Hey guys-- From a non-engineer civilian, let me express my gratitude at being able to listening in, as a slack-jawed rube, to your high-end ruminations about "aero dynamic windows" and "whispering gallery devices," which send me scurrying to Google. You give this mere mortal much voyeuristic pleasure.
Bill K7RY -----Original Message----- From: [email protected] <[email protected]> Sent: Thursday, April 01, 2021 00:30 To: [email protected] Subject: time-nuts Digest, Vol 200, Issue 49 Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker] (Dana Whitlow) 2. Re: Best frequency to start for GHz synth ? (Bob kb8tq) 3. Re: Best frequency to start for GHz synth ? (Dave ZL3FJ) 4. Re: Best frequency to start for GHz synth ? (Bruce Griffiths) ---------------------------------------------------------------------- Message: 1 Date: Wed, 31 Mar 2021 15:45:39 -0500 From: Dana Whitlow <[email protected]> Subject: [time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker] To: ew <[email protected]>, Discussion of precise time and frequency measurement <[email protected]> Message-ID: <CADHrwpdrp6ZJ=j7q4e5gygn9xuf-ojtefkb5vloxm3bctqq...@mail.gmail.com> Content-Type: text/plain; charset="UTF-8" I have not yet heard what GB wants to do, but if it's long range work (return time of 10's of sec or longer), the problems related to T/R switching, Tn degradation of the receiver, etc, get a lot more tractable than one might suppose. At Arecibo, the S-band radar was intended solely for long range work. A big part ot T/R switching was to use separate (optimized) feeds for transmitting and receiving, and swap feeds during turnaround. The receive feed was covered by a carefully- fitted sliding cover during transmit times, which provided excellent isolation. There was a microswitch to sense cover position and which would block transmission if it was not satisfied. Feed horn turnaround time was about 7 seconds as I recall. The transmitter was basically operated CW, and the "imaging" technique was "range- Doppler". So, the transmitter was run for slightly under the round-trip travel time, then feed turnaround was initiated, timed to finish shortly before the leading edge of the return was expected. The receiver would do its thing for the duration of the return. Note that it was also necessary to completely shut down the beam current of the transmit Klystrons during receive so that shot noise on the beam did not spoil the receiver's noise temperature. After the receive interval was finished, the feeds were again swapped and a new cycle was started. During each transmit period the crew of scientists would have time for a preliminary look at the just-recorded data to see if anything was going wrong. OTOH, Arecibo's 430 MHz ISR for ionospheric studies clearly had to have almost instantaneous turnaround time, and arrangements were rather more complicated (more so than I can take time to describe at the moment). But they worked well, and loss in the receive state of some big PIN switches in the path was tolerably low. The first 35-40 dB of TX-RX isolation came from use of a "turnstile junction", with the remainder coming from the PIN switches. For both radars, the non-participating receivers would also be covered, but with a simpler flap arrangement, some powered by small DC motors and some by small pneumatic cylinders. Dana (retired from Arecibo Dec 2016) On Wed, Mar 31, 2021 at 2:30 PM ew via time-nuts <[email protected]> wrote: > During my days at UTC I was among other things responsible for our > Industrial Laser Group. We sold some 50 KW CW CO2 lasers! We had the > only aero dynamic window that allowed a vacuum on one side. When not > in use you put a pencil through it. Patented. > Bert Kehren In a message dated 3/31/2021 3:17:21 PM > Eastern Standard Time, [email protected] writes: > > > On 3/31/2021 11:57 AM, Lux, Jim wrote: > > > > > In some ways it's like high power laser labs. It's not the direct > > beam you worry about - nobody is going to put their hand in the beam path. > > It's the stray reflection when something gets bumped and falls > > across the optical bench and reflects a stray beam at 0.01% power > > into your > eyes. > > I did consulting at Coherent Laser Group working on CO2 lasers. > In that lab, actually, many people had the misfortune of accidentally > putting their hand or arm in the invisible beam. You could see the > scars on their arms. There were also accidents where the laser burned > the ceiling, etc. Very scary place to work; fortunately, I never got > injured. They made lasers up to 1kW optical power out. > > Rick N6RK > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe > send an email to [email protected] To unsubscribe, go to > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe > send an email to [email protected] To unsubscribe, go to > and follow the instructions there. ------------------------------ Message: 2 Date: Wed, 31 Mar 2021 22:16:01 -0400 From: Bob kb8tq <[email protected]> Subject: [time-nuts] Re: Best frequency to start for GHz synth ? To: Poul-Henning Kamp <[email protected]> Cc: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=utf-8 Hi Some of the early 100 KHz resonators were ring shaped. The British really pioneered this side of things ( while the US was still doing bars …) back in the 1930’s. AFIK the mode is not a whispering gallery. Given the low frequency of a 100 KHz resonator, a “not space limited” design might get to some pretty insane Q values. Meter level dimensions probably would be involved. Good luck sourcing the raw quartz :) :) :) ( …. and yes, that’s only the first of a long list of issues ….). Bob > On Mar 31, 2021, at 3:23 PM, Poul-Henning Kamp <[email protected]> wrote: > >> If you were going insane on a fountain, you likely would go with one >> of the sapphire whispering gallery devices as the start of your >> chain. A good one will blow a quartz crystal based part away …. > > That reminds me: > > I think the first quartz-crystal at Bell Labs was ring-shaped, do you know if > that used a whispering gallery vibration mode ? > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [email protected] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. ------------------------------ Message: 3 Date: Thu, 1 Apr 2021 15:43:48 +1300 From: "Dave ZL3FJ" <[email protected]> Subject: [time-nuts] Re: Best frequency to start for GHz synth ? To: "'Discussion of precise time and frequency measurement'" <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset="UTF-8" Louis Essen was THE man - hence to the Essen Ring quartz oscillator which was a development from Dye's original work on that particular quartz configuration. The British PO used a bank of Essen Ring references as their standard immediately prior to- and I think during most of- WW2. Not sure re oscillation mode but IIRC the rings had to be suspended from several silk threads. DaveB, NZ -----Original Message----- From: Bob kb8tq [mailto:[email protected]] Sent: Thursday, April 01, 2021 15:16 To: Poul-Henning Kamp Cc: Discussion of precise time and frequency measurement Subject: [time-nuts] Re: Best frequency to start for GHz synth ? Hi Some of the early 100 KHz resonators were ring shaped. The British really pioneered this side of things ( while the US was still doing bars …) back in the 1930’s. AFIK the mode is not a whispering gallery. Given the low frequency of a 100 KHz resonator, a “not space limited” design might get to some pretty insane Q values. Meter level dimensions probably would be involved. Good luck sourcing the raw quartz :) :) :) ( …. and yes, that’s only the first of a long list of issues ….). Bob > On Mar 31, 2021, at 3:23 PM, Poul-Henning Kamp <[email protected]> wrote: > >> If you were going insane on a fountain, you likely would go with one >> of the sapphire whispering gallery devices as the start of your >> chain. A good one will blow a quartz crystal based part away …. > > That reminds me: > > I think the first quartz-crystal at Bell Labs was ring-shaped, do you know if > that used a whispering gallery vibration mode ? > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [email protected] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there. ------------------------------ Message: 4 Date: Thu, 1 Apr 2021 15:54:55 +1300 (NZDT) From: Bruce Griffiths <[email protected]> Subject: [time-nuts] Re: Best frequency to start for GHz synth ? To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=UTF-8 An interferogram showing the nodes etc. of such a resonating quartz crystal ring was posted by me in either February or March 2020. Bruce > On 01 April 2021 at 15:16 Bob kb8tq <[email protected]> wrote: > > > Hi > > Some of the early 100 KHz resonators were ring shaped. The British > really pioneered this side of things ( while the US was still doing > bars …) back in the 1930’s. AFIK the mode is not a whispering gallery. > > Given the low frequency of a 100 KHz resonator, a “not space limited” > design might get to some pretty insane Q values. Meter level dimensions > probably would be involved. > Good luck sourcing the raw quartz :) :) :) ( …. and yes, that’s only > the first of a long list of issues ….). > > Bob > > > On Mar 31, 2021, at 3:23 PM, Poul-Henning Kamp <[email protected]> wrote: > > > >> If you were going insane on a fountain, you likely would go with > >> one of the sapphire whispering gallery devices as the start of your > >> chain. A good one will blow a quartz crystal based part away …. > > > > That reminds me: > > > > I think the first quartz-crystal at Bell Labs was ring-shaped, do you know > > if that used a whispering gallery vibration mode ? > > > > > > -- > > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > > [email protected] | TCP/IP since RFC 956 > > FreeBSD committer | BSD since 4.3-tahoe > > Never attribute to malice what can adequately be explained by incompetence. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe > send an email to [email protected] To unsubscribe, go to and > follow the instructions there. ------------------------------ Subject: Digest Footer _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe send an email to [email protected] %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s ------------------------------ End of time-nuts Digest, Vol 200, Issue 49 ****************************************** _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
