Comments on the Omni VI series Filters
Tech-Ed by Ken Brown, N6KB
All Omni VI versions have a 15 KHz bandwidth,
two-pole crystal filter as the 1st filter in the 9 MHz I.F. This filter is
in the receive signal path at all times for all modes.
The next filter in the Omni VI is a 2.4 KHz bandwidth 8 pole crystal filter,
also in the 9 MHz I.F. It is always in both the TX and RX signal path for all
modes except FM.
The third filter in an Omni VI is also in the 9 MHz I.F. It is only in the
RX signal path, and it can be switched in or out. It is controlled by the
NAR button in options 1 and 2. In option 3 Omni VI and in the Omni VI +
there is space for two narrow optional filters in the 9 MHz I.F., and they are
controlled by the N-1 and N-2 buttons. You can use one or the other, or
neither, but not both cascaded. When you select one of these filters it is
cascaded with the 2.4 KHz, 8 pole filter and the 15 KHz, 2 pole filter mentioned
above. The 9 MHz I.F. optional filter(s) can be used in any mode except
FM. They are only in the RX signal path not TX.
The next filters in the Omni VI are on the Pass Band Tuning board. This is
the 6.3 MHz I.F. One of four filters on this board can be selected using
the 2.4, 1.8, 500 and 250 buttons on a version 1 or 2 Omni VI. On a
version 3 or Omni VI+ there is no 2.4 button. You are using the 2.4
(stock standard) filter whenever you don't have 1.8, 500 or 250 selected.
You always use one and only one at a time, they are not cascadeable.
Since you operate so much SSB, you will probably want either the #218 1.8 KHz
filter as your narrow 9 MHz option filter, or perhaps the #220 2.4 KHz, or one
of INRAD's filters. Or, you may find that you like CW much more with the
Omni VI than you ever have before. There is still hope for you. You
may decide on the #217 500 Hz filter instead. With a version 1 or 2, you
only have one 9 MHz option filter space.
It is my understanding that the only stock filters in the Omni VI are the 15 KHz
2 pole and the 2.4 KHz 8 pole in the 9 MHz I.F., and the 2.4 KHz filter in the
6.3 MHz I.F. This leaves you one slot to fill in the 9 MHz I.F. in a
version 1 or 2, and two 9 MHz slots to fill in a version 3 or VI+. In all
versions, there are 3 slots open in the 6.3 MHz I.F., assuming only the 2.4 KHz
stock filter is installed.
I am sure you will love the Omni VI. It is a great radio.
73 DE N6KB