Don, I've done the bridge null adjustment several times. The red c55 trimmer capacitor is very touchy. Using a ceramic screwdriver, I'm able to get the reading in the 7 to 10 range, but after a few moments, or hours, it will read 30 and sometimes up to 90 at 7100KHz into a dummy load on 5w requested power.
With requested power set to 10w, voltage drops from 13.5 to 12.9 when pressing tune. (atu set to calp) It seems the biggest current change in current (before KAT2 vs after KAT2) is on 30m, 12m, and 10m. Is it normal for current to increase after installing KAT2? Are these numbers in harmony with what you'd expect? I don't have a watt meter, so I'm relying on the RF probe. Here are the before and after measurements: Band Power Current 80 9.7 2.2 40 9.2 2.0 30 9.4 2.1 20 9.7 2.1 17 11 2.1 15 9.3 2.0 12 9.4 2.2 10 9.6 2.3 80 11.2 2.7 40 10.8 2.3 30 10.0 2.9 20 10.8 2.5 17 10.5 2.4 15 10.4 2.5 12 8.2 2.5 10 8.5 2.9 What I'm experiencing, is it normal and expected? Thanks, --mark/ae0mm ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Tuesday, September 25, 2018 5:58 PM, Don Wilhelm <donw...@embarqmail.com> wrote: > Mark, > > First, set the CAL CUR in the K2 menu to 3.50 - and also make certain > the power supply voltage as displayed on the K2 display is not dropping > significantly during a TUNE. If it drops more than 1 volt suspect your > power supply or the power cable. A low supply voltage can cause the K2 > to report HI Cur - the K2 tries to maintain the power requested, and a > lower voltage requires greater current. > > Note that at least 2 watts is required to calibrate the KAT2 wattmeter > and to do a TUNE. > > The first step in bringing up the KAT2 is to balance (null) the > wattmeter. Adjust the trimmer capacitor for the lowest reading in ATU > menu CALn. > > After that, connect a good 50 ohm dummy load and do the CALP setting. > Use an external wattmeter that you trust, or the measurement of the RF > voltage with the RF Probe will work, but requires some calculation in > between adjustments. The external wattmeter is quicker. > > With the ATU menu set for CALP, the relays should be set to open all > paths to the capacitors and to short out the inductors, so I doubt that > those relay measurements are of value - unless one of the relays has an > unsoldered pin 1 or pin 10 which will not allow it to switch. > Check the schematic to see which relay pins should be closed and which > should be open. > > 73, > Don W3FPR > > On 9/25/2018 5:35 PM, AE0MM via Elecraft wrote: > > > Just installed the KAT2 in a newly assembled K2. At power levels greater > > than 8.0 watts, the K2 was displaying the high current warning. The KAT2 > > power calibration was calibrated by measuring voltage with the K2's RF > > probe at the feed point to a dummy load. > > I removed the KAT2 and remeasured the power across all bands. Again, power > > was calculated based on DC voltage from RF probe at dummy load feed point. > > The impedance of the feedline and dummy load were retested. (49 to 51 ohms > > over the amateur radio bands, measured with a sark-110 calibrated using a > > set of reference loads) > > Here are the results: > > Band Power At Load K2 Current > > 80 9.7 2.2 > > 40 9.2 2.0 > > 30 9.4 2.1 > > 20 9.7 2.1 > > 17 11 2.1 > > 15 9.3 2.0 > > 12 9.4 2.2 > > 10 9.6 2.3 > > After remeasuring power, the KAT2 was reinstalled, and its power meter > > verified correct at 5 watts. With the KAT2 reinstalled, rechecked K2 > > current draw at 10 watts on all bands. For each band it measured 20% to 30% > > higher than without the KAT2. > > With the power level on the K2 set to one watt and the ATU set to CALP, I > > used the RF probe to measure a few points on the KAT2 control board, and > > the input from the RF board. At the one watt level, there is approximately > > 1v drop between K17 pins 2/9 and 4/7. ______________________________________________________________ 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
