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My Guess is It's An Antenna Specialists
- Thread starter HomerBB
- Start date
I've spent the last hour considering and modifying this new model, and except for the pattern changing a little I don't see why I can't get a match by adding this inductor.
Maybe Eznec will not do what I've tried to do adding a physical element for the matcher without using the Eznec's matching features...which I don't know how to use.
I suggest that a SD'r design is probably better in all regards except it does not provide the radiator to ground feature. Another advantage is it uses no matching device...which increases the losses.
Good luck with this new antenna Homer.
Maybe Eznec will not do what I've tried to do adding a physical element for the matcher without using the Eznec's matching features...which I don't know how to use.
I suggest that a SD'r design is probably better in all regards except it does not provide the radiator to ground feature. Another advantage is it uses no matching device...which increases the losses.
Good luck with this new antenna Homer.
Bob, I think these horizontal radials make the antenna stick around about 25 ohms with any tap points I have available. I've also tried to maintain a good Eznec Average Gain result in my models, and that limits the tap point locations I have to consider.
I did adjust the radiator down to 97" inches and the reactance got better, but the resistive part raised up a little. Even so, I was still in the low range of 25 ohms. The gain also started to decrease, and at some point the resistance began to drop down again as I got to 97".
I think I did try and tweak this matcher dimesions, but I'll have to do it again to make sure I did all the iterations I could think of.
I have had mixed results trying to add what I refer to as series inductive elements in the process of trying to make an antenna resonant resulting in a good match...and without using the matching feature provided by Eznec.
My model for the I-10K with my ideas for the physical trombone matcher on the model seems to work fine, but my model for a Maco V58 does not. Go figure.
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Bob, a good question, but what stub are you referring too?
This will take a little explaining, and I hope I'm up to it, and I can be clear with my words. If you were here by my side...explaining this would be pretty easy as I see things.
If your use of the term TL is to mean transmission line function in Eznec...the answer is no, I did not use the transmission line feature on these particular models.
However, there is a function noted in Eznec called L Network (LN). I did not try that feature either, because I do not understand the use or the distinctions it provides. I can find some words in the manual on the use of LN, but I missed it if Roy gave examples and models for its use. His manual looks to me to be designed more for the pretty well informed about RF.
When I talked to Roy before I bought his product he told me he specifically designed his interface to NEC to make everything easier to use with the NEC technology for the users.
Since Eznec has this L Network function available as a programing feature, it may not be possible for Eznec to handle the physical matcher simply by adding the physical device to the model...like I tried to do.
What I did in my efforts to try and match an antenna like the I-10K, V-58, and Homer's new find...was to try and make a physical matcher...just as the dimensions look on the real antenna. I got this idea that if that matcher was a series type device...maybe Eznec could handle such a device just like the physical antenna does. My efforts to match some of my models has been hit or miss...so I'm not confident in any results I made in this regard, but I tried. I'm also of the opinion that incorporating the matching device on certain antennas is not accentual to seeing antenna results that are also close to correct. Of course the matching will be off the mark and SWR will not be correct.
Frankly I don't think I have ever seen a model where the physical antenna required a matching device, whether the modeler used my physical matching design idea or the Eznec L Network feature. I don't think anybody talks about any differences this might make to the model's performance either, excepting the SWR will be bad. So, go figure.
I also don't think I ever have seen a model that used the L Network feature, but if I did...there was never enough detailed information provided about the model for me to try and figure out the use of the L Network feature.
I don't know for sure, and I can only guess, but in modeling simple antennas like vertical CB stuff...it may only require us to model the primary radiating elements in order to get a good enough idea about performance and still stay within the limitations were AG shows good.
When I look at models produced by one of the notables in the art...I don't see any of them modeling the matching device if one is necessary for the antenna to work, whether or not the use of a physical matcher, like I tried to make, or using the L Network feature.
'Doc, although your comment vaguely approaches an answer to my lack of understanding on this subject, I think I understand that much. I also think this Eznec LN feature probably allows for two, maybe more, different type circuit configurations for this feature.
Now it could be that all other members here on the forum, except me, knows all about the use and application for this Eznec matching devices feature...how they work, what they do, and how they are modeled, but I don't.
Why don't you give me a little help on how and what to do with the NL feature using Eznec. I would consider that to be some helpful information to pass on. And if you can't do that, maybe you could use your skills to complete the model I started, and fix it right.
I will be more than glad to send my work on to you and save you some time.
Can you help me? Other's will be welcome to try and help me out here also.
i mean the hairpin/beta/stub or whatever you chose to call the parallel wires shorted at the far end on homers antenna,
i don't see nec showing anything magic by incorporating the hairpin other than improve the match, you are not alone in thinking the matcher is not needed to make a good model,
the hairpin acts the same as a section of shorted transmission-line,
i know cebik treats them as a transmission-line in his beta match article and talks about the TL function in nec,
what is an i-10k's trombone setup, and how should it be handled in nec?.
i don't see nec showing anything magic by incorporating the hairpin other than improve the match, you are not alone in thinking the matcher is not needed to make a good model,
the hairpin acts the same as a section of shorted transmission-line,
i know cebik treats them as a transmission-line in his beta match article and talks about the TL function in nec,
what is an i-10k's trombone setup, and how should it be handled in nec?.
Bob, just for clarification.
I was just thinking about your comments above, and wondered if you might have meant that the wire that goes from the radiator to ground...should make the radiator show a short at the feed point.
Of course in all cases where I tried my idea of adding a inductor to one of the antennas I mentioned earlier, the connection always had a shorting effect on the feed point.
This is why I referred to these inductors as being in series between the ground and the radiator, and why I though Eznec might be able to provide the model with tuning capabilities, and I could avoid trying to use the L-Network feature which I don't fully understand.
I was writing while you were posting.
This is in answer to your question.
Here is a full view and a closeup of the trombone matcher I added to my I-10K.
View attachment I-10K with trombone matcher..pdf
I no longer have access to Cebik's work, would you have a link to the article I could get at...that you could reference?
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Thanks Bob. I haven't tried to open Cebik's Website in a long time, but I saw somewhere that we had to pay to see his stuff sometime after his death, and I never did want to pay.
I will look close at this Cebik report.
Here is the matching results for the two I-10K models I posted earlier. It shows the difference in match I got using the trombone design I added to the model without a matcher.
View attachment My I-10K matching results with and without a matcher.pdf
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Marconi, somehow i misread the tape on the antenna dimensions. Everything is 106.25" long.
Also, I shortened the vertical radiator to 102.5".
Also, I shortened the vertical radiator to 102.5".
Shame on you Homer I had to by a tape measure with digital read out for my wife she never could figure those little lines out or are you like me too lazy to go find those glasses you only need for reading ! ( lol ) Now I guess we wait for Mr . Marconi to figure out the new numbers .
357, I have not been making notes on my modeling efforts for Homer's new found antenna, because I didn't anticipate all this interest in this very old idea...at least as far as my modeling is concerned. So, without notes indicating earlier results...I would have to repeat all that work.
However, I recall making several models with different element lengths ranging between the 108" suggested in the ads we saw, and the 104" that Homer originally reported. I also shortened the radiator to around 97", but none of these models ever showed me anywhere near 50 ohms resistive at the feed point or I would have posted such results.
I requested "Doc and other's for help using the Eznec L-Nework for this model earlier, because I also said earlier "...I wasn't sure my idea of adding a physical model as a matcher for my Eznec models needing matching...was working as I had hoped." All of my previous experiences with this idea had given me mixed results. But I tried the idea anyway.
Since no other antenna modeler with experience on this forum has come forward with any assistance using the Eznec L-Network feature, I don't believe my retrying some updated dimensions now...would make this antenna show better results and a much improved match.
As I noted above, in all the dimensional iterations I have tried, none improved the match anywhere close to 50 ohms resistive.
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