(Work in progress)
These days, you can buy an antenna analyzer for a few thousand rands easily. But for me, being a radio amateur is about tinkering.
K6BEZ provides the inspiration. Use your choice of an Arduino or a PIC to drive a DDS and to measure the forward and reverse voltages and provide an output to a PC or an LCD screen or whatever. This gives you the SWR only. Measure a few more voltages and you can determine the resistance and the reactance as well. You still can't tell whether the load is inductive or capacitive, but you can work that out by moving the frequency a bit and re-measuring the reactance.
The bridge part of the American QRP Club Micro908 and the EA4FRB SARK 100 are remarkably similar -- the diode polarity for Vz are reversed, and the Micro908 has more gain in the Vr path but those are trivial differences really.
ZS1BTY in Homebrew http://www.sarl.org.za/forum/topic.asp?TOPIC_ID=12085 and http://www.sarl.org.za/forum/topic.asp?TOPIC_ID=13923.
Here's ON5KN's version -- I'll probably go with his component values. This one measures only three voltages -- you can get Vr/Vref from the other three voltages with some math.
For now I'm going with the LM324 because they're easily available. These are specced to work down to ground, so no worries there. The LMC6484 and TLC279 are pin compatible for easy upgrade and the TLC279C can handle below-rail voltages if that proves to be a problem.
I bought a couple of QRP Labs Si5351A synthesizers. They're a lot cheaper than the DDS-60 and go all the way up to 200 MHz so I'm kind of waiting to find out what the negatives are (I was worried about the Si5351A putting out a square wave rather than the sine wave produced by DDS solutions, but KV4GB says that this is not a problem. I guess I will have to verify that.
QRP Labs have Arduino code, as does GitHub. I'm using the latter because excellent documentation.
The PIC is cheaper? Well, not really. I can get a cheap Chinese Arduino Uno for less than $3, and that includes the clock and the power supply and the programmer. The PIC18F4620 that K7BEZ uses goes for about the same, maybe a bit more, but needs a PCB and a crystal and a programmer if you don't already have one. And the Arduino is more powerful and comes with all kinds of libraries, like the Si5351 support mentioned earlier. You can get cheaper PICs, and the performance difference is not that great, so I have no great preference either way. A PIC will probably run longer on the same set of batteries, dunno.
UT2FW's analyser includes a buffer amplifier for the DDS.
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