Don: Many thanks for the tips! RFC3 looks to be right. T2 was sitting right on the board but I was able to pry the side next to T3 up so that it is certainly clear of all the leads around it and there was no change. So I guess I will have to wait a day or two until I get home and have a go with an RF probe. I did do a few DC measurements and noticed that the emitter voltage of the driver, Q6, is about 0.25 V rather than the 0.4 V specified in the manual (at 0.1 W power setting...the manual doesn't clearly specify the power setting for the DC checks). I wondered if the beta of Q6 might be a bit weak...but it doesn't quite feel like what would drop the power by 10 dB. The bias is about right...around 1.05V. Thanks & 73, Steve VE3SMA
----- Original Message ----- From: Don Wilhelm <w3...@embarqmail.com> To: Steve Kavanagh <skavanag...@yahoo.ca>; "Elecraft@mailman.qth.net" <Elecraft@mailman.qth.net> Cc: Sent: Saturday, November 8, 2014 5:35 PM Subject: Re: [Elecraft] [K2] Low TX Output on Higher Bands Steve, When comparing the RF voltages between bands, I meant to say to use 30 meters instead of 20 meters as stated. The idea is to compare one band that is producing full output with another band that has the low output. 73, Don W3FPR On 11/8/2014 2:24 PM, Don Wilhelm wrote: > Steve, > > I have found that behavior in K2s that have some problem with RFC3. > Make certain the leads are well stripped and tinned (you should see > some tinned wire above the board) and RFC3 is wound on the right core > - I have found a few where the builder used the black powdered iron > core instead of the ferrite core. > > The winding of T2 can reduce the power on higher bands, but not as > severe as you have, but check anyway to be sure T2 is wound as > indicated in the manual and spaced 1/16 to 1/8 inch above the board. > > You will likely have to do some modified transmit troubleshooting > using the test points indicated in the manual, but at a higher power > setting than 5 watts (I would recommend 10 watts setting). At each > test point, compare the RF voltage for 20 meters with that for 15 > meters. When you find the place where the RF voltage for 15 meters is > substantially less than that for 20 meters, you have identified the > output of the failing stage. > > 73, > Don W3FPR > > On 11/8/2014 10:42 AM, Steve Kavanagh wrote: >> As I proceed with checking the new-to-me (S/N 5133, bare-bones, no >> options) K2 out, I'm finding that the maximum transmit power output >> drops markedly as the frequency goes up. If I set the power to >> maximum, I can get the following approximate powers (on CW): >> >> 80m: 15 W >> 40m: 15 W >> 30m: 15 W >> 20m: 7 W >> 17m: 4 W >> 15m: 4 W >> 12m: 1.5 W >> 10m: 1.5 W >> >> > ______________________________________________________________ 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
