Frequency counter reference Crystal inquiry..  - Page 1
Forum section: electronics / beginners

author: mkube396
author_rank: Regular Contributor
timestamp: May 13, 2015, 04:03:30 am
content: keep in mined i am just playing around and experimenting on this older freq counter i am not just out to just polish a turd here, but if it works sweet.I picked up a Elenco F-1300 frequency counter ta swap meet for $25This frequency counter has no TCXO or OCXO in it just a crystal resonator and in the manual good to 10ppm. Is it freezable to add a TCXO or even a OCXO? i know a OCXO would be over kill but if it can accept the square wave single it seems simple enough to just remove the unnecessary parts and hack one in as long as i can supply the power.I found info online that some one had done this mod with info but that it.. before i attempted it i just want to know if it can be done.and if i do a OCXO how do i deal with the VFC pin?12v inputhttp://www.ebay.com/itm/ISOTEMP-OCXO131-191-10Mhz-OCXO-OSCILLATOR-square-wave-/300620785295?pt=LH_DefaultDomain_0&hash=item45fe65268f5v inputhttp://www.ebay.com/itm/ISOTEMP-131-100-OCXO-OSCILLATOR-10MHZ-square-wave-/300579197899?pt=LH_DefaultDomain_0&hash=item45fbea93cbor TCXO 5v inputhttp://www.ebay.com/itm/ONE-PIECE-OF-PRECISION-0-3ppm-10MHz-10-000000MHz-TCXO-/151191552022?pt=LH_DefaultDomain_0&hash=item2333b80016This is a pic from a link i found

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 13, 2015, 04:17:40 am
content: To what end?Do you need the increased accuracy? Do you just want to screw with it?If you don't know what to do with a VFC pin, I would guess not, and you should leave it as-is. If you need better assurance, you can calibrate it against something else, or just measure another (known stable and accurate) frequency and see what the discrepancy is.Tim

author: mkube396
author_rank: Regular Contributor
timestamp: May 13, 2015, 04:32:28 am
content: Quote from: T3sl4co1l on May 13, 2015, 04:17:40 amwell to "screw with it" and get increased accuracy.and that's why i am on here if some one can explain how the VFC pin works..I have limited knowledge and i am kind of self teaching myself as i go. if i brick it o well i am out $25 and some parts..

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 13, 2015, 07:58:33 am
content: You probably won't see much, I think VCXOs are usually in the +/-1kHz tunable range. You'd see a few lower digits change as you vary the control voltage, and not much else (plus probably not having a reference to calibrate it against).Maybe more interesting to look over the circuit itself, see what chips they used, what the logic diagram is? Dunno. As you say, it's only $25, so do with it what you like!Other ideas might be, improved front end comparator / level control / prescaler for higher frequencies, etc.? Not much use if you don't have a scope to prove operation, or faster signal generators / scope to see that it's working.Bonus points would be getting the count correct while using a prescaler. That might be tough without ripping out all the logic, though.Tim

author: JBaughb
author_rank: Regular Contributor
timestamp: May 13, 2015, 08:09:06 am
content: Quote from: T3sl4co1l on May 13, 2015, 04:17:40 amBeing honest, I don't like responses like these. Some are here to learn (and let me make it clear that Im not saying you're doing this) but responses like these make me feel like people think "if you don't already have the knowledge, then don't bother". Thats the worst way to encourage electronics learning and hacking.I mean, Im just thinking about how I would feel if, when I was 8 and taking apart whatever I could get my hands on to see how it worked, my dad came up to me and took it away, saying that if I didn't already know how it worked, it wasn't worth looking into.I understand steering someone away from a dangerous modification (such as high power electronics for an novice) but those of us who have more knowledge should be helping and encouraging those who are curious but don't have the knowledge (and let me specify that I fall on both sides of that line depending on the subject).Anyway, sorry for the rant.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 13, 2015, 08:26:34 am
content: Quote from: JBaughb on May 13, 2015, 08:09:06 amOh god... have I become one of those?In my defense, I offer my thought process: it sounds like you're trying to improve it in some way (curiosity about the crystal, specs). But not knowing anything about why, or to what end, or whether it's any use at all. Concentrating on the crystal alone seems very strange, given the number of circuits in the whole thing. There's a lot of bits (literally!) to learn about, though it may seem rather opaque being made of little chips and traces running around randomly.To put it in a perhaps more familiar analogy, it's like you bought a beater car that barely runs, and asking if replacing the stereo will improve gas mileage.Now, if you don't know jack about either of these things, you might have no idea whether that's even a reasonable thing or not. So if I was overly dismissive, I apologize.Whatever you do, pleasedoentertain your curiosity! We need more kids with screwdrivers in this world.Tim

author: mkube396
author_rank: Regular Contributor
timestamp: May 13, 2015, 10:47:48 am
content: i suppose i am trying to cram a Chevy big block V8 in a 98 ford Taurus not trying to offend anyoneBut how do i know i cant if i don't try?so i must try i did order a TCXO two days ago i am going to attempt it but was wondering on the OCXO option..Ido have an older Hitachi V-1060 scopeand i can take the counter to a cal lab when done it just is not free. or compare it agents my two amateur radiosand tune off WWV.

author: alank2
author_rank: Super Contributor
timestamp: May 13, 2015, 01:19:53 pm
content: Sometimes you are better off to leave the VFC pin disconnected unless you can provide it a voltage that you know isn't going to fluctuate with temperature. When I was playing with ocxo's/vcxo's/tcxo's I found that trying to use the VFC pin made it tougher for stability. I was going for stable and could correct for the frequency not being perfect in software though.

author: hamguy
author_rank: Newbie
timestamp: March 24, 2016, 02:57:09 am
content: Quote from: T3sl4co1l on May 13, 2015, 08:26:34 amTim-First, the crystal oscillator time base is the heart of any counter. If the TB is accurate, so will be the count of an input. So, that is why one would concentrate on the crystal when considering a modification to increase accuracy. There is really nothing else in the counter that affects the accuracy of the counter.This counter counts the number of timebase cycles in one cycle of input and then calculates the frequency. This makes for nice short gate times even with high resolution and high frequencies.Mkube396-As to the VFC pin, some of these VCXOs don't even have the VFC pin connected. It should not be needed anyway. Don't be afraid to experiment though, but also don't be afraid to do some research on the Web too.-g

author: VK5RC
author_rank: Unknown
timestamp: March 24, 2016, 08:45:22 am
content: Have you seen K5CMs website and SpectrumLab, easy to get to sub Hz levels if careful.

author: babysitter
author_rank: Frequent Contributor
timestamp: March 24, 2016, 09:29:35 am
content: If you haven't bought another oscillator yet, you might go for a type without electronic frequency control. Or you go for a type with a VREF out and EFC, that VREF is there exactly to be used as a voltage to derive the efc voltage from. Connect a potentiometers ends to VREF and GND, the wiper to EFC in. Done. No magic.Also, check what output signal from the oscillator you already need... I suppose you need ttl level, don't go for a sine output oscillator then, but you better confirm this by looking at the chips around where the clock signal actually goes to.The oscillator specs shall somewhat match the counters ability... you will not need a oscillator with 10.0000000000 MHz if you can only show 10.000000 MHz on the display.Last but not least you don't have just a supply voltage but also a supply current. A OCXO needs a lot more power for heating up from cool state. It needs less power to maintain temperature, but still way more than TCXO etc. OCXOs prefer being powered on continously, if you turn it on with the counter it will drift for seconds to minutes, and it might retrace to a slightly different frequency after a power cycle.

author: LogicalDave
author_rank: Regular Contributor
timestamp: March 07, 2018, 07:20:55 pm
content: For those considering this, there's an excellent post on upgrading the frequency standard in the Elenco F-1300 here:http://www.diyaudio.com/forums/equipment-and-tools/259369-elenco-1300-universal-counter-timebase-mod.htmlI too have an old Elenco F-1300 and wanted better accuracy than the XO provides. I bought a high accuracy (claimed 0.1ppm, actual ~0.2ppm) TCXO on eBay for $10 (here:https://www.ebay.com/itm/10mA-TCXO-10MHZ-Sliver-Precision-Crystal-Oscillators-0-1PPM-10-000MHZ-3PPB/232187568538). I mounted the TCXO to the enclosure bottom deadbug style with hot glue and followed the post directions and voila...a much more accurate counter!You have to remove the old timebase components - X32, R29, C34, C35, C36 and C361 and then install the TCXO (see photo).The only caveat for others considering this is that the F-1300 only has 7+1 digits of resolution so at 10MHz, you have 1Hz resolution (0.1ppm) and if you are looking at VHF/UHF frequencies, your resolution is 100Hz. That said, it's pretty quick and with the TCXO, it's considerably more accurate. The TCXO uses less than 10mA and is on frequency almost instantly.For those considering the mod: 1) Disconnect power!!! 2) unscrew the 4 screws in the black feet at the bottom 3) Lift top cover off (the back panel can remain attached to the PCB) 4) use hot-air to remove the parts specified in the OP 5) Install the TCXO as shown. 5) reassembled and test!

author: medical-nerd
author_rank: Regular Contributor
timestamp: March 07, 2018, 07:50:15 pm
content: HiyaBeware!!This path can lead you down to the psychologically damaging realm of time-nuttery!!Next you will be getting a range of crystal standards for comparison, hacking frequency counter sample times, vintage frequency standards, GPS frequency standards, rubidium etc......I'm reformed now - only got a couple of rubidiums, a couple of Z3801A's, a vintage HP106 and a handful of crystal standardsI still don't know the time.....Cheers