Don, Great---thanks for the explanation! This is exactly the procedure I followed, but I did inadvertently move beyond the peak on the high bands---those caps are a bit touchy. I resolved it by doing just as you suggested and the peak was easily achieved. Just noting the curiosity, that's all.
73, --Ethan, K8GU/3. On Fri, Feb 7, 2014 at 10:05 AM, Don Wilhelm <[email protected]> wrote: > Ethan, > > The reason you are to first tune the BPF during receive is to get them close > to the correct settings. > You should find the peak during transmit close to the peak observed during > receive. > Certainly some of the BPF inductors and capacitors could be tuned to an > improper mixer product if adjusted farther from the correct point. You have > the VFO frequency which is 4913 kHz away from the correct frequency and any > harmonic of the BFO that could be present in the RF content prior to the > BPF. There will also be other mixing products that you could tune the BPF > to (but you shouldn't). The purpose of the BPF is to eliminate the > undesired mixer products. > > When tuning the BPF on TX, start with the power set between 1.5 and 2 watts. > If it climbs above about 5 watts, exit TUNE and re-enter to bring the power > down again and continue to find the peak. > > 73, > Don W3FPR > > > On 2/7/2014 9:00 AM, Ethan Miller K8GU wrote: >> >> All, >> >> I breathed life into K2/10 #7372 (love that serial number) last night. >> This is going to be fun little radio despite being a 15-year-old >> design! >> >> I noticed one thing that I wanted to ask the assembled experts here: >> When peaking the TX BPF capacitors, there was a perceptible and >> easily-found peak; but, if I got off the peak too far, the transmitter >> power would increase rapidly to >10 watts as I tuned in the wrong >> direction. This must be normal or expected? I did not monitor the >> transmitter spectrum while doing this, so I don't know if it's a loud >> spur that's normally suppressed or an amplifier somewhere is >> conditionally-stable? >> >> > -- http://www.k8gu.com/ Repair. Re-use. Re-purpose. Recycle. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
