[Mobile-Portable] IC706

[Gary Pearce KN4AQ]

At 02:59 PM 1/17/2007, you wrote:
>...
>Didn't have an attenuator handy to rule out the overload problem. Wasn't 
>using the preamp, of course. And was ignorant of the how to turn down the 
>RF gain (combo of RF gain/squelch is selectable and I didn't)
>73
>
>Larry K3VX

The 706 has a 20 dB attenuator readily available - just hold down the 
"pre-amp" button for two seconds and you get the attenuator instead.

The squelch/RF gain control can be set for "dual mode" - clockwise for 
squelch, counterclockwise for RF gain, with "straight up" being the 
dividing line.  You do that in the initial setup menu.  But that control's 
effect is fairly late in the process and may not do what you're looking for.

Front-end overload from 3 miles away is unlikely.  And while the energy at 
16 kHz may be minimal, most receiver's filters are not very sharp at 15 
kHz.  The ARRL labs tested the 706 at 20 kHz and found the receiver to be 
70 dB down at 20 kHz.  Alas, they didn't publish the slope from 15 to 20 
kHz.  My guess is that the receiver is hearing pretty well at 16 or even 17 
kHz, well in to the adjacent channel.  For comparison, my Yaesu 8900, 
generally a pretty good receiver for rejecting intermod, is poor at 
adjacent channel rejection at 20 kHz - only 58 dB down.  My on-air 
experience confirms it - I can hear some hash from strong, 20 kHz adjacent 
channel signals that the 706 doesn't hear.

This being a contest, maybe some of the stations were punching the audio a 
little harder than usual, filling out that spectrum.

73,
Gary KN4AQ




ARVN: Amateur Radio//Video News
Gary Pearce KN4AQ
508 Spencer Crest Ct.
Cary, NC 27513
kn4aq at arvidnews.com
919-380-9944
www.ARVidNews.com