Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).
Video distribution amplifiers are a very good and inexpensive solution to this problem. Think I paid $5US for my 24 port one (which is actually 3x dual 1 in 4 out units). I converted one of them from 75 ohm to 50Ω and didn't bother doing the rest as it made no discernible difference for timing purposes. On Thu, Nov 8, 2018 at 10:23 AM George Atkinson via time-nuts < time-nuts@lists.febo.com> wrote: > > The 9478 is an excellent unit but slightly unconventional. It does not > discipline the internal OXCO to the external standard when present. It has > a 10MHz PLL VFO tat is locked to either the internal OCXO or external > refernce depeding what is available. If the external reference is present > te VFO is locked to that and the internal OCXO is on but not used. If the > external refernce is missing the internal OXCO is used. Effectively when > used with an external reference the internal OXCO is a backup. > The service manual is out on the web nd it would nt be difficult to > re-configure a 9478 as a dumb 10MHz Distribution unit but this would b a > waste. 19" video distribution amplifiers are out there too. > I do have a spare NOS Austron modular 3U 19" rack with distribution > modules in it but I'd have to check exactly what it has and I'm in the USA > at the moment. If you are interested I can look when I get bck next week. > Robert G8RPI > > ___ > 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.
Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).
The 9478 is an excellent unit but slightly unconventional. It does not discipline the internal OXCO to the external standard when present. It has a 10MHz PLL VFO tat is locked to either the internal OCXO or external refernce depeding what is available. If the external reference is present te VFO is locked to that and the internal OCXO is on but not used. If the external refernce is missing the internal OXCO is used. Effectively when used with an external reference the internal OXCO is a backup. The service manual is out on the web nd it would nt be difficult to re-configure a 9478 as a dumb 10MHz Distribution unit but this would b a waste. 19" video distribution amplifiers are out there too. I do have a spare NOS Austron modular 3U 19" rack with distribution modules in it but I'd have to check exactly what it has and I'm in the USA at the moment. If you are interested I can look when I get bck next week. Robert G8RPI ___ 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.
Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).
It seems to be a very good price. There is a Racal Dana 9480 fully equipped with 40 outputs listed on eBay Germany for EUR 795. Nice to have but I don't need 40 outputs. vy 73 Heinz DH2FA, KM5VT Von meinem iPhone gesendet > Am 04.11.2018 um 15:05 schrieb Dr. David Kirkby > : > > On Sun, 4 Nov 2018, 11:51 David C. Partridge wrote: > >> FWIW it is trivial to modify these video distribution amps for 50 ohm >> output - you just need to change the output resistors form 75 ohm to 50 ohm >> on the board after the op-amp. >> >> David > Three was a discussion about the particular video amplifier here some years > back, as they were on eBay and someone on this list made us aware of it. > > Part of the discussion was converting to 50 ohms, but someone pointed out > it was pushing the limits of the op-amp. > > But I don't like the form factor of the unit either. > > I have for some time looking for another distribution amplifier, but I was > offered this at £150 including delivery. I think I will take it. > > Dave. > ___ > 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.
Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).
On Sun, 4 Nov 2018, 11:51 David C. Partridge FWIW it is trivial to modify these video distribution amps for 50 ohm > output - you just need to change the output resistors form 75 ohm to 50 ohm > on the board after the op-amp. > > David > Three was a discussion about the particular video amplifier here some years back, as they were on eBay and someone on this list made us aware of it. Part of the discussion was converting to 50 ohms, but someone pointed out it was pushing the limits of the op-amp. But I don't like the form factor of the unit either. I have for some time looking for another distribution amplifier, but I was offered this at £150 including delivery. I think I will take it. Dave. ___ 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.
Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).
Hi One would *guess* that the PLL bandwidth in the 9578 is wider than what you see in a typical GPSDO. As long as they don’t both line up at the same point, noise and phase peaking should not be a big deal. Depending on how clean your GPSDO is, the 9578 might clean things up a bit. For timing / high precision, putting another PLL into things is going to add some delay and possibly some temperature dependence. Since you are running normal test gear, neither of those issues should be significant enough to impact anything. In this environment 75 ohms vs 50 ohms is also not a big deal, but it will have slightly more impact, fix it if you can, don’t sweat it if you can’t. Bob > On Nov 4, 2018, at 5:44 AM, Dr. David Kirkby > wrote: > > I want a distribution amplifier to distribute 10 MHz from an HP GPS > receiver to various bits of test kit - spectrum analyzer, VNA, signal > generators, HP 5370B time interval counters, signal generators etc. > Currently I am using 75 ohm video amplifiers, but I suspect that is sub > optimal. I also don't like the form factor of this amplifier - I would > prefer a 19" rack mount unit. > > Does anyone know how well the Racial 9478 performs? If my understanding is > correct this is not simply an amplifier, but has its own internal high > stability reference oscillator, which then feeds 9 independent outputs, all > of which have their own amplifier. The internal OCXO will phase lock that > to an external reference. > > Fundamentally, it does not seem a great idea to me to lock one OCXO to GPS > then lock a second OCXO to the first OCXO. But maybe I am mistaken. > > I have the chance to buy one for £150 (GBP) but are a bit worried the > performance. > > Any comments? > > Dave. > ___ > 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.
Re: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate).
Racal overall has a reputation for making very high quality instruments, Since the OCXO is an option,and the price is right on the DA, I’d probably buy it. Also thinking since its an option the OCXO can probably be switched out of circuit or removed entirely. Im guessing Racal thought that adding an OCXO would be a feature for shops that did not have a frequency standard and/or one that used a different frequency than ‘standard’ like a TV station. So everything would be phase locked to a master clock irrespective of frequency. Content by Scott Typos by Siri On Nov 4, 2018, at 6:50 AM, David C. Partridge wrote: FWIW it is trivial to modify these video distribution amps for 50 ohm output - you just need to change the output resistors form 75 ohm to 50 ohm on the board after the op-amp. David -Original Message- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Dr. David Kirkby Sent: 04 November 2018 10:44 To: time-nuts@lists.febo.com Subject: [time-nuts] Racal Dana 9478 frequency distribution system with option 04B high stability oven (5x10^-10/day aging rate). I want a distribution amplifier to distribute 10 MHz from an HP GPS : Currently I am using 75 ohm video amplifiers, but I suspect that is sub optimal. ___ 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.
