Guy, Here is my experience;
The image may be nulled to about -80dBc at a fixed frequency but it will degrade either side of this (to about -70dBc at +/- 4KHz). You can certainly hear the image if it is strong enough. The present software only supports one set of quadrature balance and IQ gain correction values so performance is not maintianed from band to band. With a fixed set of corrections applied on 40m I see about 60dB of image rejection on all bands up to 20m. It degrades on the higher bands. I'm hoping that when the impulse generator code is made available the SDR will be able to optimize it's image rejection on any selected frequency. David. KM5TZ ----- Original Message ----- From: "Guy Olinger, K2AV" <[EMAIL PROTECTED]> To: <FlexRadio@flex-radio.biz> Sent: Monday, May 22, 2006 5:10 PM Subject: [Flexradio] Placing 22khz image in order of magnitude > It would be helpful if someone could tell me about the degree that an > image comes through in a properly adjusted SDR1000 setup? The > following is an entirely plausible situation at an existing contest > station. > > 40m, listening on 5 ele quad to NE suspended from and spaced across > 170' of catenary. > > QTH is Middle Atlantic states. Listening on frequency to pip-squeak EU > CW signal using QRP rig to end-loaded whip on apartment balcony. Let's > say .5 microvolts in the RX just for calculating convenience. Likely > in the noise for SSB, but not so for narrow cw filter settings on a > quiet night. Particularly not in the noise for the SDR 1000 settable > filters. > > CW contest station in New England 22 kHz off frequency is running 1.5 > kw working to his SW on a beam antenna. Signal at our station is 30 db > over 50-microvolt-S9 or 1.5 millivolts. Unwanted signal is 70 db above > wanted at the antenna terminal. > > Let's further say that the station ~22 off is in the bad spot for > images, the image is the same tone as the desired signal or close > enough to be in the passband being used. > > Is the image audible? If so, how loud is the image compared to the > desired signal? > > 73, Guy. > > > > > Scanned for viruses by Blue Coat > http://www.WinProxy.com/ > > _______________________________________________ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ > FlexRadio Homepage: http://www.flex-radio.com _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
