Fw: [softrock40] Re: Dynamic range measurements of SR V6

Terry Fox wb4jfi at knology.net
Mon Oct 2 20:09:54 CDT 2006

----- Original Message ----- 
To: softrock40 at yahoogroups.com 
Sent: Monday, October 02, 2006 7:32 PM
Subject: Re: [softrock40] Re: Dynamic range measurements of SR V6

I also measured 96 dB dynamic range with my sdr board using a FST3253. At 2.5 KHz spacing 84 dB.My 3 dB MDS was a bit lower using INA163s I was also using a stock sound card. My generators were also a pair of 8640Bs Frank wa1gfz

Phil Covington <p.covington at gmail.com> wrote: 

  --- In softrock40 at yahoogroups.com, Marco <ik1odo at ...> wrote:
  > Hi all,
  > I performed some more tests on IMD and dynamic range of the SoftRock 
  > V6 (original and modified). Here is a summary of the results.
  > For all measurements, the reference bandwidth is 2.4kHz, the signal 
  > spacing is 15kHz and the frequency is around 7050kHz.
  > Instuments used: two HP 8640B signal generators, HP 8494A and -B step 
  > attenuators, Olektron power combiner. Levels checked with an HP 8566B 
  > spectrum analyzer. Power bandwidths and S/N measured with a Fluke 
  > 8920A digital RMS voltmeter. All instruments have traceable calibration.
  > 1) Unmodified SoftRock, Soundblaster USB 16bit audio interface 
  > (16bit, 48kHz, better antialiasing and response than the usual AC97 
  > found in PCs)
  > MDS: -105dBm
  > blocking dynamic range: 96dB
  > IMD3 dynamic range: not measurable (blocking occurs by saturation of 
  > the audio interface)
  > IIP3: -
  > 2) same as (1), soundcard Audiophile 192 (24bit, sampling at 96kHz)
  > MDS: -110dBm
  > Blocking dynamic range: 100dB
  > IMD3 dynamic range: 93dB
  > IIP3: +29dBm
  > 3) same as (2), post-mixer amp voltage gain reduced from 500 times 
  > (5kOhm/10Ohm resistors on the opamp) to 90 times (900Ohm/10Ohm)
  > MDS: -110dBm
  > Blocking dynamic range: 110dB
  > IMD3 dynamic range: 96dB
  > IIP3: +34dBm
  > 4) same as (2), post-mixer amplifier has been replaced by a couple of 
  > OP27G powered from +/-12V. Opamp gain is now 200 times (2kOhm/10Ohm)
  > MDS: -110dBm
  > Blocking dynamic range: 115dB
  > IMD3 dynamic range: 102dB
  > IIP3: +43dBm
  > My comments:
  > a) I don't see any saturation in the FST3253 at least up to +10dBm 
  > (not checked over that)
  > b) the IMD products seem to come mainly from the opamp and audio 
  > interface. Low power, low voltage opamps are the limit here
  > c) some front-end gain is advisable to raise the MDS and stabilize 
  > the impedance seen by the mixer, if the opamp and audio interface can 
  > handle the strong signals. Noise from the opamp dominates the noise 
  > floor, of course; measured noise figure here is approx. 30dB
  > d) IIP3 figures appear very good, but the real performance is limited 
  > by the poor image suppression and the 2nd order audio harmonic 
  > generation in the chain. With only two tones at the input the 
  > spectrum becomes a real forest, such that it's difficult to find a 
  > clean spot to see the IMD products. So, probably we have to talk 
  > about SFDR (spurious free dynamic range) or the system. Much harder 
  > than a simple IMD3 measurement.
  > Next step: to test different mixer topologies (switch followed by an 
  > active integrator, as proposed on the HPSDR group, and some other
  > 73 - Marco IK1ODO

  Hi Marco,

  Very interesting results. I will be particularly interested in your
  measurements of an active integrator version.

  73 de Phil N8VB

Messages in this topic (4) Reply (via web post) | Start a new topic 
Messages | Files | Photos 
Change settings via the Web (Yahoo! ID required) 
Change settings via email: Switch delivery to Daily Digest | Switch format to Traditional 
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe Recent Activity
  a..  53New Members
  b..  18New Files
Visit Your Group 
  a.. Ham radio antenna 
  b.. Ham radio repeaters 
  c.. Ham radio sales 
  d.. Ham radio store 
  e.. Ham radio outlet 
Yahoo! TV
Staying in tonight?

Check listings to

see what is on.

Y! GeoCities
Share Your Resume

Show off your

talent and skills.

Yahoo! Groups
Start a group

in 3 easy steps.

Connect with others.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://amrad.org/pipermail/tacos/attachments/20061002/77100733/attachment.html

More information about the Tacos mailing list