On Tue, 2008-04-29 at 13:16 +0000, Marinus Loewensteijn wrote:
> I am reading up on new technology that has come about since I left ham radio
> back in 1985. Interesting to read about using multiple filters and then
> controlling the bandwidth by "shifting" one filter's passband in regards to
> the other.
My Corsair II does that shift well and achieves a quite narrow CW
bandwidth using the two (9 MHz and 6.3 MHz) SSB filters by shifting the
second IF. I have added a CW filter but I ran the radio a long time
without the CW filter because the IF shift worked so well.
That advantage of the CW filter is that I can pick the tone I want to
listen to.
>
> In the Omni-C filters are "cascaded" and (if I am correct) the bandwidth is
> the same as the narrowest filter. I have been thinking about getting a 500
> Hz (400 Hz) CW filter while being well aware that the audio filters do an
> admirable job.
>
> Browsing the old Inrad website I find that there is a 1000 Hz filter. I
> wonder what the benefits of using such a filter could be in the Omni-C. (I am
> asking since I saw one posting in which the gentleman mentioned he was using
> a 1.8 KHz filter and the 500 Hz audio filter and thought that was about the
> perfect combination)
>
1000 Hz would be perfect for 850 shift RTTY which is uncommon in ham
radio these days. I found a commercial signal like that on 30 meters
last week but I couldn't copy it.
1800 or 2100 are nice SSB bandwidths, I think, and I often add a speaker
or DSP filter to roll off SSB and CW audio at about 2100 Hz. 400 or 500
Hz are nice CW filter bandwidths in most any radio, narrower in some
gets to ringing on noise and I find it harder (after a while especially)
to pick out CW against the ringing tone.
> Many thanks in advance
> Marinus,ZL2ML
73, Jerry, K0CQ
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