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. Message: 6 Date: Wed, 26 Oct 2005 12:00:52 -0500 From: KD5NWA <[EMAIL PROTECTED]> Subject: Re: Noise floor survey Did you calibrate your software with a known signal source? Otherwise the reading is meaningless. I ordered a XG2 and I will use it to calibrate all my radios and measure their sensitivity including two SR- 40's. That reading of -100dB with the radio off is very high, most get -140dB or lower. By tomorrow I should have my SR-40 tested for sensitivity and calibrated and will post the result. I live in a 40 meter free zone, so it's hard to test the SR-40 because of electrical noise. During the weekend I went snooping around for my noise source, found nothing inside my house that would do it. But I found that a 300+KV line one house away from me is now activated and is the source of my noise. I followed the line for miles and it's nothing but horrific noise the whole distance. I'm going to have to move. I did find one thing though, I used a OHR 40 meter transceiver, and it could pick up a lot of signals even with all the noise, and they were quite readable. That is a nice little radio. At 12:21 PM 10/26/2005, you wrote: >Hi, >I would like to make a survey of the noise floor of your rigs. I am not >looking for any calculations for the noise density, just tell me your >sound card resolution and what you see at the bottom of your frequency >spectrum of the Powersdr or sdradio software. This is what I get: >Maker of rig: my own >Sound card:16 bits >Line at bottom of spectrum with radio off: -100dB >Line at bottom of spectrum with radio on: -65dB >Frank > > > > > >Yahoo! Groups Links > > > > 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/
