Re: Softrock sensitivity.
Martin, just to confirm that the recording I made was using 1 microvolt signal.
73 de Graham G3ZOD FISTS #8385
--- In email@example.com, "Martin Sole" <hs0zed@...> wrote:
> I tried 4.7k for R7 and R8 but my opinion is that it is too much and
> compromises the performance though the gain is about the same as the 20m 6.2
> TXRX. With the 1k resistors and using Rocky I need to add about 18dB offset
> to the S meter for S9 at -73dBm.
> The next bit of your message Alan got a bit confusing. You said 1mV, Graham
> said 1 uV. Listening again t sounds like it could certainly be 1mV!
> 1mV is -47dBm. Adding 27dB attenuation would be -70dBm, still huge. If you
> meant 1uV that's -107dBm adding 27dB attenuation would be -134dBm, that's
> weak 0.045uV, way more than I need.
> 4.7k resistors give me about 6dB SINAD for a 1uV (-107dBm) input. Putting
> them back to 1k drops that to about 4.5dB but with a flatter noise floor. A
> resonant 40m antenna gives about a 7 to 10dB increase in noise over nothing
> connected so now I'm starting to wonder if I really do have a problem. Think
> I am going to have to rig something up using the Orion as a reference and
> see what that sounds like in comparison. Could well be all for naught but
> still my audio does not sound as strong as Grahams signal if that was 1uV.
> Martin, HS0ZED
- 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