AmateurRadio.com

The W1 power meter LEDs give you relatively discrete output information for the lower two ranges (0.1w to 1.4w) and (1.5w to 14w).  But in the high range (over 14w) the LEDs are only displaying 10 watt intervals.  For instance in the high range, when the second LED is lit you don't know if your operating just 20 watts or 29 watts.  It won't trip the next LED until it crosses the 10 watt boundary in the high range so it can be useful to look at the measurement on the computer if you are operating QRO.   I'm not complaining.  I understand that the meter is primarily intended as a QRP meter and for QRP power (less than 15 watts) it offers plenty of information.

My antenna's native SWR at 15m (~21.08MHz) is around 2.5 so it requires tuning (impedance matching).  After my LDG auto tuner spends a ridiculous amount of time trying to find a match it settles at 1.7 SWR according to the W1 Wattmeter, while the indication on the Autotuner is that it believes the SWR is 1.5 or better, while the radio on the other side of the W1 meter sees a SWR over 2.5.  I only see this behavior on 15m so I think there is some strange impedance reaction occurring in the W1 wattmeter that is changing the reactance on the jumper to the radio.  I've tried a few different jumpers, swapping jumpers, etc.  But it always presents an abnormally high SWR to the radio at 15m.  Now when I transmit into a dummy load I don't see this behavior, so it is some combination of SWR / reactance present at W1 that causes a impedance mismatch downstream toward the radio.  I have more investigating to do but for now I am choosing to not use the W1 Wattmeter in-line when operating on 15m.

The CP1 directional coupler is not entirely transparent and raises the SWR by a bit as signal passes through it.  You would expect there to be losses according to the -20 db taps (one forward and one reverse).  This should work out to about 0.08% loss but I wouldn't expect it to raise the SWR. It adds about 0.1 to your SWR  and occurs even if the forward and reverse couplers are switched "off" and shunt their respective loads to the on-board 50 ohm resistors.  I'm unsure what accounts for that slight SWR bump but be aware that CP1 contributes some very small losses.

So the Elecraft Mini-modules are fun to build; and with enough jumper cables, can be combined for experiments and general augmentation of other equipment in your shack.  So go out there, build some kits and experiment.  It's a rewarding experience.

I'm trying to decide what I'm going to build next.