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!



I believe it will work fine with just one improved filter, assuming
that the Inrad really has a better shape factor. Having better shape
factors on both would aid in interference rejection in some
situations, of course.

I've never used an R70, but I couldn't recommend setting it up so
that your SSB bandwidth is significantly narrower than stock at all
times. Ultra-narrow audio is fatiguing to listen to and is _less_
understandable in most situations.

My own preference would be to go with a wider SSB filter (for
clearer audio and better intelligibility), but one with excellent
shape factor and ultimate rejection.

I like adjusting the carrier point so that I can get audio down
below 100 Hz and have a filter significantly wider than 3 kHz for
all listening except when there's very bad adjacent channel
interference, in which case I'd temporarily use a narrower filter or
narrow it up with bandpass tuning.

Preferences vary.


With every good wish,



Kevin, WB4AIO.
--
http://kevinalfredstrom.com/