Martin, You may be reading too much into the instructions. It is not required that the power on 20 meters be lower than on 40, it just usually happens that way. The fact that you have the same power output on 20 as you have on 40 is not necessarily an indication of a lack of 2nd harmonic suppression.
Look at the schematic and you will see that there are two 1000 pF capacitors added to the LPF on 40 meters, and the cutoff frequency when tuned to 40 will be lower than when tuned to 20. The green winding is used on 40, 30 and 20 while both the red and green windings are used on 80. Normally the red winding should be squeezed a bit and the green winding spread out somewhat. Count the number of turns to be certain L1 and L2 are wound correctly. Count the number of times the wire goes through the center of the core rather than counting around the outside. I would not trust the front end of a scanner to determine the relative strength of a 2nd harmonic. If you wish to do that, put a tuned circuit between the antenna and the input to the scanner to give the front end of the scanner some selectivity - it likely is wide open for broadband coverage. The KX1 power display has a lot of granularity, but you can obtain a smooth relative reading from the KXAT1 by reading the voltage from the forward side of the wattmeter with a DMM. One easy to reach place for this voltage is pin 5 of P3. 73, Don W3FPR > -----Original Message----- > > I completed my KXB3080 modification tonight but during testing I > discovered that I am getting pretty much the same transmit power out > (1.8W with 10V) on 40m as 20m (according to the KXAT1 this is the only > watt-meter I have) into a 50 ohm load. I took the board out and > squeezed the green turns on L2 of the LPF1 board together as tightly > as I could and replaced the board back into the case, but it didn't > make any difference I still get the same power out on 40m as 20m. I > understand that this may be an indication that the harmonic > suppression is not working correctly as I should be getting about .6W > lower power on 20m (I certainly was before the mod!) > > _______________________________________________ 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
