[Icom] Filtering at 9 MHz vs. 455 kHz

[Michael Brown]

Hi Rick=0D
=0D
I bought a used 746 probably around 6 months ago=0D
now, and it came with the Icom 500hz filter in the=0D
9 Mhz IF, and an Inrad 400 hz filter in the 455 khz=0D
IF. It works out really well for me. I've never had a=0D
250 hz filter in any rig, so I don't really know how=0D
that would work. A few years back, I contacted=0D
Inrad, and was wondering about putting in 250 hz=0D
filters in my Kenwood 850. They advised against it=0D
and said two 400 hz filters would be their=0D
recomendation. So, that is the the route I went,=0D
and it worked out very well also. =0D
=0D
73 - Mike K9MI=0D
=0D
=0D
-------Original Message-------=0D
=0D
From: icom@mailman.qth.net=0D
Date: Friday, September 13, 2002 1:34:56 PM=0D
To: icom@mailman.qth.net=0D
Subject: [Icom] Filtering at 9 MHz vs. 455 kHz=0D
=0D
ICOM'ers,=0D
=0D
I have an IC-746 (original, not PRO) and do primarily CW on 40m. After=0D
suffering through several instances of adjacent frequency interference, I=
=0D
decided to buy a filter. The IC-746 has two places where filters can be=0D
placed, the 9 MHz and the 455 kHz IF stages. So now I needed to find out=0D
which 500 Hz filter to buy. The suggestion from the HRO store was to filt=
er=0D
at the 455 kHz stage (naturally, the more expensive of the two options),=0D
while a call to ICOM suggested that both stages should be filtered (an ev=
en=0D
more expensive option).=0D
=0D
I ended up installing the more expensive ($180) 455 kHz filter (500 Hz=0D
bandwidth). I am quite pleased with the performance, but wonder if I will=
=0D
get significantly improved filtering performance if I also place a 500 Hz=
=0D
filter in the 9 MHz IF stage.=0D
=0D
Since I have been wondering what the 250 Hz filter is like, an alternativ=
e=0D
approach is to buy the 250 Hz filter and put it in the 9 MHz stage. Then,=
 I=0D
should be able to switch in either 250 or 500 Hz.=0D
=0D
Does any have an opinion about how these filters should be used across th=
e=0D
two IF stages? And, is there enough difference between the 250 Hz and 500=
 Hz=0D
filters to justify having both?=0D
=0D
Thanks and 73,=0D
=0D
Rick=0D
KF6UEB=0D
----=0D
Your Moderator: Dick Flanagan W6OLD, icom-owner@mailman.qth.net=0D
Icom FAQ: http://www.qsl.net/icom/=0D
=2E

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