Hello" Endfed people"
I recently got a Fair Rite NiZn core (F-R 595202080) Material 52, size FT 140.
Initial permeability is 250, which is twice the value of material 61.
Loss factor is 45, a bit more than 61 material but still very good compared to material 43.
So the core is good for low loss transformers.
I tried a 1:64 transformer for my endfed antenna with 3 turns primary and 24 turns secondary. Primary capacitance 100 pF. Here are the results:
The SWR measurement was done with a 3k3 load resistor, which matches the impedance of my endfed quite good.
Has anyone else experience with material 52?
Not personally, but I’ll wager if you join the Facebook group “End Fed Half Wave Antennas” it will have been discussed to death I followed that page for 6 months, but the volume of posts was very high (and repetitive), and the level of vitriol too high. Best to join, read, and leave!
Efficiency will be very low with a single FT140-52 core - 56.2% for a 2:14 ratio on 40m. You would need two or preferably three cores to improve it. Alternatively go to the FT240-52 core. Another issue is whether there will be enough inductance to reach 80m. You’ll probably need multiple cores for that as well. All this discussed on that (private) facebook group John mentioned:
73, Gerard - VK2IO
Thanks for your replies. Yes the SWR measurement shows a lack of inductance at 3.6 MHz. My antenna runs from 7 MHz, so it’s ok I think. I have not done a back to back measurement to determine the power loss yet, but there will probably be more experiments.
Thanks also for the info on the FB group. I will check. There was nothing to be found on the reflector.