> I am not certain what you mean by the phrase "the RF watt meter built > into the rig reads correct on 80 and 40, but does not reflect > the lower > power output on the higher bands, its still pegged". What do > you mean > by "pegged"?
The watt meter in the rig indicates 10 plus watts out even though the power out is 5 watts at full power. The RF sense circuit does reflect the lower power, with say 2 point something volts out of the RF pickup instead of the 4 plus volts when the rig puts out 12 watts. Below about 2 volts the RF sense voltage falls off like it should and the watt meter on the front panel starts going down. > > Is the internal RF meter indicating a high RF voltage? If so, you > should believe that the RF voltage is really high and > something is wrong > with your test setup. The detector used in the basic K2 is a simple > diode detector and does accurately reflect the RF voltage, and the > microprocessor calculates that value to watts with the > assumption that > the load is 50 ohms resistive. The voltage reads something like 4 point something volts on 80 and 40 at 12 to 14 watts out, and as I go up in bands and the power falls off, the output voltage drops to something like 2 volts (from memory). I tried an experiment by loading this voltage down with a 10k to ground at the DMM leads and did not see any change except on the watt meter reading on the rig, which went down a bit. I do not suspect a problem with the RF sense circuit. > > Is your load at the time of these measurements a good 50 ohm > resistive > dummy load? Yes. > > If you do have a good 50 ohm dummy load on the K2, then I > would strongly > suggest that you check your connecting coax link before doing > anything else. I tried 2 cables, both are likely 75 ohm as I don't have any rg8x to bnc cables, but the cables are short, like 2 feet long. I will try some rg8x into bnc to 259 adaptors just to be sure. > > What kind of power meter are you using? How has its accuracy > been verified? 2 different ones, and yes, they are in the ballpark. > > We need to know exactly what your setup is before we can provide > informed answers to your questions. > > How are you measuring the current draw? Is this the > indication on the > K2 or are you using some other measuring device? Only by the K2 readout. I suppose its just a rough reading. > > All in all, what I can say at the moment is that the base K2 will > control its power output according to the RF voltage indicated at the > internal diode detector. That detector is not a wattmeter > and needs a > good 50 ohm resistive load in order for the K2 to control the > power output. This does not seem to work past 80 and 40 meters, it does seem to be close on 80 and 40 meters, set the rig for 2 watts out and I get close to 2 watts out and the bar graph power meter indicates 2 watts out. Above 40 meters, the power out is low, the rf sense voltage is lower, but the power is lower then the bar graph indicates. > > As far as adjusting C21 - adjust any of the bandpass filter > elements at > a power of 2 watts or lower. Attempting to adjust them at > higher power > levels can lead to incorrect alignment due to several other factors. I tried it both ways, at 2 watts and full power, and at as low a power I could read on the watt meter, does the same thing, but I think its just some sort of resonance... > > How are you determining that the harmonic content "goes way > up"? That > is unusual and indicates that you have a problem with soldering or > incorrect components somewhere. While I was probing T1, T2, and T3. Its not a valid test of the output of the rig, but under say half power, the signals look clean and normal, as you turn the power up, the harmonics go WAY up past the fundamental frequency. The reason I noticed this is because my O scope was doing a poor job at measuring the signal levels at the various transformer ins and outs. I don't know if this is valid at all, as even at the 2 watt level, power is down on the bands above 40 meters. > > The usual cause of high current draw coupled with low power output is > the Low Pass Filters and/or the T4 circuitry. Do you have T4 > properly > wound? I think so. It looks like figure 6-30 on page69 of the book. 2 turns of green wire, 3 turns of white wire, and the two bare wire links, all pulled tight to the board. > > 73, > Don W3FPR Thanks, Brett N2DTS _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
