On Fri, 04 May 2007 09:33:59 -0700, Richard Clark wrote:

As a simple test, pass one very short wire through one bead and measure
its Z (give us a complete description of resistance AND reactance) over
frequency. This will confirm what type material you are using and will
remove unnecessary complexity. Type 43 should show a frequency peak
roughly ten times above your current data's frequency peak.

73's
Richard Clark, KB7QHC


I did find out that part of my test setup was flawed.
My adapter from the VIM probe to the coil did very naughty things.
The new setup completely isolates the balun from any surrounding
influences and stray L/C is minimized.

Testing the bead material properties.
The beads I am using are supposed to be Type 43, DigiKey #240-2119-ND
aka Steward 28B1250-000. They are .875" high, 1.25" OD and .75" ID.

Using piece of wire 3" long bent into a U shape. Measurements are
Magnitude and Angle of the vector.

Freq.
(MHz) Bare Wire Single Bead Two Beads
..5 .58 @ 29.0 4.62 @ 68.2 9.0 @ 70.3
1 .74 @ 46.0 8.09 @ 70.2 15.8 @ 71.0
2 1.15 @ 62.1 14.36 @ 70.2 28.0 @ 70.4
4 2.08 @ 74.7 25.30 @ 67.0 49.6 @ 66.3
8 4.04 @ 81.8 42.00 @ 61.6 81.7 @ 60.3
16 8.01 @ 85.5 68.50 @ 56.4 132.7 @ 54.0
32 15.93 @ 87.3 105.40 @ 46.9 204.0 @ 42.3
64 31.80 @ 88.4 145.10 @ 37.4 279.0 @ 27.9
110 56.30 @ 89.0 181.00 @ 30.6 333.0 @ 13.2


Remeasuring the Balun.
With the new setup, there is not a big difference in the terminated
measurements, but the peak in the open impedance of the primary winding
went from ~7 Mhz up to 11.4 Mhz.


Freq.
(MHz) Open Inductance 200 Ohm Termination
..5 275 @ 74 49.6 @ 9.2
1 491 @ 72 51.1 @ 5.4
2 897 @ 69 51.8 @ 3.8
4 1731 @ 59 52.0 @ 3.4
8 3710 @ 31 52.4 @ 4.4
16 3460 @ -51 52.6 @ 7.2
32 1261 @ -78 51.9 @ 14.4
64 591 @ -84 51.2 @ 35.7
110 291 @ -83 86.8 @ 76.7

Peak 11.4 Mhz 4850 @ -9.0

--Teh