Wait, shouldn’t the sensor be before the antenna tuner? I don’t think a sensor should be connected where it’s not 50 ohms.
Al W6LX/4 > On Apr 7, 2023, at 9:22 PM, Dave New, N8SBE <n8...@densbe.com> wrote: > > Alan, > > I tried changing the SensorCal entry, but you are correct there isn't enough > range. It only cut the reading by less than half. > > When I change the MtrScale entry, it changes the meter scale, but it still > shows over 800W (and runs over the smaller scales) in text on the screen. > > I did a visual inspection of the sensor board, but without a schematic I > couldn't check the resistor and capacitor values. I couldn't find a > schematic for the P3 TX Mon sensor board. Do you have one handy? I did find > schematics for the sensors themselves in the W2 documentation. > > And yes, the SWR is way low, about 1.5, compared to what my KAT500 shows for > the antenna side of the tuner (I have one of those display boxes on the > KAT500, so I can see all the tuner values). I have the P3 sensor between my > KAT500 and the antenna feedline using a short coax jumper between the KAT500 > and the sensor, which is currently going to a 75 ft coax run to a ZS6BKW > window-line fed dipole in an inverted vee configuration. In the past, I've > seen 'raw' SWR of 2.5 to 4:1 or so on 80m in particular. On 40m right now, I > have 2.93 antenna SWR shown on the KAT500, which is corrected to 1.18 SWR > reflected back to the KPA500 or the K3s if the KPA500 is in bypass mode. > Given my setup, the P3 SWR should agree closely with the KAT500 antenna-side > SWR, but it is about half. > > 73, > -- Dave, N8SBE > >> On 2023-04-07 17:15, Alan Bloom wrote: >> Hi Dave, >> There is a "SensorCal" entry in the Transmit Monitor Menu, but I don't >> think it has enough range to correct such a large error. >> There is also a "MtrScale" entry to set the full-scale power on the >> meter display. Does the reading change when you change the scale? >> In addition to the I/O board, the problem could also be on the Sensor >> board (the small board that connects the sensor RJ45 connector to the >> I/O board). If one of the resistors on this board went open or >> shorted it could cause a power error. Is the reverse power reading >> way off as well? (i.e. does the SWR read wrong for SWR not close to >> 1:1?) If so, that could be due to a resistor problem on the Sensor >> board. >>> I'm wondering if the new revision I/O board is somehow incompatible with >>> the older TX Monitor board, >> No I don't think so. There was a minor change in the sensor design at >> one point but it was just a capacitor change to improve the detected >> bandwidth so the envelope would display correctly. (The same sensors >> are used for the W2 wattmeter.) >> 73, >> Alan N1AL >>> On 4/7/23 12:12, Dave New, N8SBE wrote: >>> So, I was the guy that had a P3 display/boot problem recently. >>> I sent it to the mother ship for repair, and they found that (get this) the >>> 12V supply was shorted to the 3.3V supply (eep!). >>> So, a new(er) I/O board (which contains the supplies) and a replacement >>> blown 3.3V LCD controller later, I have an (almost) fully functional P3 >>> again. >>> EXCEPT, the TX Monitor function is now funky. It claims that my K3s is >>> putting out 873 (or so) watts! I've tried both sensors (I had a 200W HF >>> sensor on the shelf since I added a KPA500 and changed to a 2KW HF sensor), >>> and although the scale max changes on the P3 display when I change sensors, >>> it still way overstates my output power. The KPA500 is showing 1360 watts >>> on the P3! >>> I unplugged/re-plugged everything, did a visual inspection of the TX >>> Monitor adapter board under a lighted magnifying glass, looking for >>> missing/broken SMD resistors or caps, but so far no soap. >>> I'm wondering if the new revision I/O board is somehow incompatible with >>> the older TX Monitor board, or maybe there is a missing 1M-ohm resistor to >>> ground on the I/O board at the sensor connector, or an incorrect series >>> resistor value there. >>> And yes, I sent a note to support, but I haven't heard back, yet. Wondering >>> if anyone (Alan?) has any ideas where this behavior is coming from. The >>> wattmeter in both my K3s and KPA500 are working normally. It's just the P3 >>> wattmeter that's gone off the deep end, now. >>> Thanks, and 73, >>> -- Dave, N8SBE >>> ______________________________________________________________ >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to n8...@densbe.com > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to alor...@sbcglobal.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
