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[WA4NJY]

   I am just getting into digital. Want to start
with using ICOM 706MKII. Is there much advantage
in using a narrow IF filter? If so, I will opt to
use my Jupiter rather than buy a filter.

          thanks,
                Ed Purvis
                 Bradenton, Fl

[WD8DKB]

Hello Ed: I'm certainly no expert on the subject but i can tell you from my own experiance that if your rig has the ability to use a narrow cw filter while using USB in the SSB mode, it can make a big difference when the band is crowded or noisey. Several rigs that I've owned allowed me to do this. After kicking in the narrow cw filter you can use the I.F. shift to move the narrow passband right to the desired signal. I use 500hz and sometimes 250 hz filters and it works great on PSK31 . I have had no experiance with other digital modes so can't comment on those. Not all rigs will allow you to do this. You'll have to research your rig a bit to find out. You don't have to have this ability to work the digital ofcourse, but it does make a big differance in my opinion. Some rigs can use split mode to accomplish this.  You use vfo-a to xmit in ssb mode and vfo-b to receive in cw mode. That way you can use the narrow cw filter for digital receive. Hope this helps a little.   Good luck and have fun. Max

[W2AEW]

I agree with Max - you don't NEED to have the narrow filters, but it CAN help in crowded conditions.  The ability to use your CW filters + IF shift is MUCH more effective than using a narrow SSB filter.  The "split" technique is very useful for rigs that don't let you select the CW filter when in SSB mode.  I described this technique in a letter I wrote to QST H&K a while back.  See the following link for a copy of that.

http://www.qsl.net/w2aew/psk31filterhk.html

73,
Alan W2AEW

[W2AEW]

...oops - I meant to add that the 706 CAN be used in the "split" mode as described above, so that you can take advantage of the CW filter + IF shift.

[N1ZZZ]

I have operated from several DX locations with the 706 and I usually run RTTY and PSK31.  In both cases, the 500 Hz CW filter works wonders to cut down adjacent QRM.  The 500Hz filter comfortably accomidates most digital modes.

There is a different way to use the CW filter for digital modes without running split.  Bascially you lie to the 706 during the setup.  You first install the filter, and then in the setup menu, tell the rig that the filter is the SSB filter.  The rig will allow you to now use it in SSB mode.  The rig will think its 2.4 kHz, but the filter will only allow 500 Hz through.  Of course this method means that you don't have a filter in CW mode unless you go back to the menu and change the setting.  You will have to used the IF shift to move the 500 Hz passband to the right area, but this is very easy if you are using a waterfall display.

You will not need the filter during most casual digital work, but during a contest or if there is a lot of QRM from a DX station, it does help.

73
Jeremy N1ZZZ