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Jerry,

What is the goal here? Is a wattmeter function really needed inside the
ubitx? Or would it be better as an external attachment that can be used
with other equipment?

For me, measurement of the reverse power is the primary measurement
needed inside the ubitx. It is useful for adjusting an external tuner
and for deciding if the ubitx is at risk from a bad load. I am using
the simple circuit at the nd6t site to get the reverse power
measurement. Right now I am using an external analog meter but I have
an adafruit ADS1015 that I am going to use when I get my ubitx working
again. I am using a little 4x4 breadboard to make an I2C bus expander
and the ADS1015 will feed into this along with the I2C lcd.

Coding for this is extremely simple. You don't even have to convert to
volts. Just display the reading from the ads1015. As it goes down you
know the reverse power is going down. If you want to do it with an
analog pin on the nano you can do that too.

Just my 2cents. FWIW.

On Sat, 05 May 2018 15:52:36 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Kees,

Consensus on the EMRFD yahoo group was that the ebay AD8307's worked
fine:

Some posts there are guessing that when boards get autostuffed from
reels there are often a few parts remaining at the end of the reel,
and the ebay sellers make the remnants available cheaply. Though if
that were truly the case, I'd expect more parts to get sold at 95%
off list price like that.

Diz already has a Stockton/TandemMatch kit at what I think is a
reasonable $12 plus shipping:
Shipping probably has to be
more than $0.70 because of the toroids. Uses 1n5711 schottky diode
detectors.

I mentioned here that I was planning to substitute a couple AD8307's
but Arv convinced me to first try biasing the 1n5711's to make them
more sensitive. /g/BITX20/message/47628
You probably already saw that, it's in this same thread.

I wrote Nano code for the Tandem Match to display forward and
reverse power in Watts, also SWR. but it's also a major rewrite of
all the uBitx code and I got lost in the weeds fiddling with other
stuff for a few weeks. I'll try to get my code going in the next few
days. The AD8307's would give more dynamic range, but I think the
1n5711's with bias will be plenty polite. Displaying Watts and SWR
from the AD8307's linear-in-dB output would be slightly more
difficult on our computationally challenged Nano. I'm planning to
use A6 and A7 for the bridge, move the paddle to digital pins D0 and
D1 (which are currently unused except when downloading firmware).

Anybody worried about smoking their expensive RD16HHF1 FET's could
use the reflected power reading to shut down the transmitter when
their EFHW antenna falls to the ground in the wind. ;-)

Jerry, KE7ER

On Sat, May 5, 2018 at 01:30 pm, Kees T wrote:

I just uploaded the current AGC and Click kit requests. This list
is to help me asses demand so I can have the correct sets of parts
ready. There does not appear to be much demand for boards only,
just complete kits.

I'll post prices later, when I receive the boards and some testing
is done.

I was looking into Don's ND6T Polite Antenna Tuner, but there does
not appear to be much interest and using it effectively may be a
problem, so it's out. I did receive a request for a "Power Level
Upgrade" kit but decided against that because there is a whole lot
of testing to be done when you get into RF Amplification.

What may make sense, unless it's already out there as an add-on
upgrade kit, is a Power/SWR capability using a simple Stockton
Bridge and a couple of AD8307's. I'm quite familiar with the bridge
and the AD8307 parts are getting really cheap <$0.50 each. Wonder
if those Chinese parts are usable at QRP specs ? Would need two
analog inputs on whatever microcontroller .......and, of course,
the ever present requirement for *someone* to provide support
firmware.

73 Kees K5BCQ