GPSDO on multiple devices - Page 1
Forum section: electronics / testgear

author: W4PJB
author_rank: Regular Contributor
timestamp: September 16, 2024, 02:18:02 pm
content: How many devices can a single GPSDO support without an amplifier? I recently picked up a Leo Bodnar LBE-1420 and it's worked perfectly split to my HP 8665B and 5350B. I'd like to tie in my 8566B and 8753C as well. Of course I could always switch them out as needed, but it would be convenient to avoid that.I understand this would party depend on the sensitivity of each device, but I'd still be interested in hearing others experiences.

author: Ringmodulator
author_rank: Regular Contributor
timestamp: September 22, 2024, 02:17:04 pm
content: Hi,I dont think, there is a good answer to your question.At first, please check if your devices have the possibility to daisy-chain the 10 MHz signal. This means, that they can output the signal from the 10MHz reference input.Then all is good.Having multiple devices connected to the gpsdo in parallel will lower the load impedance for the gpsdo and lead to a lower signal level.A device may tolerare this, or not. It will depend ond the input impedance of the devices and some have a high impedance, where it does not matter so much.YAdditional, ou might get multiple reflections on the 10MHz lines and some devices may be upset by this.Therefore this is not good practice.But we as hams love to tinker, so just give it a try...I suggest the use of a video distribution amp, which often can be bought used very cheap.For example Extron DA devices. There are therads about this in the eevblog forum.I would not care about the 75 ohm impedance and some of them can be easily converted to 50 ohms, but im my exprience, this is not neccesary.73,Chris

author: fourfathom
author_rank: Super Contributor
timestamp: September 22, 2024, 02:51:01 pm
content: Yes, usually we use a distribution amp or similar, although depending on the number of the devices you want to connect (and their input sensitivity) you may be able to use a resistive splitter. You do want to maintain a reasonable impedance on these connections, otherwise waveform distortion may create problems.You can buy a surplus video distribution amplifier (and as suggested, the 75 Ohm impedance is close enough to not be a problem). I got one made by Extron off of ebay. Or you can buy a purpose-built amplifier like this:https://tapr.org/product/tadd-1-rf-distribution-amplifier/.My little company also makes one. This uses SMA connectors rather than the typical BNC, because it is typically used with multiple SDR receivers. Of course SMA/BNC adaptors are cheap, and I also use it with my test equipment:https://turnislandsystems.com/clock-distribution-buffer/

author: 4thDoctorWhoFan
author_rank: Regular Contributor
timestamp: September 22, 2024, 02:56:58 pm
content: I also used one of those Extron boxes. There is plenty of room inside the box so I combined the GPSDO, power supply & the Extron distribution amp into one unit. Oh, I also changed all the 75Ω resistors to 50Ω.

author: artag
author_rank: Super Contributor
timestamp: September 22, 2024, 07:27:13 pm
content: I have encountered video distribution boxes that do sync-tip DC restoration on the video signal. You probably don't want that.