Paul, Rather than trying to do your proposed test, I would suggest you look carefully at the T/R switch area first. Typical problems are diodes oriented wrong (check against the Parts Placement diagram in the back of the manual). A broken lead (or unsoldered, poorly tinned, etc.) of RFC3 could cause similar problems - be certain RFC3 is wound on a ferrite core (dark gray) and not one of the black cores.
73, Don W3FPR Paul Fletcher wrote: > > Don Wilhelm-4 wrote: > >> A drop in signal at the receive output of the LPF could also be caused >> by a T/R switch problem. >> >> > > Update so far. Having terminated the LPF's in a 50 ohm resistor I can > definitely confirm all of the LPF's are fine. I measured swr and monitored > in / out on the scope and loss is negligible. As soon as I reinstate W1 the > output of the LPF is pulled low (50% of level when terminated with 50 ohms). > I guess the next step is to do the same check with the chain broken after > the T/R switch and progressively work down the chain. The is no ground short > on the input to the band pass filters at DC. I can't directly terminate the > T/R switch at W6 because of the DC bias so what value blocking cap should I > use? > > Any other thoughts appreciated. > > 73 Paul M1PAF > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.709 / Virus Database: 270.14.76/2517 - Release Date: 11/21/09 > 02:47:00 > > ______________________________________________________________ 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
