[time-nuts] Modern signal generators

[Richard (Rick) Karlquist]

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> 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> 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> 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> 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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