Tuned Circuit Selectivity

[Phil Hobbs]

On 5/7/19 10:05 AM, John Larkin wrote:

On Mon, 6 May 2019 17:52:11 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 5/6/19 3:37 PM, bitrex wrote:
On 5/6/19 12:31 PM, Phil Hobbs wrote:
Measurements 59 Megacycle Meter

They should have called it the Magnificent Measurements 59 Megacycle
Measuring Meter

You might suggest that to their marketing department. It would be
less hyperbolic than some names I've seen.

They later changed their name from Measurements Corp. to Boonton Radio
Corp. and then got bought by HP. They made a lot of good stuff--Q
meters, dip meters, true-RMS AC voltmeters, and so on. I especially
like their three-terminal capacitance meters, the Boonton 72 series.

Cheers

Phil Hobbs

I have several 72's and I love them. They are ancient and none has
ever broken.

https://www.dropbox.com/s/7k57wicymctj3s0/boonton-72.jpg?dl=0

1 pF full scale! With a bias input for making C-V curves.

Well, one did fail when an intern connected a couple KV to the bias
terminals. Ex-intern.

I have four of them as well, a 72A, a 72C (analogue) and two 72BDs
(digital).

One of my digital ones needed its pushbutton switches cleaned, but never
any other problems.

On the 2 pF scale, once it's warmed up and zeroed it'll sit there
reading 0.000 pF all afternoon. Wave your hand nearby and it'll read a
few femtofarads and then back to zero. Really a good gizmo.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 5/7/19 2:28 PM, Cursitor Doom wrote:

On Mon, 06 May 2019 23:41:42 -0700, nuny@bid.nes wrote:

I built one decades ago (with replaceable coils, ooh) from ARRL plans
which assumed you knew about good wiring practices. I didn't, and
eventually tore it apart and rebuilt it with every new lesson I
learned. Wish I still had it.

Been there, done that!
I've just had a rummage through my many rooms of old test gear and
discovered I have a Boonton GDM I'd forgotten all about! This is actually
a valve one, by the look of it, with about a dozen plug-in coils. THIS is
one I've never tried. Maybe it could rescue my perception of GDMs! (if it
doesn't, it and all the others will be heading for the reclycling
facility.)



If it's a Model 59, it's a beautiful thing.

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Cursitor Doom]

On Tue, 07 May 2019 07:12:30 -0700, John Larkin wrote:

Here's my Q meter. The voltmeter is a 0.2 pF SD14 sampling probe.

It uses series voltage boosting, from a very low impedance source. Q
calculated from -3 dB frequencies.

https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?dl=0

https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?dl=0

Nice work! I do actually own a bespoke, discrete Q-meter which is about
the size of a modern oscilloscope. I can see it from the distance but
can't get anywhere near it owing to it being surrounded by 'moat' of
other vintage test equipmnent. I'd post a pic, but I don't have a
telephoto lens to hand, nor do I have a photo hosting site ATM either.
Shame, really must do something about that. How do you rate Dropbox?



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[Cursitor Doom]

On Tue, 07 May 2019 15:28:27 -0400, Phil Hobbs wrote:

On the 2 pF scale, once it's warmed up and zeroed it'll sit there
reading 0.000 pF all afternoon. Wave your hand nearby and it'll read a
few femtofarads and then back to zero. Really a good gizmo.

What methodology are they using to measure these very low capacitances?




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[Cursitor Doom]

On Tue, 07 May 2019 15:30:20 -0400, Phil Hobbs wrote:

If it's a Model 59, it's a beautiful thing.

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and have
a play with it this weekend coming.

Thanks, Phil.



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This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
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[John Larkin]

On Tue, 7 May 2019 20:39:40 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Tue, 07 May 2019 07:12:30 -0700, John Larkin wrote:

Here's my Q meter. The voltmeter is a 0.2 pF SD14 sampling probe.

It uses series voltage boosting, from a very low impedance source. Q
calculated from -3 dB frequencies.

https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?dl=0

https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?dl=0

Nice work! I do actually own a bespoke, discrete Q-meter which is about
the size of a modern oscilloscope. I can see it from the distance but
can't get anywhere near it owing to it being surrounded by 'moat' of
other vintage test equipmnent. I'd post a pic, but I don't have a
telephoto lens to hand, nor do I have a photo hosting site ATM either.
Shame, really must do something about that. How do you rate Dropbox?

Dropbox is free, with 2 or maybe 4 Gbytes. I have a terabyte, for
something like $8 a month. I use it to work from here to home to the
cabin to the laptop, instead of carrying memory sticks around. I do
the cabin monitoring and temperature controls through a shared Dropbox
folder too.

https://www.dropbox.com/s/gcblxjjji13yqnl/Cabin.jpg?dl=0


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Tue, 7 May 2019 21:55:54 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Tue, 07 May 2019 15:28:27 -0400, Phil Hobbs wrote:

On the 2 pF scale, once it's warmed up and zeroed it'll sit there
reading 0.000 pF all afternoon. Wave your hand nearby and it'll read a
few femtofarads and then back to zero. Really a good gizmo.

What methodology are they using to measure these very low capacitances?

There are manuals online, with schematics.

Basically they apply a 1 MHz sine (sometimes other freqs on different
models) to one end of the cap and measure the current on the other
end, with RF circuits and amps and a phase-sensitive detector. Lots of
RF gain gives sensitivity.




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John S]

On 5/7/2019 5:06 PM, Cursitor Doom wrote:

On Tue, 07 May 2019 15:30:20 -0400, Phil Hobbs wrote:

If it's a Model 59, it's a beautiful thing.

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and have
a play with it this weekend coming.

Thanks, Phil.

DON'T throw it away! I'll buy it for a reasonable price.

 

[Dave Platt]

In article <qavo1n$f13$1@dont-email.me>, John S <Sophi.2@invalid.org> wrote:

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and have
a play with it this weekend coming.

Thanks, Phil.


DON'T throw it away! I'll buy it for a reasonable price.

Darned right.

A few years ago I did a bake-off between several dipmeter I own or
could borrow: my Model 59, a B&W 600 (tube), a Heathkit solid state
(the 1250 I think) and their HM-10 tunnel-diode dipper, and the "dip
meter" plug-in coils for an MFJ 1259. The "test subject" was a
section of Airdux inductor, wired to an air-variable
capacitor... should be a nice high-Q resonator.

The goal was to see how far away from the test coil I could hold the
dipmeter probe-coil, and still get a readable "dip" at the resonant
frequency. The further away, the less coupling and "pulling".

The MJF coils were essentially useless... couldn't get a meaningful
dip unless the coil was touching the test coil, or nearly so, and it
wasn't particularly stable or easy to read.

The HM-10 was almost as bad.

The Heathkit 1250 could get a dip from an inch or two away.

The B&W did a bit better than the 1250.

The Model 59 was getting a detectable dip from 4-5" away. Very, very
good sensitivity.

I'd love to test one of the Millen GDOs but the only times I've seen
one in decent condition, for sale with its various coils, the price
being asked has made me back away slowly.

 

[piglet]

On 08/05/2019 12:15 am, John Larkin wrote:

On Tue, 7 May 2019 21:55:54 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Tue, 07 May 2019 15:28:27 -0400, Phil Hobbs wrote:

On the 2 pF scale, once it's warmed up and zeroed it'll sit there
reading 0.000 pF all afternoon. Wave your hand nearby and it'll read a
few femtofarads and then back to zero. Really a good gizmo.

What methodology are they using to measure these very low capacitances?

There are manuals online, with schematics.

Basically they apply a 1 MHz sine (sometimes other freqs on different
models) to one end of the cap and measure the current on the other
end, with RF circuits and amps and a phase-sensitive detector. Lots of
RF gain gives sensitivity.

The Boonton 72 measures the capacitance between the two test terminals
while rejecting stray capacitance to ground which is neat.

I only need to use it once or twice a year but it is unbeatable.

piglet

 

[piglet]

On 09/05/2019 12:17 am, John S wrote:

On 5/7/2019 5:06 PM, Cursitor Doom wrote:
On Tue, 07 May 2019 15:30:20 -0400, Phil Hobbs wrote:

If it's a Model 59, it's a beautiful thing.

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and have
a play with it this weekend coming.

Thanks, Phil.


DON'T throw it away! I'll buy it for a reasonable price.

Would $3,900 be reasonable? An Ebay seller is offering a set with the LF
and MF heads as well as the more common HF/VHF head.

piglet

 

[John Larkin]

On Thu, 9 May 2019 09:23:14 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 08/05/2019 12:15 am, John Larkin wrote:
On Tue, 7 May 2019 21:55:54 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Tue, 07 May 2019 15:28:27 -0400, Phil Hobbs wrote:

On the 2 pF scale, once it's warmed up and zeroed it'll sit there
reading 0.000 pF all afternoon. Wave your hand nearby and it'll read a
few femtofarads and then back to zero. Really a good gizmo.

What methodology are they using to measure these very low capacitances?

There are manuals online, with schematics.

Basically they apply a 1 MHz sine (sometimes other freqs on different
models) to one end of the cap and measure the current on the other
end, with RF circuits and amps and a phase-sensitive detector. Lots of
RF gain gives sensitivity.





The Boonton 72 measures the capacitance between the two test terminals
while rejecting stray capacitance to ground which is neat.

I only need to use it once or twice a year but it is unbeatable.

piglet

It's great for semiconductor C-V curves.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Hobbs]

On 5/9/19 4:19 AM, piglet wrote:

On 09/05/2019 12:17 am, John S wrote:
On 5/7/2019 5:06 PM, Cursitor Doom wrote:
On Tue, 07 May 2019 15:30:20 -0400, Phil Hobbs wrote:

If it's a Model 59, it's a beautiful thing.

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and have
a play with it this weekend coming.

Thanks, Phil.


DON'T throw it away! I'll buy it for a reasonable price.


Would $3,900 be reasonable? An Ebay seller is offering a set with the LF
and MF heads as well as the more common HF/VHF head.

piglet

I paid $135 for one of the HF/VHF and $120 for the UHF one. They work
perfectly.

Cheers

Phil

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 5/8/19 8:40 PM, Dave Platt wrote:

In article <qavo1n$f13$1@dont-email.me>, John S <Sophi.2@invalid.org> wrote:

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and have
a play with it this weekend coming.

Thanks, Phil.


DON'T throw it away! I'll buy it for a reasonable price.

Darned right.

A few years ago I did a bake-off between several dipmeter I own or
could borrow: my Model 59, a B&W 600 (tube), a Heathkit solid state
(the 1250 I think) and their HM-10 tunnel-diode dipper, and the "dip
meter" plug-in coils for an MFJ 1259. The "test subject" was a
section of Airdux inductor, wired to an air-variable
capacitor... should be a nice high-Q resonator.

The goal was to see how far away from the test coil I could hold the
dipmeter probe-coil, and still get a readable "dip" at the resonant
frequency. The further away, the less coupling and "pulling".

The MJF coils were essentially useless... couldn't get a meaningful
dip unless the coil was touching the test coil, or nearly so, and it
wasn't particularly stable or easy to read.

The HM-10 was almost as bad.

The Heathkit 1250 could get a dip from an inch or two away.

The B&W did a bit better than the 1250.

The Model 59 was getting a detectable dip from 4-5" away. Very, very
good sensitivity.

I'd love to test one of the Millen GDOs but the only times I've seen
one in decent condition, for sale with its various coils, the price
being asked has made me back away slowly.

I have one of those too, but I've never turned it on. I'll give it a
try when I have a chance.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 5/9/19 12:30 PM, Phil Hobbs wrote:

On 5/8/19 8:40 PM, Dave Platt wrote:
In article <qavo1n$f13$1@dont-email.me>, John S  <Sophi.2@invalid.org
wrote:

https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html

Well, *if* that isn't the one I have it's identical in appearance at
least. I'll have to get it out properly for comparison purposes and
have
a play with it this weekend coming.

Thanks, Phil.


DON'T throw it away! I'll buy it for a reasonable price.

Darned right.

A few years ago I did a bake-off between several dipmeter I own or
could borrow:  my Model 59, a B&W 600 (tube), a Heathkit solid state
(the 1250 I think) and their HM-10 tunnel-diode dipper, and the "dip
meter" plug-in coils for an MFJ 1259.  The "test subject" was a
section of Airdux inductor, wired to an air-variable
capacitor... should be a nice high-Q resonator.

The goal was to see how far away from the test coil I could hold the
dipmeter probe-coil, and still get a readable "dip" at the resonant
frequency.  The further away, the less coupling and "pulling".

The MJF coils were essentially useless... couldn't get a meaningful
dip unless the coil was touching the test coil, or nearly so, and it
wasn't particularly stable or easy to read.

The HM-10 was almost as bad.

The Heathkit 1250 could get a dip from an inch or two away.

The B&W did a bit better than the 1250.

The Model 59 was getting a detectable dip from 4-5" away.  Very, very
good sensitivity.

I'd love to test one of the Millen GDOs but the only times I've seen
one in decent condition, for sale with its various coils, the price
being asked has made me back away slowly.





I have one of those too, but I've never turned it on.  I'll give it a
try when I have a chance.

I paid $81 for it with a complete set of coils.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Cursitor Doom]

On Wed, 08 May 2019 18:17:22 -0500, John S wrote:

> DON'T throw it away! I'll buy it for a reasonable price.

What on earth makes you think I'd throw it away??

I've had a chance to examine it further today and it's the same as Phil
posted about, Model 59 with the pluggable coil set, mint condition,
amazingly. No plans to sell it for the foreseeable future. Don't need the
money. Got money, want time.



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protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Cursitor Doom]

On Thu, 09 May 2019 09:19:10 +0100, piglet wrote:

Would $3,900 be reasonable? An Ebay seller is offering a set with the LF
and MF heads as well as the more common HF/VHF head.

piglet

Seems a fair price to me. If we were living in 2040, that is.
Some people are just plain greedy.



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