[TenTec] Hi Cut / Lo Cut - Orion

["Ten-Tec Inc. Amateur Radio Sales" <sales@tentec.com>]

I'll try to explain Hi Cut / Lo Cut succinctly:

We (Ten-Tec) had a long discussion about whether HI CUT / LO CUT is a 
bandwidth value or a passband tuning value when deciding how to update the 
display on the Orion - it's actually some of both.

For an example of why LO CUT (and HI CUT) are both a PBT and a BW value, 
try this:

Tune in a CW signal.  Put your CW offset (using SPOT) at 600 to 700 
Hz.  Tune the CW signal to match the SPOT tone.  Put the BW value at 1000 
Hz, PBT at 0, select LO CUT.

As you rotate the LO CUT control clockwise, the PBT value increases as one 
side of the filter is moved towards the center of the passband.   Because 
this also has the effect of narrowing the total filter bandwidth, the BW 
value is also updated to reflect the total BW available.  As the CUT is 
narrowed, however, it is also possible to move past the center frequency of 
the filter until the CW signal you are listening to eventually 
disappears.  The BW will still show a value of maybe 450 Hz or so, as that 
is now the BW of the available "distorted" filter after moving one side in 
towards or past the original center frequency.

If only the BW was adjusted, not the HI CUT or LO CUT or the PBT, when the 
filter was narrowed to 450 Hz you'd still hear the CW signal in the center 
of the filter.  As opposed to PBT, where the filter BW is constant and the 
filter is then moved back and forth across the center frequency.  HI or LO 
CUT moves one side of the filter or the other towards or past center 
frequency.

The PBT and BW values are supposed to update on screen graphics and text - 
unfortunately compounding the confusion is a bug that is present when HI 
CUT is adjusted.  LO CUT shows the adjustment of PBT and BW values 
simultaneously, while HI CUT only shows the BW update, not the PBT value. 
This needs to be corrected.

Scott Robbins, W4PA



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