[time-nuts] 10MHz dist amps

[Anders Wallin]

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 <jra at febo.com> 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 <actast at hotmail.com> 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
> >>
> >> actast at hotmail.com
> >>
> >> "Peace is not the absence of violence, but the presence of Justice"
> Both MLK and Albert Einstein
> >>
> >> ________________________________
> >> From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of John
> Ackermann. N8UR <jra at febo.com>
> >> Sent: Wednesday, October 23, 2019 11:54 AM
> >> To: ew via time-nuts <time-nuts at lists.febo.com>
> >> 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" <
> docdailey at gmail.com> 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
> >>> _______________________________________________
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