Ken,
If you are refering to the Y2 filter in the Omni VI+, i changed mine
from the stock 2.4 khz to an Inrad 2.1 filter. I also have optional
filters in the chain as well as the Inrad SSB roofing filter. The
signal is extremely clean and i have received excellent unsolicited
reports on the audio. I would say that experimenting and testing could
be beneficial for some.
73 Paul (N6MYA)
Ken Brown wrote:
>Hi Cal,
>
> There are two common way of generating a SSB signal. There is the
>phasing method, and the more common filter method. In the filter method
>a double sideband signal is generated by a balanced modulator, and the
>unwanted sideband is rejected by a filter, leaving only one sideband.
>Almost every SSB transceiver uses the filter method, and shares the
>sideband selecting filter used in transmitting with the receive function
>in the transceiver. In the Ten-Tec Omni VI radios this filter is 2.4 kHz
>bandwidth 8 pole crystal filter with a center frequency of 9.0015 kHz.
>The transmit signal for SSB and CW modes goes through this filter, and
>in the case of SSB this filter's characteristic determines the opposite
>sideband rejection, and along with the audio circuitry and your
>microphone, it determines the bandwidth of your transmitted SSB signal.
>This filter also determines the maximum bandwidth of your receiver,
>because it is always in the receive signal path, regardless of other
>optional filters in either the 9 MHz IF or the 6.3 MHz IF. (Please note
>that in FM mode this filter in neither in the transmit or receive path)
>Normally this "default" filter is never changed, and will always
>determine your SSB transmit bandwidth. Optional filters in either the 9
>MHz IF or the 6.3 MHz IF only affect receive function, as they are not
>in the transmit signal path.
> It is possible, but generally not advisable, to change the default
>filter. There are two reasons I have heard of for doing this. One is to
>produce "High Fidelity" SSB. There are a number of good reasons not to
>do this. The most obvious is that it consumes more spectrum in our
>crowded bands. Another reason not to use a wider filter in the transmit
>signal path is that it can degrade the carrier rejection. The balanced
>modulator is not perfect, so some carrier is generated and then
>attenuated by the opposite sideband rejecting filter.
> A second reason for changing the default filter would almost only
>be considered by people, such as myself, who don't operate SSB, or have
>another radio to use for SSB. By putting a narrower filter in the
>"default" filter position it is possible to improve the receiver
>selectivity. Selection of the filter has to be done with care, so that
>the bandpass coincides with the bandpass of any other optional filters
>in the 9 MHz IF. The SSB transmit bandwidth would become narrower than
>normal, making the SSB signal probably not pleasant to listen to. It
>could possibly make for a good pile-up busting SSB signal, if the
>filter, BFO frequency and operators voice were all matched just right.
> All of the above applies to the Omni VI radios. There could be some
>differences in the Omni D. I am not familiar with that radio. I am
>certain however that as long as you do not change the stock "default"
>transmit and receive 9 MHz IF filter, your transmitted signal will not
>be changed.
>
>
>
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