David, As I understand the SDR mic input, the mic slider is a software scaler. It does not effect the input to the sound card. The higher the mic gain on the SDR has to be in order to get a given power output, the worse the signal to noise of the Delta 44 will be. In order to get the full benefit of the dynamic range of the Delta 44 by using all of its bits, the mic gain slider should be set around 10. By using a preamp, you raise the input to the card and increase the signal to noise. For example, my PR-20 mic puts out about 25 mV peak to peak into 600 ohms under normal speech conditions. This requires a setting of about 40 on the mic slider for normal power out. If I put a 1 KHz tone into the mic input at 275 mV peak to peak, the slider can be moved down to 10 for the same power output. Since the slider is lower, the signal to noise is better. A preamp with about 21 db of gain would be needed to let the PR-20 work well with a mic slider setting of 10.
I hope this helps. 73, Tom W0IVJ David Little wrote: >Having read the recent discussion, and remembering when I asked some of the >same questions on the Flex-Radio SDR-1000 support forum, I have to again >ask: how do you eliminate the inherit noise of the M Delta 44 and Power SDR? > >Either the noise is there, or it isn't. > >I bought the Break Out Box Eliminator on the suggestion that this would >help, but later discovered the same amount of noise with all cables >disconnected from the M Delta 44, and all cards removed from the computer >but the M Delta 44 and Video Card. > >With no cable connected to the M Delta 44 Card, and no other cards in the >computer but the video, nothing but keyboard and mouse connected, when I >turn the Mic audio up all the way, the Mic level on the Power SDR will >fluctuate between -4dB and -1.9dB when the MOX is activated. After all the >admonishments from everyone on why this doesn't mean anything, I have to ask >the obvious question - why does it show up? > >I am using a Heil GM-5, and have a hard time getting above QRP power before >the internal noise overcomes the Mic audio. When I turn the Mic gain high >enough to get response from the Mic, the noise in the monitor tells me that >the interaction between the sound card and the rig software is making more >noise than the Mic. > >I have heard the suggestion that you need to use a preamp or a W2IHY EQ box >with preamp. I have run one before, the preamp is great for matching mics. >Having said that, the 10 band EQ built into Power SDR should be good for >something, if an outboard one was necessary, it wouldn't have been added to >the software. > >Also, if external preamp is needed to mask the internal noise, is this >really the correct solution to provide a clean signal with clear audio? > >I have also heard the suggestion that you really need a better sound card >than the M Delta 44 to use the SDR-1000. Isn't the M Delta 44 the card that >originally shipped with the Flex 1000? > >I don't know the answers to these questions, but common sense would suggest >to me that the card that is recommended be compatible with the software that >runs the rig. Also, I would believe it would be more desirable to correct >the noise than to try to cover it up with more Mic gain from a preamp. > >Again, I don't know the answers, but would like to know the most direct >route to getting the SDR-1000 to perform with the PowerSDR software using >the M Delta 44 sound card. I know that some folks out there are having good >luck with this combo, so apparently they have discovered the secret. > >I really would appreciate some direction on this that will provide positive >results. > >Thanks, > >David >KD4NUE > > > > > > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Brian C >Sent: Thursday, May 08, 2008 12:43 PM >To: flexradio@flex-radio.biz >Subject: [Flexradio] Min into ch 3 of Delta 44 > > > >George, I key my SDR1K using a mic plugged into channel 3 of the Delta 44. >It works fine using a mouse to activate MOX. Also works with a foot switch >wired to the multi-plug at back of SDR. Computer is a Dell Dimension 8400 >(3.0 gig dual core processor) with 1/2 gig RAM and latest standard release >of PowerSDR or K6JCA SVN 2173 release. Always keyed SDR1K this way; never >had a problem. > >Brian > > >Subject: [Flexradio] MOX not working with mic plugged directly intochannel 3 >of Delta 44To: [EMAIL PROTECTED]: ><[EMAIL PROTECTED]>Content-Type: text/plain; >charset=windows-1252 Everything I've read on the reflector indicates that a >microphone plugged into port 3 input of the Delta 44 and then keying with >MOX via a mouse should work. It doesn't.I have to key with a hand mic >plugged directly into the 8 pin port of the SDR-1000, then port 3 accepts >the tx audio and transmits it. Am I missing some setup in PowerSDR? Finally >got some decent audio out of the SDR-1000 with a Behinger 802 as a preamp >for the mic. GeorgeN7BUI >_________________________________________________________________ >With Windows Live for mobile, your contacts travel with you. >http://www.windowslive.com/mobile/overview.html?ocid=TXT_TAGLM_WL_Refresh_mo >bile_052008 >_______________________________________________ >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/ > > > > > > _______________________________________________ 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/
