At 01:16 PM 3/4/2007, Tim Ellison wrote: >Here is an explanation of what might be going on. > >If when you experience the condition where the noise floor is 20 dB >lower than expected and you are NOT hearing any signals, something is >probably amiss with the DDS. > >This phenomenon you are experiencing is when the DDS gets "stupid", >meaning that the software can not communicate or control the DDS. This >isn't a problem with the DDS but is more of a symptom than the actual >root problem. As soon as you cycle the rig PowerSDR re-established >communication with the DDS and all is usually well again.
One sure cause of the DDS getting stupid is it getting too hot. That puppy dissipates a lot of heat, and in the older SDR1000s without a heatsink, you need a fairly decent airflow (100 LFPM or better) over the top of the DDS or it WILL overheat, even in an airconditioned lab. I haven't tried it with warm air flowing, just with 25-30C lab air. It might be that even if you flow air across it, if the air is at, say, 40C, you're going to have problems. Might even be the case with a heatsinked DDS, but I don't have any of those to experiment with. >-Tim, W4TME > > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Larry Loen >Sent: Sunday, March 04, 2007 2:24 PM >To: Frank Mayer >Cc: FlexRadio reflector >Subject: Re: [Flexradio] Receive Attenuation Glitch > >Frank Mayer wrote: > > > Larry, > > I have noticed the same thing here on and off. It seems to be some > > kind of issue in the communications line (Parallel port of SDR-1000 to > > the computer). Not everybody seems be experiencing it. My switching > > > the preamp positions also will bring the receive back up. Since I > > have installed a good PCI parallel card in the computer I haven't had > > any more issues. I even had the issue using the USB-to-Parallel > > cable. Then I installed a USB hub in the computer and that made it > > much better. But this new parallel card seems to have done the trick > > Larry. I got it from TigerDirect for 14.99. Here is the link: > > http://www.tigerdirect.com/applications/searchtools/item-details.asp?E > > dpNo=1003991&CMP=EMC-TIGEREMAIL&SRCCODE=WEBLET03SHIP > > > <<http://www.tigerdirect.com/applications/searchtools/item-details.asp?>http://www.tigerdirect.com/applications/searchtools/item-details.asp?> > > EdpNo=1003991&CMP=EMC-TIGEREMAIL&SRCCODE=WEBLET03SHIP> > > Frank > > >I'll keep it in mind. > >I already have a customer PCI card, but maybe it's not as good as I >think. > >It isn't really a big issue for me, in the end, but I thought I'd >mention it primarily because of at least the superficial similarity to >the "Preamp" problem being still discussed. > > >Larry WO0Z > > > >_______________________________________________ >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/ > >_______________________________________________ >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/ James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875 _______________________________________________ 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/
