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 <kb...@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@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 <kb...@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 <jim...@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 >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
