GPSDO Distribution box - Page 1
Forum section: electronics / beginners

author: Moriambar
author_rank: Unknown
timestamp: October 31, 2020, 05:02:21 pm
content: Hi.I'd like to buy one GPSDO (aliexpress is literally flooded with them) but I'm puzzled about the distribution box (egthis one).I do not understand why I should need one of those modules: are they necessary for day to day use, or do they actually are needed for a specific task?I think I won't need more than one device using the GPSDO at a time; the 8 outputs are fine but the thing costs almost double than the lone GPSDO…Can someone enlighten me plz?Cheers

author: geggi1
author_rank: Frequent Contributor
timestamp: October 31, 2020, 06:27:31 pm
content: If you have several instruments that need timing you must have a distribution unit. When you are only using one instrument or unit the distribution is not needed.

author: Electro Fan
author_rank: Super Contributor
timestamp: October 31, 2020, 06:55:46 pm
content: Quote from: geggi1 on October 31, 2020, 06:27:31 pmYes, +1, the distribution box is only needed if you are going to use the GPSDO to provide clock to multiple devices - which can be very useful but they can be purchased separately from the GPSDO and added later as needed.fwiw, BG7TBL has much newer devices than the 2014 models in the link; I'm sure there is a BG7TBL distribution model that was made in 2018 (and maybe newer) and likewise the BG7TBL GPSDO's have newer models too.

author: Moriambar
author_rank: Unknown
timestamp: October 31, 2020, 08:27:35 pm
content: Quote from: Electro Fan on October 31, 2020, 06:55:46 pmYes, but the photos aren't quite up to date: one customer photo for that link reports a 2020 module.If I actually knew how to get a reliable source I would…

author: ledtester
author_rank: Super Contributor
timestamp: November 01, 2020, 09:17:19 am
content: Reminds me of this video of repurposing a video distribution box to carry a GPSDO signal:https://youtu.be/chrzrod3tQYAlso found this one:https://youtu.be/UWxubYsFXT4

author: Paul Rose
author_rank: Regular Contributor
timestamp: November 05, 2020, 05:26:03 pm
content: Quote from: ledtester on November 01, 2020, 09:17:19 amI did that same 75 => 50 mod to a nearly identical unit from the first video. Impedance was established for inputs and outputs by (fairly chunky and easy to solder) 75 ohm SMT resistors, so it was pretty obvious what to do.It worked great. Way more ports than I needed, but that's OK.

author: tkamiya
author_rank: Super Contributor
timestamp: November 06, 2020, 01:11:19 am
content: Here's how it works....Your GPSDO will become the "Master Clock" in your lab. This will be the device that is considered "correct" and "standard" for your lab. It typically have one output.If you have only one equipment that can take external reference, you connect it to GPSDO and that is it. If you have more than one equipment that needs external reference, you have options. Most of the times, you can use a Tee connector and daisy chain a few. This is very commonly done. But if you connect too many, signal may not be strong enough, or it could potentially cause interference between equipment.Or, if you have to have more than a few, you can use a distribution amplifier. It will split off the reference signal (from GPSDO) in multiple ways. Most distribution amplifiers provide isolation and amplification. You can daisy chain them and supply reference signal to dozens of equipment. You can also (usually) reach longer distances. In my personal lab, I have a master distribution amplifier and children distribution amplifier for total of 48 outputs.

author: nctnico
author_rank: Super Contributor
timestamp: March 19, 2021, 02:43:39 pm
content: Don't want to start a new thread but want to share some up-hackery. I have been looking for a 10MHz distribution amplifier myself for a while. I really don't like the BNCs on the one from BG7TBL but the electronics look to be designed nicely otherwise. So I hatched a plan: replace the BNC connectors with better ones!The electronics after removing the crappy BNC connectors.The picture from Ebay shows the rear side of the front panel has a solid ground plane so my idea is to make the holes larger (if necessary) and solder in flange mounted BNC connectors. The flange mounted connectors are supposed to be mounted using M3 screws but I didn't want to have a sea of screw heads.Much to my annoyment the unit I got didn't have a ground plane on the front panel. After some contemplating about the best option: milling / drilling a piece of aluminium sheet or making a new PCB front, I decided to make a new PCB front. For milling / drilling I'd need to draw a template anyway which is just as much work as drawing a PCB.A flange mounted BNC (TE part number 1-1337446-0 ) and the new front panel. Unfortunately I made it in too much of a hurry so the holes where too small; I had to enlarge them:Ready for soldering using hot-air. I shielded the center pins so they don't get blasted with hot air.Added some wiring (which I fixated on the board using hot-glue later on)Done! I took the opportunity to put the BNCs as far apart as possible. Unfortunately there is a typo in the textSoldering the connectors may seem odd but these flange mount connected have a huge surface area so the solder joint is very strong.

author: tkamiya
author_rank: Super Contributor
timestamp: March 19, 2021, 05:08:19 pm
content: I agree. I don't like those original BNC either. They contact the center pin from two side and that they are neither 50 ohm or 75 ohm. It won't matter for this application but I do not buy them. They are widely used in CCTV market.