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!)