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.