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Base More Pattern Overlays
- Thread starter Marconi
- Start date
I agree overlays are a busy mess. Some overlays lap over others, and appear invisible. I could set the (*) as the active pattern for each antenna in the group posted, but that would make a sheet for each antenna. Try looking at the group as a whole. I see more similarities that make little differences...than we can actually see just using a radio.
Alexis, I am still in favor of using minimal parts in trial testing and matching in order to maybe get a base line for comparison 1st. Then add features and try and determine any differences that my occur, like on raising the antenna, adding filter, switches, different coax, length, and meters. I don't build a model by just adding stuff to the model...I set the basic dimensions as best I know, and see what happens with the bare bones model. It it show problems, then I address same on a one at a time basis and go from their.
My position on the matter supports my contention that in all my comparison work for some year now shows CB vertical mono poles as such show relative little differences...that sometimes we cannot detect just using our radio and meter. So, IMO we see here details that just don't seem to matter much...with a few exceptions.
If we consider many other more important actors brought to light by folks like Bob85, The DB, and some other's that have long left us...we might easily see issues that just go by without due consideration...out of convenience alone. In the end some issues make the most obvious differences with our CB antenna performance or the lack...and IMO those are the ones that can go ignored.
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I'm noticing a common theme with them all which basically sums up my thoughts for years.....
Not even half a S point difference between best and worst at low angle and to get any worthwhile difference you need to go horizontal/mult-element. Even if you throw in a basic 1/4 wave ground plane vertical into that mix it's barely half a S point.
So to sum up if you're getting a monopole vertical just buy what you think is the best build quality. Or just get 9ft of copper pipe for the vertical section, four 9ft lengths of wire for the radials and make a simple ground plane antenna.
Not even half a S point difference between best and worst at low angle and to get any worthwhile difference you need to go horizontal/mult-element. Even if you throw in a basic 1/4 wave ground plane vertical into that mix it's barely half a S point.
So to sum up if you're getting a monopole vertical just buy what you think is the best build quality. Or just get 9ft of copper pipe for the vertical section, four 9ft lengths of wire for the radials and make a simple ground plane antenna.
I agree, but there are a few exceptions that show some notable improvements in gain at some angle. If the antenna has other problems, like Bob85 has been telling us about for some time, Common Mode Currents on the feed line...then we should consider it.
Your CB antenna could be disappointing to operate...and you might not even know you have a problem.
A seeming easy way to try and determine these conditions is to add a 3'-6' foot section of added coax at the radio end of you station. If the match or frequency changes noticeably...then you probably have some CMC working badly on the feed line / mast.
A functional Field Strength Meter mint also show such currents present around the shack.
I agree,
people do see a difference but its not the antenna if the change is significant,
its how they are installed
factors other than the antenna itself can make more difference than any small difference in antennas,
you can either include the mast coax & ground wires in the model to see what unwanted currents are doing, or isolate them all so you don't need them in the model
things like local obstructions you can't include in a model can make a significant difference,
vector 4000 has 2 advantages,
it puts current maxima higher above ground which gives it the highest low angle gain when mounted on the same mast,
it also puts current maxima higher above local obstructions,
imho the improvement can be more than just putting current maxima higher above ground.
people do see a difference but its not the antenna if the change is significant,
its how they are installed
factors other than the antenna itself can make more difference than any small difference in antennas,
you can either include the mast coax & ground wires in the model to see what unwanted currents are doing, or isolate them all so you don't need them in the model
things like local obstructions you can't include in a model can make a significant difference,
vector 4000 has 2 advantages,
it puts current maxima higher above ground which gives it the highest low angle gain when mounted on the same mast,
it also puts current maxima higher above local obstructions,
imho the improvement can be more than just putting current maxima higher above ground.
Thanks for the models, I had a bit of difficulty reading them I have to say, though zooming did help as you suggested.
Models are good I think I like seeing them. What I have found is that most antennas have needs in order for their maximum performance to be realized. As such my advice is go for the least fussy one for your install.
These days I have also concluded (along with a thread on this forum) that a very desirable characteristic is to have an antenna that does not have lots of spikes and nulls in its spread of elevation angles. Some antennas are much more prone to CMC issues and is one reason I rate the Gain Master. I have had consistently better DX results on 11m using it for both Sporadic E and F2 layer long haul. Overall it ticks all the boxes.. all currents in phase, high current centre, CMC is minimized by design, lowest angle of radiation, meaning efficient long hops.
Other antennas seemed to have "bad days" much more often but when I put the GM up
I just DX much more reliably. I have tried 1/2 wave silver rods, IMAX2K, T2LT and various mobile whip antennas, base and centre loaded (not less than 1.7 in length)
Some of those seem to have noticeably less gain, more than 1/2 dB at higher angles I bet they don't E layer quite as well. And that becomes quite critical when that is the ONLY dx you are going to get in sunspot minima.
All the ones that are similar to where the I10K characteristically "dips inwards" gain wise at approx 30 degrees might potentially not do as well on the E layer, maybe, just a thought anyway. It looks like about 7dB less than the lowest angle lobe, if I am reading it correctly.This summer I was doing 2,000 mile contacts via what I believe to be multi hop E layer contacts with the GM, it was awesome.
A 7dB loss is roughly like going from 200W down to 40W for those angles, not to mention your RX as well. That could very much be a case of you not being heard or you not hearing the DX station call/reply when your signals back and forth are hovering around the S1-S2 which on my most interesting and longest E layer DX of the summer were.
Models are good I think I like seeing them. What I have found is that most antennas have needs in order for their maximum performance to be realized. As such my advice is go for the least fussy one for your install.
These days I have also concluded (along with a thread on this forum) that a very desirable characteristic is to have an antenna that does not have lots of spikes and nulls in its spread of elevation angles. Some antennas are much more prone to CMC issues and is one reason I rate the Gain Master. I have had consistently better DX results on 11m using it for both Sporadic E and F2 layer long haul. Overall it ticks all the boxes.. all currents in phase, high current centre, CMC is minimized by design, lowest angle of radiation, meaning efficient long hops.
Other antennas seemed to have "bad days" much more often but when I put the GM up
I just DX much more reliably. I have tried 1/2 wave silver rods, IMAX2K, T2LT and various mobile whip antennas, base and centre loaded (not less than 1.7 in length)
Some of those seem to have noticeably less gain, more than 1/2 dB at higher angles I bet they don't E layer quite as well. And that becomes quite critical when that is the ONLY dx you are going to get in sunspot minima.
All the ones that are similar to where the I10K characteristically "dips inwards" gain wise at approx 30 degrees might potentially not do as well on the E layer, maybe, just a thought anyway. It looks like about 7dB less than the lowest angle lobe, if I am reading it correctly.This summer I was doing 2,000 mile contacts via what I believe to be multi hop E layer contacts with the GM, it was awesome.
A 7dB loss is roughly like going from 200W down to 40W for those angles, not to mention your RX as well. That could very much be a case of you not being heard or you not hearing the DX station call/reply when your signals back and forth are hovering around the S1-S2 which on my most interesting and longest E layer DX of the summer were.
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What about an Imax 2k, 24' long, at 44' to coax connector. Not insulated from the mast, no common mode choke, mast isolated from earth at 10' above the ground?
It has <1.7 SWR on 15m, <1.5 SWR on 12m, <1.2 SWR on 11m, and <1.3 SWR on 10m up through 28.600.
It has <1.7 SWR on 15m, <1.5 SWR on 12m, <1.2 SWR on 11m, and <1.3 SWR on 10m up through 28.600.
Homer, what frequency are you tuning at to start. Maybe 21 mhz bottom of the lowest band? How about radials?
Do you have a picture that describes this setup better. I'm afraid I'm missing something...I can't even get close with your description for some reason. I sure don't see any multi-banding and my Imax models are able to do that...if I build it to specs and use slanted radials.
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Tuned to 27.205 Mhz.
No radials except 5 guy wires on the mast pipe are conductive. They are 8' down from the feedpoint.
Its just an Imax 2000 on a 44' metal mast, but the bottom 10' is wooden. Mast is 10' wood, then 34' metal. No choke on the feedline.
I'll get a photo later/soon.
No radials except 5 guy wires on the mast pipe are conductive. They are 8' down from the feedpoint.
Its just an Imax 2000 on a 44' metal mast, but the bottom 10' is wooden. Mast is 10' wood, then 34' metal. No choke on the feedline.
I'll get a photo later/soon.
Homer, I remember a multiband wire antenna I worked on with you sometime back. I have not been able to find that model in the 5000 models in my Eznec folder. Can you help me remember?
I have a recollection of an Imax doing the same. My Imax uses a transformer to match and that is not the same as a mutual variable inductor like Solorcon developed for the A99 and Imax. That could be making the difference. This model of your idea so far is not making a multiband BW curve.
When I use a transformer I can't even change the length of the antenna a bit...to try and improve resonance if needed. I have to first delete the TF'r, fix the resonance issue, then reapply the TF'r with the new match readings. It is like chasing my tail.
The TF'r talkes hold of the model and seemingly hold the match over a very nice broad range of matching resulting in a broad band width.
I have a recollection of an Imax doing the same. My Imax uses a transformer to match and that is not the same as a mutual variable inductor like Solorcon developed for the A99 and Imax. That could be making the difference. This model of your idea so far is not making a multiband BW curve.
When I use a transformer I can't even change the length of the antenna a bit...to try and improve resonance if needed. I have to first delete the TF'r, fix the resonance issue, then reapply the TF'r with the new match readings. It is like chasing my tail.
The TF'r talkes hold of the model and seemingly hold the match over a very nice broad range of matching resulting in a broad band width.
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So, am I to think they are acting like slanted down radials then?
I can't be sure, but I believe the Imax is said to work mulit-band with or without radials. Again that could be the case with their mutual variable inductor matching.
If I'm right, then IMO that matching Solarcon developed should be considered a Ham Operators better tool, instead of a dummy load.
Homer, I maybe looking for discussions that are old, and like in this case are buried in a totally unrelated thread. I'm still having short term memory problems due to the Joe "you know the thing!" Biden's China Covid 19 bat virus, and it gets me frustrated when I can't remember.
My model is not working as you described above.
My model is not working as you described above.
Forget the bandwidth thing and treat that as informational. This antenna, like the A99, has been used as a multiband ham antenna for a long time.
Otherwise, it is simply an Imax 2k mounted 44' in the air.
As for the guys being radials, I don't think so being 9' down from the feedpoint.
Otherwise, it is simply an Imax 2k mounted 44' in the air.
As for the guys being radials, I don't think so being 9' down from the feedpoint.