[time-nuts] Modern signal generators
Richard (Rick) Karlquist
richard at karlquist.com
Wed Dec 12 20:56:48 UTC 2018
The TI/NationalSemiconductor LMX2594 and LMX2595 have the best
phase noise floor FOM at -236.
The AnalogDevices/LinearTechnology LTC6952 has the best flicker at -281.
It requires an external VCO. The LTC6951 with an on board VCO is
almost as good.
Although these are state of the air for a synthesizer-on-a-chip,
it is easy to beat them if you roll your own with a mixer as
a phase detector.
Rick N6RK
On 12/12/2018 12:44 PM, Ulrich Rohde wrote:
> Who makes it ?
>
> In a message dated 12/12/2018 3:43:23 PM Eastern Standard Time,
> richard at karlquist.com writes:
>
> FWIW, the HMC832 has FOM of -226. The best synth on a chip
> now available AFAIK has FOM of -236. That's 10 dB better.
>
> Rick N6RK
>
> On 12/12/2018 10:46 AM, Dr. Ulrich L. Rohde via time-nuts wrote:
> > I did some phase noise measurement and the 8751 is much better then the rest on the market
> >
> > Sent from my iPhone
> >
> >> On Dec 12, 2018, at 1:20 PM, Bob kb8tq <kb8tq at n1k.org <mailto:kb8tq at n1k.org>> wrote:
> >>
> >> Hi
> >>
> >> Just to save others the time digging, the 7851 uses a HMC832 VCO + fractional N PLL on a chip as
> >> the heart of its synthesizer. Yet another “way to go” if building a quick and simple signal source.
> >>
> >> ===
> >>
> >> No argument at all about other parts of the radio having their limits. PA performance certainly is one
> >> of those areas.
> >>
> >> Bob
> >>
> >>> On Dec 12, 2018, at 12:42 PM, Dr. Ulrich L. Rohde via time-nuts <time-nuts at lists.febo.com <mailto:nuts at lists.febo.com>> wrote:
> >>>
> >>> My feeling is
> >>> A Because of the low sunspot cycle the large signal performance of the RX is less a topic, the ICOM 7851 dynamic range, synthesizer and frequency concept is winning but expensive
> >>> B The power amplifier from 100 W to 1500 Watt need to be catching up to the old Collins tube Amps with negative feedback, producing - 45 dB or better IMD products.
> >>>
> >>> The military amplifier are fast on , reliable , durable and expensive... initially.
> >>>
> >>> The noisy blower may be a bad thing.
> >>>
> >>> I “only “ run 1 KW, and I am happy with it
> >>>
> >>> 73 de N1UL
> >>>
> >>> Sent from my iPhone
> >>>
> >>>> On Dec 12, 2018, at 10:47 AM, Bob kb8tq <kb8tq at n1k.org <mailto:kb8tq at n1k.org>> wrote:
> >>>>
> >>>> Hi
> >>>>
> >>>> Usually on HF, the issue is large signal rejection. Phase noise very definitely
> >>>> gets into that part of things. Other components in the signal chain do as well.
> >>>> Once the synthesizer is no longer the weak link in the chain, spending more
> >>>> to improve it (vs spending on the other components) probably does not make
> >>>> a lot of sense. Since the synthesizer is *far* from ideal, that sort of begs the
> >>>> question of just how troublesome the other parts are and how much better a
> >>>> device *could* be built.
> >>>>
> >>>> This does seem to be wandering a bit from a Time related topic …..
> >>>>
> >>>> It does illustrate the point that “good enough” may be way far away from
> >>>> “pretty good” and yet even more distant from “as good as it gets”. The
> >>>> question on any system is always “how good do you need / what are you
> >>>> doing?” ….
> >>>>
> >>>> Bob
> >>>>
> >>>>> On Dec 12, 2018, at 8:49 AM, jimlux <jimlux at earthlink.net <mailto:jimlux at earthlink.net>> wrote:
> >>>>>
> >>>>> On 12/11/18 3:26 PM, Bob kb8tq wrote:
> >>>>>> Hi
> >>>>>> As I said, just how rational using these parts in a radio …. not at all clear to me.
> >>>>>> Back when I went to school, stuff that was this noisy was not in the “greatest” category.
> >>>>>> That was a *very* long time ago.
> >>>>>> Oddly enough best performance synthesizers have gotten better. (as the posted
> >>>>>> presentations very clearly show). Just why a “high end” radio uses a less than
> >>>>>> ideal synthesizer likely relates more to cost (even at a price of thousands of dollars)
> >>>>>> than to anything else.
> >>>>>
> >>>>> Or "good enough" performance - driving to a 3 dB NF for a HF receiver while maintaining good strong signal performance is probably not worth it
> >>>>>
> >>>>>
> >>>>>> Indeed cost also drives things like GPSDO’s and GPS modules. We often are not
> >>>>>> very eager to acknowledge that fact.
> >>>>>> Bob
> >>>>>
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