On Fri, 21 Feb 2014 14:27:17 -0600, Tim Wescott <tim@seemywebsite.really> wrote:>On Fri, 21 Feb 2014 12:00:28 -0800, George Herold wrote: > >> Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. >> I could use a 200MHz VFO (say 150 to 250 MHz or something like that) >> I don't need much stability, a part per thousand for a several minutes >> would be enough. >> So what's the simplest way to get there? An LC oscillator (I've got >> some nice tunable few pF caps) >> There's also a VCO from Maxim. (max2607) that looks easy. >> http://datasheets.maximintegrated.com/en/ds/MAX2605-MAX2609.pdf Would >> the manually tunable cap be more stable than the VCO? > >In general a manually tunable cap is more stable, yes. > >Maxim used to suck at delivery, I've avoided them for so long that I >don't know if they still do. > >Basically they denied that they ever discontinued parts, but on the other >hand they'd only make a run of a particular chip when they got enough >orders to make up a batch. So if you're a low-volume customer and you >want something that doesn't move fast, you're screwed.They don't deny it (better not). They discontinued an amplifier on me, after I'd built and tested the prototypes. Nice part but they decided to get out of the market. When my boss told me that they'd dropped it, the first words out of my mouth were "I told you so". A lot of other engineers use their stuff but I've always found something else that works. We're not low volume, so not everyone has been burned. Yet.>That was a decade ago -- people with current experience are welcome to >speak up.Last year.
200MHz VFO
Started by ●February 21, 2014
Reply by ●February 21, 20142014-02-21
Reply by ●February 21, 20142014-02-21
On Friday, February 21, 2014 3:00:28 PM UTC-5, George Herold wrote:> Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. > > I could use a 200MHz VFO (say 150 to 250 MHz or something like that) > > I don't need much stability, a part per thousand for a several minutes would be enough. > > So what's the simplest way to get there? An LC oscillator (I've got some nice tunable few pF caps) > > There's also a VCO from Maxim. (max2607) that looks easy. > > http://datasheets.maximintegrated.com/en/ds/MAX2605-MAX2609.pdf > > Would the manually tunable cap be more stable than the VCO? > > > > Thanks, > > George H.These things are cheap and way better than anything you can make. They're hard to beat even in volume: http://www.minicircuits.com/products/Oscillators.shtml
Reply by ●February 21, 20142014-02-21
On Friday, February 21, 2014 5:56:10 PM UTC-5, Joerg wrote:> > > What some of the Chinese vendors do is copy an example design from a > > datasheet or app note, verbatim. It seems to work.Many times the datasheet or app note is the circuit the device manufacturer developed under contract to an end user. So there's no "seems to work" to it.> > > > -- > > Regards, Joerg > > > > http://www.analogconsultants.com/
Reply by ●February 21, 20142014-02-21
On Friday, February 21, 2014 3:27:17 PM UTC-5, Tim Wescott wrote:> On Fri, 21 Feb 2014 12:00:28 -0800, George Herold wrote: >=20 >=20 >=20 > > Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. >=20 > > I could use a 200MHz VFO (say 150 to 250 MHz or something like that) >=20 > > I don't need much stability, a part per thousand for a several minutes >=20 > > would be enough. >=20 > > So what's the simplest way to get there? An LC oscillator (I've got >=20 > > some nice tunable few pF caps) >=20 > > There's also a VCO from Maxim. (max2607) that looks easy. >=20 > > http://datasheets.maximintegrated.com/en/ds/MAX2605-MAX2609.pdf Would >=20 > > the manually tunable cap be more stable than the VCO? >=20 >=20 >=20 > In general a manually tunable cap is more stable, yes. >=20 >=20 >=20 > Maxim used to suck at delivery, I've avoided them for so long that I=20 >=20 > don't know if they still do. >=20 >=20 >=20 > Basically they denied that they ever discontinued parts, but on the other==20>=20 > hand they'd only make a run of a particular chip when they got enough=20 >=20 > orders to make up a batch. So if you're a low-volume customer and you=20 >=20 > want something that doesn't move fast, you're screwed. >=20 >=20 >=20 > That was a decade ago -- people with current experience are welcome to=20 >=20 > speak up. >=20 >=20 >=20 > Do you need turn-on to turn-on stability, just something that keeps on=20 >=20 > frequency once it's tuned, or what? If you want to tune it mechanically==20>=20 > and you care at all about getting it dead nuts on then the mechanical=20 >=20 > design can get painful -- that's part of the reason why everyone uses=20 >=20 > synthesizers these days. >=20 >=20 >=20 > --=20 >=20 >=20 >=20 > Tim Wescott >=20 > Wescott Design Services >=20 > http://www.wescottdesign.comI never had ***any*** problems with Maxim. The only downside to their avail= ability is /sometimes/ you need to go with MIL or industrial grade for quic= k delivery, and of course that costs more, but not really a whole lot more,= won't amount to a hill of beans in small quantity. If you go with a propri= etary part, one that no one else makes, you're taking a risk no matter whic= h semi you go with. There are vendors out there who can dig up parts from a= nywhere if you really need them, so discontinued is never a catastrophe.
Reply by ●February 22, 20142014-02-22
upsidedown@downunder.com wrote:> > On Fri, 21 Feb 2014 12:00:28 -0800 (PST), George Herold > <gherold@teachspin.com> wrote: > > >Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. > >I could use a 200MHz VFO (say 150 to 250 MHz or something like that) > > That is a quite broad range +/-25 % > > >I don't need much stability, a part per thousand for a several minutes would be enough. > > An FM broadcast tuner with 100 MHz +/-10 % tuning range would be a > good reference.The FM broadcast band is only 20 MHz wide in the US. 88 to 108 MHz. With high side injection and the common 10.7 MHz IF, the LO is 98.7 to 118.7 MHz -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
Reply by ●February 22, 20142014-02-22
On Fri, 21 Feb 2014 23:03:49 +0200, upsidedown@downunder.com wrote:>On Fri, 21 Feb 2014 12:00:28 -0800 (PST), George Herold ><gherold@teachspin.com> wrote: > >>Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. >>I could use a 200MHz VFO (say 150 to 250 MHz or something like that) > >That is a quite broad range +/-25 % >There are lot of octave-range VCOs on the market, maybe just a tad more. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
Reply by ●February 22, 20142014-02-22
On Fri, 21 Feb 2014 16:04:22 -0800 (PST), bloggs.fredbloggs.fred@gmail.com wrote:>On Friday, February 21, 2014 5:56:10 PM UTC-5, Joerg wrote: > >> >> >> What some of the Chinese vendors do is copy an example design from a >> >> datasheet or app note, verbatim. It seems to work. > >Many times the datasheet or app note is the circuit the device manufacturer developed under contract to an end user. So there's no "seems to work" to it.However, in many cases a recently hired engineer is set to write these application notes to familiarize with company products :-)
Reply by ●February 22, 20142014-02-22
On Fri, 21 Feb 2014 22:02:09 -0800, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Fri, 21 Feb 2014 23:03:49 +0200, upsidedown@downunder.com wrote: > >>On Fri, 21 Feb 2014 12:00:28 -0800 (PST), George Herold >><gherold@teachspin.com> wrote: >> >>>Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. >>>I could use a 200MHz VFO (say 150 to 250 MHz or something like that) >> >>That is a quite broad range +/-25 % >> > >There are lot of octave-range VCOs on the market, maybe just a tad more.Unfortunately a large tuning range also means extreme sensitivity to VCO control voltage fluctuations. To get to the 1000 ppm requirement by the OP, the VCO control voltage must be clean to a few mV. I have seen far too many radios with PLL (and hence VCO) in which dirty control line voltage is causing severe phase noise and as a consequence other bad things, like reciprocal mixing.
Reply by ●February 22, 20142014-02-22
upsidedown@downunder.com wrote:> On Fri, 21 Feb 2014 16:04:22 -0800 (PST), > bloggs.fredbloggs.fred@gmail.com wrote: > >> On Friday, February 21, 2014 5:56:10 PM UTC-5, Joerg wrote: >> >>> >>> What some of the Chinese vendors do is copy an example design from a >>> >>> datasheet or app note, verbatim. It seems to work. >> Many times the datasheet or app note is the circuit the device manufacturer developed under contract to an end user. So there's no "seems to work" to it. > > However, in many cases a recently hired engineer is set to write these > application notes to familiarize with company products :-) >I have experienced exactly such examples. The first one right after getting my degree. Due to my hobby I could hit the ground running but that was not at all the case for most of the mates there. Most could solve anything back to the Maxwell equations, strictly on paper, but not even repair their own TV set. By chance I met one of them during a business trip. "Hey, how's it going? Where did you end up?" I asked. "Oh, I started at [insert major semiconductor manufacturer here]" ... "Interesting. So what are you doing there?" ... "Writing application notes". I could not believe it. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●February 22, 20142014-02-22
On Sat, 22 Feb 2014 08:59:20 +0200, upsidedown@downunder.com wrote:>On Fri, 21 Feb 2014 22:02:09 -0800, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Fri, 21 Feb 2014 23:03:49 +0200, upsidedown@downunder.com wrote: >> >>>On Fri, 21 Feb 2014 12:00:28 -0800 (PST), George Herold >>><gherold@teachspin.com> wrote: >>> >>>>Hi guys, The 200 MHz. frequency synthesizer thread got me thinking. >>>>I could use a 200MHz VFO (say 150 to 250 MHz or something like that) >>> >>>That is a quite broad range +/-25 % >>> >> >>There are lot of octave-range VCOs on the market, maybe just a tad more. > >Unfortunately a large tuning range also means extreme sensitivity to >VCO control voltage fluctuations.I wouldn't have it any other way. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
