Hi Now you've probably seen this before. This is my Agant 53131a Universal counter frequency counter and it's a very good unit. Highly recommend it if you can. uh, pick one up on eBay It's an older Uh model.

They've got a newer model out now, but it's a really nice uh instrument. and I've done a couple of previous videos on this I got it from an auction. Uh, score Really? Dirt Cheap basically along with my Rubidium Frequency standard so click here if you want to watch the previous videos I've showed actually uh, calibrating this thing or the internal oscillator in this thing. Hence, today's video.

while this is a really good Uh frequency counter, its standard oscillator building is horrible. It is practically a joke. It's like, you know, just a 5 PPM SC cut crystal or whatever it is with a Dicky little pot on the back that you got to adjust it's it's worthless. So to make this thing usable, you've either got to put an external Uh reference in from a ridium oscillator or anything like that or get one of the higher stability internal options.

And they're normally very expensive of course. But I Found this on eBay and this is one of these. Uh, this is a high stability oven based oscillator and this is what you need for one of these things. Sure! I've got myself a Rubidium Uh frequency standard from the C CSO no less.

it is Uh was the main frequency stand at the Commonwealth Scientific Research uh in Institute here in Australia whatever it stands for and research organization and it was good enough for them. Uh, it should be good enough for us. It actually uses a Stanford research um Prs1 rubidium oscillator in it. this GPS locked and it's got backup power supplies and all that sort of jazz.

Anyway, that's fine and dandy and I've got this super accurate rubidium standard here in the lab that I can hook up and my frequency coun is really accurate but hey, you don't always have it available and uh, well, you know, convenient. Anyway, always hooked up. So I Thought it'd be nice just to upgrade this puppy with this oven oscillator so it can be used Standalone and it's going to be pretty accurate. So this thing only cost me.

um I think it was $70 delivered on uh eBay So let's take a look at it, fit it inside and uh, see if we can, uh, check out its performance. Now here are the various uh time base options for this: HP Frequency Counter HP Agilant What is it now? I Think it's maybe they've officially changed their name now to key site Oh I don't know I don't care. Jeez, it's always going to be HP or at least agilant. Anyway, yeah, the standard oscillator 5 PPM Temperature stability.

It's just. it's just garbage. Like it. You know it is absolutely useless.

It really is. Don't even bother uh, using the frequency counter with the building oscillator. Anyway, you can get option1 with the medium oven. oh you know, two times 10^ 7 not bad.

then you can jump up 2.5 * 10 power- 9 for the high stability oven and then they got the ultra high stability oven which doesn't look a huge in terms of temperature stability, but it just has better aging. So if you are buying one of these things on eBay by the way, that's only for that model. the higher up model, not for the one that I've got. But um yeah, you know.

so we've got a replacement oscillator. Let's see if it specs are at least as good as this. and if you are going to pick these up on eBay then yeah. Check the photos and description carefully.

If you can get one with at least the medium oven in there, then that's what you want. But if you can't hey look 70 bucks on eBay Brilliant! So this is from a company called Chongo. If I'm pronouncing it correctly, Information Communication Co limited and it's the STP Uh 2145 A 10 MHz reference operates at 12 volts. Not all of them operate at the same voltage.

so if you're buying one of these, just uh Beware Anyway, um I don't know who actually uh designed this board. A few people have design their own options. It's got a trim pot here and it's got a jumper link which allows you to uh adjust. This one's currently set to adjust from the trim pot here.

and if you have a look at the bottom of the board here there, it's actually missing some circuitry and this is actually a digital analog converter which is what the uh real one inside the uh agant, the genuine one has inside the agant if you get that option. So the software. There's calibration software well calibration routines inside the Uh frequency counter itself to actually calibrate this thing so this one just doesn't have it. presumably I could populate the parts on there.

get the schematic which is readily available and do that, and let the software in the unit calibrate itself. but nah, I don't need to do that anyway. I'm just uh, happy to uh set the trim pot and uh, see what happens Now it'll be interesting to see whether or not this house spot on this thing is uh coming from this eBay uh seller which I'll provide the Linkin uh down below. hopefully they're still available by the time you watch this now.

I've actually got the data sheet for this thing. uh, presumably I couldn't get it from the manufacturer itself. so I presume this is the same manufacturer, but anyway, it's exactly the same Partners number. So I'm going to run with that.

Um, this is a really pretty Schmick ovenized oscillator. You can get them in different frequency ranges. this is a 10 MHz one of course, but uh, very high stability. We're talking about uh, you know, 5 * 10- 11.

That's very impressive. and I think we'll have look is pretty comparable with my Um Stanford Research Prs1 Rubidium Oscillator as well. Now it does come in different grades here and um, this MV 89 I Can't find this part number on here so I'm not sure if it's exactly the same. That's why I'm just maybe a bit skeptical.

It's not exactly the same data sheet Anyway, it does have different uh grades available if you are buying uh, these sorts of things. They do come in different um, well, not initial tolerance GR grades, but stability grades. But really, these things are designed to be uh, calibrated after they're adjusted after they're installed. They have frequency adjust pins, hence the pot going into a pin on the unit.

You can actually adjust the frequency over a range. So that's why. uh, in these data sheets, you won't actually find an absolute specification for its frequency. It's not there.

Don't confuse this aging spec up this high. This stability or aging spec up here with the absolute accuracy. It is not the same thing. Now, if you compare it, specs here to my Stanford research Prs1 which is used in my Rubidium Oscillator which is the actual rubidium unit itself inside my CSO unit which has been absolute adjusted.

Uh, by the way, it's a similar sort of thing. You have to actually adjust it and uh, calibrate it. My one has cuz it's a former Um Csiro standard for the Australian Defense Force. So hey, it's good enough to calibrate the Australian Defense Force Gear.

It's good enough for us anyway. Uh, look at this. This oven oscillated pretty darn good. Look at the short-term stability like over 1 second which is the Allen deviation.

Uh, we're talking about less than 2 * 10^ -2 over the 1 second. And where it is. here we go. on the Uh Ruidan one, it's basically an order of magnitude better.

We've only got less than 2 * 10^ - 11. So in terms of the Allen deviation there, over 1 second, this ovenized oscillator is better Auto magnitude better than that. uh, Rubidium? uh reference standard I've got awesome. But in terms of actual long-term aging, which is kind of like, you know, more important when you're using it for a reference.

in most cases, look the ovenized oscillator over here we're only talking about. You know, depends on what grade you get, of course. but even the best grade here 5 * 10 ^ of -9 per year. So look at the Ruidan one over here.

Where we talking about here we go aging yearly: 5 * 10 powerus 10. So now the rubidium oscillator is actually in order of magnitude better than the ovenized oscillator over the span of a year. And if you've got one of the lower grade uh, Rubidium here, which I'm not sure what this one is cuz can't find an exact data sheet, but um anyway. uh yeah, it could be The rubidium could be like two orders better stability than the ovenized oscillator.

and then the Rubidium oscillator is going to be like an auto mag. Itude better Again, look voltage sensitivity here to uh basically that's the sensitivity to the power supply change of 1 volt difference in your power supply voltage 2 * 10 the power - 11 and we're only talking about you know, 10 The power - 10 over here for the same thing on the oven oscillator and the oven oscillator actually warms up. Uh, pretty good to Uh spec. less than 15 minutes to get 5times 10 Power - 8 which is more than good enough as a oven uh, standard for this thing, but I'll let it warm up for more than that and the phase noise as well for this thing.

basically the same as the Rubidium oscillator which is a super low noise Ruidan one at 10 HZ minus 130 DBC per Hertz and uh, exactly the same spec here on the Rubidium. Now I've actually seen inside uh, this thing before so I won't bore you with the details, but basically there's a huge cutout in here and it's got the three mounting holes there for the internal oven osilla. And sure enough, this is actually designed as a a proper upgrade compatible clone of the Agilant unit apart from the a mentioned uh digital to analog converter circuitry on there. So yes, it looks like the uh, the it does line up with the Uh holes on there and uh, it comes with standoffs and screws and everything.

So I'm just going to screw that in and uh, whack it Right on over here to the headers and it should be good to go. Now Just one little interesting as side and a trap for young players with Uh oscillators. Any sort of Crystal oscillator like this. If you're really talking, you know, if you're really critical about your measurements on this thing, don't just have it sitting out here like this.

Plug it in and then, uh, you know, adjust your trim pot out here. Why? Well it's not because the thermal effects or anything like that, because this is an oven. it's going to stabilize its own temperature so that shouldn't be a problem. But uh, crystal oscillators are actually susceptible to orientation like that extremely slightly uh, subject orientation.

It's due to gravity. That pesky thing. You can't beat gravity due to the Uh micr structure and the Mount of the crystal inside there. You can actually get very subtle frequency differences in this thing so you want to actually calibrate it in that particular orientation preferably screwed into there.

And sometimes if you just the act of uh, putting moving up the til in bail on this thing can actually affect the frequency. Just a smidget might be hard to measure, but in theory it can do it. And that mounted In there very nicely. Perfect.

and the header cable just goes on over now. I'll power it up I'll uh before when I do the calibration I'll put the uh cover on and stuff like that. but for the moment I will just stick the power in. A really annoying aspect of this: the fan always stays on, but uh, it's powering up and uh, self test.

Is there an indicator on the screen that we have an internal oven? Nope. Now this thing actually has a lead on it uh to indicate that the oven is on, but maybe that's the oven is actually, uh, stabilized to temperature so it might take uh, you know that recommended 15 minutes or whatever for that lead to come on. So I'll just leave it for a little while with the case off, see if that lead comes on. And by the way, with this oven installed, it's drawing 33 wats or hereabouts.

Um, it. I Expect it to take a fair bit of power, so let me just disconnect that and we'll measure it again. Yeah, there we go. 26.5 one, so significantly less.

Uh Power So that thing sucking what 7 odd Watts or there abouts. And by the way, if you're wondering what these sort of Aging figures mean here like uh, plusus 1 * 10 ^ of -8 per year What does that minus8 mean? Well, when you talk about this sort of stuff, you're always talking in terms of PPM or parts per million. So for a 10 Mahz reference oscillator like this one, parts per million is 1 * 10^ - 6 * 10 Mahz is gives you uh 10 Herz here. So that's 10^ minus 6 and then you go down by an order of magnitude or get better by an order of magnitude looking at 0.1 PPM 10^ - 7 or you're going to have a 1 Herz error or 1 Hertz uh drift.

Basically maximum plus - 1 Herz drift over. Well, sorry, let's go down 01 PPM 1 * 10^ - 8. So if you had that oscillator there that had a an aging characteristic of you know that spec of plusus uh 1 * 10- 8 per year you're looking at, you could say that this is a 01 PPM uh stability oscillator over a year and it's going to drift plusus 0.1 Hertz and these other specs Here you treat those exactly the same so the warmup time accuracy. So after 15 minutes, it's going to be uh able or accurate to where you previously set it to + - 5 * 10^ of - 8.

So basically 0 plus- 0.5 Hertz within 15 minutes and yes, the lead did finally come on I forgot to uh, time that but yeah, it was probably 10 minutes. 15 tops. something like that. So yeah, um, well, within spec.

So that is a thermostat lock now of course. The interesting thing to note is that once you got the power on I've switched this thing off you, you'll notice there's no display. But as I said, the fan always continuously runs because this internal oven oscillator is always powered up. And really, if you're serious about your uh, standards and your oscillators, you're just going to leave this sucker running and it's going to draw Uh 17 Watts by the way, on standby.

Oh what a shocker! I'm just looking at my power meter now 70 Watts just to keep uh, this sucker running. But anyway, as we saw before, there was no indication on the front panel that it was actually working. But as I said, we can actually enter the calibration menu on this thing which if this thing did have the Dack on it, we just hold down this button and cow secure. Oops.

Okay, um, this can be secure or unsecure. Now the manual I think gives you a code for this so you have to press this again and Cal count is six. So this thing has been calibrated six times. There you go.

Okay, I've held that down and presumably it's going to be the factory code which I think is 53131a I won't bore you with the details I'll see if it works 53131 Cal Unsecure, we're in like Flynn Beauty Aha no. I Thought this would actually uh, give us the option. but of course though, it doesn't because this module doesn't have that. uh, Dack on it.

so obviously it's detected that and normally it would give you the option in here to uh, calibrate the time Base by Supply an external 10 MHz reference so we don't have that. So unfortunately, um, we don't really know um if this thing's using the internal oscillator unless we actually, uh, play around with the uh, well, feeding the signal in and measuring the output and checking the output frequency for drift and all that sort of jazz. Now just as a very quick indicator here: I've got it connected to my other uh counter here. my Riyal DG 4162 it's got a external counter and I've got the reference for this hooked up to my 10 MHz Rubidium.

Um, and you can see I've just powered this thing back on I've moved it. Um, so the other switched off and now you can see it's actually drifting up like that and that's exactly what I expect. now. um, unfortunately the only bad thing about having the oven oscillator in this is that you that lead indication.

you don't have it unless you actually wir that lead indication out to the front or the rear panel or something. You wouldn't know that that thermostat's locked in so you just got to trust it and you know, wait 15 minutes after it Powers up or whatever. But eh, that's okay. and the interesting thing is, look, it's actually counting back down now so it's sort of over shot, maybe in temperature and now it's coming back down.

So yeah, it' be interesting to actually graph that switch on. but unfortunately, um I tried to get U some software for this Ryo because it's got you know ethernet and USB interfaces and try and actually get the data out and actually plot that but it looks like no bloody software comes with the Ryo that allows you to do that. It's really annoying. it's got like the drivers and everything so you could yeah write a lab view thing for it or you know some other thing, use some other software to do it.

but anyway, it was rather annoying. So geez Mongle. and the other annoying thing is is I also wanted to get data out of this thing and it I don't have a Gpib uh board or cable. um but it had a Serial port on the back.

so I thought beauty. So I I finally got a managed to find a serial cable here. a rare I don't know I lost the damn thing if you following my tweets. but uh, it turns out that the serial port on this is not for communication like data extraction.

uh it's only for connecting to a serial printer. D So yeah, I can't extract data from this I'm going to have a hard time extracting data from this so please excuse me that I'm not going to actually be able to log this stuff and actually get a graph of the frequency I couldn't be bothered. So I'm going to increase the gate time here to 1 second so that'll update the Uh display here at 1 second and look at that. That's not bad at all now.

I'm This is much better than what it was before, So straight off the bat, look at this where Prett Not bad at all of course. uh, it's now running on the internal ovenized oscillator on this thing which has it's not been 15 minutes yet, hasn't uh locked in at all and I'm feeding the output from my Rubidium oscillator over here. So and this frequency is uh, the rubidium locked or the rubidium uh referenced frequency of the output of this ovenized oscillator or I believe it is I believe it automatically switches the ovenized oscillator through to the output instead of the internal one it should be now. I've shown this in a previous video which I'll link in which I won't bore you with the details, but this is a way that you can visually compare the Uh drift or the or you can calibrate or trim these oscillators.

Channel one here. The yellow one is my 10 MHz uh reference signal from my Rubidium Uh reference standard and I'm triggering from that channel and this blue one down here Channel 2 is the 10 MHz output from the ovenized oscillator from the output terminal on the Uh 53131a counter. You can see it's slightly drifting like that very slowly and if I start my stopwatch there at that point and time how long it takes to go all the way through a full cycle like that, then we'll see an interesting effect on the interesting comparison to the frequency displayed on the front panel. And I time that at 40.8 seconds.

And if we put 40.8 seconds, uh, into here, well, 40.8 and we invert that we get 024 Hertz What do we get on here? Not .02 Well, it was 024 There we go. 024 Hertz Bingo That is the direct error compared to our Ruidan reference standard and I've actually left this for some time now and yes, the lead's been on for ages. So I don't think it's going to uh, age, you know, like it's going to warm up and uh, comeing to spec a huge amount more than what we've already got. So I might get in there now and just trim that pot at the right tongue angle.

Of course, it's all about the tongue angle and uh, see if I can, uh, zero that thing out compared to my rubidium oscillator. But as it stands as I got this thing from uh eBay Is that how warm is that? Oh yeah, it's fairly warm. Um, it's certainly not too hot to touch anyway. uh as I got this from eBay they must be like, uh, trimming them before they, uh, send them.

But like you know, 0.026 Herz there we're only talking. You know? uh Point uh, you know 2.7 * 10- 9 is it? Yeah, it's not much at all. it's not out by much. so anyway, you can see the slight drift on that I'm going to get in there tongue is at the correct extended correct angle.

you can tell what I was talking and here we go. Oh yeah, look, we're just oh slightest tweak on that and it drifts back I mean jeez, you barely touch that. There's not much travel range in that at all. Wow.

I'm like I'm I'm just lightly touch in that thing and oh yeah, there's nothing in it, there's nothing in it. So the uh trim range of this thing is very very slight. But anyway, look at that. beautiful and if I go up to 10 seconds uh, gate time there then we'll get an extra digit on our display and uh, you know this isn't this waveform method isn't a bad way to uh do it I've shown in previous video which I'll link in I've shown uh, different ways to actually uh, do this.

There's a couple of ways, but there we go. we've GED ourselves an extra uh digit there and uh yeah, that's not too bad at all. I might tweak it a little bit back. Unfortunately with the display like this, the thing is like you've got a gate time of 10 seconds here so it makes it hard to adjust this.

But if you do, the waveforms here. but as you can see, when you get down to this sort of level, it's really hard to see the drift in there. Look at that. I Mean you know, can you see that drift with your eye? It's you know, it's practically impossible.

Yet we're out and there you go. I Basically, don't think I'm going to be able to get it any better than that. Look at that. I mean you know just the slightest hair touch on that pot and of course there is going to be some drift over time and you can set up our data loging and stuff to actually, uh, do that in comparison with the Rubidium Oscillator and even you know, GPS lock the thing.

Oh, you can do all sorts of weird and wonderful things and spend weeks and weeks characterizing, uh, something like this. but this thing, uh, we've just improved, uh, the accuracy and stability of this thing by a couple of orders of magnitude with a 70 buck aftermarket uh, add-on there. So if you can, if You' got one of these, or you're looking at getting a frequency counter, then uh, you can pick one up pretty cheap. especially because if it might have the uh, the cheap ass standard Crystal oscillator in it, then get one of these aftermarket uh add-ons They work really well.

I Don't know. sort of the comparison between the one with the Uh where if you add extra circuitry for the D2a converter, you'd have to, you know figure out which one's more stable the D TOA converter or the pot adjustment and I don't know that they've got that trim range cuz that's a 10 turn trimmer and this thing was just so delicate. so I haven't actually looked into the Um circuit details there. We probably have to adjust the series resistor um in that from the wiper into that thing to adjust the range.

um to narrow the range down or something like that. So anyway, I'm pretty darn happy with that. That is a Bobby de TLA it really is. this oscillator.

Um, this uh, ovenized oscillator is a really good, quite a high spec one. It's awesome and for about 70 bucks, uh, assembled and uh tested. Yeah, it's not a brand new oscillator, it's probably Salvage from somewhere. something like that as these things typically are.

you can buy them just separately on eBay um and I Believe a couple of people out there have actually design boards. they're probably like Open Source Hardware or something design boards uh that I think fit different types of on the market and uh, things like that. So yeah, well worth doing. but I Just bought this one.

It was just no fuss. It was already assembled and and it looks like it was already uh trimmed to frequency cuz it was pretty darn close to spot on. Almost as good as you can get it. Um, so it's drifted a little bit there since I've been uh, yapping on.

but anyway, that's an absolute Beauty so hope you found that interesting. Catch you next time! Um.