Don Thanks for the reply. I have a pretty decent Daiwa power meter. It tracks very well on the other bands and matches the displayed power output of the K2. I think the power level displayed by both the K2 and the Daiwa meter are correct. I do have a decent scope that I could use to verify this.
My first suspicion would be a bad low-pass filter, but the 20m band works fine whereas the 17M band doesn't. I suppose I could have a marginal 20/17m low pass filter that is good enough for 20m but too low for 17m. I only get about 65W on 17M. I'd also need to have a bad 15/12/10 low pass filter. I suppose I could have screwed up assembling two filters. I've been staring at the schematic. Since it happens at both high-power and low-power, I think it has to be a problem in the bandpass filters. When I assembled the chokes, I pulled tight on the wire to try to make nice tight cores. In the process, I broke one of the cores in the 15/12/10M low pass filter. I superglued it back together. I'm waiting for a replacement part. If the problem was restricted to this band, I'd suspect my repair. After breaking one core, I was much more careful about pulling too hard. I didn't wind the rest of the cores very tightly at all. I wonder if they are too loose. I also have an MFJ analyzer. I'm thinking of disconnecting the RF cable from the RF board to the KPA100 and hooking it up. I should be able to switch through the bands and measure the impedance at various frequencies. My guess is that it will show a bad impedance above 17M, but it won't give me any hint as to why. I wonder if a stuck relay on one of the other bandpass filters might cause something like this. I've read though the mail archives and found some suggestions about testing for this. ---- Don Wilhelm <[EMAIL PROTECTED]> wrote: > Rich, > > First question - is your KPA100 wattmeter properly calibrated? If not, this > can be the single source of your problem. > > Second question - how are you determining power output? The K2 power display > will be from different sources when you add and remove the KPA100. If you > are relying on the K2 display indications in both cases, I again refer you to > the first question (because the KPA100 wattmeter is not in the circuit when > you remove the KPA100 and the wattmeter may be indicating too low). > > The power output that you report for the base K2 is quite normal, and the > power gain of the KPA100 is lower on 17 meters than it is on say 40 meters. > > If you are using an external wattmeter to determine the power let us know > that, and if you have a 60 MHz or higher 'scope with a 10x probe that you can > use to measure RF Voltages, that would be handy in the absence of a good > external wattmeter (you said you already have a good dummy load). > > 73, > Don W3FPR > > > -----Original Message----- > > > > I just finished the KPA100 for my K2 this week. The K2 and > > associated accessories were purchased within the last month. > > Without the KPA100, I get 10W or more on each band. Most bands > > provide about 15W, but 10M barely makes the 10W rated output with > > about 10.5W. I think the K2 is just fine. > > > > I added the KPA100 board this week. I get full power on 20m and > > below, but I only get about 70W on 17M and above. If I select > > 50W with the power control, I get 50W out. As I increase power, > > the amplifier tops out. I'm connected to a good dummy load. The > > SWR is 1:1. I'm connected to a good 32A power supply. > > > > If I set the power level for 10W, I can only get about 7W on > > these bands. If I unplug the KPA100 and recheck the K2 > > alignment, I get more than 10W on all bands as stated above. It > > seems as if the KPA100 attenuates the RF signal at frequencies > > above 18mhz. I've inspected the low-pass filters for poor solder > > joints, incorrect number of windings or wrong parts. Everything > > looks good to me. > > > _______________________________________________ Elecraft mailing list Post to: [email protected] 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
