That noise floor is going to vary all over the place depending on your PC's noise level, your sound card, the amount of ground loops you have in your setup.
What I'm going to try to do this weekend is measure on one PC, and several sound cards, so the only variable is the sound card and see which ones do a better job. The SR-40 is going to be running on batteries to cut down ground loop noise. I will be using a SG-2 to be the signal source to do the comparison. I had ordered a Delta-44 from a vendor and there was a problem with my address not matching the credit card, which is nonsense, anyway they said they would talk to my bank and get it straighten out. I found out yesterday that they just dropped the order and didn't bother telling me, what a bunch of idiots. Now I will have to buy it somewhere else. I was hoping to use that card as the reference to compare against. At 11:15 AM 10/27/2005, you wrote: >Cecil, > >Did you calibrate your software with a known signal source? Otherwise > >the reading is meaningless. >That's part of the reason why I asked for both the floor and the amount >of noise when the radio on. I agree, that the dB unit is meant to be how >many dB lower than the reference, which is normally specified for 1mW >(dBm) and the particular impedance too. I was hoping for multiple >responses so I kept the question to a minimum. > >I got the radio noise very close to the quantization sound card noise >since my last email. I put a 10uF and 1000uH LPF on several of my ICs >and added a BPF before the QSD. Right now it's a 50ohm input output >impedance MAR-6 MMIC attacking the BPF going through a TI 5 ohm quad >switch to 0.22uF capacitors. I'll put a 1:4 transformer to get better >impedance matching very soon. In powersdr , the noise floor is -150dBm >with the radio off and -135dBm with it on. Sdradio gives me -100dB. > >Also in Powersdr, with the radio off, I get a NEAR DC peak of 70dB above >the noise floor. For sdradio it is 20dB above the noise floor. I suspect >that it is my motherboard 16 bit sound card that has a DC problem. > > > >But I found that a 300+KV line one house away from me is > >now activated and is the source of my noise. >Do those lines give off tons of harmonics? Can you just put aggressive >filtering at the frequency of interest? > >Frank >PS I am still waiting for more responses for the noise floor. > Cecil Bayona KD5NWA www.qrpradio.com I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ... ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
