On Sep 6, 7:34*pm, Buster wrote:
Hi, i just purchased an ICOM R70 and have a question. *Could someone
please tell me if the 455kHz filter used in the third I.F. Needs to be
the same width as the second I.F.? *For example, if I put an Inrad 2.1
or even 1.8 kHz filter (third IF) with the stock 2.3 kHz second IF
filter what would be the result of the PBT? *Would it be better to
replace both IF filters (SSB) with Inrads for better selectivity or
should I just leave the stock 9 MHz filter in place? *Thanks!

The 3rd IF is 455 KHz. The SSB ceramic filter is good.I don't think it
needs to be upgraded (believe it is Murata metal CFx455x series). The
AM ceramic is too wide and has poor -6/-60 shape factor. As far as I
remember,Inrad doesn't have any small size filters like the original
Muratas, just the larger 2nd IF at 9.01xx MHz. The original FL-xx
series are quite decent. And they cost an arm and a leg because they
are crystal ones.That applies to both (Inrad and Icom). KIWA had
some moderately priced ceramic filters at 455KHz . Make shure they
match the pcb holes before buying them. This is critical . Using wire
jumpers in rf circuit (even shielded) may lead to excessive signal
bleedthrough and defeat the whole purpose of doing it. R-70 had
pretty high specs for it's time. Enjoy!