one of the most important spec is the channel to channel separation. Do you have done some measurements?
Luciano www.timeok.it On Thu 17/12/15 20:44 , Anders Wallin <[email protected]> wrote: > First prototype assembled today, tested with 12 VDC SMPS wall-wart supply > and with 12 V lead-acid battery. > Compared against a SRS FS710 and a Symmetricom 6502 and John Ackermann's > 2007 plot: > http://www.anderswallin.net/2015/12/frequency-distribution-amplifier-first- > tests/[1] > > What does the 6502 do differently? It is maybe 5 to 8 dBc/Hz better both > in > PN and AM from around 1 kHz and out. > > My 'ultra-low-noise DC-supply' in the form of a lead-acid battery improves > things somewhat, but some spurs still remain: > http://www.anderswallin.net/wp-content/uploads/2015/12/2015-12-17_fda_spurs > _and_comments.png[2] > interpretations and explanations are welcome! > The board was not enclosed in a metal can for these tests. > > The regulator is an LP38798 > http://www.ti.com/lit/ds/symlink/lp38798.pdf [3] > > Anders > > On Tue, Dec 1, 2015 at 12:54 AM, Bruce Griffiths wrote: > > > Anders > > U101 only needs to have a gain of 1 at dc so replace R104 and R105 with > a > > capacitor connected to ground. > > Adjust the other components of the gain determining network > > accordingly.Also the junction of the power supply divider R102 and R103 > > should be heavily capacitively bypassed to ground and a resistor placed > > between this junction and U101's noninverting input. > > > > Excess Sub Hz PN is usually due power supply noise or thermal > fluctuations > > due to air currents/ convection. > > Most of the so called super regulator circuits should be more than quiet > > enough with an LM329 reference.A damped LCR filter at the input will > > improve the PSRR at switchmode output frequencies. > > > > Bruce > > > > > > > > On Tuesday, 1 December 2015 9:02 AM, Anders Wallin > [email protected]> wrote: > > > > > > HI all, > > I need to build a few distribution amplifiers (>90% for 10MHz, sometimes > > maybe 5MHz) and instead of reinventing the wheel I decided to try to > > modernize the TADD-1 into an all (almost) SMD design. Here are some > draft > > sketches: > > > > > http://www.anderswallin.net/2015/11/frequency-distribution-amplifier-plans- > a-k-a-smd-tadd-1/[4] > > > > Does this sound/look reasonable or crazy? > > Any suggestions for op-amps to try and/or compare to the AD8055? > > What causes the extra phase-noise below 1 Hz offset in John A's result: > > > https://www.febo.com/pages/amplifier_phase_noise/amplifier_phase_noise.png > [5] > > > > Suggestions for a low noise DC-regulator circuit? The 12-24VDC supplied > to > > this board will most likely come from a switched-mode PSU, so filtering > of > > common-mode noise is mandatory. > > I found the TI LP38798 shown in the schematic by googling - if someone > has > > a proven a measured design that would be a safer choice. In any case > more > > filtering (e.g. ferriites) is probably a good idea. > > > > This design will be available on my blog or on github when it is done - > if > > anyone is interested. > > > > Thanks, > > Anders > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [6] > > and follow the instructions there. > > > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [7] > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [8] > and follow the instructions there. > > > > Links: > ------ > [1] > http://webmail.timeok.it/parse.php?redirect=http://www.anderswallin.net/201 > 5/12/frequency-distribution-amplifier-first-tests/[2] > http://webmail.timeok.it/parse.php?redirect=http://www.anderswallin.net/wp- > content/uploads/2015/12/2015-12-17_fda_spurs_and_comments.png[3] > http://webmail.timeok.it/parse.php?redirect=http://www.ti.com/lit/ds/symlin > k/lp38798.pdf[4] > http://webmail.timeok.it/parse.php?redirect=http://www.anderswallin.net/201 > 5/11/frequency-distribution-amplifier-plans-a-k-a-smd-tadd-1/[5] > http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/pages/ampl > ifier_phase_noise/amplifier_phase_noise.png[6] > http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-bin/ma > ilman/listinfo/time-nuts[7] > http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-bin/ma > ilman/listinfo/time-nuts[8] > http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-bin/ma > ilman/listinfo/time-nuts > Message sent via Atmail Open - http://atmail.org/ _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
