Rick Frazier wrote in message ...

Ok for the QRP to barefoot operator, but what about someone that at least
occasionally uses an amplifier?

The only thing I can think of is using more turns in the transformers
and thus lowering the coupling ratio. This would increase the QRO
capability but at the expense of QRP capability. I designed the QROP
Meter to just barely handle 200W so it could easily handle 100W. It's
not designed to be used with an amplifier. I don't have an amplifier,
so 1500W capability was not a priority for me.

The closest thing to what you are looking for is the Tandem Match
Directional Wattmeter project that Roy alluded to. It's available in
the _ARRL Antenna Book_. In fact, I got the idea of separating the RF
and DC grounds from the Tandem Match Directional Wattmeter. You'll
also notice my QROP Meter and a few of the homebrew SWR/wattmeter
designs out there have similarities to the Tandem project, such as the
directional coupler design and the noninverting logarithmic op amp.

Believe it or not, I wanted even more QRP capability (like 1mW instead
of 200mW) than my project actually delivers. However, I found several
constraints:
1. Op amps have offset voltages, and these constrain the accuracy of
low-power measurements. Chopper amps have extremely low offset
voltages, but giving them a 10V input while the power supply is turned
off destroys them.
2. The active rectifier has limited accuracy. It's fine in dealing
with 100mV, but it would be useless in rectifying 10mV.
3. The LM3914 chip has limited accuracy. The internal comparator
amplifiers have a few mV of offset voltages.

I've got a couple of swr/wattmeters (two meters) that provide everything I
need, though they are a bit difficult to read at QRP levels. Autek WM-1
is one of them and currently available, and the other is a SignalCrafter
30 (may not be full name and model, but also not available any more).
Both have ranges for 20w, 200w and 2000w full scale, and show average or
peak readings. They tend to match one another pretty well, especially
considering the WM-1 is less than a year old and the other is probably 20
years old....

Will your meter be able to perform as well? I've found that most LED
based metering circuits are horribly inaccurate compared to a needle based
meter....

My QROP Meter needs to have diode pairs that are properly matched, and
the proper resistance value for the noninverting logarithmic op amp
will vary from one unit to another. If you don't bother to properly
match the diodes or if you don't select the right resistance value,
the instrument will be just as crude as the conventional products
manufactured by MFJ and other companies. Of course, the need to
customize every single unit would kill the manufacturability, and this
would explain why the products on the market are so crude.

On the other hand, I'd love to see a new meter available, particularly one
that would work from qrp levels all the way up to legal limits.... while
providing both SWR and Power metering. I really really dislike dual
needle interpreted displays.

That's even MORE ambitious than my QROP Meter. I'm sure this
QRP-to-1500W instrument could be designed and built, but it would be
MUCH more complicated and expensive than my device. I'm not sure the
market would bear the cost of such a device, which may cost $1000 for
all I know. I highly doubt that even my QROP Meter has a viable
market. Also remember that the QRP-to-1500W device would have to
compete with antenna analyzers, which are only around $300 and show
FAR more detail than an SWR meter. True, you can't transmit 100W
(much less 1500W) into an antenna analyzer, but antenna analyzers
allow you to tune up without emitting a single mW from your
transmitter.

Jason Hsu, AG4DG