Tom Thompson wrote: > Dana, > > The question of sensitivity still remains as far as I can tell. Can you > borrow an attenuator and bring the XG1 down to the noise floor on both > yours and Joe's radio. The 10 dbm difference may be a calibration > issue rather than a sensitivity issue unless you can still hear signals > on your Yaesu that you cannot hear on your SDR. > > 73 Tom W0IVJ > > > N1OFZ wrote: > >> Hi all, >> >> I spent some time last night pouring over the ECO's and determining >> which ones were done to my radio. I did end up taking off the BPF >> board to get a better look at the RFE. Also during this process I >> reviewed the block diagrams that Peter sent (thanks!). >> >> Today with the help of Joe (AB1DO) I was able to test my radio >> against his radio. When we hooked up the XG1 my radio was showing >> the XG1's signal at about S3. It was also quite a bit off frequency >> and suffered from some serious image issues. After a few runs at >> calibrating it and tweaking it back on frequency we ran it against >> Joe's SDR. The result were that the calibrating (with a good signal >> source) seems to help significantly. My radio still seems to be >> about 10 dBm down from his but I believe it to be because his radio >> has the newer preamp (ECO025). We listened to a signal that was >> showing around -90 dBm on my radio vs. his which was showing about >> -80 dBm.
This is just not possible with the way we do calibration. Something else is amiss. After calibration against a known source, BOTH of your radios should read -90 dBm if you present -90 dBm at the antenna terminals. That is because the calibration process removes all of the system differences at the calibration frequency. NOW, you can have a higher NOISE FLOOR than Joe. That is entirely possible. Calibrate your radio so that BOTH OF YOU read the exact same meter readings given the same source (and the peak on the display shows up at the same level on the display). Set your filter to 500 Hz. Read the METER in Signal Avg setting. TURN THE TONE OFF. The meter reading will be of the average cumulative noise power in the 500 Hz filter. THIS IS the definition of MDS as measured in the ARRL labs. It is mathematically equivalent to what they do. Good luck, Bob N4HY >> > >> '73 >> Dana N1OFZ >> >> -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "Taking fun as simply fun and earnestness in earnest shows how thoroughly thou none of the two discernest." - Piet Hine _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
