[Icom] Filtering at 9 MHz vs. 455 kHz

Fri, 13 Sep 2002 15:31:27 -0600

I find , on all dual IF filtered rigs that I've used, that the addition of the
455 khz filters (2nd IF) makes a bigger difference in every case... the 9 mhz
(1st IF) will narrow down the passband somewhat, but it really helps the shape
factor when both are inline and selected... 73 de Jordan...

Donnie Garrett wrote:

> Rick:
> I have had both and the 455 Khz works best.   73''s Don / WA9TGT
>
> ----- Original Message -----
> From: "Clifford, Rick" <[email protected]>
> To: <[email protected]>
> Sent: Friday, September 13, 2002 1:32 PM
> Subject: [Icom] Filtering at 9 MHz vs. 455 kHz
>
> > ICOM'ers,
> >
> > I have an IC-746 (original, not PRO) and do primarily CW on 40m. After
> > suffering through several instances of adjacent frequency interference, I
> > decided to buy a filter. The IC-746 has two places where filters can be
> > placed, the 9 MHz and the 455 kHz IF stages. So now I needed to find out
> > which 500 Hz filter to buy. The suggestion from the HRO store was to
> filter
> > at the 455 kHz stage (naturally, the more expensive of the two options),
> > while a call to ICOM suggested that both stages should be filtered (an
> even
> > more expensive option).
> >
> > I ended up installing the more expensive ($180) 455 kHz filter (500 Hz
> > bandwidth). I am quite pleased with the performance, but wonder if I will
> > get significantly improved filtering performance if I also place a 500 Hz
> > filter in the 9 MHz IF stage.
> >
> > Since I have been wondering what the 250 Hz filter is like, an alternative
> > approach is to buy the 250 Hz filter and put it in the 9 MHz stage. Then,
> I
> > should be able to switch in either 250 or 500 Hz.
> >
> > Does any have an opinion about how these filters should be used across the
> > two IF stages? And, is there enough difference between the 250 Hz and 500
> Hz
> > filters to justify having both?
> >
> > Thanks and 73,
> >
> > Rick
> > KF6UEB
> > ----
> > Your Moderator: Dick Flanagan W6OLD, [email protected]
> > Icom FAQ: http://www.qsl.net/icom/
> >
> >
>
> ----
> Your Moderator: Dick Flanagan W6OLD, [email protected]
> Icom FAQ: http://www.qsl.net/icom/