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Bill Turner wrote:
On Sat, 15 Nov 2003 23:08:53 -0700, Wes Stewart wrote: snip The only problem was keeping the GDO hidden from the metrology guys since they couldn't "calibrate" and service them so they wanted them gone. __________________________________________________ _______ Great story, Wes. But why couldn't the metrology guys figure out a cal procedure? I suspect the Not Invented Here syndrome, right? -- Bill, W6WRT More likely the results of corporate policy. The last place I worked kept the records on the mainframe, rather than use dedicated software to track the ISO9001 data because, "®That's the way we've always done it!©". That is like some test fixtures have elaborate setup and calibration instructions, wile others are labeled, "Calibration not required" I told the cal lab the label should read, "Calibration not possible". ;-) -- Michael A. Terrell Central Florida |
On Sun, 16 Nov 2003 05:09:01 -0800, Bill Turner
wrote: |On Sat, 15 Nov 2003 23:08:53 -0700, Wes Stewart wrote: |snip |The only problem was keeping the GDO hidden from the metrology guys |since they couldn't "calibrate" and service them so they wanted them |gone. | |_________________________________________________ ________ | |Great story, Wes. But why couldn't the metrology guys figure out a cal |procedure? I suspect the Not Invented Here syndrome, right? The worst thing that could happen to our equipment was for it to go to "Calibration." I had more than one piece of equipment "accidentally" dropped and broken when they tired of maintaining it. If they did this to an HP/Boonton 250 Rx meter what do you think would happen to a Model 59? The best we could do was get an "inactive" sticker put on the equipment. This took it out of the cal cycle but theoretically meant that we couldn't use it for anything. Also there were the everpresent management directives to get rid of inactive equipment to reduce inventory costs. Imagine how much expense could be written off if Hughes Aircraft Co (now Raytheon) got rid of a Model 59 GDO g. Might have been enough to reinstate my retiree medical benefit that was promised to me for 33 years and then taken away. But that's another story. Wes |
On Sun, 16 Nov 2003 05:09:01 -0800, Bill Turner
wrote: |On Sat, 15 Nov 2003 23:08:53 -0700, Wes Stewart wrote: |snip |The only problem was keeping the GDO hidden from the metrology guys |since they couldn't "calibrate" and service them so they wanted them |gone. | |_________________________________________________ ________ | |Great story, Wes. But why couldn't the metrology guys figure out a cal |procedure? I suspect the Not Invented Here syndrome, right? The worst thing that could happen to our equipment was for it to go to "Calibration." I had more than one piece of equipment "accidentally" dropped and broken when they tired of maintaining it. If they did this to an HP/Boonton 250 Rx meter what do you think would happen to a Model 59? The best we could do was get an "inactive" sticker put on the equipment. This took it out of the cal cycle but theoretically meant that we couldn't use it for anything. Also there were the everpresent management directives to get rid of inactive equipment to reduce inventory costs. Imagine how much expense could be written off if Hughes Aircraft Co (now Raytheon) got rid of a Model 59 GDO g. Might have been enough to reinstate my retiree medical benefit that was promised to me for 33 years and then taken away. But that's another story. Wes |
Hi Paul,
ARRL QST had nice article on a modern GDO May 2003 QST page 54 A Modern GDO--The "Gate" Dip Oscillator Bloom, Alan, N1AL 73 jimbo Paul wrote: I'm not using a Millen and this post isn't a troll as someone else suggested. The meter I use started out life as a Tradiper (Japanese) but because it was hopelessly outdated and used old germanium trannies with enough lead inductance to tune a VoA transmitter, I decided to rip its guts out and rebuild from scratch.The actual chassis/meter/facia etc was quite high quality, so it made sense. I got this nice circuit from the UK equivalent of the ARRL Handbook and set about building it. It used 2 SK88 FETs and the output of this oscillator could be adjusted to keep its impedence as high as poss for each test, thereby giving really good dips when even quite heavily loaded low Q circuits were tested *provided* they were physically big enough to shove the sense coil into. The sense coils are about 3/4" in diameter, which although fine for large, out-of-circuit component measurements, is *hopeless* for getting in close on a circuit board with subminature components a fraction of the size. That's the main problem I face with all GDMs, though: they all seem to have relatively huge sense coils relative to today's component sizes :-( -- "I expect history will be kind to me, since I intend to write it." - Winston Churchill |
Hi Paul,
ARRL QST had nice article on a modern GDO May 2003 QST page 54 A Modern GDO--The "Gate" Dip Oscillator Bloom, Alan, N1AL 73 jimbo Paul wrote: I'm not using a Millen and this post isn't a troll as someone else suggested. The meter I use started out life as a Tradiper (Japanese) but because it was hopelessly outdated and used old germanium trannies with enough lead inductance to tune a VoA transmitter, I decided to rip its guts out and rebuild from scratch.The actual chassis/meter/facia etc was quite high quality, so it made sense. I got this nice circuit from the UK equivalent of the ARRL Handbook and set about building it. It used 2 SK88 FETs and the output of this oscillator could be adjusted to keep its impedence as high as poss for each test, thereby giving really good dips when even quite heavily loaded low Q circuits were tested *provided* they were physically big enough to shove the sense coil into. The sense coils are about 3/4" in diameter, which although fine for large, out-of-circuit component measurements, is *hopeless* for getting in close on a circuit board with subminature components a fraction of the size. That's the main problem I face with all GDMs, though: they all seem to have relatively huge sense coils relative to today's component sizes :-( -- "I expect history will be kind to me, since I intend to write it." - Winston Churchill |
Bill Turner ) writes:
Also, a GDO is likely to be much less expensive than the three separate items. Bill, W6WRT That's always been some of its appeal. Throw one together, or buy one, and you get a tool for finding the rough frequency of a coil. But you also get that ability to figure out an unknown L or C, you get a signal generator, you get a wavemeter (which also still has potential use), you get a general purpose oscillator that you can connect a crystal to, and you get likely some other uses that don't immediately come to mind. They date from a time, late forties is when they started becoming popular but I'm uncertain if the concept was there before, when the average ham had little test equipment, and even labs and repair places might not have all that much of it. It was a handy little unit, relatively easy to build, that did give good returns. Of course, a lot of recent equipment isn't conducive to as easy use with a GDO, with self-shielding toroids and the rest shielded in cans. Construction isn't nearly as wide open as in the days of tubes. But whether it's worth having likely depends on a mindset. If someone wants to load down on tons of test equipment, then a GDO is likely redundant. But a GDO can have its uses, especially if one doesn't have a wide-range signal generator. Michael VE2BVW |
Bill Turner ) writes:
Also, a GDO is likely to be much less expensive than the three separate items. Bill, W6WRT That's always been some of its appeal. Throw one together, or buy one, and you get a tool for finding the rough frequency of a coil. But you also get that ability to figure out an unknown L or C, you get a signal generator, you get a wavemeter (which also still has potential use), you get a general purpose oscillator that you can connect a crystal to, and you get likely some other uses that don't immediately come to mind. They date from a time, late forties is when they started becoming popular but I'm uncertain if the concept was there before, when the average ham had little test equipment, and even labs and repair places might not have all that much of it. It was a handy little unit, relatively easy to build, that did give good returns. Of course, a lot of recent equipment isn't conducive to as easy use with a GDO, with self-shielding toroids and the rest shielded in cans. Construction isn't nearly as wide open as in the days of tubes. But whether it's worth having likely depends on a mindset. If someone wants to load down on tons of test equipment, then a GDO is likely redundant. But a GDO can have its uses, especially if one doesn't have a wide-range signal generator. Michael VE2BVW |
james ) writes:
Hi Paul, ARRL QST had nice article on a modern GDO May 2003 QST page 54 A Modern GDO--The "Gate" Dip Oscillator Bloom, Alan, N1AL 73 jimbo Paul wrote: But is it really modern, or just a rehash of what's come before? I haven't seen the article, but in thirty years of reading the magazines (and I've seen plenty of back issues from before that), there has been very little change. Most of the articles are a small variant on a previous article, with any real change being about coil forms ("I didn't have what the previous article used", or "I noticed these things that would make a GDO, so I built one around them") or variable capacitor. Admittedly, when solid state devices came along, there had to be some change since people did want to make use of them. The original ones were likely pretty bad, using bipolar transistors, and of course there was the Tunnel diode one from Heathkit. Once FETs came along, the GDOs were back to basically a tube circuit, albeit with low supply voltage. There have been the occasional outrageous scheme, switchable coils, or making use of an existing signal generator or building a whole GDO along such lines, but they never really held. Next time a GDO article was published, it was back to simplicity. If I was building one, I'd make sure it had a good reduction drive. I'd certainly put in a buffer for an output, as a signal generator or to feed a frequency counter. The latter then means the dial doesn't require much effort, and the readout will be much much better than any GDO from before. Maybe I'd even build a plug-in that has switchable coils, but the whole thing is shielded, for those times when you just wanted a signal generator. But I'd also be looking at the circuitry of the Millen Solid-state GDO, from the early seventies. It was a more extensive design, but of course it costs virtually nothing for those extra active devices. They found they had to put a variety of chokes in the thing to isolate the oscillator from the B+ line, so there weren't false dips. The Heathkit from the eighties seemed rather interesting. Again, it was a more complicated design. I can't remember what the extra circuitry amounted to. That design did generate some similar home made circuits at the time. Michael VE2BVW |
james ) writes:
Hi Paul, ARRL QST had nice article on a modern GDO May 2003 QST page 54 A Modern GDO--The "Gate" Dip Oscillator Bloom, Alan, N1AL 73 jimbo Paul wrote: But is it really modern, or just a rehash of what's come before? I haven't seen the article, but in thirty years of reading the magazines (and I've seen plenty of back issues from before that), there has been very little change. Most of the articles are a small variant on a previous article, with any real change being about coil forms ("I didn't have what the previous article used", or "I noticed these things that would make a GDO, so I built one around them") or variable capacitor. Admittedly, when solid state devices came along, there had to be some change since people did want to make use of them. The original ones were likely pretty bad, using bipolar transistors, and of course there was the Tunnel diode one from Heathkit. Once FETs came along, the GDOs were back to basically a tube circuit, albeit with low supply voltage. There have been the occasional outrageous scheme, switchable coils, or making use of an existing signal generator or building a whole GDO along such lines, but they never really held. Next time a GDO article was published, it was back to simplicity. If I was building one, I'd make sure it had a good reduction drive. I'd certainly put in a buffer for an output, as a signal generator or to feed a frequency counter. The latter then means the dial doesn't require much effort, and the readout will be much much better than any GDO from before. Maybe I'd even build a plug-in that has switchable coils, but the whole thing is shielded, for those times when you just wanted a signal generator. But I'd also be looking at the circuitry of the Millen Solid-state GDO, from the early seventies. It was a more extensive design, but of course it costs virtually nothing for those extra active devices. They found they had to put a variety of chokes in the thing to isolate the oscillator from the B+ line, so there weren't false dips. The Heathkit from the eighties seemed rather interesting. Again, it was a more complicated design. I can't remember what the extra circuitry amounted to. That design did generate some similar home made circuits at the time. Michael VE2BVW |
On Sun, 16 Nov 2003 09:49:49 -0800, Bill Turner
wrote: On Sun, 16 Nov 2003 14:45:47 GMT, "Michael A. Terrell" wrote: I told the cal lab the label should read, "Calibration not possible". ;-) -- _________________________________________________ ________ LOL! -- Bill, W6WRT A decade ago I had a struggle with those instruments idiots referring to ISO 9000, had an old fully working 30 years old Wande&Goltermann SPM-1 instrument for telex channels, with mark and space marked, but they would give me a new digital possibly from HP, costing in the region of $10000 - without the channel marks, but solid state. After a dispute they agreed to check the calibration, and it was better than they could measure, so they had to let it pass, but I damaged their day! I was told that if any tubes broke down it was forbidden to change them, and it was a political decision to discard such old instruments 73 Jan-Martin LA8AK http://home.online.no/~la8ak/c.htm -- remove ,xnd to reply (Spam precaution!) |
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