I just completed a Lite II and a QRP 2000 synth from SDR kits. Both working well it seems though I am not sure about the receiver sensitivity. Are there specifications or measurements that indicate what to expect in terms of S+N:N or MDS? I can hear a signal at 1uV but nothing much really below that although the signal is visible. I have about a -125dBm noise level with no antenna (or the generator) connected and can easily distinguish a signal close(ish) to that but cannot hear it. Similar results in Rocky and psdr.
Seems to me it might be more sound card or software than receiver. But not sure how to determine what a typical set of input and output values might be.
- http://www.wb5rvz.com/sdr/sr_lite_ii/04_opamp.htmOn Wed, Jun 1, 2011 at 5:35 AM, Tony Parks <kb9yig@...> wrote:[Attachment(s) from Tony Parks included below]
The feedback resistors are supposed to be 4.99k resistors. The schematic page for the Lite II kit is included with this note.
On Wed, 2011-06-01 at 17:04 +0700, Martin Sole wrote:
Tony Parks kb9yig@... http://www.kb9yig.com
Okay, well I’m not convinced it’s working right yet. Here’s another thing I have just noted. In addition to the Lite I that am referring to I also have a TXRX 6.2 partially built for 20 and 30 metres. The receiver seems noticeably livelier. Connecting an antenna makes the noise jump up a good 10dB on 30 or 20 but has no obvious effect on the noise with the Lite II. About the only thing I can figure is a difference with the op-amp. The 6.2 and 6.3 have LT6231 op amps with 4.99k resistors in the feedback but the Lite II has the same LT6231 op-amp (changed from a TLV2462) but with 1k resistors in the feedback. It also has 1 resistors in the op –amp output. Just wondering about that.
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Alan
Sent: 01 June 2011 15:41
Subject: Re: [softrock40] Re: Softrock sensitivity.
----- Original Message -----
Subject: RE: [softrock40] Re: Softrock sensitivity.
> I'm still left with not being able to hear much below 1uV and that seems
> me to be about 20dB deafer than I would expect.
Sorry but I'm not familiar with how the figures compare with actual
If you search the messages you will find what others have said.
for example <http://groups.yahoo.com/group/softrock40/message/53438>
73 Alan G4ZFQ
--Cheers,RobbyRichard R. (Robby) RobsonAmateur Radio Station WB5RVZ