S-meter.
Mr S. is rigth. 6dB equals 1 s-unit.
And yes there is a standart for how much uV should produce a S unit.
Ofcourse especially with CB rigs they are a bit on the brigth side
But it is oke to get a indication, as long as you know what your receiver is measuring (alc etc.)
Now, it is easy to "verify" a dB.
Most of us have accurate powermeters. (bird etc).
by doubling the power say from 100mW to 200mW you will "gain" 3dB.
So the difference on S-meter with changing that value is a indication of about 3dB.
The problem is this "methode" is reasonable accurate upto about 1dB.
any assuption about <1dB would be a educated guess.
And there we kick in what MrS says.
1dB, on a already "strong" signal is meaningless.
And would need "real" measuring equipment to be noticable.
Oke...What happens if we are testing with stations far away...as that is what we all do...
Complex "faults" come into play. Reflections of buildings/traffic and much much more.
But say we still measure upto 6 dB of difference in signal strength.
That can only indicate either there is a "fault" or there is difference in "main" antenna pattern. That is different then gain. (it wouldnt be fair if we measured gain from a beam on the side of the beam now is it?).
Bare in mind another thing....!
We are measuring on a vertical omnidirectional.
We are trying to point out "the antenna produces a better signal".
We are having difficulties with stations as there are not many active and we are also testing on Dx etc.
There are two things important:
One...is the "improvement" we made to a antenna working cause it lowers the loss of the antenna ? or:
More importantly......:
The antenna has a 3 dimensional pattern. If we compress that pattern in such a way it becomes stronger at the horizon. It means it is getting weaker somewhere else.!
To indicate: if i switch between between a beam 30 feet up or 100 feet up there will be a major difference ! The higher one will produce a large signal on DX.
But the lower one can produce a big signal within the continent.
Now you could even phase them in such a way they both produce "a high" angle than the single bottum one....but thats another story.
What it comes down to is that it is exactly what one does by trying to push the biggest gain under one direction.
So it is only logical that the antenna will perform less in other situations.
A good example is the sproadic E propagation wich needs a high angle radiation..
So actually "bad" antennas can have outstanding signals
Thats why one should measure as first described.
Kind regards,
Henry
11 meter Dx antenna systemx
It is already a known fact that if antennas are too close to each other they will have influence. This is not always measurable with a SWR meter.
The "rules' for antenna measuring is you put several wavelengths between them.
Yes, i know that is "a wide figure" but 2..3 WL is known as sufficient.
The reason for that is that within the near field of a antenna the radiation pattern is building up. Now the guru's have got different opinions of what is happening within that near field. Im not speaking about guys like us, but the pro's.
Any measurement within that near field is also "useless" as neither the true radiation pattern has buildt up and we dont know what is happening.
Secondly, please dont forget about "ground reflections"
The receiving antenna should be say 10 to 20 wl away.
There should be a additional antenna in between to pick up those ground reflections.
The sugestion (on that other thread) about using one mast to test the antenna isnt good as you still have a variable wich is time (especially with disctance station).
(ofcourse all the futher normal things in regards to heigth coax length etc.)
The thing i dont know: why everyone keeps debating about how things are measured...
It is already a known fact.
Every other measurement is "certainly valuable" but cant be used in "court".
In regards to the S-meter.
Mr S. is rigth. 6dB equals 1 s-unit.
And yes there is a standart for how much uV should produce a S unit.
Ofcourse especially with CB rigs they are a bit on the brigth side
But it is oke to get a indication, as long as you know what your receiver is measuring (alc etc.)
Now, it is easy to "verify" a dB.
Most of us have accurate powermeters. (bird etc).
by doubling the power say from 100mW to 200mW you will "gain" 3dB.
So the difference on S-meter with changing that value is a indication of about 3dB.
The problem is this "methode" is reasonable accurate upto about 1dB.
any assuption about <1dB would be a educated guess.
And there we kick in what MrS says.
1dB, on a already "strong" signal is meaningless.
And would need "real" measuring equipment to be noticable.
Oke...What happens if we are testing with stations far away...as that is what we all do...
Complex "faults" come into play. Reflections of buildings/traffic and much much more.
But say we still measure upto 6 dB of difference in signal strength.
That can only indicate either there is a "fault" or there is difference in "main" antenna pattern. That is different then gain. (it wouldnt be fair if we measured gain from a beam on the side of the beam now is it?).
Bare in mind another thing....!
We are measuring on a vertical omnidirectional.
We are trying to point out "the antenna produces a better signal".
We are having difficulties with stations as there are not many active and we are also testing on Dx etc.
There are two things important:
One...is the "improvement" we made to a antenna working cause it lowers the loss of the antenna ? or:
More importantly......:
The antenna has a 3 dimensional pattern. If we compress that pattern in such a way it becomes stronger at the horizon. It means it is getting weaker somewhere else.!
To indicate: if i switch between between a beam 30 feet up or 100 feet up there will be a major difference ! The higher one will produce a large signal on DX.
But the lower one can produce a big signal within the continent.
Now you could even phase them in such a way they both produce "a high" angle than the single bottum one....but thats another story.
What it comes down to is that it is exactly what one does by trying to push the biggest gain under one direction.
So it is only logical that the antenna will perform less in other situations.
A good example is the sproadic E propagation wich needs a high angle radiation..
So actually "bad" antennas can have outstanding signals
Thats why one should measure as first described.
Kind regards,
Henry
11 meter Dx antenna systemx
B
BOOTY MONSTER
Guest
[=Henry HPSD;262366]Hello Guys,
It is already a known fact that if antennas are too close to each other they will have influence. This is not always measurable with a SWR meter.
The "rules' for antenna measuring is you put several wavelengths between them.
Yes, i know that is "a wide figure" but 2..3 WL is known as sufficient.
(Mr.S wrote
I agree Completly
The reason for that is that within the near field of a antenna the radiation pattern is building up. Now the guru's have got different opinions of what is happening within that near field. Im not speaking about guys like us, but the pro's.
Any measurement within that near field is also "useless" as neither the true radiation pattern has buildt up and we dont know what is happening.
Secondly, please dont forget about "ground reflections"
The receiving antenna should be say 10 to 20 wl away.
There should be a additional antenna in between to pick up those ground reflections.
The sugestion (on that other thread) about using one mast to test the antenna isnt good as you still have a variable wich is time (especially with disctance station).
(ofcourse all the futher normal things in regards to heigth coax length etc.)
The thing i dont know: why everyone keeps debating about how things are measured...
It is already a known fact.
Every other measurement is "certainly valuable" but cant be used in "court".
In regards to the S-meter.
Mr S. is rigth. 6dB equals 1 s-unit.
And yes there is a standart for how much uV should produce a S unit.
Ofcourse especially with CB rigs they are a bit on the brigth side
But it is oke to get a indication, as long as you know what your receiver is measuring (alc etc.)
(Mr.S wrote
There is a program out there called TRX manager which is a Cat program for controloing modern rigs. It has a Uv meter along with S meter so it actually will display a UV now it may not be 100% accurate because it is going by the radios circuitry but it will give a number with more resolution. Compared to a standard bar graph or needle type. "TRX Manager"
Now, it is easy to "verify" a dB.
Most of us have accurate powermeters. (bird etc).
by doubling the power say from 100mW to 200mW you will "gain" 3dB.
So the difference on S-meter with changing that value is a indication of about 3dB.
The problem is this "methode" is reasonable accurate upto about 1dB.
any assuption about <1dB would be a educated guess.
(Mr.S wrote
Bingo, I have and still use this method to confirm the readings I am seeing.
And there we kick in what MrS says.
1dB, on a already "strong" signal is meaningless.
And would need "real" measuring equipment to be noticable.
Again, spot on Henry were not seeing the little bit of difference between these antennas with S meters unless it happens to be a major gain or loss.
Oke...What happens if we are testing with stations far away...as that is what we all do...
Complex "faults" come into play. Reflections of buildings/traffic and much much more.
But say we still measure upto 6 dB of difference in signal strength.
That can only indicate either there is a "fault" or there is difference in "main" antenna pattern. That is different then gain. (it wouldnt be fair if we measured gain from a beam on the side of the beam now is it?).
Bare in mind another thing....!
We are measuring on a vertical omnidirectional.
We are trying to point out "the antenna produces a better signal".
We are having difficulties with stations as there are not many active and we are also testing on Dx etc.
There are two things important:
One...is the "improvement" we made to a antenna working cause it lowers the loss of the antenna ? or:
More importantly......:
The antenna has a 3 dimensional pattern. If we compress that pattern in such a way it becomes stronger at the horizon. It means it is getting weaker somewhere else.!
To indicate: if i switch between between a beam 30 feet up or 100 feet up there will be a major difference ! The higher one will produce a large signal on DX.
But the lower one can produce a big signal within the continent.
Now you could even phase them in such a way they both produce "a high" angle than the single bottum one....but thats another story.
What it comes down to is that it is exactly what one does by trying to push the biggest gain under one direction.
So it is only logical that the antenna will perform less in other situations.
A good example is the sproadic E propagation wich needs a high angle radiation..
So actually "bad" antennas can have outstanding signals
Thats why one should measure as first described.
Kind regards,
Henry
11 meter Dx antenna systemx
Mr.S:Good Post Henry
It is already a known fact that if antennas are too close to each other they will have influence. This is not always measurable with a SWR meter.
The "rules' for antenna measuring is you put several wavelengths between them.
Yes, i know that is "a wide figure" but 2..3 WL is known as sufficient.
(Mr.S wrote
I agree Completly
The reason for that is that within the near field of a antenna the radiation pattern is building up. Now the guru's have got different opinions of what is happening within that near field. Im not speaking about guys like us, but the pro's.
Any measurement within that near field is also "useless" as neither the true radiation pattern has buildt up and we dont know what is happening.
Secondly, please dont forget about "ground reflections"
The receiving antenna should be say 10 to 20 wl away.
There should be a additional antenna in between to pick up those ground reflections.
The sugestion (on that other thread) about using one mast to test the antenna isnt good as you still have a variable wich is time (especially with disctance station).
(ofcourse all the futher normal things in regards to heigth coax length etc.)
The thing i dont know: why everyone keeps debating about how things are measured...
It is already a known fact.
Every other measurement is "certainly valuable" but cant be used in "court".
In regards to the S-meter.
Mr S. is rigth. 6dB equals 1 s-unit.
And yes there is a standart for how much uV should produce a S unit.
Ofcourse especially with CB rigs they are a bit on the brigth side
But it is oke to get a indication, as long as you know what your receiver is measuring (alc etc.)
(Mr.S wrote
There is a program out there called TRX manager which is a Cat program for controloing modern rigs. It has a Uv meter along with S meter so it actually will display a UV now it may not be 100% accurate because it is going by the radios circuitry but it will give a number with more resolution. Compared to a standard bar graph or needle type. "TRX Manager"
Now, it is easy to "verify" a dB.
Most of us have accurate powermeters. (bird etc).
by doubling the power say from 100mW to 200mW you will "gain" 3dB.
So the difference on S-meter with changing that value is a indication of about 3dB.
The problem is this "methode" is reasonable accurate upto about 1dB.
any assuption about <1dB would be a educated guess.
(Mr.S wrote
Bingo, I have and still use this method to confirm the readings I am seeing.
And there we kick in what MrS says.
1dB, on a already "strong" signal is meaningless.
And would need "real" measuring equipment to be noticable.
Again, spot on Henry were not seeing the little bit of difference between these antennas with S meters unless it happens to be a major gain or loss.
Oke...What happens if we are testing with stations far away...as that is what we all do...
Complex "faults" come into play. Reflections of buildings/traffic and much much more.
But say we still measure upto 6 dB of difference in signal strength.
That can only indicate either there is a "fault" or there is difference in "main" antenna pattern. That is different then gain. (it wouldnt be fair if we measured gain from a beam on the side of the beam now is it?).
Bare in mind another thing....!
We are measuring on a vertical omnidirectional.
We are trying to point out "the antenna produces a better signal".
We are having difficulties with stations as there are not many active and we are also testing on Dx etc.
There are two things important:
One...is the "improvement" we made to a antenna working cause it lowers the loss of the antenna ? or:
More importantly......:
The antenna has a 3 dimensional pattern. If we compress that pattern in such a way it becomes stronger at the horizon. It means it is getting weaker somewhere else.!
To indicate: if i switch between between a beam 30 feet up or 100 feet up there will be a major difference ! The higher one will produce a large signal on DX.
But the lower one can produce a big signal within the continent.
Now you could even phase them in such a way they both produce "a high" angle than the single bottum one....but thats another story.
What it comes down to is that it is exactly what one does by trying to push the biggest gain under one direction.
So it is only logical that the antenna will perform less in other situations.
A good example is the sproadic E propagation wich needs a high angle radiation..
So actually "bad" antennas can have outstanding signals
Thats why one should measure as first described.
Kind regards,
Henry
11 meter Dx antenna systemx
Mr.S:Good Post Henry
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