Fair-Rite have come to the party and offered samples so my R&D can continue.
I have asked for a toroid of similar dimensions to the part I already have (5961001701), type 61 material.
The key difference with the requested part (2631801202) is the material type 31.
The ยต for 31 is 10x greater than for 61. 10 turns on a 61 toroid should be the same as 1 turn on a 31 toroid.
or
10 turns on a 31 toroid should provide a lower frequency -20dB point than a 61 toroid.
The penalty is that 31 has a lower upper frequency limit, but that should be OK. The type 61 toroid balun I have developed already has a greater bandwidth than the antenna I have built. The balun has a wider bandwidth than equivalent commercial biconic antennae. So you might wonder why I don't stop and have a beer in celebration of my self-acknowledged genius
So while the theory tells me the 31 material will be a Cinderella solution, the practice might be a little different. I anticipate I will need to play around with the number of turns to trade bandwidth for attenuation. Just like before.
I have built two identical antenna so I can calibrate them Once I have done that, one antenna will be spare. I was planning on selling the second biconic but I doubt anyone will be willing to pay enough for it. If anyone was to ask the price for me to make/sell one of these biconics, that question alone would suggest they can't afford it. So far I have a waiting list of zero.
If I keep it, I can very easily and cheaply make another set of elements that plug-in to create a biconic with a different frequency range. That will be a lot easier if I can make an ultra-wideband balun so I can change-out elements without changing the balun.
The cost/effort of trying the 31 toroid is cheaper/easier/faster than making another set of hubs.
I have started to order the parts for my cheap-as 3 port, X-Y balun balance tester. It might take a while for those items to get through the Christmas crush of presents clogging the mail system.
The more I learn about baluns, the more skeptical I am of the performance of some of the commercial biconics I see advertised. Any unbalance in the performance of the balun will distort the beam pattern. Few, if any, antenna datasheets include a plot of the actual measured 3D beam pattern. I have seen simulated beam patterns, no doubt based on theoretically perfect baluns. Some might say it doesn't matter because the antenna only has to receive in one direction. That chain of thought ignores the effects of the beam not pointing where it should. If I was in the market for an EMC antenna, I would be focusing on the measured beam pattern and not relying on the data sheet and brand name.
I am expecting another pause on this project until I get the 31 toroids and build the 3-port balun balance tester.
Fluffy cats and cute pets always attract lots of views so here are mine.