DIY 10 MHz Distribution Amplifier - Requirements Gathering - Page 1
Forum section: electronics / testgear

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 17, 2018, 11:07:53 am
content: I just did a quick count and I have 10 peices of test gear with external 10 MHz inputs, Agilent SA, VNA, Sig-gene, Rigol scopes and AWGs. I also have a Nortel (Trimble) GPSDOlike this one.There's only 1 x 10 MHz output on my GPSDO so I'm looking to design a PCB that will go inside, probably with SMA PCB edge-mount connectors down one edge so I can drill a line of holes in the case and mount it inside. I've looked online at various designs andthis one by Brian Doreyseems well thought out with a front end filter to remove harmonics plus sine and square wave outputs.So the questions are:1. What are the needs input-wise of the range of test gear that has 10 MHz external inputs and would the design above cover most stuff?2. Does something like this already exist that covers my requirement? If I can buy for $20 from eBay I won't bother.I'll share any design I come up with on the forum. Corrected typo

author: jpb
author_rank: Super Contributor
timestamp: March 17, 2018, 11:31:22 am
content: Brian Dorey's design looks nice but it may be a little under-powered for some instruments. For example my TTi TF930 counter requires 1Vrms for its external reference input which I find a constant source of annoyance as most other systems will make do with less. But it may be worthwhile checking your instruments.I don't think you'll get anything decent on ebay for $20.The one I'll probably get is the one by BG7TB (of GPSDO fame), there is a review of it here (it is 8 rather than 10 output but you may be able to use a couple of passive splitters for some instruments):http://www.reeve.com/Documents/Articles%20Papers/Reeve_10MHzDist.pdfbut it seems to be more like $100 than $20.The other option is to daisy chain as most instruments have a reference out as well as a reference in but then you need to have them on all the time and noise may be added.

author: SeanB
author_rank: Super Contributor
timestamp: March 17, 2018, 03:28:13 pm
content: Video distribution amplifiers are probably the easiest thing to use. 1 75R input, with generally a 75R resistor to define input impedance, and then a set of amplifiers to give a 75R output. AC coupled in most cases, and with enough gain to give a usable output for almost all equipment as it has to drive more than 1V into 75R for video in any case, and generally will work up to around 14MHz without issue.If I ever get something that needs it I already have a 30 output video amplifier with modules from Opamp Labs doing all the work, including power supply, each in an octal plug in module.

author: don.r
author_rank: Frequent Contributor
timestamp: March 17, 2018, 04:01:09 pm
content: Quote from: SeanB on March 17, 2018, 03:28:13 pmI agree. Many are easy to modify for 50 ohm as well if desired by simply stacking a 150 ohm resistor on top. I did that with an Extron ADA 6 300 HV for my GPSDO and it works fine. See Gerry Sweeney's Distribution Amplifier video on youtube (he actually replaces the 75ohm resistors with 50ohm). The Extron ADA series has at least 300MHz bandwidth.

author: Shock
author_rank: Super Contributor
timestamp: March 18, 2018, 05:36:25 am
content: The Extron distribution amps are an easy mod and they aren't all that expensive I paid about $10. I expect supply far outstrips demand. The Extron ADA 6 300MX HV is a high bandwidth total overkill model. The ADA 4 model has plenty of outputs as well.

author: Harb
author_rank: Regular Contributor
timestamp: March 18, 2018, 05:45:12 am
content: I just used a VDA .........1 in 50 out , a change of resistors and it was happy driving all the outputs into 50 ohms

author: deepskyridge
author_rank: Regular Contributor
timestamp: March 18, 2018, 01:11:27 pm
content: Quote from: Harb on March 18, 2018, 05:45:12 amWhat he said. I have one installed in my rack. Did the resistor change to 50 ohm.Gary

author: kj7e
author_rank: Frequent Contributor
timestamp: March 18, 2018, 02:41:25 pm
content: Bought an ESE ES-208, 12 output 10MHz bandwidth VDA on eBay for $19 shipped the other day. The input is a high impedance loop, so a 50Ohm term is all that's needed on the input. Ill put it apart and once it gets here;http://www.ese-web.com/208.htm

author: DaJMasta
author_rank: Super Contributor
timestamp: March 18, 2018, 03:02:48 pm
content: Something like this:https://circuitmaker.com/Projects/Details/DaJMasta/Seven-Output-10MHz-Distribution-Amplifier?It's a bit of a pain to get higher power output out of these things, since the power requirements means you likely have to go to single amps per package, but up to about 1Vpp, you can use quad opamps. This has been enough for my externally referenced stuff. I've also got a square wave output version floating around on the circuitmaker, and since you can just use logic gates for everything, you can get a full TTL swing easily enough and then if you need a purer tone, can get decent results with a simple filter on the output.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 18, 2018, 05:14:34 pm
content: Thanks, I'll check that out although I'm going to have to install Circuitmaker to look at the schematic. I like the idea that it has optional gain setting / low pass filter on the front end. Any chance of a .pdf?I found the circuit below for the LT6550/1 (triple/quad) on page 16 ofthe datasheet.This driver IC is actually the same one used byBrian Dorey's design. The LT6550/1 drives into overload if the input goes over 1.25 volts on a 3 V single rail supply as shown which is exceeded by the output of my GPSDO (I measured 1.8 Vpp driven into 50today). So maybe I need to put some kind of front end in front of it and it would be neat to allow for an adjustment so that different levels of input can be catered for.However, if I made Vcc = 5 V, then the input of 1.8 Vpp I'm providing would be OK as long Vin max doesn't exceed 5-1.75 V = 3.25 V so I would bias the input to 3.25/2 = 1.625 which I could achieve by tweaking the input potential divider resistor values.Any thoughts? I should wait until I see the circuitmaker.com design

author: awallin
author_rank: Frequent Contributor
timestamp: March 18, 2018, 06:21:11 pm
content: I've been tinkering with this design:https://www.ohwr.org/projects/pda-8ch-fda-8ch/wiki/frequency-distribution-amplifierif you care about phase-noise (and ADEV) you need to have clean DC-rails and decemt PSRR in the amp. From a medical-rated AC/DC 9V brick I use a common-mode choke, then a BNX025 filter and then LDOs LT1936/LT3015 - seems to work for me.There are designs that paralllell two LMH6702's and get about 3dB better phase-noise, but around -160 dBc/Hz-ish for a 10 MHz carrier is doable with op-amps. There are probably discrete transistor designs that do a bit better - if you really need it..this page has links to some other designs:https://www.ohwr.org/projects/pda-8ch-fda-8ch/wiki/similar-projects(might add the ones mentioned in this thread!)

author: DaJMasta
author_rank: Super Contributor
timestamp: March 18, 2018, 06:34:18 pm
content: Quote from: Gandalf_Sr on March 18, 2018, 05:14:34 pmSort of annoying little "feature", and I don't know if there's an easy way to do .pdfs, so here's some screen captures of each:http://www.medpants.com/pics/7%20distribution%20amp.jpghttp://www.medpants.com/pics/4%20distribution%20amp.jpgSimilar designs to what you've seen, no doubt, but the board's laid out and ready to be built up. I never made boards of the 7 way amp (I made ones with the same schematic and almost the same layout that had a few more bits to supply a GPS unit and a monitor for a custom GPSDO), but I have some spare boards of the 4 way amp I could pass along for postage.

author: David Hess
author_rank: Super Contributor
timestamp: March 18, 2018, 06:56:25 pm
content: Quote from: Gandalf_Sr on March 17, 2018, 11:07:53 amThe worst case and what I would design for is TTL level inputs which depending on exactly what is happening and amount to the 1 Vrms that jpb mentioned.QuoteAs SeanB said, video distribution amplifiers can often be modified to handle 10 MHz distribution.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 18, 2018, 07:10:07 pm
content: It seems you have many devices so an Extron Video Distrubition amplifier mod is probably the way to go. (I bought a couple of these but still haven't got around to modding them... one day).I created a 1:4 10MHz and added a pulse stretched 1PPS output for my lab equipment, based on LT6551IMS. Seems to work fine (but I'm no test nut). Another EEVBlog member built one from a PCB I had spare and seemed happy. I imagine this has too few outputs to be useful to you.

author: edpalmer42
author_rank: Super Contributor
timestamp: March 18, 2018, 07:25:25 pm
content: Is it really worth the time and effort to design and build your own distribution amplifier when video distribution amps are so readily available for a reasonable price? To me, it feels like a lot of work with relatively little payoff. I can think of lots of other projects I'd rather work on.In any case, here's another amp that has been discussed on the Time-Nuts list:http://tapr.org/kits_tadd-1.html.Another slightly different idea is to combine a frequency divider with a distribution amp. Time-nuts often need this sort of thing.http://www.perdrix.co.uk/FrequencyDivider/index.htmlEd

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 18, 2018, 07:29:48 pm
content: Quote from: edpalmer42 on March 18, 2018, 07:25:25 pmProbably not but if you only need <=4 outputs then a simple daughter board means you can fit it all together in the same box as your GPSDO and save space.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 18, 2018, 07:55:36 pm
content: Thanks for all the input guys and offers, I have a lot to chew onI looked for old distribution amps but I design PCBs for a living so this is a very simple project for me if I can just decide what to put in it, I could also make a batch of PCBs and you guys can get them for cost if you like.I also want a PCB that I can fit inside my GPSDO that uses SMA connectors, buying 10 BNC-BNC leads would be expensive and I have loads of cheap SMA leads from eBay (as well as some expensive ones).Am I over-thinking the input, one of the first designs I linked to had a $6 IC to filter at a cut off of 15 MHz to suppress the harmonics, themedpants designuses a simple (optional) capacitor to form a low pass filter although I haven't checked what the -3dB point would be for that arrangement, it might be all that's needed. What do you guys think?I'm also wondering what the best way would be to allow the user to adjust for different input levels without changing components; what's the best way to do this?I think I'll design for 9 or 12 outputs and then add a 1 pps (stretcher) and two TTL outputs, is that enough?

author: DimitriP
author_rank: Super Contributor
timestamp: March 18, 2018, 07:55:45 pm
content: Quote from: NivagSwerdna on March 18, 2018, 07:29:48 pmIf you use a large enough extron box, you can fit the GPSDO in it and still save spaceThe idea that the GPSDO is "bought" but the distribution amplifier is "made" seems backwards to me.But hey! I'd rather read a thread about another 10MHz distribution amplifier than "what scope/multimeter/probes/soldering iron to buy"Or yet tweaking another headphone amp if we can do some cross forum complaining

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 18, 2018, 08:20:12 pm
content: Just modeled 470and 270pF in LT Spice, looks like it would be -16 dB at 10 MHz

author: DaJMasta
author_rank: Super Contributor
timestamp: March 18, 2018, 08:24:53 pm
content: Quote from: Gandalf_Sr on March 18, 2018, 07:55:36 pmIf you've got a PPS output from the GPS already, it's simple enough to just put it through an inverting buffer and drive some lines - even directly from a GPS unit, the adjustment step size is usually <40ns for a lot of modern ones, so you can get good raw accuracy and of course the normal stability over time from just buffering the output directly.If you want to have TTL squarewave outputs, I would treat it as a mixed domain board, and isolate your analog ground from your digital one. I'd also put a ferrite or a small inductor between the main power rail and the opamp power supply for a little more high frequency rejection, since the digital logic will probably be fast enough switching to make a bit on the power rails even with normal decoupling.As for whether it's enough.... how many instruments do you really have that can take the input? I've got a scope, SA, RF gen, arb gen, counter..... and 7 outputs is plenty for that, which seems like a ton of equipment already, some of which really don't benefit much from it in most situations... so 9-12 seems like more than enough. That said, it's much cheaper to build in the extras early on, so maybe going all out is nice just because it will be plenty into the future. I prefer BNCs just because the equipment you hook up is usually BNC stuff and the actual 1-2m cables can be gotten cheaply, but decent quality BNCs are definitely the most expensive part of the project if you make it yourself.I guess one other tip if you end up using a design like the one I linked: if you use a rail to rail opamp and bias them right in the middle instead of the skewed one as I have, you should be able to squeeze a little more amplitude out of the outputs. The way it's setup, driving all four outputs into 50 ohm loads makes the chip raise 10-20C over ambient, so there's not a ton of overhead if you use quad amp chips, but there is a bit available. I just ran into an issue where a low noise quad amp was going to be more expensive if I wanted rail to rail, so instead of getting the most out of my 5V single ended supply, I adjusted the bias point down to compensate for the volt and a half or so you need to be away from the top rail, and that gives you less maximum amplitude to play with.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 19, 2018, 03:45:07 pm
content: Here's an early version, no power supplies and only 8 channels of sine distribution. One area I'm not sure about is the coupling from U3.2 and 3.3 into the driver amps. You'll see this is a hybrid with the front end from one of the linked circuits and the output section from the LT6551 data sheet. Any input welcome.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 19, 2018, 03:56:26 pm
content: I added RF 1:1 isolation transformers onto the outputs of mine a lahttps://www.tapr.org/~n8ur/TADD-1_Manual.pdf

author: David Hess
author_rank: Super Contributor
timestamp: March 20, 2018, 12:18:11 am
content: Quote from: Gandalf_Sr on March 18, 2018, 07:55:36 pmIf the output stage is linear as with an operational amplifier, then an adjustable voltage divider at the input of the operational amplifier can adjust the output level. 10 MHz is well within the capability of a trimmer potentiometer.I have never seen any distribution amplifier designs do it but a current switched output stage which drives a termination shunt resistance instead of a series termination could have an adjustable output voltage just by changing the current. Some analog function and pulse generator designs did this to control positive and negative pulse height or slew rate using a current driven diode bridge.Another way is to use analog switches for the output stage with an adjustable reference. I know of a couple of people who built precision square wave calibrators this way.

author: ArthurDent
author_rank: Super Contributor
timestamp: March 20, 2018, 01:12:43 am
content: I scanned through the previous posts and I didn't see this mentioned. On the video amps where the input and output have 75 ohm resistors, there is no reason to remove them and possibly damage the circuit board, just solder a 150 ohm in parallel to get 50 ohms.

author: Cerebus
author_rank: Super Contributor
timestamp: March 20, 2018, 02:52:13 am
content: Quote from: NivagSwerdna on March 19, 2018, 03:56:26 pm+10 on this.Isolation transformers have got me out of trouble so many times in the past with pro audio gear. Connecting a rack's worth of gear together with a DC path all the way through almost guarantees that it will cause you trouble at some point. Plus point is that RF isolation transformers are cheap; if sir needs to ask the price of good AF signal isolation transformers like Jensens, sir cannot afford them (they're on the close order of £50 each).

author: Dwaine
author_rank: Frequent Contributor
timestamp: March 20, 2018, 07:40:15 am
content: I bought Extron ADA 4 300M off eBay for $20.00. I think I’m going to add a rubidium module and have one input for my GPSDO.Nice little project.

author: TurboTom
author_rank: Super Contributor
timestamp: March 20, 2018, 08:02:16 am
content: I also opted for the isolated outputs -- if you've got (or just like) to syncronize a function generator that's not ground-referenced, you're in trouble without. Moreover, ground loops can really ruin your day... Figured out a very compact circuit that directly bolts onto the LPRO101 Rb oscillator and uses the LT6553 video distribution amplifiers. It provides five +7dBm sine outputs and three digital ones (2.5V, 3.3V, 5V). Fits in a very compact enclosure, see here if you like:https://www.eevblog.com/forum/projects/made-a-nice-_home_-for-my-efratom-lpro-101/msg1250122/#msg1250122Cheers,ThomasP.S. I used LAN isolation transformers which also include common mode chokes to reduce capacitive coupling - works very well. Edit: Link corrected

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 20, 2018, 10:15:58 am
content: OK, I am convinced that isolation transformers are better, I like Coilcraft for quality and they now offer a range of transformers;this PFD3215-222MEpart is pretty cheap at about $0.70 each. Any thoughts as to which inductance value would be better and why?Also, in my schematic above, I use 3 of the 4 Op Amps in the MAX4383 package as voltage follower buffers (the 3rd is unconnected but the idea is that it will drive the TTL logic output circuitry), so that means that they simply convert from very high to very low impedance but what (if any) interface components are recommended before they drive the input of the LT6551 video Amplifiers? At present I have them driving through 10n capacitors (C13/C14) into the voltage -biased high impedance inputs of the LT6551s. Is this OK? Do voltage followers need a load? Also I read in The Art of Electronics that it's preferable to have 1k resistors in the 100% -ve feedback loop. I think this project would be better (more universal) if it had some form of AGC on the input stage.

author: Cerebus
author_rank: Super Contributor
timestamp: March 20, 2018, 11:58:58 am
content: Quote from: Gandalf_Sr on March 20, 2018, 10:15:58 amJust pick it on the quoted bandwidth it will handle. If there are graphs of insertion loss versus frequency, then pick for lowest insertion loss at your frequency of interest. You're in luck with that datasheet as it quotes both. So for 10MHz the *-472 and *-682 parts would seem to be your best bet, the *-103 would also perform OK. If you ever want to squeeze a 1MHz signal through it, go for the *-103 as a compromise part.

author: jpb
author_rank: Super Contributor
timestamp: March 20, 2018, 07:03:29 pm
content: I've just bought an Extron ADA 6 300MX HV off ebay for £25 inc postage, it arrived in a couple of days and seems to work nicely (just feeding a 10MHz in from my generator and connecting the output to a scope).Thanks to all who suggested this route. I can't decide whether to build my GPSDO into it or keep it separate and perhaps try to improve it a 10MHz filter and perhaps a low noise linear supply as well as doing the resistor mod.

author: klaus11
author_rank: Unknown
timestamp: March 22, 2018, 08:34:57 am
content: Another Extron project,https://www.jackenhack.com/reference-10-mhz-distribution-amplifier/I also have ADA 6 300MX HV, rather, waiting for the shipment to arrive.

author: Shock
author_rank: Super Contributor
timestamp: March 22, 2018, 11:43:49 pm
content: There is also the Charles Steinmetz modshttps://doc.xdevs.com/doc/Extron/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf

author: CJay
author_rank: Super Contributor
timestamp: March 23, 2018, 07:24:58 am
content: Quote from: NivagSwerdna on March 18, 2018, 07:10:07 pmI also have an Extron, same model I think as the one Gerry Sweeney modded.They work nicely without the mod, well enough that I am not planning to mod it any time soon unless I suddenly find myself with a pile of resistors and a few days where all my other commitments magically vanish.

author: Dwaine
author_rank: Frequent Contributor
timestamp: March 23, 2018, 03:23:08 pm
content: Any recommendations for a good linear power supply to replace the switch mode one?

author: CJay
author_rank: Super Contributor
timestamp: March 23, 2018, 05:08:11 pm
content: The Time Nuts guys seem to like the Power One Linear supplies (now Bel) but I'm not sure you'll get one to fit in the Extron case...

author: DaJMasta
author_rank: Super Contributor
timestamp: March 23, 2018, 06:30:11 pm
content: Quote from: Dwaine on March 23, 2018, 03:23:08 pmRather than that, you can just use a linear regulator on the output of a switchmode supply. If you can keep the voltage drop low, you don't lose a ton of efficiency, and if you use a linear regulator with good PSRR combined with a bit of bulk capacitance and either a ferrite or a smallish power inductor between the switcher and the linear reg, you can get a pretty dang clean power rail without too much fuss. While a clean signal is desirable, the stuff taking the distributed reference also can deal with a bit of noise from an external source, especially with a power level of several dBm on the primary tone.

author: TheSteve
author_rank: Unknown
timestamp: March 23, 2018, 06:43:21 pm
content: I have never seen a commercial 10 MHz distribution system that uses isolation. Are they just cheap when they build them or do they figure it isn't required?

author: DaJMasta
author_rank: Super Contributor
timestamp: March 23, 2018, 08:11:22 pm
content: I haven't seen any evidence that it's required, and none of the lab distribution amps I've seen use it either. Basically, while you want a clean signal, it's not really a "signal level" sort of thing (at least, not when it's at a few dBm) and there is no loop to boost noise from a ground loop to a problematic size.If you've got special power concerns in your lab or want to use your reference into some project that is very susceptible to noise, maybe there's some value in it, but I don't think test equipment with 10MHz inputs will care.

author: TheSteve
author_rank: Unknown
timestamp: March 23, 2018, 08:42:42 pm
content: Thanks for the reply. I've always figured a clean signal was the most important part. It can be tough to beat the internal oscillators phase noise(on some higher end gear anyway) with an external reference so you don't want your distribution system to add additional noise to the system. I do think it is important for each output from a distribution system to have its own amplifier so there is no change in levels etc when connecting additional devices.

author: klaus11
author_rank: Unknown
timestamp: March 24, 2018, 02:42:41 pm
content: How much effort to isolate? is it possible in Extron ADA?

author: texaspyro
author_rank: Super Contributor
timestamp: March 24, 2018, 05:23:38 pm
content: Quote from: klaus11 on March 24, 2018, 02:42:41 pmIt can be very easy with transformer coupling the output... but using magnetics can open a bit of a can of worms of other issues.

author: klaus11
author_rank: Unknown
timestamp: March 24, 2018, 07:43:34 pm
content: This is a good reference without transformer coupling:https://www.allaboutcircuits.com/projects/how-to-eliminate-ground-loops-with-signal-isolation/

author: Dwaine
author_rank: Frequent Contributor
timestamp: May 12, 2018, 04:57:49 am
content: Got my FE-5680a today. Starting the project now. Fed it with 15volts and 5 volts. The 1pps and 10mhz sine look pretty good. Runs nice and toasty. Going to see what the outputs look like after I put it into the Extron Video distribution box.

author: BravoV
author_rank: Super Contributor
timestamp: May 12, 2018, 10:29:41 am
content: Subscribed

author: Shock
author_rank: Super Contributor
timestamp: May 12, 2018, 02:23:45 pm
content: There are a few Extron ADA 6 300MX HV units on ebay right now for $25.This gives you about 4-5 inputs each with 6 outputs, enough for the whole neighborhood.Attached are the specs, users guide and brochure. TheSteinmetz mod recommendations can be found here.

author: CJay
author_rank: Super Contributor
timestamp: May 14, 2018, 12:47:34 pm
content: Quote from: Dwaine on May 12, 2018, 04:57:49 amBe nice to that FE5680A and give it a heatsink, they need one, there are lifespan problems if you run them 'barefoot' and don't manage the temperature..

author: mark03
author_rank: Frequent Contributor
timestamp: May 19, 2018, 12:40:11 am
content: Has anyone tried powering additional circuitry, e.g. a GPSDO, from the existing power supply in the Extron 6 300MX? I measure ~ 17.5V open circuit, 16V loaded by the distribution amp. Would like to piggyback a TruePosition GPSDO board on the same rail if I can get away with it.

author: Shock
author_rank: Super Contributor
timestamp: May 19, 2018, 03:54:00 am
content: Quote from: mark03 on May 19, 2018, 12:40:11 amMy GPSDO won't fit (understatement) so it's not an option for me, also I have plans to add more functionality.Gerry discuses the power supply a little in his video.The question that comes to mind is your GPSDOs current requirements. I'd be replacing the caps though for sure, due to the age of the Extron units it's highly recommended (by me hah). The supply design must be ok for noise spec wise, you would think the circuit would be impacted otherwise. A scope is going to let you know anyway and everyone's lab/workshop and definition of a clean supply is different.I'd have no idea if it would create any noise issues, but if you think about the Extron as another signal and buffering stage on the same supply as the GPSDO I don't see how it could be to adversely affected and could be ruled out with an isolated bench supply and scope performing comparison tests.Personally though I wouldn't have mounted a FE5680A style RbDO in there to begin with, I like the idea of the Extron as just a distribution box for signals that can be bypassed to troubleshoot. But I can understand if you have a GPSDO PCB and there is empty space to fill.

author: mark03
author_rank: Frequent Contributor
timestamp: May 19, 2018, 04:14:54 am
content: Quote from: Shock on May 19, 2018, 03:54:00 amI still need to measure the current requirements. But the fit will be fine. I really like the idea of having this all in one box, and I needed a box for the GPSDO anyway.Re: switchers in or near a GPSDO, I'm not sure how paranoid to be. FWIW, the TruePosition GPSDO has two switching power supplies right there on the board... perhaps followed by LDOs.

author: jpb
author_rank: Super Contributor
timestamp: May 19, 2018, 10:17:12 am
content: Quote from: Shock on May 19, 2018, 03:54:00 amI agree with this, though of course everyone's requirements are different. I might want to distribute more than one reference (e.g. square wave and sin wave or an offset frequency for doing dual balanced mixer stability measurements perhaps) and want to switch between them.Also, I plan to fit a low noise linear supply as well as a mains filter and perhaps splitters and buffers - there is endless fun to be had.If connecting to an FE5680A which I think has quite a lot of phase noise, another use for the space might be to have an OCXO that is phase locked to the reference to clean things up before distribution.

author: 4thDoctorWhoFan
author_rank: Regular Contributor
timestamp: May 19, 2018, 02:08:06 pm
content: Quote from: mark03 on May 19, 2018, 12:40:11 amYou probably should use a little separate power supply.Below are a few pix of mine. I have a little 12V supply and the GPSDO mounted on the bottom plate. I connected the 12V supply to the same AC input so it still only needs just the one AC input to power everything.Of course, since it's a GPSDO, I drilled a hole for the Antenna input on the back. Cut a rectangle on the front to insert the LCD display.The first 3 rows of BNC's on the back are all for the 10Mhz. The bottom row of BNC's are for the 1pps signal.P1010139 (2)P1010140 (2)P1010142 (2)P1010141 (2)