this evening I had some free time to spend for starting my very simple
tests with ferrite rods. Picture 1 in the attached zip file shows one of the
rods (about 10mm diameter x 200mm long) together with a short piece of
plastic tube that I have used to adapt the rods to a larger-diameter slotted
aluminium tube - shown in picture 2. As you can see, the longitudinal
cut on the tube is not really regular and "clean". I'm not very good at
working with metals. Nevertheless, I hope it will do the job, that is acting
as a shield between the rods and the coil. Picture 3 shows two of the
three rods I used, each inserted in a short piece of plastic pipe and
protected with heat shrink tube and some masking tape.
Finally, picture 4 shows the very provisional setup that I
used to try measuring Q of an LC pair composed by a 2-gangs variable
capacitor plus a 55-turns coil wound over the aluminium tube containing the
ferrite rods. I performed several measures, with 1, 2 or 3 rods inside the
tube. I saw that using 3 rods increases the inductance significantly. For
example, at an intermediate position of the varcap, resonance was at
1037KHz with only 1 rod inside the tube, but it was at 767 KHz with 3
rods.The Q value also increases slightly using 3 rods, even thought in
my tests I got only a miserable figure of about 30. Anyway, I
decided to go with 3 rods for my next step, that will be to try Litz wire for the coil and see
what happens.
Note: pics 3 and 4 will be
attached to a re-sent of this message.
Regards
D.
