Marconi's I-10K with trombone matcher that works.

[Marconi]

With the help of 954 on Quack Shack, I think I'm on the trail of getting this I-10K to working at or very close to a perfect match with the trombone matcher added to my model.

I sent the model to 954, and almost immediately he noticed an issue with resonance for the model. I just modeled the antenna as close to specs as I could get...using my manual and taking measurements, so I never looked at resonance for the model. I still don't understand this anomaly, but I may have to redo the model closer to specs, using the proper taper in the radiator and the radials. For now, these elements in the models below are straight wires, with no taper. I just took a guess as to the average diameters for the radiator and the radials. That may be the problem, but I really don't think so.

I have not tried to tune the model using T1 & T2 like Jay instructs, but I did adjust the tip V7 longer than expected to get this tune at 18' feet high where the match is almost perfect for a 5/8 wave radiator. I was able to get the match down in frequency to 27.205 mhz where it belongs by making it longer for some reason. I don't think this added length should to be construed as the antenna being a .64 wave as some might try to suggest, because the model shows the antenna longer than specs indicate. But, we'll see.

I added another model that is the same, but raised to 19' feet. This was done just to give NB an idea of what I see happen on moving or raising a perfectly tuned antenna just 1' foot. We were discussing this issue regarding his SP500 in another thread here on WWRF.

I don't like the looks of the pattern, but I haven't really compared my other I-10K models to this one as yet. So, this model still needs some work. For those other Eznec modelers out there, the Average Gain Report for this model is not good, just to let you know. I'll have to play with the location of the source. Right now the model is using a split source at the feed point.

View attachment I-10K with trombone matcher.pdf

NB, check out the big difference in the modeling feed point impedance between these two on their Source Data Reports, moving this almost perfectly tuned antenna up just 1' foot. This is not a real world test, but I've seen what I though was the same thing going on in my real world work, and this is why I take notice of this going on.

I believe what you say, but this is what I find, in modeling and in real world testing. I would be very surprised if you could tune your SP500 at 10' feet, and get a perfect 50/0 result on your MFJ249, and then on raising...see the same result using a tuned feed line in 1/2 wave multiples or not.

Changes in physical height of an antenna typically change feed point impedance, not changes in feed line length...unless the feed point impedance is changing for some other reason.

 

[Needle Bender]

Try setting the main radiator element at 255.75" from where it meets the bottom connector bolt to the top hat for ~27.2MHz

262.25" for a .64

I believe the Penetrator is seeing it's own radial system to the degree that it mostly ignores earth ground.

 

[Marconi]

Try setting the main radiator element at 255.75" from where it meets the bottom connector bolt to the top hat for ~27.2MHz

262.25" for a .64

I believe the Penetrator is seeing it's own radial system to the degree that it mostly ignores earth ground.

If you add the wire #2 to wire #3, 72" + 191.25" for model #2, you'll get 263.25" overall. This is measured from the bottom of wire #2 to the top of wire #3, and does not include the length for the top hat, so electrically this model is longer than it looks already and is longer than the actual antenna, which I set at 257.375" for 27.205 mhz. So, we're close on the math. Do you own an I-10K?

NB, the measurements I used here are controlled by the element diameters and I just guessed at an average diameter out of convenience, so I could use two wires and no taper.

In order for us to consider specific measurements and their effects, I will have to set the radiator and radial elements to the specs using taper.

There may be another issue that has to be considered as well. The radials in this model are symmetrical, and the radials on the I-10K are not. That could make a difference as well, because the feed point location is set right over one of the radials and this makes the feed point for my model #2 and #3 in error relative to the real antenna. I did this and used straight wires, because it allows for convenience in modeling and tweaking the antenna. Now that I feel good about the trombone matcher working as expected, I need to fix the antenna and try and duplicate to the "T" for the specs. No more convenience in the model, just a lot of work and a lot more to consider with each adjustment.

A model with 22 wires and over 400 segments is not so simple to work on, without loosing your mind or vision...trying to consider everything necessary. Before I start experimenting with the matcher and length, I want to really get it as close to specs as I can.

I know you're anxious to prove your point regarding the .64 over the .625 element, but that will have to wait until the model is more correct.

 

[Needle Bender]

If you add the wire #2 to wire #3, 72" + 191.25" for model #2, you'll get 263.25" overall. This is measured from the bottom of wire #2 to the top of wire #3, and does not include the length for the top hat, so electrically this model is longer than it looks already and is longer than the actual antenna, which I set at 257.375" for 27.205 mhz. So, we're close on the math. Do you own an I-10K?

NB, the measurements I used here are controlled by the element diameters and I just guessed at an average diameter out of convenience, so I could use two wires and no taper.

In order for us to consider specific measurements and their effects, I will have to set the radiator and radial elements to the specs using taper.

There may be another issue that has to be considered as well. The radials in this model are symmetrical, and the radials on the I-10K are not. That could make a difference as well, because the feed point location is set right over one of the radials and this makes the feed point for my model #2 and #3 in error relative to the real antenna. I did this and used straight wires, because it allows for convenience in modeling and tweaking the antenna. Now that I feel good about the trombone matcher working as expected, I need to fix the antenna and try and duplicate to the "T" for the specs. No more convenience in the model, just a lot of work and a lot more to consider with each adjustment.

A model with 22 wires and over 400 segments is not so simple to work on, without loosing your mind or vision...trying to consider everything necessary. Before I start experimenting with the matcher and length, I want to really get it as close to specs as I can.

I know you're anxious to prove your point regarding the .64 over the .625 element, but that will have to wait until the model is more correct.

I don't own one but the theory should be fairly consistent across the board, I use the M Squared formula 11803 / freq(mhz) x .625 then I subtract the average circumference of the radiator and that usually gets me a 1:1 with very low reactance if any.

11803/27.2=433.95 x .625=271.25-13(top hat)-2.5"(average circumference)=255.75" for .625+6.5"=262.25" for .64 but I thought the top hat was 13". Add an inch if it's only 12" and our measurements are within 5/8".

I remember reading on a forum about someone who had an I10k and got better performance around 100 miles away by extending it to .64 and I was hoping you would try it for a few days to see if you noticed anything.

 

[Marconi]

I don't own one but the theory should be fairly consistent across the board, I use the M Squared formula 11803 / freq(mhz) x .625 then I subtract the average circumference of the radiator and that usually gets me a 1:1 with very low reactance if any.

11803/27.2=433.95 x .625=271.25-13(top hat)-2.5"(average circumference)=255.75" for .625+6.5"=262.25" for .64 but I thought the top hat was 13". Add an inch if it's only 12" and our measurements are within 5/8".

I remember reading on a forum about someone who had an I10k and got better performance around 100 miles away by extending it to .64 and I was hoping you would try it for a few days to see if you noticed anything.

Yea, I understand NB, but it's hard to fully consider guys that probably use just one incident in their radio work to try and set their ideas in granite...like God did for Moses.

If I could find the test report that set this original idea for a .64 wavelength for a Broadcast monopole being better than a .625, you likely wouldn't believe that either. Could someone go thru the steps of doing such a thing and see the results you imagine? Yep! I suppose so, anything is possible.

I use the old "Take a minute, stand back, and think about this." formula to just try and get close, then I tune as best I can. I know on thing for sure, I've never gotten it totally perfect, as you might suggest.

I would also like to understand more about the HyGain idea for raising the radials in their ground plane mounts. I think they still produce some antennas with this design. That said however, I don't believe for one minute that this design will fully and completely decouple the antenna from the Earth affects like you claim, but it is an idea to consider and try to prove.

Regardless of what we hear, there are just too many variables to handle for this antenna business to be and easy process that always can give us perfect results, and for sure in CB.

I'll get off my soap box for now, I posted an image of the I-10K, section 6, on the Top Hat. I guess this section could have changed however. My antenna is pretty old.

I also post an image from Maxwell's 2001, Second edition of Reflections II, page 20-16, Chapter 20. Read this, it may be enlightening on the subject and supports what I been saying since back in the late 80's or early 90's when I originally read the Ballantine report to the newly forming US Broadcast Industry, and the counter report by Japanese engineers that the .64 produced the most gain. There is a distinction to be had here, that only understanding can provide. ^^ ab v c^^

View attachment I-10K Top Hat .pdf

View attachment Maxwell on .64 wave theory..pdf

 

[Needle Bender]

Well, according to Maxwell a 1/4 wave has 5db gain over an isotropic and a 5/8 has 3 db gain over a 1/2 wave. Those are numbers I used to hear back in the '70s, not 1.2db for a 5/8 over a 1/2 and a 1/4 wave is .85db less than an isotropic like I've read lately.
It sounds like the ideal length is 7495 / mhz or 275.5" for a .6346 at 27.2 minus average circumference= 273" minus 10" top hat= 263" or 21' 11" for tuning at 27.2 but where do you measure on the I10k because it looks like it has a 45 degree plate at the base of the vertical radiator.
I would guess the most direct path and measure from the top bolt to the top hat 263" then adjust the trombone for middle C :blink:
I need to find a copy of Reflections by Maxwell. I found that interesting reading.
Thanks Marconi

 

[Marconi]

Dimension Error Notes on my I-10K model.

I was in the process of verifying my dimension notes for my I-10K and I noted these problems with the model.

In addition to some errors I made in dimensions, I also noted there are errors on the physical antenna as well. I ignored these errors before, so I'll just try and estimate what the design calls for in these areas. The main problem for errant cuts and bolt holes a little off center may make for some skewing in the match, since all these errors are in the matching setup area.

I modeled the radials to be symmetrical to the centerline of the antenna radiator out of convenience, and as noted earlier the physical radials are 1.25" inches offset from the center line of the radiator. IMO this may make some significant difference in how the model responds to specific measurements that NB and I might use, while trying to prove his idea of any performance advantage for a .64 over a .625 wave.

I don't wish to make more of this than necessary, but the model is probably far more sensitive to the data entry construction than the real antenna.

Right now I'm waiting for World Radio 954, to get back with some Eznec advice on procedures concerning data entry for the wires. I may just decide to do the model over from scratch, if I'm wrong in my thinking on this issue.

This project may be harder that the original model. We'll see.

 

[Needle Bender]

Marconi are you actually going to put up your I10k? If so why not try Maxwell's dimensions and get as close to .6346(263" at ch.20) as possible and see if that doesn't float your boat and give you that elusive 1:1 swr with 0 reactance?
You might want to adjust it for your favorite frequency if it's higher than 27.2 so it doesn't go over length. It will still be within a 1/4" of a 5/8 wave(.625) on ch.1 if you set the .6346 on ch.40= 261" for the perfect 11m Maxwell I10k.

 

[Marconi]

Well, according to Maxwell a 1/4 wave has 5db gain over an isotropic and a 5/8 has 3 db gain over a 1/2 wave. Those are numbers I used to hear back in the '70s, not 1.2db for a 5/8 over a 1/2 and a 1/4 wave is .85db less than an isotropic like I've read lately.
It sounds like the ideal length is 7495 / mhz or 275.5" for a .6346 at 27.2 minus average circumference= 273" minus 10" top hat= 263" or 21' 11" for tuning at 27.2 but where do you measure on the I10k because it looks like it has a 45 degree plate at the base of the vertical radiator.
I would guess the most direct path and measure from the top bolt to the top hat 263" then adjust the trombone for middle C :blink:
I need to find a copy of Reflections by Maxwell. I found that interesting reading.
Thanks Marconi

You guys just don't get it. Maxwell is talking about free space models if he is comparing something to and isotropic. Real Earth makes a big difference to those results, and there the differences are minimal.

Well NB, like I've commented before, sometimes we find ourselves chasing our own tail, with numbers all over the place. I would guess that Maxwell might be the best source considering..... I used Jay's formulas.

You will note in my original post of model #2, the hand written notes, the antenna worked out to be 263.25" overall length from the bottom of wire #2 to the tip of wire #3, not including the top hat. Regardless of the math or the number, this model tuned out to that length to get the nice match it shows, which is almost perfect, and far from what a 5/8 radiator with horizontal 1/4 radials and no matcher will show, SWR over 20.0:1.

Excuse my notes all over the image.

View attachment Jay's tuning formulas..pdf

 

[Marconi]

Marconi are you actually going to put up your I10k? If so why not try Maxwell's dimensions and get as close to .6346(263" at ch.20) as possible and see if that doesn't float your boat and give you that elusive 1:1 swr with 0 reactance?
You might want to adjust it for your favorite frequency if it's higher than 27.2 so it doesn't go over length. It will still be within a 1/4" of a 5/8 wave(.625) on ch.1 if you set the .6346 on ch.40= 261" for the perfect 11m Maxwell I10k.

Something to consider, if I get the energy and the creek don't rise.

Look at this image and see the 2" wire going from the physical feed point to where it connects to the matcher, 2" inches away. This 2" is radiating, and will make a difference in the antenna's electrical length. I didn't consider that in my model either. Just found another missing 2" inches. This ain't bean bag.

View attachment 6406

 

[Needle Bender]

You guys just don't get it. Maxwell is talking about free space models if he is comparing something to and isotropic. Real Earth makes a big difference to those results, and there the differences are minimal.

Well NB, like I've commented before, sometimes we find ourselves chasing our own tail, with numbers all over the place. I would guess that Maxwell might be the best source considering..... I used Jay's formulas.

You will note in my original post of model #2, the hand written notes, the antenna worked out to be 263.25" overall length from the bottom of wire #2 to the tip of wire #3, not including the top hat. Regardless of the math or the number, this model tuned out to that length to get the nice match it shows, which is almost perfect, and far from what a 5/8 radiator with horizontal 1/4 radials and no matcher will show, SWR over 20.0:1.

Excuse my notes all over the image.

View attachment 6405

Not bad, you're only a 1/4" off! :tongue:

 

[Marconi]

I'm still waiting for my bud 954, to get back with his Elmer's ideas on the Eznec question at hand. Then maybe I'll redo this I-10K.

 

[Needle Bender]

You're making me want to get one just to try the performance at the different lengths myself since it's so easy to tune it for both swr and reactance.

 

[Marconi]

You're making me want to get one just to try the performance at the different lengths myself since it's so easy to tune it for both swr and reactance.

Are you assuming that T1 and T2 do just what you've heard about the tuning? Or is what you've heard, even more vauge than that?

PM me where you're located?

 

[Needle Bender]

I guess I have to go back and figure out which are T1 and T2, unless they are the two halves of the trombone match. I'm thinking the upper half adjusts the resonance / swr and the bottom half sets the reactance. I don't see why even a shorter 19' 6" size like the maco v58 couldn't be tried with the I10k having so much tuning range. It's sure a flexible design.