[TenTec] Roof filters

[Bill Tippett]

I wrote:
  > TT 1800  - 1400 Hz (in CW mode only, 1900 in SSB)

YT1NT replied:
  >Roofing filter has one BW in CW, another in SSB?

         I finally figured out what is going on.
Orion always automatically centers the passband
of the roofing filter selected and also automatically
truncates any response below 0 Hz.  If you have Spot
Pitch set to X, the upper edge of the 1800 Hz filter
(which is actually ~1900 Hz BW) will be at X + (1900/2).
For example, if I am listening with Spot Pitch = 400,
the upper edge is 400 + 950 = 1350 Hz.  The lower edge
is still 0 Hz, making it appear that the filter only
has 1350 Hz BW.  In fact it is actually 1900 Hz but
the LF response is truncated below 0 Hz.

         At any rate this makes the 1800 Hz filter
a very nice filter to use for rapid scanning in CW such
as when doing S&P in contests.

                                 73,  Bill  W4ZV