Spectrum not clean.
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My K2 is full operative since 10-febr, today I decide to see in the
spectrum analizer how clean is the output and check the power output in a calibrated power meter. The K2 has the ATU inside, so aditional filter in in line with the output. Power is 13.2W from 3.5 to 18, down to 12W at 21Mhz, 6.5 at 24Mhz and 7 at 28. The spectrum has 2 spurious signals at 21 Mhz, up and down the carrier there are 2 signals 45 db down and spacing 1.41Mhz from carrier. At 24 Mhz spurius are up and down too, -43 db from carrier an spaced 312 Khz. At 28 Mhz sigs are -53 db down and spaced 484Mhz. Spectrum in the other bands down 21Mhz was very clear. Any idea about how to eliminate or reduce this spurious signals, and get some more power at 24 and 28Mhz ? Thanks. Jesús, EA1DAV. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Jesus,
While the spurious output from the K2 is specified at -40 dBc or better, and all the spurs that you report meet that specification, I do admire your goal to keep the spectrum as clean as possible. The specs do state that -50 dBc is typical. A bit of calculation on the 15 meter spur indicates that the 3rd harmonic of the BFO may be mixing with the VFO frequency. I would be inclined to try a low pass filter with a cutoff frequency near 8 MHz before the BFO input to the transmit mixer. Your spurs only occur on bands where the VFO is lower than the output frequency, and on those bands, the bandpass filters are more critical to the elimination of spurs. You should check to be certain all the components in the BPF are correct for those bands. As for the low power on 12 and 10 meters, the first place to look is T2. Be certain the turns are spaced and positioned just like the diagram in the manual and it should be mounted 2 to 3 mm above the board. It will self support on its leads. 73, Don W3FPR > -----Original Message----- > > My K2 is full operative since 10-febr, today I decide to see in the > spectrum analizer how clean is the output and check the power output in > a calibrated power meter. > The K2 has the ATU inside, so aditional filter in in line with the output. > Power is 13.2W from 3.5 to 18, down to 12W at 21Mhz, 6.5 at 24Mhz and 7 > at 28. > The spectrum has 2 spurious signals at 21 Mhz, up and down the carrier > there are 2 signals 45 db down and spacing 1.41Mhz from carrier. > At 24 Mhz spurius are up and down too, -43 db from carrier an spaced 312 > Khz. > At 28 Mhz sigs are -53 db down and spaced 484Mhz. > Spectrum in the other bands down 21Mhz was very clear. > > Any idea about how to eliminate or reduce this spurious signals, and get > some more power at 24 and 28Mhz ? > > > Thanks. Jesús, EA1DAV. > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.3/699 - Release Date: 2/23/2007 1:26 PM _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Hi Dom, thanks by your fast answer, as usual. For now i rebuild the T2
transformer, the new one is at 2 mm from pcb and is exactly as the manual show. No diference at power was noted at any band, just as before. Recheck at band pass filters parts was also done, and all is rigth there. So i think that as you say, this K2 meet specifications. I would be happy if it meet in hight bands as in lowers do, but not all is perfect. I continue inspected for mistakes. Regards. Jesus, EA1DAV. Don Wilhelm wrote: > Jesus, > > While the spurious output from the K2 is specified at -40 dBc or better, and > all the spurs that you report meet that specification, I do admire your goal > to keep the spectrum as clean as possible. The specs do state that -50 dBc > is typical. > > A bit of calculation on the 15 meter spur indicates that the 3rd harmonic of > the BFO may be mixing with the VFO frequency. I would be inclined to try a > low pass filter with a cutoff frequency near 8 MHz before the BFO input to > the transmit mixer. > > Your spurs only occur on bands where the VFO is lower than the output > frequency, and on those bands, the bandpass filters are more critical to the > elimination of spurs. You should check to be certain all the components in > the BPF are correct for those bands. > > As for the low power on 12 and 10 meters, the first place to look is T2. Be > certain the turns are spaced and positioned just like the diagram in the > manual and it should be mounted 2 to 3 mm above the board. It will self > support on its leads. > > 73, > Don W3FPR > > >> -----Original Message----- >> >> My K2 is full operative since 10-febr, today I decide to see in the >> spectrum analizer how clean is the output and check the power output in >> a calibrated power meter. >> The K2 has the ATU inside, so aditional filter in in line with the output. >> Power is 13.2W from 3.5 to 18, down to 12W at 21Mhz, 6.5 at 24Mhz and 7 >> at 28. >> The spectrum has 2 spurious signals at 21 Mhz, up and down the carrier >> there are 2 signals 45 db down and spacing 1.41Mhz from carrier. >> At 24 Mhz spurius are up and down too, -43 db from carrier an spaced 312 >> Khz. >> At 28 Mhz sigs are -53 db down and spaced 484Mhz. >> Spectrum in the other bands down 21Mhz was very clear. >> >> Any idea about how to eliminate or reduce this spurious signals, and get >> some more power at 24 and 28Mhz ? >> >> >> Thanks. Jesús, EA1DAV. >> >> > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.446 / Virus Database: 268.18.3/699 - Release Date: 2/23/2007 > 1:26 PM > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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