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Grid Dip Meters
Hi gang, I've never had a lot of luck with GDMs for some reason. Even with a decent meter, it seems such a drag tuning across such a vast range looking for a tiny, easily-missed dip which you have to screw out of the meter by forcing the sensing coil so far into the circuit concerned you practically break the circuit board. Am I alone in finding this potentially invaluable device practically useless in practice? Is there a more viable alternative? p. -- "I expect history will be kind to me, since I intend to write it." - Winston Churchill |
"Paul Burridge" wrote in message ... Hi gang, I've never had a lot of luck with GDMs for some reason. Even with a decent meter, it seems such a drag tuning across such a vast range looking for a tiny, easily-missed dip which you have to screw out of the meter by forcing the sensing coil so far into the circuit concerned you practically break the circuit board. Am I alone in finding this potentially invaluable device practically useless in practice? Is there a more viable alternative? p. -- First rule is to get a good dip meter- the stuff made for the amateur community is very poor- the Eicos, Heath Millen etc. Pick up a Measurments model 59. With this meter you can take a 1/2 wave wire- say at 2M and hold the meter a couple inches from the center and see a huge dip. Other meters don't even respond when held to the wire. Dips on conventional L-C circuits can easily be full scale. Dale W4OP |
"Paul Burridge" wrote in message ... Hi gang, I've never had a lot of luck with GDMs for some reason. Even with a decent meter, it seems such a drag tuning across such a vast range looking for a tiny, easily-missed dip which you have to screw out of the meter by forcing the sensing coil so far into the circuit concerned you practically break the circuit board. Am I alone in finding this potentially invaluable device practically useless in practice? Is there a more viable alternative? p. -- First rule is to get a good dip meter- the stuff made for the amateur community is very poor- the Eicos, Heath Millen etc. Pick up a Measurments model 59. With this meter you can take a 1/2 wave wire- say at 2M and hold the meter a couple inches from the center and see a huge dip. Other meters don't even respond when held to the wire. Dips on conventional L-C circuits can easily be full scale. Dale W4OP |
"Paul Burridge" wrote in message ... Hi gang, I've never had a lot of luck with GDMs for some reason. Even with a decent meter, it seems such a drag tuning across such a vast range looking for a tiny, easily-missed dip which you have to screw out of the meter by forcing the sensing coil so far into the circuit concerned you practically break the circuit board. Am I alone in finding this potentially invaluable device practically useless in practice? Is there a more viable alternative? p. -- It is kind of hard to get the proper coupling on PCB style coils. You may have to use a link coupling system (came with some of the Millens); also solid state circuits can have fairly low Q circuits, again making it hard to see the dip. Those were intended for larger tube circuit designs, not PCB based gear. Pete |
"Paul Burridge" wrote in message ... Hi gang, I've never had a lot of luck with GDMs for some reason. Even with a decent meter, it seems such a drag tuning across such a vast range looking for a tiny, easily-missed dip which you have to screw out of the meter by forcing the sensing coil so far into the circuit concerned you practically break the circuit board. Am I alone in finding this potentially invaluable device practically useless in practice? Is there a more viable alternative? p. -- It is kind of hard to get the proper coupling on PCB style coils. You may have to use a link coupling system (came with some of the Millens); also solid state circuits can have fairly low Q circuits, again making it hard to see the dip. Those were intended for larger tube circuit designs, not PCB based gear. Pete |
THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T.
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THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T.
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On Sat, 15 Nov 2003 17:06:34 -0500, " Uncle Peter"
wrote: It is kind of hard to get the proper coupling on PCB style coils. You may have to use a link coupling system (came with some of the Millens); also solid state circuits can have fairly low Q circuits, again making it hard to see the dip. Those were intended for larger tube circuit designs, not PCB based gear. Item 2.4 described on http://home.online.no/~la8ak/5c.htm is the solution for dipping pcb coils, and you don't need a griddipmeter, at all. Another problem with the pcb coil is low Q-value, and if the coil is loaded too much it won't dip with any arrangement tried. also described some GDMs on http://home.online.no/~la8ak/5a.htm - haven't got the time to re-edit these pages Jan-Martin LA8AK -- remove ,xnd to reply (Spam precaution!) |
On Sat, 15 Nov 2003 17:06:34 -0500, " Uncle Peter"
wrote: It is kind of hard to get the proper coupling on PCB style coils. You may have to use a link coupling system (came with some of the Millens); also solid state circuits can have fairly low Q circuits, again making it hard to see the dip. Those were intended for larger tube circuit designs, not PCB based gear. Item 2.4 described on http://home.online.no/~la8ak/5c.htm is the solution for dipping pcb coils, and you don't need a griddipmeter, at all. Another problem with the pcb coil is low Q-value, and if the coil is loaded too much it won't dip with any arrangement tried. also described some GDMs on http://home.online.no/~la8ak/5a.htm - haven't got the time to re-edit these pages Jan-Martin LA8AK -- remove ,xnd to reply (Spam precaution!) |
Yep...He probably bought it from you.
Tracy On Sat, 15 Nov 2003 17:23:50 -0600 (CST), (Bill Turner) wrote: THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T. |
Yep...He probably bought it from you.
Tracy On Sat, 15 Nov 2003 17:23:50 -0600 (CST), (Bill Turner) wrote: THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T. |
GDOs are sort of dated by now. i build one last year when i was just
getting back into hamming. i found very little use for it over the last 3 months that i have actively been homebrewing. let me explain why ... a gdo is primarily used to check for resonance of a tuned circuit. if you knew the inductance and the capacitance, you could easily compute the resonanating frequency youself. as another poster mentioned, getting a dip is a fight. so, what i do use is a combination of three things: an rf probe with a high impedance voltmeter, a test oscillator and a frequency counter. all these things are in themselves pretty useful. but i seldom go wrong in getting properly tuned circuits. i have a test oscillator (see the schematic http://farhan.net.co.nr/testosc.gif). i plug in a coil with a 330pf capcitance in series between the base of the vfo transistor and the ground. and measure the frequency on the counter. that gives me a pretty accurate (within 1%) measure of the coil's inductance. it involves a bit of calculating, but once i have cast the values, there is seldom need to change them. i tend to do simple maths in my head using 10MHz as starting value for resonance (100pf with 2.5uH). I can now scale up or down without resorting to a calculator. As for peaking a circuit, it is best done by the ear or using an oscilloscope. peaking by the ear is probably the best, if u can manage it. now, i dont mean to be rude, but frankly very few people have the ear to be able to tune for best fidelity rather than loudness. it takes patience and care (i have very little of either). so, i depend upon a scope. it is a little like knowing morse. it is the best mode of communicating, but not all want to use it. a poor man's alternative is using the RF probe. the RF probe will never show distortions. But it can show clear peaks while tuning up a circuit. be sure that you also terminate the output of the tuned stage properly! otherwise you maybe be tuning away from the sweet point. i would rather that you invested into building a simple PIC based counter. It is pretty accurate, you will never need to caliberate it. (I never got around to caliberating mine, it is off by 1.5KHz at 10MHz). That with the test oscillator, you would be completely informed about your coils. An RF probe is a 10 minute project and if you already have a good VOM, you might not need a High impedance voltmeter. I brewed my own voltmeter to keep things completely homebrewed. the counter can always be used with all your projects as a standard read out. The rf probe will the most useful tool in tuning up any transmitter. The voltmeter is indispensable. - farhan |
GDOs are sort of dated by now. i build one last year when i was just
getting back into hamming. i found very little use for it over the last 3 months that i have actively been homebrewing. let me explain why ... a gdo is primarily used to check for resonance of a tuned circuit. if you knew the inductance and the capacitance, you could easily compute the resonanating frequency youself. as another poster mentioned, getting a dip is a fight. so, what i do use is a combination of three things: an rf probe with a high impedance voltmeter, a test oscillator and a frequency counter. all these things are in themselves pretty useful. but i seldom go wrong in getting properly tuned circuits. i have a test oscillator (see the schematic http://farhan.net.co.nr/testosc.gif). i plug in a coil with a 330pf capcitance in series between the base of the vfo transistor and the ground. and measure the frequency on the counter. that gives me a pretty accurate (within 1%) measure of the coil's inductance. it involves a bit of calculating, but once i have cast the values, there is seldom need to change them. i tend to do simple maths in my head using 10MHz as starting value for resonance (100pf with 2.5uH). I can now scale up or down without resorting to a calculator. As for peaking a circuit, it is best done by the ear or using an oscilloscope. peaking by the ear is probably the best, if u can manage it. now, i dont mean to be rude, but frankly very few people have the ear to be able to tune for best fidelity rather than loudness. it takes patience and care (i have very little of either). so, i depend upon a scope. it is a little like knowing morse. it is the best mode of communicating, but not all want to use it. a poor man's alternative is using the RF probe. the RF probe will never show distortions. But it can show clear peaks while tuning up a circuit. be sure that you also terminate the output of the tuned stage properly! otherwise you maybe be tuning away from the sweet point. i would rather that you invested into building a simple PIC based counter. It is pretty accurate, you will never need to caliberate it. (I never got around to caliberating mine, it is off by 1.5KHz at 10MHz). That with the test oscillator, you would be completely informed about your coils. An RF probe is a 10 minute project and if you already have a good VOM, you might not need a High impedance voltmeter. I brewed my own voltmeter to keep things completely homebrewed. the counter can always be used with all your projects as a standard read out. The rf probe will the most useful tool in tuning up any transmitter. The voltmeter is indispensable. - farhan |
On Sat, 15 Nov 2003 22:05:45 GMT, "Dale Parfitt"
wrote: | |"Paul Burridge" wrote in message .. . | | Hi gang, | | I've never had a lot of luck with GDMs for some reason. Even with a | decent meter, it seems such a drag tuning across such a vast range | looking for a tiny, easily-missed dip which you have to screw out of | the meter by forcing the sensing coil so far into the circuit | concerned you practically break the circuit board. Am I alone in | finding this potentially invaluable device practically useless in | practice? Is there a more viable alternative? | | p. | -- | | First rule is to get a good dip meter- the stuff made for the amateur |community is very poor- the Eicos, Heath Millen etc. Pick up a Measurments |model 59. With this meter you can take a 1/2 wave wire- say at 2M and hold |the meter a couple inches from the center and see a huge dip. Other meters |don't even respond when held to the wire. Dips on conventional L-C circuits |can easily be full scale. Yep. I have two 59s and they are great. I got rid of two Millens. They are better than anything else but the 59. As to usefulness, a short war story. Another engineer and I were working on an AGC problem in the early Phoenix missile i-f amplifier. Phoenix being a monopulse radar had a three channel receiver with very tight agc tracking requirments (both gain and phase). The agc voltage was fed to each of the three channels via feedthru caps in the walls of a very well shielded and gasketed chassis. Nevertheless, there was obvious crosstalk. The other guy said to me, "Wes, do you have a GDO?" I said, "Sure." A couple of younger engineers who were watching this asked, "What's a GDO?" So we poke the coil of the Model 59 into the chassis and find a nice resonance at the i-f in the agc wiring. The feedthru capacitance and wiring inductance were resonating at i-f. We had millions of dollars worth of test equipment in our lab and I doubt that we could have devised a test for this without heroic efforts. 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. Wes N7WS |
On Sat, 15 Nov 2003 22:05:45 GMT, "Dale Parfitt"
wrote: | |"Paul Burridge" wrote in message .. . | | Hi gang, | | I've never had a lot of luck with GDMs for some reason. Even with a | decent meter, it seems such a drag tuning across such a vast range | looking for a tiny, easily-missed dip which you have to screw out of | the meter by forcing the sensing coil so far into the circuit | concerned you practically break the circuit board. Am I alone in | finding this potentially invaluable device practically useless in | practice? Is there a more viable alternative? | | p. | -- | | First rule is to get a good dip meter- the stuff made for the amateur |community is very poor- the Eicos, Heath Millen etc. Pick up a Measurments |model 59. With this meter you can take a 1/2 wave wire- say at 2M and hold |the meter a couple inches from the center and see a huge dip. Other meters |don't even respond when held to the wire. Dips on conventional L-C circuits |can easily be full scale. Yep. I have two 59s and they are great. I got rid of two Millens. They are better than anything else but the 59. As to usefulness, a short war story. Another engineer and I were working on an AGC problem in the early Phoenix missile i-f amplifier. Phoenix being a monopulse radar had a three channel receiver with very tight agc tracking requirments (both gain and phase). The agc voltage was fed to each of the three channels via feedthru caps in the walls of a very well shielded and gasketed chassis. Nevertheless, there was obvious crosstalk. The other guy said to me, "Wes, do you have a GDO?" I said, "Sure." A couple of younger engineers who were watching this asked, "What's a GDO?" So we poke the coil of the Model 59 into the chassis and find a nice resonance at the i-f in the agc wiring. The feedthru capacitance and wiring inductance were resonating at i-f. We had millions of dollars worth of test equipment in our lab and I doubt that we could have devised a test for this without heroic efforts. 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. Wes N7WS |
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i use my GD-meter when building antennas and tuning
antennas and traps to frequency. Although the calibration is quite inexact, it's always possible to listen to the GD-meters frequency on the receiver. "Paul Burridge" On Sat, 15 Nov 2003 17:23:50 -0600 (CST), Turner) wrote: THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T. 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 use my GD-meter when building antennas and tuning
antennas and traps to frequency. Although the calibration is quite inexact, it's always possible to listen to the GD-meters frequency on the receiver. "Paul Burridge" On Sat, 15 Nov 2003 17:23:50 -0600 (CST), Turner) wrote: THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T. 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 :-( |
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 |
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 13:27:49 +0000, Paul Burridge
wrote: On Sat, 15 Nov 2003 17:23:50 -0600 (CST), (Bill Turner) wrote: THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T. 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. sorry I don't really see your point. I bought my Tradipper in 67, and it has been very useful since then, I may not use it so often now because I've also got a Philips GM3121. Mine operatet satisfactorily - as original - up to 140MHz, but the 2M coil is no coil at all, only a short between to pins on the connector. Have described how to improve on this on http://home.online.no/~la8ak/m2.htm The other modification is to use external +12V since the battery would normally be flat when needed, but the original version had "positive- ground", and some minor changes had to be done LA3JA later bought the same model, but this had a very bad intermittent contact in the tuning capacitor, so I couldn't repair it. DL7QY described a dipmeter covering up to 1GHz, but I haven't really felt I needed it because it is other ways to check ressonance than using a GDM, and 1GHz is still not the highest frequency I need to cover 73 Jan-Martin, LA8AK http://home.online.no/~la8ak/c.htm -- remove ,xnd to reply (Spam precaution!) |
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!) |
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!) |
On Sun, 16 Nov 2003 13:27:49 +0000, Paul Burridge
wrote: On Sat, 15 Nov 2003 17:23:50 -0600 (CST), (Bill Turner) wrote: THERE MUST HAVE BEEN SOMETHING WRONG WITH YOUR MILLEN. BILL T. 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. sorry I don't really see your point. I bought my Tradipper in 67, and it has been very useful since then, I may not use it so often now because I've also got a Philips GM3121. Mine operatet satisfactorily - as original - up to 140MHz, but the 2M coil is no coil at all, only a short between to pins on the connector. Have described how to improve on this on http://home.online.no/~la8ak/m2.htm The other modification is to use external +12V since the battery would normally be flat when needed, but the original version had "positive- ground", and some minor changes had to be done LA3JA later bought the same model, but this had a very bad intermittent contact in the tuning capacitor, so I couldn't repair it. DL7QY described a dipmeter covering up to 1GHz, but I haven't really felt I needed it because it is other ways to check ressonance than using a GDM, and 1GHz is still not the highest frequency I need to cover 73 Jan-Martin, LA8AK http://home.online.no/~la8ak/c.htm -- remove ,xnd to reply (Spam precaution!) |
On Sun, 16 Nov 2003 09:48:50 -0800, Bill Turner
wrote: On 16 Nov 2003 16:56:27 GMT, (Michael Black) wrote: 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. _________________________________________________ ________ This would be a good way to go in the sense of not requiring a calibrated dial, but a GDO is necessarily a broadly tuned device simply because a single tank circuit is a broadly tuned device. A high degree of precision is neither needed nor even possible. ....because frequency it is pulled when dip occurs and when you adjust excitation for best reading on the meter Still, I like the concept. -- Bill, W6WRT 73 LA8AK -- remove ,xnd to reply (Spam precaution!) |
On Sun, 16 Nov 2003 09:48:50 -0800, Bill Turner
wrote: On 16 Nov 2003 16:56:27 GMT, (Michael Black) wrote: 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. _________________________________________________ ________ This would be a good way to go in the sense of not requiring a calibrated dial, but a GDO is necessarily a broadly tuned device simply because a single tank circuit is a broadly tuned device. A high degree of precision is neither needed nor even possible. ....because frequency it is pulled when dip occurs and when you adjust excitation for best reading on the meter Still, I like the concept. -- Bill, W6WRT 73 LA8AK -- remove ,xnd to reply (Spam precaution!) |
In article , Wes Stewart
writes: 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. Dunno why you guys want to pick on metrology departments. It's up to CORPORATE to see that metrology departments do their thing properly. Most of them do. I worked in one for a bit over two years (Ramo-Wooldrige) and everything was done according to factory information and procedures. RCA Corporation was done the same way. On the other hand, Electro-Optical Systems (a Xerox division) was terribly lax that way and any department could tag something out of service and have it stored. EOS Corporate put such loose controls on it that anyone could go into the storage area and "requisition" anything, no questions asked. Len Anderson retired (from regular hours) electronic engineer person |
In article , Wes Stewart
writes: 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. Dunno why you guys want to pick on metrology departments. It's up to CORPORATE to see that metrology departments do their thing properly. Most of them do. I worked in one for a bit over two years (Ramo-Wooldrige) and everything was done according to factory information and procedures. RCA Corporation was done the same way. On the other hand, Electro-Optical Systems (a Xerox division) was terribly lax that way and any department could tag something out of service and have it stored. EOS Corporate put such loose controls on it that anyone could go into the storage area and "requisition" anything, no questions asked. Len Anderson retired (from regular hours) electronic engineer person |
hi
This gdo uses three fet and runs off two aa batteries, nice project. The coils are built with bnc connectors. jimbo Michael wrote: 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 |
hi
This gdo uses three fet and runs off two aa batteries, nice project. The coils are built with bnc connectors. jimbo Michael wrote: 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 |
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