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Base New Vector 4K radiator at 0.75 - 0.82 - 0.875 wavelength.

Discussion in 'CB Antennas' started by Marconi, Feb 27, 2018.

  1. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Bob here are the Free Space models at 323" - 356" - 380" inches for the radiator lengths.

    A few years ago I tried to get a NV4K model to work while making the radiator 0.875 wavelengths, but with no success. I just did the same today, by modifying a Vector model to specs in Free Space that works well at 3/4 wavelength, and again no luck.

    I will spend some more time on these two and see if I missed anything.

    Notice how your 7/8 wave does better with the match than Donald's 0.82 wavelength. IMO, this is simply because your 7/8 wavelength is much closer to a 1/4 multiple at 1 wavelength.

    As I've commented before...I cannot question the ability to tune a Vector with a gamma match to various lengths. However. when I tried making my Sigma 4 - 30' feet long, I could not find a match anywhere within the range of the gamma adjustment. I messed with it for a big part of 2 days, adjusting, recording, and testing the match with my analyzer, but no-way-no.

    I also remember Booty Monster having issues tuning his Vector homebrew but maybe I missed finding out what he did to solve his problem. I have a recollection that HomerBB also had some issues too, but he will have to tell us what was going on in that regard...I think I missed that one too. I believe they both made there antennas longer than 3/4 wave, but again I'm not sure.

    I mentioned at some point in the past. all I could see was the frequency dropping when you guys made the radiators longer, and the attached SWR bandwidth curve reports show exactly that. That said however, I can only simulate a gamma.



    I question if a gamma can adjust out this much inductance unless modified too.
     

  2. bob85

    bob85 Supporting Member

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    The vector & sigma will tune to an acceptable vswr over a wide range of radiator lengths Eddie,
    old style vectors were supposedly 7/8waves, i ended up shorter than 7/8wave for best signals,
    using stock sirio length or longer was going backwards even though more of the radiator was above the houses and current maxima higher above ground
     
  3. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Bob I intended to post my models in my last post earlier, but got caught up in the update. Now I can't post a PDF file. I'll have to plan on posting jpeg files if I still have permission for those uploads.

    I will say again, I can't question your success at matching the longer radiators. I understand that both Homer and Booty Monster possibly used longer radiators and apparently they report that their home brews work better that anything else they have bar none.

    My models at 0.82 and 0.875 produce patterns that look like a 3/4 wave radiator with 4 horizontal 1/4 wave radials...and we all know that one is a cloud warmer at best.

    Edit: Bob here are the models in Free Space.
     

    Attached Files:

    #3 Marconi, Feb 28, 2018
    Last edited: Mar 1, 2018
  4. bob85

    bob85 Supporting Member

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    That style antenna has been sold at various lengths from about 27.5ft to about 30.5ft & they all give a low vswr,

    we have swapped the radiators around on an old style vector & avanti sigma4,

    i can imagine the longer versions having a bit more high angle radiation but not like a 3/4wave ground plane cloudwarmer,

    they still outperform any 5/8wave at my old location so i don't know why your model says it all falls apart when you extend beyond 3/4wave,

    or why you could not tune your sigma for a low vswr when you extended it,
    its been a long time since i adjusted one Eddie

    to get in the ball park i leave the gamma rod where it is & move the strap up or down to find lowest vswr, then adjust the gamma rod,
     
  5. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Bob, here are my Vector models over Real Earth. I also modeled a typical 3/4 wavelength GP with 4 horizontal radials...just to show the high angled pattern it will make over Real Earth that is referred to as a cloud warmer.

    I checked my models above and found I had made an error in the first model I did at 356" inches. I started with the 323" inch model in free space and just changed the length of the radiator to 356" inches to simulate Shockwave's ideal length at 0.82 wavelength. The model was of course bad in all respects due to the change in the radiator length. I tried a few adjustments and then I thought maybe I should try changing the segment count and/or length. Every iteration on my models after that was no-way-no, and I did not realize I had made such a change to the segments...which messed up the results in some regards.

    Today, I checked the models and found the mistake.

    I also name the models incorrectly using V2K instead of V4K...so I've changed the titles too...in case anybody notices or I try to recall what the models are later. That title could be taken for an Imax too. Getting old and the eyes are getting worse.

    All the models below show prefect Average Gain Test results in Free Space. Again, this was done to insure all models over Real Earth were based on a model with a good AGT result = 1.

    All models are set at 27.205 MHz with the exception of the last model set at 23.200 MHz...where the 380" inch radiator model shows to be resonant.

    In each of the other two models I started with my 323" 3/4 wavelength model in Free Space. All I did after that was to change the radiator lengths to 356" inches and then to 380" inches. Then I set the FS models to Real Earth models by adding back the mast and the losses. I'm reporting those PDF results below.

    These models are not matched with a gamma match, and a gamma is intended to add capacitance to these inductive antennas and lower the reactive part of the match to a point near or at resonance. I have yet to try that here and see if I can simulate a gamma effect for these very long radiator lengths.

    I will attempt to add a load with capacitance to offset the inductance and make the radiator look shorter.


    5 - PDF files below:

    1. is a 3/4 wave GP with 4 horizontal 1/4 radials over Average Real Earth at 36' feet to the mount. This model was done to show the cloud warming patter such antenna made it the Real World.

    2. are the models with radiator lengths set at 323" - 356" - 380" in Free Space. The first page includes the Eznec Control Center page that shows the Average Gain Test results for each model =<> 1...at the bottom of the page.

    3. are the three models noted above with various radiator lengths over Average Real Earth at 36' feet to the feed point.

    Nothing was done to the last two models except to change the radiator length as has been suggested in this thread as note here. A stock 0.75 wl New Vector 4K to start with. A Shockwaves recommendation for best gain at a distance at 0.82 wl, and Bob's suggested 0.875 wl.

    Bob has corrected this 0.875 wl to be a bit less than noted here, but I did not model his idea yet without a more accurate length if available.

    4. I added a modified model of the 380" (7/8 wavelength) Real Earth model with a 200' foot feed line added. I also included the coax losses. This model is noted as "wTL" in the title for the model.

    5. is another modified model of the 7/8 wavelength, 380" inch model over Real Earth and the frequency set at the 23.2 MHz...the resonant frequency indicated in the SWR bandwidth curve report for that model. The model also includes a 200 foot feed line. This was done to see it the antenna gain improved with the model set at resonance.
     

    Attached Files:

  6. bob85

    bob85 Supporting Member

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    I can't explain why your models show the 7/8 been a cloudwarmer,

    im sure some of the advantage i saw over my 5/8waves must have been due to the extra height over local obstructions,

    having used them & experimented with them for years its hard to imagine the 7/8 vector been as bad as the models tells us,
    on the other hand i could see an improvement shortening the radiator & setting the basket as long as possible with the old style vector,

    going too short back near 3/4wave was worse but that may have been moving current maxima below the surround buildings,

    was it a coincidence that me & Donald ended up at similar electrical lengths by adjusting the antenna in essentially the same way using fringe signals,

    Henry is in an nice open radio location & he found no advantage to extending the radiator over 3/4wave.
     
  7. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Bob, regardless of what these models show, I would be an idiot to believe a gamma could not tune an antenna that is as inductive as the examples being considered here. However, IMO, there is a bit more to the particular construction of a good working gamma. I could be wrong, but I don't think just any old gamma will do in such a situation. I'm pretty sure my Sigma 4 gamma can't tune out that much inductance...I tried that before and I could not find a match anywhere with the tip extended out about 2' feet and less.

    Avanti, Antenna Specialists, and maybe a few others might not have considered the longer radiator idea back then, because in the US the antenna makers were having trouble in CB with the control agencies in the government over antenna heights already.

    Within the last few years Sirio redesigned the Vector and it is reported among other things...they used the best design software CST. Apparently Sirio didn't consider or realize the advantage in a longer radiator either. We got our heads-up from Donald about their New Vector 4K?

    Bob, IMO Sirio was likely concerned with wind and weather problems they were already seeing in Europe for the old Vector. I recall you were complaining about that issue.

    Did Henry talk about the issue for making the S4/Vector longer in his article on "The
    Avanti Sigma 4," and did he test the idea or just give his opinion?

    www.cb-antennas.com
    check the right column, 2nd box, click "Sigma IV."

    Bob, I don't know what HomerBB is up to these days, but he may be the only one capable of giving us a real world report on your idea...that a longer than 3/4 wavelength will produce more gain in the distance.

    If I was still up to the task I would start tomorrow.
     
    #7 Marconi, Mar 3, 2018
    Last edited: Mar 3, 2018
  8. HomerBB

    HomerBB Sr. Member

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    I would have to dig back through some old forum posts to get exact answers to some of your questions, but as my limited memory serves me, the last and most successful V4k I homebrewed had 106.5" basket radials and a 31" diameter ring. I had trouble matching until I built a gamma with a tube somewhere around 17" long x 3/4" diameter with a rod 30" long. It was dicey finding a working relationship between the rod extension amount and the strap from the vertical to the rod location. Once found it did a great job over a significant bandwidth. I tried a 7/8^ length, but believe I backed it down to 3/4^ (27'6") for my best results. Additionally, I added a bracket at the bottom of the cone to hold the radials out from the vertical about an inch. I could make no tuning progress with the radials attached against the vertical with no standoff.
    See this thread
    https://www.worldwidedx.com/threads/vector-4000-remake.144592/
     
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  9. bob85

    bob85 Supporting Member

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    Sirio originally made the 7/8 version much like the CTE lw-150 saliut if not exactly the same,

    who knows why they extended the basket & shortened the radiator,
    we started seeing CST images of the gainmaster around the time Sirio changed the vector,
    afaik Donald obtained the CST image of the vector,

    when i swapped my vector radiator for my sigma radiator because i got fed up with fixing snapped vectors i put the one of my vector radiators with the avanti basket & gamma for my buddy up the road,

    we had no issues getting a low vswr & the antenna worked well,

    The Avanti gamma is teflon & a nice tight fit,
    Sirio gamma is some kind of plastic tube & fits like a turd in a piss pot, worst gamma i ever saw.
     
  10. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Thanks Homer. I seem to recall both you and Booty Monster discussing your gamma match issues at some point, but I don't remember any of the final details. I remember being curious in that regard however.

    IMO, the dimensions you gave in the linked thread shows dimensions that I calculate to 0.82 wavelength. See in the link on posts #2 & #7. This is a radiator length similar to what Donald recommended as showing him the best gain at a distance.

    I have a model of the Vector over real Earth with the dimensions showing 0.82 wl = 29.7' feet or 356" inch for the radiator and 4 x 107" radials.

    Again, this is Shockwave's idea for Vector radiator length that provides the most gain at a distance.
    It shows a pattern that is much better than the 380" inch 7/8 wavelength model at the lowest angle to the horizon, but both of the longer than 3/4 wave models are trending toward the higher lobe becoming dominant.

    Below are the overlays for these 3 models. The (*) beside the title of the model shows the dominant gain and angle results for the model and the details are located to the lower right hand side of the page.
     

    Attached Files:

    #10 Marconi, Mar 3, 2018
    Last edited: Mar 3, 2018
    HomerBB likes this.
  11. bob85

    bob85 Supporting Member

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    As far as i know Henry tested different length radiators in his back yard Eddie,
    you would have to ask him for any details,

    what length radials are you using, old style 90" or new style 107" ?

    380" is about 6" longer than a stock 7/8 vector,
    my signals got worse when i extended beyond stock length but it still tuned acceptably with the stock sirio gamma.
     
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  12. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Well Bob, I think I finally did what I promised you a long time ago when I told you I was determined to learn to model with Eznec5 saying, "...I want to try and prove your testing your Vector Hybrid was just like you were telling folks."

    Honestly though, I haven't quite done that yet, but I just had to say it. I think however, that I maybe I have proven Donald was right about his 0.82 wavelength radiator idea, but I'm not sure he would be pleased to see such a small difference.

    I told you the other day I was not finished and I wanted to try and modify my model to take care of the inductance in the model with my simulation for a gamma match.

    Here is Donald's 0.82 wl = 356" inch model that has been fixed just like I thought it might. It shows a modest improvement in gain over my model of the 3/4 wave NV4K model I have set at 323" inches.

    The model responded just like I was tuning the gamma match. I could possibly tweak the model to better numbers, but it will not change the gain one bit. I saw the gain staying steady on 4.63 dbi in the final iterations before I stopped piddling.

    I'm not sure yet about the 7/8 wl model, but your new info on the radiator length will be helpful in getting started with that model.

    BTW, these Vectors models are a close to specs as I can get them. The radials are very close to 107" inches 106.99" inches to be exact. Remember, I'm the guy that always pesters everybody and pisses some off about the specs and the dimensions. I try and do my research on that score too...even if being accurate on dimensions might not make much difference in the end. Maybe 6" inches on your 7/8 wave won't make much difference either.

    I'm still waiting on Shade Tree Mechanic to get us his dimensions, so I have another viewpoint to consider.

    Bob, you're the man!
     

    Attached Files:

    #12 Marconi, Mar 3, 2018
    Last edited: Mar 4, 2018
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  13. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I didn't forget, keep up the good work guys!
     
  14. bob85

    bob85 Supporting Member

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    something i noticed about 7/8 vectors is altering the radiator a few inches does not effect vswr as it does with other antennas,

    i doubt you would see much if any difference in signal extending a 1/2wave by 6 inches & retuning because its well short of 5/8wave, but you do see a difference with a vector that is already too long,

    you could reasonably expect that having more of the radiator above local obstructions gives the extended version the advantage,
    current maxima is also higher above ground so gain should be higher too,

    that does not hold up in my tests, i saw a drop in performance extending beyond stock 7/8 so something else is happening that takes more away than i gain by having a better view over obstructions & current maxima been higher above ground.

    conversely shortening from stock 7/8 gave me an increase in signal strength even though i was lowering current maxima & less of the radiator was above the local obstructions,

    bear in mind that sweeping the radials up towards the radiator electrically shortens the radiator so it needs to be longer than the same radiator without radials for resonance,
    how much longer when using 4 x 107" radials at that diameter & spacing i don't know.
     
  15. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Homer, here are some measurements off of an old Vector knockoff LW150 gamma as tuned when I took it down. I did not measure the radiator length however. I do not know the frequency, but the guy was into CB and on sideband in the top of CB. These measurements are as tuned when I took the antenna down.

    The base tube is 5/8" x 14.25" inches.
    The overall rod is 35" x 3/16" inches.
    The exposed rod is 20.5" x 3/16" inches.
    The Center of the dog bone is 32" inches from the base @ the feed point.
    The dog bone is overall 7" inches long and is 3/4" wide made of aluminum flat stock about 1/16" thick.
    Center of rod to center of radiator is 6" inches.

    If these gamma images work I'll post two paper images of this antenna from my file...in a PDF file in another post below. You might be able to get some ideas about dimensions from the images.

    upload_2018-3-4_12-12-49.jpeg

    upload_2018-3-4_12-14-34.jpeg

    upload_2018-3-4_12-15-43.jpeg

    upload_2018-3-4_12-17-7.jpeg

    upload_2018-3-4_12-19-5.jpeg

    upload_2018-3-4_12-20-15.jpeg

    upload_2018-3-4_12-21-46.jpeg
     
    #15 Marconi, Mar 4, 2018
    Last edited: Mar 4, 2018
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