While I agree with most of your post, measuring PEP power from a
modulating audio signal is not quite as simple as it looks. The terms
"peak" and "average" power typically are associated with a CW signal.
If you are using the nano as a DC voltmeter then you are probably
measuring a CW signal, not modulated SSB signal.
Measuring a CW signal doesn't help much in setting mic gain to prevent
IMD distortion in a SSB signal.
While all kinds of stuff can be calculated from forward and reverse
power, much of it doesn't help much with someone trying to make a
contact on 7277khz. What you *really* need to know at that specific
point in time is if your tuner is providing a proper match between the
antenna and the transmitter. And it is reverse power that is the best
measure of that.
tim ab0wr
On Tue, 8 May 2018 18:26:01 -0600
"Arv Evans" <arvid.evans@...> wrote:
Tim AB0WR, and others...
Peak power is based on a calculation from average power, or from a
peak power
(doubler) type detector. The Arduino provides capability to do that
calculation,
either from peak to average or from average to peak. By using a
calibrated detector
to measure RF voltage and a current transformer to measure RF current
it is possible
to use software to calculate feed-point impedance at the measurement
location.
Dr. Bill will probably be quick to point out that this does not take
into account any phase
relationships, but neither do traditional forward and reverse power
meters. If your
forward power peak and reverse power dip do not coincide then there
may be a
problem with impedance match involving phase angle errors in the
measurements.
An SWR bridge can be designed to subtract reflected power from forward
power, or
to provide separate readouts for each of them. If using a NANO as
the DC voltmeter
it becomes possible to use forward and reflected power to provide many
different
displays (DB, FWD, REF, SWR, RF Volts, RF Amperes, Watts, Efficiency,
Impedance,
etc.).
It is also possible to install a 1 meter long pickup antenna a few
yards from the
antenna to monitor near-field signal strength and display it on the
NANO DC meter
reading, in DB, Volts, or some other relative field intensity
measurement. Using such
a pickup will tell you whether the FWD peak or REF dip represents
maximum power
into the aether.
Antennas, feed-lines, output filters, and final amplifiers are complex
interrelated
subjects that usually require complex analysis of each component to
arrive at an
accurate statement of fact.
Arv K7HKL
_._
On Tue, May 8, 2018 at 4:47 PM, Tim Gorman <tgorman2@...> wrote:
How are you going to get pep power on voice using the nano in order
to set your mic level? How many ubitx users have even implemented a
mic gain control?
Not everyone uses an antenna that is perfectly resonant on all
frequencies. If you never see any reverse power then your antenna
setup is probably unique.
I'll repeat, probably 99% of people that think they are seeing SWR
on their consumer swr meters are actually seeing nothing but a
reverse power reading. You are saying that most amateurs are not
getting sufficient information from their swr meters.
I disagree. They are getting exactly what they need.
tim ab0wr
On Tue, 08 May 2018 15:08:42 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:
Yes, you want peak power to minimize distortion.
But peak or average, some indication of forward power is better
than none for this.
If I have blown a PA fuse, I'd expect to see zero reverse power.
And if that is all I could see, I'd think all was well.
Once you have the two ADC voltage readings from a Tandem match,
the resources required for computing forward and reverse power
and SWR are given in post 48223. Quite insignificant. And I
have the Nano pins.
SWR is an easy and customary way of showing at least some aspects
of how the antenna system is doing. Most hams are comfortable
with it. For me, showing forward and reverse power would be
sufficient. Also showing SWR seems a reasonable thing to do, and
trivial. Just reverse power, not enough information
