Steve Ellingson (Virginia Tech)
This page is http://www.ece.vt.edu/swe/eta/AB/
09 Nov 2005 UT 1000. Completed new (no-match) active balun, active balun cartridge
26 Oct 2005 UT 1000. New (no-match) design info, minor revisions.
04 Oct 2005 UT 1000. In box mounting & test result.
20 Sep 2005 UT 1000. Posted predicted response plots.
18 Sep 2005 UT 1000. Posted revised schematics + BOM.
In reverse chronological order.
|A cartridge consisting of 2 active baluns, ready for mounting inside an antenna stand. November 5, 2005|
|Inside look at a "production" balun. November 5, 2005|
|Test of first active balun, all boxed up. Stimulus crudely provided by some RG-58 with inner conductor attached to one terminal and shield attached to the other (i.e., no balun). S12 looks just like what is expected. No evidence of oscillation up to 3 GHz. Front-to-back isolation is huge (> 50 dB) despite cheesy RF connections internal to box -- go figure. October 4, 2005|
|Active balun in box. Note the cheesy RF connections. Still, seems to work fine. October 4, 2005|
|The active balun as it stands now: complete board; just need to stuff it in an enclosure (what could possibly go wrong?!). Measured input 1 dB compression point to be -2.8 dBm at 38 MHz; drinks about 160 mA at 12V. September 13, 2005|
|Result from the experiment depicted below. Yeah!! Gain is 23.1 dB (accounting for loss through the hybrid & cables). Bandwidths: 28-45 MHz (1 dB), 25-50 MHz (3 dB), 16-81 MHz (15 dB), but of course these will be jostled about when a real antenna is used instead. September 13, 2005|
|Complete path through both sides of the balun, using a hybrid to provide a 100-ohm differential input. September 13, 2005|
|Result from the experiment depicted below. A bit odd that the flat response seems to have melted a bit; not sure why. Apparently no big deal since that we get flatness back when we have both sides driven (see above). Both sides are virtually the same. September 13, 2005|
|Complete path through one side of the balun. September 13, 2005|
|Result from the experiment depicted below. September 9, 2005|
|Transformer installed on the PCB and set up for measurement. September 9, 2005|
|Result from experiment depicted below. September 9, 2005. Addendum: On Sep 12, 2005, we did the same measurement for the other side and it was the same to within less than 1 dB.|
|One (single-ended) side of the input match installed on the PCB and set up for measurement. September 9, 2005|