Which If Should I Put An Optional Filter Into; What's Different Between If Filters For 9Mhz Vs. 455Khz; What Are The 9Mhz If Filters Best For; What Are The 455Khz If Filters Best For - Icom IC-746 Faq

radio itself. Reported assembly times range from 1-4 hours per filter, depending upon the
skill and care of the installer.
Finally, some claim that there is an insertion loss to the Inrad filters vs. the Icom filters.
However, it's been demonstrated that dropping the noise level also drops the S-meter reading,
possibly accounting for the reports. Bench tests do not show any insertion loss. Your ears
may vary.
eHam.net has several user reviews on Inrad crystal filters at:
http://www.eham.net/reviews/detail/1499
4.11

Which IF should I put an optional filter into?

Realistically, the performance differences between using filters in the 9Mhz IF vs. the
455Khz IF are fairly small and will probably go unnoticed in normal operation.
Most people make this decision based upon slot availability and filter cost.
4.12

What's different between IF filters for 9Mhz vs. 455Khz?

455Khz IF filters tend to have superior performance characteristics while 9Mhz IF filters
tend to be less expensive.
There are other differences (filter blow-by, ultimate rejection, earlier roofing, etc...), but
usually it all comes down to cost. When money is no object, you'll want to use one of each.
On a tight budget, you'll do fine with whatever you can afford.
4.13

What are the 9Mhz IF filters best for?

When dealing with interference from nearby signals, the sooner you reject the unwanted
signals from your RF chain, the better. So a single narrow IF filter in a 9Mhz slot will
sometimes outperform a single filter in a 455Khz slot.
4.14

What are the 455Khz IF filters best for?

455KHz filters tend to have superior shape factors, which seem to do a better job of
eliminating background noise and allow tighter adjacent channel rejection. So a single
narrow IF filter in the 455KHz slot will sometimes outperform a single filter in a 9MHz slot.
4.15

How do I get the best results from TPBT?

TPBT works best when the 9Mhz and 455Khz IF filters have closely matching bandwidths.
Non-matching bandwidths will still work, but are less intuitive, which can cause confusion.
There are several techniques to using TPBT. The one described below has the virtue of
simplicity.
IC-746 FAQ
Page 55 of 113
2003-02-08