[HomeBrew] linear scale analog watt meter

[Steven Weber]

I built a BLT with air variable caps and the biggest -2 core Diz sells. To
make it complete, I added a SWR bridge and a nice 4", 500 uA meter. 

I didn't want to pull apart the meter to redo the scale for watts, so added
a bunch of stickers to point to the .5, 1, 2, 3 and 4 watt points. Looks
like crap. Got to thinking it would be nice to have a linear scale, but to
do that the voltage from the SWR bridge needs to be squared. 

I looked through an old National Linear applications book and found a
fairly simple circuit which would square an input voltage and convert it to
a current to drive a meter. Just what I needed. So, I built it and works
FB. 100 on the meter now equals 1 watt, 200 to 2 watts, ect. 

I put the circuit up on my web page, direct link is
<http://www.qsl.net/kd1jv/Linear_analog_SWR_meter.HTM>

The only down side to the circuit is it needs to be run on three 9V
batteries, as it needs a regulated -15 volt supply. It also needs a couple
of dual transistors, which only seem to be available in SMT today. I
happened to have a LM3086 transistor array which worked fine, but don't see
those listed in the catalog anymore.  

72,
Steve, KD1JV
"Melt Solder"
White Mountains of New Hampshire
http://www.qsl.net/kd1jv/