Re: VLF: T106-52 cores on VLF

[DK1IS <DK1IS@kabelmail.de>]

Hi Stefan,

I think the problem are the airgaps between the cores. Perhaps you´ll 
get a little better result if you grind down the coatings at the inner 
front ends of the cores. Although its nearly impossible to get  really 
smooth fitting surfaces in this way there should be some improvement. 
Due to the low conductivity of the core material the loss of coating 
shouldn´t have appreciable disadvantages.
73,
Tom, DK1IS
- still working at his remote garage RX site.


Am 27.04.2016 um 20:20 schrieb DK7FC:
> Hi VLF,
>
> I've done a quick experiment with the T106-52 cores which could give 
> some more ideas regarding these cores for a compact VLF coil.
> I wound a coil with 0.5mm enameled cu wire, 85 turns at 33mm diameter. 
> Inside the coil there are 5 of these cores stacked on another. In 
> parallel there is a suitable C of 1 uF.
> https://dl.dropboxusercontent.com/u/19882028/VLF/20160427_195530.jpg
>
> The resonance was found at 7.49 kHz. The 3 dB bandwidth is (7.64-7.36) 
> kHz = 280 Hz. Q = 27. L = 452 uH.
> Without the cores inside, the resonance frequency rises to 14.54 kHz 
> and the bandwidth is (15.12-14.07) kHz = 1.05 kHz. Q = 14. L = 120 uH.
> Hmm, so in this configuration, the effective µr (ur) seems to be just 
> 3.75! :-/
> That means i still need half of the number of turns for a single layer 
> VLF transmit coil?!?
> 73, Stefan
>
>
> .