I bet the GM will SUCK for higher angle DX due to the lowered TOA. I've noticed the Penetrator doesn't hear dx when my neighbor 2 miles away hears it on his Starduster.
Maybe some truth to the rumor that the Merlin55 outperforms the I-10K, but if so, I bet only with regard to higher angle DX.
Hey Marconi, when you get time maybe you could try modeling a .64 with the additional .015 at the bottom not the top, as I believe it must still top-terminate at the 270° current phase point.
Seems your eznec representation shows a higher angle & less gain for the .64 compared to the .625 and that would be wrong as the .64 is already known to have a few degrees lower TOA and a hair more gain.
You're right 007, that's what these models show.
I've heard similar stories as you note, but nobody has ever shown me an ounce of support for the idea that a .64 makes more gain at lower angles than a .625. I sometimes post the chart below to support my ideas. I suggest you read the captions below the images carefully for the true meanings of these charts.
This chart probably originated from the testing of the 5/8 wave idea back in the 1920-1930's and it doesn't show the .64 wavelength at all. Would you consider this chart strange in that it doesn't indicate a .64 wavelength? If you have a reference for the claim you note, then I would appreciate the reference of a link to it.
I make no claims for the accuracy of my models, they are what they are, and I'll encourage and consider any critique that will give me better knowledge. In this case with models, I use them simply to support my thinking about what knowledge and trends they might reveal, trying not to make claims out of thin air. I'll change my mind on any topic with good arguments or if I'm convinced I'm wrong thru reliable type evidence. I'm here to learn something and not to defend bad ideas to my dying breath, even though I'm sure I have a few.
I didn't use tapper in either model. I arbitrarily made the radiator tubing diameter .75" and the radials .50" just to try to get closer than thin wire will get me to the real physical antenna. My Eznec version is limited to 20 segments per model total, so I can't get too ambitious in my efforts.
There are guys out there with more and better knowledge on Eznec and they can surely prove or disprove these models if that is necessary.
007, I was as surprised as you were in these results, right or wrong.
Regarding the raised GP on the HyGain Penetrator. I have always thought this feature added something positive to that antenna design, but it was just a guess with me cause I can't prove anything---not even real world experience with that one. You'll have to wait till I get excited enough to get a better version or one of our local modelers will have to try and model it for us.
I just know enough to be dangerous sometimes.
Another thing I noticed about the .625 vs. .64 is, the .64 should be much more efficient to match, because it seems at some point just beyond the .625 length---something happens with the radiator where the value of R and X both drop down much closer to the desirable range considered good. So, the matching requirements should be much less and therefore it should provide for much less loss in matching or transformation. Whatever advantages that might really have in the real world---I do not know.
I also disagree that the GM will suck with higher angle DX, because if you check the pattern I posted for the 5/8 wave dipole you will see there is still a nice gain noted between 10 to 25 degrees. There is also a 40 degree lobe area with some gain, but I don't think that will be very productive except maybe for backscatter when conditions permit.
