Replacing the FL-30 with the wider FL-70 in my IC-729
A few days of trying out the new wider bandwidth filter has led me to the conclusion that fine tuning of the BFO frequency is mandatory after every IF filter replacement. I had previously done a filter change on a TS-140 and to get the same result I had to adjust the exact BFO frequencies for USB and LSB. The Kenwood and the Icom require different procedures because they are constructed differe ntly but the the aim of the BFO adjustments is the same: shift the sideband envelope so that it fits the window presented by the new filter, with due regard to the desired audio frequency response. Some operators have a higher pitched voice while some have lower pitched (bassy) voice. Aside from the selection of microphone, an adjustment of the BFO injection frequency can modify performance of the IF filter to do a low cut or boost or high cut or boost. There are several ways to implement BFO offsets. We myst remember that offsetting is a necessity unless there are separate IF filters for USB,