Philip Covington wrote: > On 8/9/07, Robert McGwier <[EMAIL PROTECTED]> wrote: >> Philip Covington wrote: >>> On 8/9/07, Robert McGwier <[EMAIL PROTECTED]> wrote: >>>> http://n4hy.org/20MeterBottom.png >>>> http://n4hy.org/6MeterBottom.png >>> Are these with a dummy load connected or operating into an antenna? >>> The 20 meter picture's baseline is about 10 db lower than the 6 meter >>> baseline. >>> >>> I would be great to see the bottom end of 10 meters also with the >>> radio into a dummy load. >>> >>> 73 Phil N8VB >>> >> >> These were in a dummy load so you could see the spurs at their worst. >> >> Your wish is my command: >> >> http://n4hy.org/20MeterBottom.png >> >> And again I caution that these are done with the beta radio. Six meters >> on my radio needs a preamp but it is utterly trivial to add one. >> >> Bob > > Thanks Bob: http://n4hy.org/10MeterBottom.png <-corrected link > > Since they are all into a dummy load it looks like the NF of the radio > degrades about 5 dB from 14 MHz to 28 MHz and about another 5 dB from > 28 MHz to 50 MHz. Is that a safe assumption? > > 73 Phil N8VB >
On all of the production radios tested so far, on 160 meters, preamp on/off there is under a 2 dB difference. This is because the preamp is tapered off to reduce BCI. The MDS is -130 dBm on 160 and in fact, in the software the preamp is disabled because of this since decreases the overload point and does not decrease the MDS (it does not improve sensitivity because of the BCI protection). If you are using a receive array, and need it, hook a preamp between the RX In/RX out. With a -120 dBm noise floor when using a -10 dB RX antenna with high directivity, many will decide it is not needed. On 20 meters, the MDS is better than my beta radio with preamp on or off and is < -130 dBm. On 6 meters, with preamp on (again, wired in the software) the MDS is many dB better than my beta radio and is only 5 dB worse than 20 meters. Lots of optimization has gone on BY BAND in the final version from what was learned from those of us with the beta prototypes. The single worst thing about the beta prototype radios is they were built by hand with ROHS parts and the person soldering was not a ROHS hand soldering expert (who is?). It took a while to get all of the cold solder joints out with NON ROHS solder! The thing I am attempting to point out with these pix and comments is not the meaasured performance of my beta radio (since the front end and the QSE have changed to much better versions) but that the LO performance is excellent compared to almost any radio I have ever owned in terms of its spurious emissions. That circuit did NOT change from beta to production. 73's Bob N4HY -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ 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 Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
