Which ebay seller for a rubuduim reference? - Page 1
Forum section: electronics / general

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 08:44:57 pm
content: There have been a few threads about these in the last couple of years, but I'm asking again anyway on the off chance someone is paying attention to ebay and they've seen something they don't need.I'm buying a handful of second hand morse keys from ebay at the moment. I'll get my re-shipper to send them to me to save some freight.While I'm at it I thought I might pick up a reference. I've had an ebay search email happening for the last 2 years or so and, while I haven't been giving it 100% attention, nothing's jumped out at me. There are a couple at the moment under a hundred bucks, but they have that weird dsub with coax in the middle. I have no idea if these connectors are available anywhere.So: Would anyone be kind enough to share some unwanted links, or point out a seller they've used before please?Thanks guys.

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 09:10:39 pm
content: HiEverything on eBay (that I have seen) for under $100 at the moment is a bit of a crap shoot. The Rb market ebbs and flows. Back a few years, there were piles and piles of $50 to $70 Rb's on the market. The "best deal" right now is the LPFRS LPRO units.http://www.ebay.com/itm/Lot-of-5-LPFRS-01-Rubidium-Frequency-Standard-AS-IS-Condition-/272086453625?hash=item3f599dcd79:g:7uEAAOSwCQNWfJUCThere is a thread here and you can read all the messy details of getting them back into working order (it's a 5 for $129 / not working deal). After DHL shipping they generally arrive for about $179 or so. He also has an auction for one piece. After shipping, it's not much of a deal compared to the 5 pieces.This:http://www.ebay.com/itm/Symmetricom-SA-22c-10MHz-1pps-Rubidium-Oscillator-Frequency-Standard-Reference-/301864945920?hash=item46488d8900:g:JLwAAOxyVaBS9RoXIs about as good as you will find on a "known good / working / modern / good seller" sort of unit. It connects with a very standard 0.1" space ribbon connector.The other thing you see are FE-5680 units. They used to be cheap and often "pps only" outputs. Now the sellers are drilling holes and putting in wires to add a 10 MHz output. There are a few gotcha's: 1) They often don't do it well 2) You need to heat treat the case after you drill the hole to retain it's magnetic shielding properties 3) The 10 MHz signal they come up with often is crap. All of that plus a higher price make them unattractive at the moment.Bob

author: edpalmer42
author_rank: Super Contributor
timestamp: February 06, 2016, 09:26:04 pm
content: You might want to PM the people who bought those groups of 5 dead standards. Maybe one of them would be willing to sell you one of their repaired units. You get a known good unit and they recoup some of their costs. Win-Win!

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 09:32:56 pm
content: HiOne thing that might help in this search - where are you re-shippng *from*? I assume the destination is New Zealand. Combining stuff from the UK and China in one box does not work so well ....Bob

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 10:12:22 pm
content: HiOften the 1 pps disciplining on these units is a bit of a let down. A unit with no PPS disciplining is probably 99% as useful in the real world as one with the function. Most people look at it and say "instant GPSDO". If you talk directly to the people who make them, one of the standard qualifiers is "PPS lock is not a GPSDO capable function".Bob

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 10:24:00 pm
content: Quote from: uncle_bob on February 06, 2016, 09:10:39 pmToo hard. Interesting, I guess. But still too hard.Quote from: uncle_bob on February 06, 2016, 09:10:39 pmLooks good to me! I'll call this one plan A and get one unless someone has a better idea in the next day or two.Quote from: uncle_bob on February 06, 2016, 09:10:39 pmThanks for the heads up.Quote from: edpalmer42 on February 06, 2016, 09:26:04 pmGood thinkingQuote from: uncle_bob on February 06, 2016, 09:32:56 pmNo kidding

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 10:33:20 pm
content: Quote from: blueskull on February 06, 2016, 10:05:20 pmThe (extensive) documentation online seems to indicate 1pps discipline is a feature. Why is it missing? Is the ebay dude upgrading the firmware?

author: TSL
author_rank: Regular Contributor
timestamp: February 06, 2016, 10:33:43 pm
content: A question that's not been asked is...What are you going to use it for ?Some of the units mentioned are square wave out and some, like particular models of FE5680, have horrendous spurs and harmonics that make them unsuitable for anything other than locking digital stuff.If you want to lock your radios, transverters, etc., it needs to be a clean sine wave the LPRO's are often used for this.

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 10:54:51 pm
content: Quote from: apelly on February 06, 2016, 10:33:20 pmHiThe 1 pps disciplining is an *optional* feature. At least it's optional if you are a major telecom customer and shopping for the absolute lowest price on your Rb's. Roughly 99% of what you see on eBay comes out of cell towers or something similar. It all was bought in high volume to custom specs. The guy with the "magic fix" apparently has worked out how to re-flash the firmware to enable the feature.Bob

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 11:10:12 pm
content: Quote from: TSL on February 06, 2016, 10:33:43 pmI did not know that. Thank you.Quote from: TSL on February 06, 2016, 10:33:43 pmYes. Thanks again.

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 11:23:33 pm
content: HiIF you are headed to microwaves, none of these devices have good enough phase noise or spurs to be useful. They are fine for running a standard line into your frequency counter. For microwave use, the normal approach is to lock up a very clean VHF crystal oscillator to the 10 MHz through a *very* narrow PLL. The output of the VHF oscillator is then multiplied to microwaves. This approach is the same as has been used in microwave "brick" frequency sources for at least the last 40 years.Bob

author: apelly
author_rank: Unknown
timestamp: February 06, 2016, 11:45:29 pm
content: Quote from: uncle_bob on February 06, 2016, 11:23:33 pmAlso interesting! But not a concern at this stage.

author: TSL
author_rank: Regular Contributor
timestamp: February 07, 2016, 01:20:05 am
content: Two excellent references on RB's and their spurs and phase noise are here....http://www.ke5fx.com/rb.htmhttp://febo.com/pages/oscillators/rubes/Complete with tests and charts