Hi Michael, Several of the answers others provided are good but maybe not complete. I could give you a long technical answer but I will try the simple ones for why the gap in coverage.
1. The A/D converter works continuously over that range but there will be images around the nyquist frequency if you don't provide adequate filtering. Nyquist is 122.88 MHz. We need a sufficient band stop around Nyquist to prevent images. 2. The FM band can have extremely strong signals, which we want to attenuate to allow wide band SCU operation. The 77 MHz cutoff was convenient to allow 4m operation for Europe while offering attenuation in the FM band. 77 MHz is the 3dB cutoff of the low pass filter. 3. The 135 to 165 MHz filter offers bandwidth to cover interesting frequencies in the 2m range while attenuating the FM band and preventing images. 4. The radio covers 60m in wide band mode but does not have a separate preselector. Since no one operates 60m in a high power multi-multi contest environment it will make no difference. I doubt that I will ever need preselectors at my home QTH. I don't even expect to need a preamp until I get to 10m and maybe even 6m given my local noise floor. The radio covers ALL current and future bands from 60 KHz to 77 MHz continuously with the exception that 100W is only available from 1.8 to 30 MHz and 50 to 54 MHz. Gerald Hope that helps. Gerald Sent from my iPad On Jun 6, 2012, at 4:48 PM, Michael Hasenfratz <[email protected]> wrote: > Could somebody explain why the SCUs have a break in frequencies from 77 to > 135 MHz? > > Also, what no 60 meters? > > Michael Hasenfratz > Sent from my iPad > _______________________________________________ > Flexedge mailing list > [email protected] > http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz > This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used > for posting topics related to SDR software development and experimentalist > who are using beta versions of the software. _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software.
