By the way, Edwin - it's possible that what you're seeing *aren't* DDS spurs. I'll do some more testing here, too, over the weekend.
Do you happen to have a Radio Shack common-mode filter? - Jeff Jeff Anderson wrote: > Hi Edwin, > > I think what you are seeing might be DDS spurs. > > I just did some additional testing with my SDR1000 that's using a Delta > 44, as well as some testing with a seperate SDR1000 that uses an Edirol > (and a different computer). > > With each console setup up similarly: > o SR = Off (spur reduction) > o PreAmp = Med > o Mode = LSB > o DDS Clock Offset = 0 (this is important for comparing one radio to > another!). It's in one of the Setup menus (you need to check the > "expert" box). > o Antenna: connect to dummy load. > > If I tune each Console to 7.002 MHz, I see spurs at exactly 1 KHz > spacing. If I then detune by *only* 1 Hz (that's Hz, not KHz), the > spurs change frequency by an amount much greater than 1 Hz, which is > what I would expect for DDS-generated spurs. > > Both my system with the Delta 44 and my system with the Edirol > experience the same problem. > > Note too: one of the spus (I think it's the one at 7.001 MHz) I can > attenuate by attaching a Radio Shack common-mode choke in series with > the cable attached to the "To Line Out" jack of the SDR - so there seems > to also be a second source for a spur at this frequency, and thus some > interaction between it and the DDS spur on the same frequency). And, if > I change the vfo by 1 Hz, it moves by the same amount, too, again > implying that it's not DDS spurs. > > Usually DDS spurs aren't a problem, because, except for certain > frequencies (around 7.15 MHz on my radio, for example), their amplitude > lies below the "atmospheric" noise floor. > > Try testing your other frequencies, too, that you show in the video. If > you move the frequency by only 1 Hz, do the spurs move by the same > amount, or by a much different amount? > > - Jeff, k6jca > > Edwin Marzan wrote: > >> Hi Jeff, >> >> The setup is very simple. Astron VS-20M Power supply, SDR-1000, Eridol >> FA66, HP Computer, MFJ Tuner (no power supply), Creative Labs >> Speakers. Switched on and off all other equipment at home and no luck. >> Receiver is calibrated with Elecraft XG-1. IF was changed from 11.25 >> (I think) to 9 or somesuch via PowerSDR. Noise level is very high here >> in the Bronx. I see the same high levels with my other transceivers. I >> don't see any other patterns other than 1 khz spacing that you noticed >> on the waterfall display. I'm going to see if my older version of >> PowerSDR exhibits this same behavior. >> >> Thanks for the suggestions! >> >> Edwin Marzan >> AB2VW >> >> >> ===================================================================================================== >> >> >> >>> Date: Thu, 10 Jan 2008 10:31:17 -0800 >>> From: [EMAIL PROTECTED] >>> To: [EMAIL PROTECTED] >>> CC: flexradio@flex-radio.biz >>> Subject: Re: [Flexradio] Mysterious Spur Visible on Panadaptor >>> >>> Mike's (w6thw) suggestion is a good one. Switch off all other equipment >>> and see if it goes away. >>> >>> Also - your noise floor looks pretty high to me (compared to what I see >>> on my SDR). What is your preamp set to? The high noise *may* be >>> indicative of an incorrectly calibrated receiver - do you have a good, >>> calibrated, RF source that you can use to calibrate the receiver >>> levels? I'm wondering if these tones are actually really far down in >>> level (below the A/D's threshold), but, because input gain is too high, >>> they're being digitized by the A/D and appearing as real (albeit faint) >>> signals) - but I'm really just guessing here. I don't know if the >>> Edirol has a preamp prior to the A/D (many A/D's do), nor if Flex >>> controls the gain of this preamp. If not, that is, if gain is only >>> applied in software, then this thought is probably wrong - but you may >>> still need to calibrate the receiver. >>> >>> By the way, if you don't have a calibrated RF generator that you trust, >>> Elecraft makes one that is perfect for something like this (I recommend >>> that all hams have one). >>> >>> If you're still not having any luck, more clues might be gained by >>> looking at the entire panadapter display (zoom all the way out) . Are >>> there any patterns? >>> >>> Also - what's the IF frequency set to? >>> >>> Thanks, >>> >>> - Jeff, k6jca >>> >>> >>> >>> Edwin Marzan wrote: >>> >>>> Hmmm.... there is a switching power supply powering another >>>> >> transceiver nearby. I'll see what happens when I turn it off. >> >>>> Thanks for the info.Edwin MarzanAB2VW >>>> >>>> >>>> Date: Thu, 10 Jan 2008 09:09:48 -0800From: >>>> >> [EMAIL PROTECTED]: Re: [Flexradio] Mysterious Spur Visible on >> PanadaptorTo: [EMAIL PROTECTED] >> >>>> Hi are you using a switching power supply if so try another one >>>> >> and see if it still there. >> >>>> Just thought it might be the same thing i had happen on all bands. >>>> >>>> >>>> >> ------------------------------------------------------------------------ >> Put your friends on the big screen with Windows Vista® + Windows >> Live™. Start now! >> <http://www.microsoft.com/windows/shop/specialoffers.mspx?ocid=TXT_TAGLM_CPC_MediaCtr_bigscreen_012008> >> > > _______________________________________________ > FlexRadio Systems Mailing List > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > Knowledge Base: http://kb.flex-radio.com/ Homepage: > http://www.flex-radio.com/ > > > _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
