Dick: The DDS-34 output (the DDS that matches the Soft66 receivers) varies with the frequency. Looking at the DDS output on a spectrum analyzer, when set at 6.2 mhz, it has output every 15 khz for nearly 3 mhz either side of the set frequency. The closest signals are approximately -20 dBC. Nearly 100 khz away from the center frequency they are -22 dBC. At 2.5 mhz away they drop to -50 dBC. My receiver input filter is wound for 80 meters. In the case of strong incoming signals on 80 meters, I have experienced hearing the same signal in multiple places.
The single frequency oscillators that can be purchased with the receiver kit are much cleaner. However I built 3 of these receivers and experienced mirroring with all three. That is, with a LO of 3870, a strong LSB signal on 3860 khz would appear as a strong USB signal on 3880 khz but I do not think this is the fault of the oscillator. -- Larry W8ER n3hkn wrote: > > > I would be interested in how bad the spurs are from using the DDS VFO. > Typically the simplistic digital VFOs produce significant spurs which > show up on the PC display making it difficult to see signals that are > equal to, or lower in strength, than the spurious signals. > > I have onr of Tony's Lite receivers as an IF on my old Kenwood > TS-520S. There is no noticeable change in normal performance with the > Softrock Lite permanently in place. I tapped off just before the > 2.5khz xtal filter and fed directly to the normal Softrock antenna > input. On receive I now have performance similar to the very expensive > radios as well as a roofing filter (pre-selector) same as the big boys. > > Dick N3HKN > > --- In [email protected] > <mailto:soft_radio%40yahoogroups.com>, Rasputin Novgorod <[EMAIL PROTECTED]> > wrote: > > > > Hi guys: > > > > I haven't been following this subject as well as I should, > > but have been intrigued with the idea of SDR, and especially > > all the neat software available. As a starter, I bought JA7TDO's > > Soft66DB2 SDR and the DDS-34 DDS board for it. If they work, > > a very economical way to get started. (available on eBay). > > > > http://zao.jp/radio/sft66db2/ <http://zao.jp/radio/sft66db2/> > > http://zao.jp/radio/sft66db2/index2.php > <http://zao.jp/radio/sft66db2/index2.php> > > http://zao.jp/radio/dds34en/index_e.php > <http://zao.jp/radio/dds34en/index_e.php> > > http://stores.ebay.com/HAMShopJapan > <http://stores.ebay.com/HAMShopJapan> > > > > I was wondering about using some of my existing hardware > > as a front-end for this? In other words, take the IF out from > > my Harris 590 radio and feed it into the Soft66DB2 SDR (bypassing > > the SDR bandpass filter on the input). Then I could use > > the Harris normally, but also have I/Q outputs so I get > > all the SDR software features. Of course, it would > > be limited by the Harris's IF filters. > > > > In other words, the Harris would be a Preselector/RF amp > > for the Soft66DB2 SDR. Please bear in mind that I barely > > know what I'm talking about. So if this is dumb, un-advisable, > > or pointless, (or an interesting idea) please let me > > know your thoughts. > > > > Sincerely > > /b > > > > > > > __________________________________________________________ > > Looking for last minute shopping deals? > > Find them fast with Yahoo! Search. > http://tools.search.yahoo.com/newsearch/category.php?category=shopping > <http://tools.search.yahoo.com/newsearch/category.php?category=shopping> > > > >
