Hmm. That's curious because I had inspected the 1:1 Guanella current balun when my Big Ear first arrived because I just had to take it apart and see what was inside, and didn't see anything alarming about the design or implementation.
So I decided to do what any curious person would do, test it and verify the loss myself.
I took another 1:1 Guanella current balun that I built and attached the two back to back after unsoldering the wires from the 3/8 x 24 studs inside the box.
I calibrated my test bed by attaching the output of the Kenwood TS-2000X set to 10-Watts with the test cables attached directly to the Elecraft DL1 dummy load and the test point attached to my Fluke 89 IV, I established a reference level of 9.911 Watts in the "thru" path.
Pthru(W) = (15.591 + 0.15)^2 / 25 = 9.911 Watts, through calibration path
Pdut(W) = (15.163 + 0.15)^2 / 25 = 9.3795 Watts, through DUTs
P(loss) = 10 x LOG (9.3795 / 9.911) = -0.24 dB total for two baluns
Assuming equal power split, where P(loss) / 2 is the loss of just one balun, the measured MFJ-2289 balun loss is -0.12 dB.
Pretty textbook if you ask me. I'd be hard pressed to build a better one.
- Myron WVØH