FWIW some measurements: http://www.anderswallin.net/wp-content/uploads/2015/12/2015-12-17_fda_test_pn.png and http://www.anderswallin.net/wp-content/uploads/2016/09/fda_2016-09-12_PN.png and https://www.febo.com/pages/amplifier_phase_noise/
my ohwr-design uses better op-amps, giving slightly below -160dBc/Hz for 10MHz carrier https://ohwr.org/project/pda-8ch-fda-8ch/wikis/home AW On Thu, Oct 24, 2019 at 5:02 AM John Ackermann N8UR <[email protected]> wrote: > Thanks, Bruce. That's pretty much it -- while the layout/lack of > shielded enclosure might have a bit to do with it, the opamps used > (MAX477) aren't super-duper low noise at the floor. The AD8055 we've > used in the lasts few batches since the MAX477 went unobtainium seems to > be a little quieter. > > Re the frequency range, the opamps are rated to I think something like > 275 MHz but there is some roll-off built into the design to reduce a > tendency toward oscillation; no real attempt was made to keep it flat > across frequency. > > There's some difference in frequency response depending on the input > level and gain setting, but in general the gain is around unity at 5 and > 10 MHz, then rises about 5 dB to peak at about 40 MHz, then it falls off > to abotu -9 dB at 100 MHz. > > At the time I designed the unit, I was young and foolish* and thought a > 5 or 10 MHz bandpass filter might be a good idea. I soon learned and > now strongly discourage including the filter unless you have a very good > reason. > > 73, > John > > * I just looked at the original design files and good Lord, they date > back to August, 2005. That thing is going on 15 years old without a > significant change, other than the opamp substitution (which was a > direct drop-in replacement). > ---- > > On 10/23/19 7:38 PM, Bruce Griffiths wrote: > > Its measured noise floor is consistent with that expected from the noise > specifications for the opamps employed. > > > > Bruce > > > >> On 24 October 2019 at 08:46 Tom Knox <[email protected]> wrote: > >> > >> > >> Hi John; > >> Amazing product, I did not realize you could use the TADD-1 for 100MHz > distribution. > >> I do have a question, as someone who has tested most of the > commercially available distribution amps on the market TADD-1's -140dB @ > 1Hz is among the very very best best in the industry, (nothing is close for > the price) but compared to the very best the noise floor is a bit higher. > Is this simply a result of a raw board instead of a shielded enclosure? > >> Thanks; > >> > >> Tom Knox > >> > >> 303-554-0307 > >> > >> [email protected] > >> > >> "Peace is not the absence of violence, but the presence of Justice" > Both MLK and Albert Einstein > >> > >> ________________________________ > >> From: time-nuts <[email protected]> on behalf of John > Ackermann. N8UR <[email protected]> > >> Sent: Wednesday, October 23, 2019 11:54 AM > >> To: ew via time-nuts <[email protected]> > >> Subject: Re: [time-nuts] 10MHz dist amps > >> > >> FWIW, I designed the TADD-1 to have equal length signal paths for all > six channels. > >> > >> 73, > >> John > >> > >> On Oct 23, 2019, 1:01 PM, at 1:01 PM, "Bill Dailey, MD, MSEng, MSMI" < > [email protected]> wrote: > >>> I am working in a project that requires me to have very similarly > >>> phased > >>> 10mhz references (beamforming). > >>> > >>> Previously I just used splitters for 10MHz but now I am graduating to a > >>> distribution amplifier. Looking for suggestions/recommendations and > >>> what I > >>> should consider. Distributing a Fury or a manually set 1111a (May have > >>> the > >>> numbers wrong on this) oscillator. > >>> > >>> 1. TADD-1 x 2 > >>> 2. 5087A > >>> 3. 58502A > >>> > >>> 2&3 are from the usual auction site and may have problems now or in the > >>> future. > >>> -- > >>> Doc > >>> > >>> Bill Dailey > >>> KXØO > >>> _______________________________________________ > >>> time-nuts mailing list -- [email protected] > >>> To unsubscribe, go to > >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>> and follow the instructions there. > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
