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IC-746 FAQ
4.19
Why is there only one optional 455Khz IF filter slot?
Nobody knows for sure, but the most popular speculation is that it made the radio cheaper.
4.20
Any tips on installing 9Mhz Inrad filters?
Neatness counts. Good soldering skills are a must. Most of the hams who have installed one
report that it was more time consuming than they expected, but nothing they couldn't handle.
KE5DC says,
"Inrad also ships two socket pins that look like they are to be used for the filter. This
doesn't work, as with the pins on the filter, the filter won't fit in between the case and the
fan. Solder the leads etc. directly on the filter pins and then trim the pins to prevent
grounding. My first attempt the pins had poked through the electrical tape and grounded
to the case. It initially seemed like the filter was more effective than it should have been.
Some playing around with the filter settings while listening to a decent signal narrowed
down the problem to the 9MHz filter, and I just redid it and it worked."
4.21
Where do I install a 2nd Inrad 9Mhz IF filter?
According to K7ZL, the place Inrad tells you to put the first filter is way over on one side in
a little opening next to a fan, and that works fine. But he has found a second location. When
you have the rig opened, if you go on a line from the 9 Mhz filters, then to the 455 Khz
filters, and keep on going towards the front panel, you will see a square metal plate on the
circuit board. He mounted his second filter on top of the metal plate, on its side, and it seems
to work fine.
However, KE5DC reports that is very difficult to prevent the cover from coming into contact
with the filter. One could mistakenly force the cover closed; putting stress on the circuit
board causing failure at some point in the future.
G0HDB has installed an InRad filter this way and can confirm KE5DC's comment about the
cover pressing on the filter and thus stressing the circuit board. He overcame this by slightly
deforming the cover to make it clear the filter; the deformation was done (very carefully!)
using the rubber-coated handle of a hammer! It only needs a small amount of extra clearance
so the deformation (a very slight bulge in the cover) is barely visible - if you didn't know it's
there you'd probably never notice it
4.22
Where can I find more information on filter characteristics?
Here are a few places on the WWW where you can find more information on filter
characteristics:
http://www.qsl.net/icom/filters.html
http://www.qth.com/INRAD/IC-756.HTM
http://www.qsl.net/ab4oj/icom/filters/filters.html
http://www.qsl.net/ab4oj/icom/passband/passband.html
http://www.icomclassic.com/tech_data/icom_filter_rev_a.xls
Page 57 of 113
2003-02-08