This is long, but bear with me a little.
For Librium and others adding to the thread about Kale’s base antenna. Here is something I have been studying lately that you might consider in defense of this idea.
If you check out the ARRL antenna book for capacitance hats or top hats you should find some technical support for how top loaded shortened radiators might improve pattern and increase the RF signal by improving the radiation resistance associated when effectively raising the current distribution on the element. This ARRL information has to do with efficiency. If the topics are technically correct, then maybe Kale’s base antenna project has some merit. So, before we chunk the idea maybe consideration for testing is the only real way to determine if it really works well or not and how it compares with other base antennas.
The same issues, regarding the use of suitable center loaded coils, are also related to topics found above by improving current distribution. These conclusions include both increased RF from the radiator and the possible development of improved (lowered) RF patterns. There are many articles expressing, in general the virtues of center loading and top loading, thus showing improvements over base and continuous loaded antennas. This also includes improved control over tuning with coiled antennas.
Can we tell the difference in operations comparing a center-loaded coil to a regular whip for 11 meters? Many will swear you can discern a difference! If the ARRL technology is accurate then it seems to bear this out? This is of course not withstanding the issues with losses usually associated with coils. The abundance of positive claims out there, using the shorter radiators with coil designs deserves some consideration. To be fair there are likely just as many positive claims made about continuous loaded 1/4 wave radiators as well. The whip has always been my personal preference, but I did not find the height and bending issues to be a problem.
In a 1/4 wave mobile whip setup I always wondered how guys were able to nail the install and get a match near 1.1:1. I have personally discovered that the ground plane in a 1/4 wave proves to me to be so vital in bringing the whip to a purely resistive match that I have to question such an installation. This just made the idea for me seem impossible unless the nature of the whip is changed somehow like adding a variable capacitor to the base as a matching device or you had a very good handle on the ground plane presented by a mobile body.
You can get close, but I find it difficult to reach 50 ohms of resistance, when making the antenna purely resistant, in a typical mobile setup. It is real hard to know exactly what to do to fix the ground plane in a mobile to match the stinger as purely resistive where you want it to resonate. Just adding inductance to the element does not necessarily get your there either. I can configure my little home-made starduster antenna I call a Marconi to a match, showing R=50, X=0, SWR=1.00 @ 27.230 for example. However, when testing with a field strength meter I can get a better power reading with the same antenna re-configured just a bit in the ground plane to show R=39, X=0, SWR=1.29 @ 26.950. As you can see, besides the change in resistance there was also a lowering in frequency when all I did was change the GP a bit (making it larger). I tried making the GP smaller too, but the resistance dropped below 30 ohms very rapidly. The 1/4 wave radiator really needs an appropriate ground plane to work against. What I conclude here is that attempting to make the match purely resistive, in this case, actually induces losses that show up as a pure match at the expense of field strength and this is not an improvement. If the field strength actually increased instead, then my conclusion would be wrong. Question: could a shorter coil type antenna overcome this by having better control over reactance?
I can get close with a 1/4 wave base type setup where I can add 6 or more ground plane radials that are a least a 102” for 11 meters. The GP configuration also has to be at approximately 45 degrees angle or the system will need a matcher to get really close. I have also found that horizontal radials, even with a worse match yields a better field strength than does the antenna with slanted down GP radials at 45 degrees. Looks like to me this angle simply adds losses just to improve match, seeing as the field strength is diminished somewhat. Such is compromise.
As already noted above, I wondered if a center loaded coil antenna would match up better, like is said to be the case by many using a well designed coil antenna on a mobile? My novice thinking back then was, that getting the actual load (the coil in this case) up away from the ground plane was what was really important to the better tune and match while maybe showing some increase in field strength. Remember my testing proved to me that a better match would not necessarily produce the best field strength in the near field using the continuous wave whip. Again, could a coil type over come this?
I will admit that just loading a center or top loaded element does not automatically insure improved performance, but even considering the added losses involved with being short and using a coil or top hat one might technically see in these examples that a shorter radiator could possibly perform just as well or better in some case as a true 1/4 wave continuous loaded element or a base loaded.
So our just stating, off hand, that Kale’s base antenna idea is impracticable and impossible might not be the best approach to understanding what a real world experience might show us. In the past I have agreed with you in discounting such claims. Now I’m not quite so sure, since I started looking at what others and the ARRL Antenna Handbook have to say about the subject, and from reports by users of several good coil type mobile antennas around, not just Kales brand. Others can probably do what he does also, but Kale’s antennas are modular, very well built, and being very light in weight is a big factor.
Look, I also love the way my Starduster works, both for TX and RX. I won't claim it will out perform a good multi-element beam, but I have seen times when it was pretty darn close and it always compares exceptionally well with the best of the longer antenna in 11 meters. Kales base design noted here is along those same lines, so let’s give Kale a chance to explain his experiences with this one, OK?
In conclusion, if the above seems reasonable to your thinking then maybe you could check out chapter 16 page 16-4 in the 19th addition of ARRL on Mobiles entitled "Base loading and Center loading." This topic gives graphic depictions comparing the improved current distribution using a center loaded 1/4 wave radiator compared to a simple whip antenna. In Figures 6 & 7 you will also see the center loading with a suitable coil generates approximately 30% more of an increase in the total current distribution over the element length. This example also shows an increased current toward the top rather than it basically being down near the base, close to ground, as in a continuous fed or base loaded radiator. To repeat, this relates to an impressive increase in radiation resistance and I don’t think any body will deny that increased radiation resistance in a radiator relates to improved emissions of radiation, regardless of the length of the element.
The comments above are just my opinions. If you disagree with something I have said or suggested or have another idea, then let’s discuss it. I am open to a better understanding as well.
For Librium and others adding to the thread about Kale’s base antenna. Here is something I have been studying lately that you might consider in defense of this idea.
If you check out the ARRL antenna book for capacitance hats or top hats you should find some technical support for how top loaded shortened radiators might improve pattern and increase the RF signal by improving the radiation resistance associated when effectively raising the current distribution on the element. This ARRL information has to do with efficiency. If the topics are technically correct, then maybe Kale’s base antenna project has some merit. So, before we chunk the idea maybe consideration for testing is the only real way to determine if it really works well or not and how it compares with other base antennas.
The same issues, regarding the use of suitable center loaded coils, are also related to topics found above by improving current distribution. These conclusions include both increased RF from the radiator and the possible development of improved (lowered) RF patterns. There are many articles expressing, in general the virtues of center loading and top loading, thus showing improvements over base and continuous loaded antennas. This also includes improved control over tuning with coiled antennas.
Can we tell the difference in operations comparing a center-loaded coil to a regular whip for 11 meters? Many will swear you can discern a difference! If the ARRL technology is accurate then it seems to bear this out? This is of course not withstanding the issues with losses usually associated with coils. The abundance of positive claims out there, using the shorter radiators with coil designs deserves some consideration. To be fair there are likely just as many positive claims made about continuous loaded 1/4 wave radiators as well. The whip has always been my personal preference, but I did not find the height and bending issues to be a problem.
In a 1/4 wave mobile whip setup I always wondered how guys were able to nail the install and get a match near 1.1:1. I have personally discovered that the ground plane in a 1/4 wave proves to me to be so vital in bringing the whip to a purely resistive match that I have to question such an installation. This just made the idea for me seem impossible unless the nature of the whip is changed somehow like adding a variable capacitor to the base as a matching device or you had a very good handle on the ground plane presented by a mobile body.
You can get close, but I find it difficult to reach 50 ohms of resistance, when making the antenna purely resistant, in a typical mobile setup. It is real hard to know exactly what to do to fix the ground plane in a mobile to match the stinger as purely resistive where you want it to resonate. Just adding inductance to the element does not necessarily get your there either. I can configure my little home-made starduster antenna I call a Marconi to a match, showing R=50, X=0, SWR=1.00 @ 27.230 for example. However, when testing with a field strength meter I can get a better power reading with the same antenna re-configured just a bit in the ground plane to show R=39, X=0, SWR=1.29 @ 26.950. As you can see, besides the change in resistance there was also a lowering in frequency when all I did was change the GP a bit (making it larger). I tried making the GP smaller too, but the resistance dropped below 30 ohms very rapidly. The 1/4 wave radiator really needs an appropriate ground plane to work against. What I conclude here is that attempting to make the match purely resistive, in this case, actually induces losses that show up as a pure match at the expense of field strength and this is not an improvement. If the field strength actually increased instead, then my conclusion would be wrong. Question: could a shorter coil type antenna overcome this by having better control over reactance?
I can get close with a 1/4 wave base type setup where I can add 6 or more ground plane radials that are a least a 102” for 11 meters. The GP configuration also has to be at approximately 45 degrees angle or the system will need a matcher to get really close. I have also found that horizontal radials, even with a worse match yields a better field strength than does the antenna with slanted down GP radials at 45 degrees. Looks like to me this angle simply adds losses just to improve match, seeing as the field strength is diminished somewhat. Such is compromise.
As already noted above, I wondered if a center loaded coil antenna would match up better, like is said to be the case by many using a well designed coil antenna on a mobile? My novice thinking back then was, that getting the actual load (the coil in this case) up away from the ground plane was what was really important to the better tune and match while maybe showing some increase in field strength. Remember my testing proved to me that a better match would not necessarily produce the best field strength in the near field using the continuous wave whip. Again, could a coil type over come this?
I will admit that just loading a center or top loaded element does not automatically insure improved performance, but even considering the added losses involved with being short and using a coil or top hat one might technically see in these examples that a shorter radiator could possibly perform just as well or better in some case as a true 1/4 wave continuous loaded element or a base loaded.
So our just stating, off hand, that Kale’s base antenna idea is impracticable and impossible might not be the best approach to understanding what a real world experience might show us. In the past I have agreed with you in discounting such claims. Now I’m not quite so sure, since I started looking at what others and the ARRL Antenna Handbook have to say about the subject, and from reports by users of several good coil type mobile antennas around, not just Kales brand. Others can probably do what he does also, but Kale’s antennas are modular, very well built, and being very light in weight is a big factor.
Look, I also love the way my Starduster works, both for TX and RX. I won't claim it will out perform a good multi-element beam, but I have seen times when it was pretty darn close and it always compares exceptionally well with the best of the longer antenna in 11 meters. Kales base design noted here is along those same lines, so let’s give Kale a chance to explain his experiences with this one, OK?
In conclusion, if the above seems reasonable to your thinking then maybe you could check out chapter 16 page 16-4 in the 19th addition of ARRL on Mobiles entitled "Base loading and Center loading." This topic gives graphic depictions comparing the improved current distribution using a center loaded 1/4 wave radiator compared to a simple whip antenna. In Figures 6 & 7 you will also see the center loading with a suitable coil generates approximately 30% more of an increase in the total current distribution over the element length. This example also shows an increased current toward the top rather than it basically being down near the base, close to ground, as in a continuous fed or base loaded radiator. To repeat, this relates to an impressive increase in radiation resistance and I don’t think any body will deny that increased radiation resistance in a radiator relates to improved emissions of radiation, regardless of the length of the element.
The comments above are just my opinions. If you disagree with something I have said or suggested or have another idea, then let’s discuss it. I am open to a better understanding as well.
