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
Tuned Circuit Selectivity
Started by ●May 5, 2019
Reply by ●May 7, 20192019-05-07
Reply by ●May 7, 20192019-05-07
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
Reply by ●May 7, 20192019-05-07
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=0Nice 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? -- 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 protocols constitutes acceptance of this condition.
Reply by ●May 7, 20192019-05-07
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? -- 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 protocols constitutes acceptance of this condition.
Reply by ●May 7, 20192019-05-07
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.htmlWell, *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. -- 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 protocols constitutes acceptance of this condition.
Reply by ●May 7, 20192019-05-07
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
Reply by ●May 7, 20192019-05-07
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 $8 a month. I use it to work from here to home to the cabin to the laptop, instead of carrying memory sticks around. I do the cabin monitoring and temperature controls through a shared Dropbox folder too. https://www.dropbox.com/s/gcblxjjji13yqnl/Cabin.jpg?dl=0 -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 8, 20192019-05-08
On 5/7/2019 5:06 PM, Cursitor Doom wrote:> On Tue, 07 May 2019 15:30:20 -0400, Phil Hobbs wrote: > >> If it's a Model 59, it's a beautiful thing. >> >> https://blog.aa6e.net/2009/10/my-new-boonton-model-59-gdo.html > > Well, *if* that isn't the one I have it's identical in appearance at > least. I'll have to get it out properly for comparison purposes and have > a play with it this weekend coming. > > Thanks, Phil.DON'T throw it away! I'll buy it for a reasonable price.
Reply by ●May 8, 20192019-05-08
In article <qavo1n$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.
Reply by ●May 9, 20192019-05-09
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
