[ICOM] 756 Pro III vs. Tentec Orion

[Bill Tippett]

N1EA:
 >I agree though a narrow filter as the first i.f. stage (roofing filter) is a
wonderful thing, but it is inconvienent if not done automatically by
switching it in and out when different modes are used.

         Orion switches roofing filters either automatically
(based on DSP BW selected) or manually.  Also, for the most
casual users, Orion's standard roofing filters are all that
is necessary.  Since 6.0, 2.4 and 1.0 kHz filters are standard
in addition to the 20 kHz, they are already narrower than
anything else on the market including the 7800, 9000 and
Inrad's Yaesu mod (except for a 600 Hz now being introduced
for the Ommi VI family).  For contesters and low band DX'ers
concerned about even better performance, Inrad's 600 Hz #762
for Orion improves 1 kHz spaced IMD about 10 dB from the
already best available 84-5 dB using the stock 1000 Hz filter
(per ARRL and Sherwood Engineering).

 >A radio with a 100 Hz roofing filter is pretty bullet proof, but
darned difficult to tune - you have to tune VERY VERY slowly.

         True, but not very practical as a roofing filter, since
it implies very strong signals +/- 50 Hz from your frequency
before they would fall within your pass band.  Practically I see
no need for a roofing filter much narrower than Inrad's 600 Hz
since this takes care of stations spaced 300 Hz away from your
TX frequency.  Two S9+30 signals spaced only 300 Hz apart will
not be very productive for either party...although I did have a
few guys try that in the CQ 160 CW this weekend!  :-)  Of course
Orion and other rigs go to 100 Hz BW in DSP IF stages following
the roofing filters, but that is for a different purpose than
the roofing filter serves (which is to eliminate in-band sources
of IMD products).

                                         73,  Bill  W4ZV