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Is the Solarcon Max2000 5/8th di-pole like ?
- Thread starter RadioDaze2.0
- Start date
Well, adding capacitive reactance would tend to electrically shorten the antenna.
Perhaps the cap is added to increase the DC isolation, improving it's ability to insulate against as much as 15kv to pass FCC regs.
Since the Imax measures correctly for a 5/8 on 11m, I'd presume the capacitive reactance is nullified by an appropriate amount of inductance in the bottom matching network.
- What I find thought provoking is the fact the phase of the radiation is being shifted above the capacitor, and how does that (Marconi?) tend to affect the pattern & TOA?
Perhaps if someone knew the value of the capacitor...?
Perhaps the cap is added to increase the DC isolation, improving it's ability to insulate against as much as 15kv to pass FCC regs.
Since the Imax measures correctly for a 5/8 on 11m, I'd presume the capacitive reactance is nullified by an appropriate amount of inductance in the bottom matching network.
- What I find thought provoking is the fact the phase of the radiation is being shifted above the capacitor, and how does that (Marconi?) tend to affect the pattern & TOA?
Perhaps if someone knew the value of the capacitor...?
I was out with my IMAX2000 yesterday at only 15 feet high on a hill and it worked very well. Even the SWR was down at only 1.4:1
I think performance is at least on par with the Gain Master for my line of sight contacts. I managed a 190 miles contact with the IMAX2000 to another station that was also on high ground. They were barely audible but we heard each other nonetheless.
Just possibly it might outperform the Gain Master for long line of sight contacts when I have it on shorter poles (normally I would have 20-25feet of poles. I suspect it may be less affected by the ground than the Gain Master is. I only put it on 15 feet of pole as I have just recovered from the flu and wanted a nice easy set up and take down.
At 15 feet the SWR was decent... normally I see a 1.7:1 or slightly higher SWR so 15 feet might have been just right for the feed impedance. I will see when I hike it up to 25 feet in the future.
The tuning rings have had no effect for me I wondered at one point if the IMAX was broke but now I am definitely warming to it as a viable static mobile antenna. It has the length to be viable at only 15 feet (in a 10mph wind as it was yesterday) which is possible to set up without any guy wires which also helped me.
I like it ! I think th Gain Master might collect dust for a few months through the summer. The IMAX is so easy to set up. (despite being quite a bit heavier than my GM)
I think the GM might have the edge for really long DX at 25 feet and above but at 15 feet the IMAX does as well if not slightly better. As the summer Sporadic E skip is coming now i.e. European skip 1,000-2,000 mile hops the IMAX will be fine for this even at lower heights I suspect.
I think performance is at least on par with the Gain Master for my line of sight contacts. I managed a 190 miles contact with the IMAX2000 to another station that was also on high ground. They were barely audible but we heard each other nonetheless.
Just possibly it might outperform the Gain Master for long line of sight contacts when I have it on shorter poles (normally I would have 20-25feet of poles. I suspect it may be less affected by the ground than the Gain Master is. I only put it on 15 feet of pole as I have just recovered from the flu and wanted a nice easy set up and take down.
At 15 feet the SWR was decent... normally I see a 1.7:1 or slightly higher SWR so 15 feet might have been just right for the feed impedance. I will see when I hike it up to 25 feet in the future.
The tuning rings have had no effect for me I wondered at one point if the IMAX was broke but now I am definitely warming to it as a viable static mobile antenna. It has the length to be viable at only 15 feet (in a 10mph wind as it was yesterday) which is possible to set up without any guy wires which also helped me.
I like it ! I think th Gain Master might collect dust for a few months through the summer. The IMAX is so easy to set up. (despite being quite a bit heavier than my GM)
I think the GM might have the edge for really long DX at 25 feet and above but at 15 feet the IMAX does as well if not slightly better. As the summer Sporadic E skip is coming now i.e. European skip 1,000-2,000 mile hops the IMAX will be fine for this even at lower heights I suspect.
When I was stuck running my Imax2K for a while, I added ~60° downward 1/4 wave radials/ counterpoise made from 6/20 guywire and saw a surprising improvement on a friend's 11m internet meter at ~12 miles. The Imax was right at 40' at the tip of the mast. It acted more like a metal 5/8 with the addition of the four-9' guy wire counterpoise radials.
I used parachute cord from the ends of the 1/4 wave guy wires down to the tie points on the roof.
YMMV !!
I have toyed with this idea. But for mobile static I find it might be a bit of a faff/tricky. I could make 2 x 1/4 wave bits of wire attached to U-Bolts on the IMAX bracket and then if need be and add parachute cord to the radial ends as you did to get them down and attached to some fence or tree stump or bush etc.
The only thing is in the ARRL handbook I read that radials need to be very precisely measured and angled to spec otherwise unpredictable effects can start occurring to radiation pattern and TOA's.
(as we know we can make a normally omni directional antenna slightly directional to the tune of 1-2dB I think...by adding just one radial in the direction where you want the pattern to be skewed.)
Could it be that your friends internet monitoring station was just in a favourable location and gain was reduced in some other directions, TOA changed a bit ?
The only thing is in the ARRL handbook I read that radials need to be very precisely measured and angled to spec otherwise unpredictable effects can start occurring to radiation pattern and TOA's.
(as we know we can make a normally omni directional antenna slightly directional to the tune of 1-2dB I think...by adding just one radial in the direction where you want the pattern to be skewed.)
Could it be that your friends internet monitoring station was just in a favourable location and gain was reduced in some other directions, TOA changed a bit ?
I will take a look when I get a chance. Quite sure that it says radials must be set up right it even has drawings of skewed radiation patterns.
Ok 22nd edition 3-17
Azimuthal radiation pattern comparing symmetric and asymmetric radials at 7.25 MHz
The paragraphs speak about pattern distortion up to 3dB (that is more gain than could be produced !) So get them wrong and it seems you can lose energy where you want it.
"Clearly even small radial length asymmetry can have a dramatic effect on the feed point impedance and resonant frequency"
Azimuthal radiation pattern comparing symmetric and asymmetric radials at 7.25 MHz
The paragraphs speak about pattern distortion up to 3dB (that is more gain than could be produced !) So get them wrong and it seems you can lose energy where you want it.
"Clearly even small radial length asymmetry can have a dramatic effect on the feed point impedance and resonant frequency"
RD2.0, thanks for the link, but in case we don't have the ARRL 22nd edition, what is the Caption noted at the beginning of the section where you read your reference?
If it is not a new article, we may be able to find the reference in an older ARRL edition.
If it is not a new article, we may be able to find the reference in an older ARRL edition.
2.0, can you tell us what the "angled specs" noted in the ARRL are referencing?
I'm not sure, but I think my Eznec models for the Imax suggest there is little difference in gain, angle, or match between different radial length and angle variations from horizontal to 45* degrees slanted down.
I also seem to recall that the longer 9' foot radials show no advantage when compared to 6' foot radials, so I would like to read this article you reference.
I might be able to help some here as I have way to many versions of said book (all but three in fact
)...22'nd edition, page 3-17 (or Chapter 3 page 17) figure 3.33 caption.
I don't have a 21'st edition, but I do have a 20'th edition. The figure and its caption does not exist in the 20'th edition. Further, there is far less information in this subtopic on radials in the 20'th edition. Therefore, this info seems to be a more recent addition to the book series.
Here is a picture of said figure and its caption. I can quote the section of the book as well, but I am not sure how much of it I am able to post here before infringing on the copyright so I will limit myself to a paragraph...
The section which starts on the previous page, and continues to the next page, talks about elevated radials in general, and includes a part of different size radials including this paragraph on the same topic...
Before this it talks about how asymmetric radials will affect impedance. After this it talks about the variation of current on the radials and the vertical element, it continues on and talks about how more radials has less sensitivity to a radial system's asymmetry as well as other nearby objects. It also states this in italics.
Which flies in the face of the so called 'common knowledge' used in the CB world that for an elevated ground system four radials is enough... Sorry, it was just a snippet that I just had to include. Back to the topic at hand...
Finally it goes on to talk about using shortened radials on large (low frequency, aka 80/160 meter) antennas where you might not have enough room for a full radial system.
Having different length or unevenly spaced radials will affect the azimuthal pattern (such as the one in the chart shown above) such things, however, won't affect the "take off angle". Angling the radials down might affect the "take off angle" on a 5/8 wavelength antenna, but not because angling the radials affects the angle of radiation. In that case what is happening is you are adding more signal with a vertical polarization that is out of phase with the upper radiation portion of the antenna causing the dominant lobe to be a higher angle lobe. The low angle lobe still exists, it is just no longer dominant. If you are working with 1/4 wavelength antennas as they are in that section of the book, you can angle the radials from horizontal to straight down and the radiation angle will not change, unless you have another problem that needs to be dealt with...
I want to point out that this section in general is assuming 1/4 wavelength antennas. I wouldn't assume that use of radials on a 5/8 wavelength antenna will have completely equal effects. For example, a 5/8 wavelength antenna has a matching system that can account for any impedance difference simply because a 5/8 wavelength antenna will need such a device anyway. Further, the current distribution will be different on such an antenna as well, the current peaks on the radials will not be as high to begin with, and as such the radiation pattern difference between radials on a 5/8 wavelength antenna should be less than if the same radials are on a 1/4 wavelength antenna.
The DB
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Thanks for the reply DB and your interest Marconi. Sorry, yes I was wrong in terms of angles of radials it is more relative to inconsistencies in non perfect radial lengths causing imbalances and whether their set up is perfectly symmetrical or not. (Which I imagine could potentially relate to radial angles (droop etc) as getting radials to be exactly 45 degrees or 90 degrees or whatever choice has been made is to all intents and purposes impossible, especially so with your own home DIY solid core copper wire ones.)
Causing unknown effects in my mind is worse than dealing with known ones on a radial less antenna. I have to say the IMAX2000 on a mere 15 feet of pole seems to be free of common mode issues that cause interference and shack RF issues so I am happy to use this in practice and run with it. (no coaxial choke or ferrite chokes being used) I will also see if any problems are encountered as mast lengths change which they tend to depending on how high I mount my antenna on the day. In essence i use between 3 and 5 poles of five feet length each slot together sectional. I will note any SWR changes and any negative effects.
I feel the construction of the MAX2000 seems good quality, it is nicely made as far as the eye can tell. Substantial hardware and construction. It feels like it screws up nicely and I appreciate the light top whip section. It does tend to flop about a lot. No wonder people rate them as an antenna with decent wind resistance.
To me it really looks like a boat/maritime antenna.
I also appreciate that grounding can reduce or increase common mode on coax/poles interdependent with the mast length so I will have to use it and see on every different height mast. But I am inclined to give the IMAX 2000 a fair shot this summer.
My initial dislike was not getting a SWR below 1.7/1.8 : 1 when my Gain Master is always 1.2:1 almost irrelevant of any changes. - 1.4:1 for me is satisfactory and is what the MAX2000 reads at 15 feet. (remember I operate at 200M ASL approx so I get the HAAT advantage despite my relative low height about the earth surface)
Once I saw this, all thoughts of trying to make my own radials for an IMAX2000 went out the window when I realized for static mobile getting them set up accurately (copper wires) will be completely impossible and as such largely detrimental.
Sometimes simple is best but I guess you have to get a little complex to know that.
PS To add I have cleaned up the threads on my IMAX2000 using Isopropyl alcohol and I can only say the dirt that came out of the screw thread holes was very surprising, lots of grime which is clearly come from the factory... that cannot be helping electrical contact so I am glad I cleaned it properly !
Causing unknown effects in my mind is worse than dealing with known ones on a radial less antenna. I have to say the IMAX2000 on a mere 15 feet of pole seems to be free of common mode issues that cause interference and shack RF issues so I am happy to use this in practice and run with it. (no coaxial choke or ferrite chokes being used) I will also see if any problems are encountered as mast lengths change which they tend to depending on how high I mount my antenna on the day. In essence i use between 3 and 5 poles of five feet length each slot together sectional. I will note any SWR changes and any negative effects.
I feel the construction of the MAX2000 seems good quality, it is nicely made as far as the eye can tell. Substantial hardware and construction. It feels like it screws up nicely and I appreciate the light top whip section. It does tend to flop about a lot. No wonder people rate them as an antenna with decent wind resistance.
To me it really looks like a boat/maritime antenna.
I also appreciate that grounding can reduce or increase common mode on coax/poles interdependent with the mast length so I will have to use it and see on every different height mast. But I am inclined to give the IMAX 2000 a fair shot this summer.
My initial dislike was not getting a SWR below 1.7/1.8 : 1 when my Gain Master is always 1.2:1 almost irrelevant of any changes. - 1.4:1 for me is satisfactory and is what the MAX2000 reads at 15 feet. (remember I operate at 200M ASL approx so I get the HAAT advantage despite my relative low height about the earth surface)
Once I saw this, all thoughts of trying to make my own radials for an IMAX2000 went out the window when I realized for static mobile getting them set up accurately (copper wires) will be completely impossible and as such largely detrimental.
Sometimes simple is best but I guess you have to get a little complex to know that.
PS To add I have cleaned up the threads on my IMAX2000 using Isopropyl alcohol and I can only say the dirt that came out of the screw thread holes was very surprising, lots of grime which is clearly come from the factory... that cannot be helping electrical contact so I am glad I cleaned it properly !
Well RD2, I believe DB is right...your reference is pretty new to the ARRL Antenna Book, and may have started in the 22nd edition.
My Eznec models for an unmatched Imax don't show the gain issues you suggest the referenced article indicates...not even close.
My unmatched Imax model shows a match that is well over 100:1 SWR, so I can't be sure of my results with this in mind...else I would post some and show why I don't agree with what I understand of your reference so far.
However, I will study DB's comments and maybe I will change my mind.
In the past I have often found that technical articles that are discussing specific radio frequencies far away <> from 11 meters...can be misleading. Plus these high-tech type results, even though likely being correct in details, tend to indicate differences that are often very small in value...which CB operators then tend to blow out of proportion. This article is different in the fact that it seems to state radial asymmetry can cause as much as a 3 db loss in gain at 7.25 mhz, and that is significant.
Regarding CMC. I have some ideas, but they are probably wrong headed also. I think only real world results might show the truth of this matter, but how do we measure gain and determine the values of CMC in testing?
Good luck in your testing and keep us posted.
My Eznec models for an unmatched Imax don't show the gain issues you suggest the referenced article indicates...not even close.
My unmatched Imax model shows a match that is well over 100:1 SWR, so I can't be sure of my results with this in mind...else I would post some and show why I don't agree with what I understand of your reference so far.
However, I will study DB's comments and maybe I will change my mind.
In the past I have often found that technical articles that are discussing specific radio frequencies far away <> from 11 meters...can be misleading. Plus these high-tech type results, even though likely being correct in details, tend to indicate differences that are often very small in value...which CB operators then tend to blow out of proportion. This article is different in the fact that it seems to state radial asymmetry can cause as much as a 3 db loss in gain at 7.25 mhz, and that is significant.
Regarding CMC. I have some ideas, but they are probably wrong headed also. I think only real world results might show the truth of this matter, but how do we measure gain and determine the values of CMC in testing?
Good luck in your testing and keep us posted.
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