10 MHz reference signal connections for spectrum analyzer and signal generator ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: April 12, 2019, 08:15:01 am
content: My spectrum analyzer (SA) and my signal generator each has an input for external 10MHz reference signal, and also I have 10MHz from GPSDO.As my SA does not have the internal tracking generator, I will use the external sig-gen.All I want is to do is a simple sweep measurement on DUT across the defined frequency range.How to connect the 10MHz signal source, topology wise, to these two equipments SA and sig-gen ?FYI, the SA has only single port which can be configured either IN or OUT for the 10MHz signal, while the sig-gen has two separated ports, IN and OUT.TIA

author: capt bullshot
author_rank: Super Contributor
timestamp: April 12, 2019, 09:49:52 am
content: You've just suggested the solution:If your GPSDO has only one output, connect this to Sig Gen ref input, Sig Gen ref output to SA ref input.Otherwise, of one can (or has), one uses an distribution amplifier for the 10MHz ref.Edit: for your purpose, most probably you won't need that external reference at all. Let the Sig Gen and the SA run on their internal refs.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 12, 2019, 11:02:32 am
content: other than that, a 50 ohm 2-way splitter maybe with equal cable length if synch is required, ymmv.

author: David Hess
author_rank: Super Contributor
timestamp: April 12, 2019, 07:07:23 pm
content: It should not matter how you hook them up as long as the signal levels are appropriate. Through the signal generator is probably the easiest since it only requires two cables.

author: 0culus
author_rank: Super Contributor
timestamp: April 12, 2019, 09:17:33 pm
content: I guess you might want to also verify that an external reference onto your sig gen also goes out. I would think it should, though, so you can daisy chain.

author: ogden
author_rank: Super Contributor
timestamp: April 12, 2019, 09:42:12 pm
content: Quote from: capt bullshot on April 12, 2019, 09:49:52 amRight. Described measurement do not need *any* frequency accuracy from signal generator. If you trust your SA indication during other measurements, this one is no different, does not require ext.ref.

author: BravoV
author_rank: Super Contributor
timestamp: April 13, 2019, 03:54:19 am
content: Thanks for all replies, really appreciate it.All noted, my acquired used SA is pretty aged, it seems like the internal xtal is aged and drifted, hence the GPSDO from the 1st place. Also the sig-gen is the new member in my T&M family.All worked and done, daisy chained from GPSDO -> sig-gen -> SA, and the marker is now spot on.I guess the best is to get a 10 MHz distributor isn't it ? Here we go, another TEA adventure begins.Thanks again.

author: Brumby
author_rank: Unknown
timestamp: April 13, 2019, 04:20:28 am
content: Quote from: BravoV on April 13, 2019, 03:54:19 amThat would eliminate any issue with having the connections for daisy chaining.If you can find an analogue video distribution box with at least 10MHz bandwidth, that should work.

author: BravoV
author_rank: Super Contributor
timestamp: April 13, 2019, 04:27:52 am
content: Quote from: Brumby on April 13, 2019, 04:20:28 amWhat potential issue/s, if the ref signal is daisy chained ?Quote from: Brumby on April 13, 2019, 04:20:28 amYeah, currently in the process looking for it, and also I'm currently considering an offer locally here of an alternative that is an alien unknown GPSDO box that has built-in distributor, worst case if the GPSDO is unworkable (no documentation what so ever on the net), at least I can salvage the distributor part + a nice box + PSU. I've searched and asked around, seems like no one knows it, even the god of GPSDO boards, author of LadyHeather.Few shots of the thingy from the seller.

author: 0culus
author_rank: Super Contributor
timestamp: April 13, 2019, 05:03:00 am
content: Unless the intermediate members of the daisy chain are also amplifying the external ref signal on it's way out, you'll likely experience losses by the end of the daisy chain.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 13, 2019, 09:47:01 am
content: Quote from: BravoV on April 13, 2019, 03:54:19 amat 10MHz its easy to diy. active distributor will need 2 or few cheap gain opamps, the passive one is the said 2-way splitter earlier...https://support.channelmaster.com/hc/en-us/articles/200383715-How-Much-Signal-Do-I-Lose-Going-Through-A-Splitter-CM-3212HD-CM-3213HD-

author: Shock
author_rank: Super Contributor
timestamp: April 13, 2019, 11:14:05 am
content: One thread on DIY distribution amps here.https://www.eevblog.com/forum/testgear/diy-10-mhz-distribution-amplifier-requirements-gathering/If you are going for an Extron the ADA 6 300MX HV is the high bandwidth model, it has several channels to distribute 10MHz, 1pps, TTL etc and 6 outputs on each means you aren't likely to run out.

author: Brumby
author_rank: Unknown
timestamp: April 13, 2019, 12:11:47 pm
content: Quote from: BravoV on April 13, 2019, 04:27:52 amFor example: 3 units with a 10MHz input and only one has a 10MHz output.

author: Shock
author_rank: Super Contributor
timestamp: April 13, 2019, 02:35:00 pm
content: Quote from: BravoV on April 13, 2019, 04:27:52 amAny deterioration in a daisy chained signal would have a cumulative effect. Noise, attenuation, effects of each instrument down the line. All things being equal, if you have a distribution amp with six outputs you get six "identical" signals.