[Boatanchors] Re-Thread: Programmable Oscillators as Crystals

[AI2Q]

Does anyone have detailed information on the phase noise specs of these 
oscillators?

Vy 73, AI2Q, Alex
Member: ARRL, FOC, RSGB, CWops, QRP-L, Antique Wireless Association, New 
England Radio Discussion Society, DXCC Honor Roll, 16ØM DXCC, 8ØM DXCC
http://home.roadrunner.com/~alexmm

----- Original Message ----- 
From: "David Stinson" <arc5 at ix.netcom.com>
To: <boatanchors at mailman.qth.net>
Sent: Sunday, May 12, 2013 10:46 AM
Subject: [Boatanchors] Re-Thread: Programmable Oscillators as Crystals


>( Reposted as requested.  Please skip if you have this already)
>
> Re: Using Programmable Oscillators as Crystals
>
> Here is an "executive summary" of the thread:
>
> 2-10-13
> This brings me to a project which is still in the "noodling" stage.
> "New" crystals can be ordered, but the price is prohibitive-
> $40 to $50 for one!
> But there is an alternative- custom frequency clock oscillators.
> You can order these programmed for any frequency you like
> for just a few dollars each.
> Voltage derived from the filaments will power them.
> May or may not need a little "buffer" stage after the
> output. This would be easy to build and install
> right at the crystal socket.
> .............................
> Here is a page from Digikey. Lowest-price for through-hole
> oscillator, programmed to order by them is $4.10 in quantites of 1.
> http://tinyurl.com/b6kxgeo
> I haven't ordered any yet but will soon.
> I'd go with the 5-Volt type for the bigger rail-to-rail swing.
> Some even have "Tri-state" control pins so switching is easy.
> ....................
> Here is a typical oscillator's datasheet:
> http://pdf1.alldatasheet.com/datasheet-pdf/view/161044/EPSON/SG-8002DB.html
> It is programmable in 0.1 KC steps up to 125 MC
> (Digikey will program it for you.  They require you to
> state the freq in the notes at the bottom of the order form
> as "x.xxxx MHz" since they don't know KC).
> .....................
>
> Here is some data from a guy that has made some measurements.
> That is not to say that yours may be different since the actual 
> programming
> frequency and other factors determine the actual results. It is still 
> worth
> while trying
> one in your application and see how it works out. Mine was to for qrp tx
> and rx.
> Tx is less of a problem as long as the spurious responses are low enough.
> Rx applications may be different. In my case up to 7 MHz seemed to be OK.
> I was also looking into using one for a plasma geneator at 13.56 Mhz.
> http://lowfer.us/k0lr/epson/epson.htm
> 73
> Bill wa4lav
> .........................
>
> 2-13
> I have several WWII sets that need crystals to operate.
> Finding "old stock" can take a very long time and purchasing
> them "new" from the few remaining suppliers is prohibitively
> expensive. So.... alternatives.
>
> I'm an advocate of leaving WWII equipment "operating as designed,"
> meaning that limited changes that are 100% reversable which
> allow the unit to live are OK. So I've often thought of
> "Borg Implants" like my simple converter to get them going.
>
> My rare SCR-274N VHF set needs crystals, especially
> for the BC-942 ( ARC-5 R-28 ) receiver.
> Programmable oscillators in both TTL and CMOS format
> set for any frequency one would wish are cheap
> and plentiful. So I decided to try them out.
>
> The BC-942 / R-28 uses a 12SH7 as an Electron
> Coupled Oscillator / Quadrupler. When using a
> regular crystal, I scoped 3 V P-T-P at the cathode.
>
> I had a couple of older can-type TTL output
> clock oscillator units for 4.000 MC,
> which puts the set on 102.9 mHz.
> I powered the oscillator with a old, weak 6 Volt battery.
> Under load, the battery sourced 5.3 Volts for Vdd.
>
> Driving the osc. straight into the stage (with a blocking cap)
> did not develop enough drive voltage, so I wound a little
> 4:1 UNUN and this developed 2 V P-T-P at the cathode,
> which appears to be just enough because the set
> came right up and played. I think a 9:1 UNUN will do better
> (it didn't).
>
> Next, I ordered four Epson programmable oscillators
> from Digikey: 4.652, 4.829, 5.722 and 5.818 mHz
> There are probably better ones out there,
> but I picked this one because it was a through-hole
> package and *cheap* ;-)
>
> http://www.doveonline.com/pdfs/SG8002DB.pdf
>
> I ordered them pre-programmed from Digikey and they arrived
> in just a couple of days. Less than $18 for four channels-
> less than half the price of a single "new" crystal.
>
> Of course, the first thing I did was hook the blasted
> battery up *backwards.*
> A little smoke sword shot out of the middle of the chip
> and it disemboweled itself......... "YAAAAAA!"
> So much for the very active 118.55 MC
> DFW airport departure freq.....
>
> When I quit banging my head on the floor,
> I connected a survivor correctly and tried again.
> The output of this chip would not work into an UNUN,
> but for a wonder, it drove the 12SH7 directly (with the
> DC blocking cap, of course) and developed the
> 2 Volts drive needed. I'm listening to the Unicoms
> on 122.8 right now. If the "jitter" is causing a problem,
> I can't hear it. Sounds like airplanes to me ;-)
>
> This CMOS chip outputs about supply voltage - .4V and it
> can be Vdd up to 7 volts, which would give me more drive.
> I'll build a little regulator to supply all four boards
> with 6.75 V and that should do it.
> Here's a sketch of what's going on:
>
> http://home.netcom.com/~arc5/ItWorks2.jpg
> ........................
> 2-19
> So here are some "shade-tree" conclusions:
>
> I used two configurations- "LO" oscillators on the same freq
> as an original crystal would have used and "HI" oscillators,
> set at the *4 freq of the first multiplier in the LO chain.
> Built them on little perf-boards mounted to the bases
> from defunct crystals.
>
> Made a 6-volt power buss from one of those
> little DC-DC "buck" converters:
> http://www.ebay.com/itm/261053380853
>
> The LO oscillators [ Fxtal MC = (Fop - 6.9 MC) / 24 ]
> need a little 4:1 voltage-boosting UNUN
> to deliver enough drive to the R-28.
> I got mine all pre-made and ready to go from
> Tanner's surplus house in Carrolton.
> He's got about a bizillion for, I think, 25 cents each.
> I also tried a 9:1, but that didn't do any better than 4:1.
> The two capacitors are there for DC blocking.
> Values not critical, but .01 uFd is "too much."
> Loads the things down a little.
> I settled on .004 uFd because I had a bunch of
> small ones on hand and they worked.
>
> Yes, I know the things are speced to drive 15 pFd load.
> I did try a simple series cap feed so the chip would
> see 15 pFd, but this didn't develop enough drive at
> the multiplier grid to work.
> I don't know "why;" that's what I have you
> Smart People for ;-)
> Compared the LO Oscillator to a crystal and found
> little difference in performance between them.
>
> The HI Oscillators [ Fxtal MC = (Fop - 6.9 MC) / 6 ]
> did not require the UNUN. 2 volts of drive appear
> to be enough when using this freq.
>
> The HI oscillators do indeed introduce a bit of jitter "phase noise"
> in the receiver, raising the noise floor noticably.
> The LO oscillators did not do so. I don't know "why not."
>
> Cost of a single new crystal: about $45.
> Cost of a single Prog Osc. substitute: about $6.
> Case closed ;-)
>
> 73 DE Dave AB5S