ETA Active Balun

Overview: Information about the ETA active balun.

Maintainer: Steve Ellingson (Virginia Tech)
This page is http://www.ece.vt.edu/swe/eta/AB/
Updates:
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.

Design Documents

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