Hi Steve,
This Unun design uses winding to winding capacitance for leakage
inductance compensation. Capacitance to leakage inductance ratio tuned
by moving primary windings within secondary windings, as shown in the
Unun photo. k increases as primary windings are physically closer to
secondary windings.
I have found it's almost impossible to use classic inductance
measurements for k measurements approaching one. My preferred method is
matching a SimSmith transformer model to measurements, as shown in the
web page under the two titles starting with "2 X FT114-43 4T:30T 3300¦¸
Load SimSmith."
SimSmith model k for this Unun is .996.
John KN5L
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On 5/21/19 7:11 AM, Steven Dick wrote:
Hi John. That UNUN appears to have very good performance without the need
for a capacitor across the primary as used in many commercial units. That
implies to me that it has relatively low leakage inductances. It would be
interesting to measure relative coupling from primary to secondary by
measuring primary inductance of the UNUN with secondary open and then
measure primary inductance again with the secondary shorted. From that, a
lot of data can be derived.
