On 14 May 2008 at 7:31, drmail377 wrote: > In the end, I would like to see if someone can design a way to > broadband the Softrock input for general-coverage. Yes without input > filtering it is possible to recieve harmonically related interference > if it exists at sufficient level, and even receive signals at the > wrong frequency (but this can be checked by listening at double and/or > triple the receive frequency). But having a "no filter" board to > swtich in along with the ham-band BPF boards would at least allow some > form of general-coverage and the ability to listen to short-wave > broadcasts, certainly worthy of a position on the BPF switch! I've > looked at this too - but again, without a pre-amplifier, the input > transformer's inductance rears it's ugly head when directly connected > to an antenna impedance. > > 73's, David I sell a bandpass filter board that has space for 6 filters and uses 2 FST3251 switches. If surface mount coils are used, it has an insertion loss of 5 to 6 dB. The board is set up to also accept small (T25 or FT-25) toroids to reduce the insertion loss. Switching is done with 3 digital lines. The two extra positions can be used as a straight through and an open.
Dave - WB6DHW <http://wb6dhw.com>
