Design Con 2015
Breaking News
Comments
Newest First | Oldest First | Threaded View
<<   <   Page 2 / 4   >   >>
Sanjib.A
User Rank
CEO
Re: More on the Dip Meter...
Sanjib.A   11/30/2013 12:15:33 PM
NO RATINGS
Cool video!! Are these instruments still in production? If I can find I would try to grab one and would like to experiment for debugging EMI/EMC issues.

ANON1249426187345
User Rank
Rookie
"Display"? That's what we call a meter, sonny..
ANON1249426187345   11/29/2013 1:28:24 PM
NO RATINGS
Now you're making me feel old.  What you call a "display" is a "meter", which is short for "galvanometer", but I don't think anyone called them that after the dawn of radio.  Permanent magnet and a coil of very fine wire.  Current through the wire makes a magnetic field which moves the needle. 

The GDO's meter has only a single scale, but meters used in VOMs and VTVMs often had several scales for various ranges.  You had to be sure you were looking that the correct one.  But we were used to that from negotiating the multiple scales of our slide rules...  Some meters (such as my 1970-vintage Olson VOM) had a strip of mirror on the surface with the scales, so that you could line up the needle with its image and avoid parallax errors in your reading.

Regarding the "gigantic" capacitor - that one's actually pretty small (as implied by the "mighty midget" name) - only 15 uF and 150 volts.  Capacitors in the TVs I took apart in my youth often had electrolytics with voltage ratings up to 450 or more.  Often the "cans" were 1.5 to 2 inches in diamaeter and 3 or 4 inches long and contained three or four capacitors.

Note the capacitance is given "MF", using "M" for "micro" rather than the Greek letter mu.  Small capacitors were specified in "mmf", or "micro microfards", rather than todays picofarads.  Instead of nanofarads, you had values like "0.001 MF".  Luckily, there was plenty of room on the parts to print this sort of thing.

zeeglen
User Rank
Blogger
Re: My cousin had one!
zeeglen   11/29/2013 10:44:03 AM
NO RATINGS
>Caleb " I think I actually paid $20!"


Love these old Heathkit teardowns!  One minor correction, the bottom slide switch is actually the diode/osc mode select; the power switch is on the sensitivity control.  In diode mode the B+ to the tube plate (anode) is turned off, then the unit could be used as a wavemeter or AM demodulator into the headphones due to rectification between the grid and cathode.


I bought a used successor the GD-1B from a fellow ham while in high school.  Think I only paid $15.  Still have it, and will email you a photo of the plug-in coil set.


grg9999
User Rank
Blogger
Re: My cousin had one!
grg9999   11/28/2013 12:05:02 PM
NO RATINGS
I had one of these years back.   Very useful gadget.  It's basically an RF oscillator with a grid current meter.  So you can use it as a signal generator to test out radios and the like.  And since it has a grid-current meter, you can put it next to a L/C circuit and you'll get a "Dip" in the grid current at resonance, so you can verify the working and frequency and approximate "Q" of a tuned  circuit.  very useful, as old radios had a lot of tuned circuits.  If you dial back the knob until it just stops oscillating, it becomes a tuned RF voltmeter, very useful in debugging and tuning up live oscillator and transmitter stages.    All of the frequency and voltage and stability aspects were very approximate and not going to put Boonton or HP out of business, but good enough for many purposes.    Heath made a smaller, newer one years later using transistors and tunnel diodes, but they were not as good as this old tube-based one.   You just could not get as good a "dip" with those low-impedance transistors and tunel diodes.

 

 

Susan Rambo
User Rank
Blogger
Re: Grid dip meter
Susan Rambo   11/28/2013 11:41:58 AM
NO RATINGS
Very nice, @Jonathan Allen. Would you paste some images of it in the comments so we can see your Eico 710? Thanks!

Michael.Thomas_#5
User Rank
Rookie
Re: Heathkits!
Michael.Thomas_#5   11/28/2013 4:54:26 AM
NO RATINGS
Early PCBs made with paper and phenolic or glue broke down under high voltage. No arcing or leakage over 1" of air.

Some military designs used a half-way system of epoxy boards with solder wrap posts. Made flying components a bit more controlled.

Cremo0
User Rank
Rookie
Frequency range
Cremo0   11/28/2013 3:53:50 AM
NO RATINGS
The frequency range covers 2MHz to 250MHZ

Bert22306
User Rank
CEO
Re: Heathkits!
Bert22306   11/27/2013 11:41:22 PM
NO RATINGS
I too noticed all those "flying" components. That's the way most tube circuits we designed, I'd say until the 1960s perhaps. That's when you started seeing PCBs, even in some tubed electronics (miniature tubes mostly).

I bought a Knight Kit VOM way back Freshman year in college, and am still using it to this day. No tubes. Just passive components hanginmg out in mid air, as it were.

David Ashton
User Rank
Blogger
Re: My cousin had one!
David Ashton   11/27/2013 9:57:07 PM
NO RATINGS
Pity you did not get the coils Caleb, I daresay it would work still.....

I have a friend who is a "ham" and he wanted me to help him make a GDO.  I found a nice circuit with a FET that does from the 100's of KHz up to the mid 100's of MHz.     If it works, maybe I should get into the kit business.....

David Ashton
User Rank
Blogger
Re: Heathkits!
David Ashton   11/27/2013 9:49:28 PM
NO RATINGS
@robotgrrl....    "Noticed the 'mighty' capacitor in your GD-1A. .... Why were capacitors so big back then?"

They have decreased a bit in size, especially high voltage electrolytics....think it;s something to do with the etching of the foil plates - and thinner foil.

But smaller is not always better - as I once found out:

http://www.eetimes.com/author.asp?section_id=36&doc_id=1284545

<<   <   Page 2 / 4   >   >>


Most Recent Comments
Susan Rambo
 
AZskibum
 
AZskibum
 
alex_m1
 
alex_m1
 
AZskibum
 
AZskibum
 
_hm
 
_hm
Top Comments of the Week
Flash Poll
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
<b><a href=Betajet">

The Circle – The Future's Imperfect in the Present Tense
Betajet
5 comments
The Circle, a satirical, dystopian novel published in 2013 by San Francisco-based writer Dave Eggers, is about a large, very powerful technology company that combines aspects of Google, ...

Max Maxfield

Recommended Reads From the Engineer's Bookshelf
Max Maxfield
27 comments
I'm not sure if I read more than most folks or not, but I do I know that I spend quite a lot of time reading. I hate to be idle, so I always have a book or two somewhere about my person -- ...

Martin Rowe

Make This Engineering Museum a Reality
Martin Rowe
Post a comment
Vincent Valentine is a man on a mission. He wants to make the first house to ever have a telephone into a telephone museum. Without help, it may not happen.

Rich Quinnell

Making the Grade in Industrial Design
Rich Quinnell
16 comments
As every developer knows, there are the paper specifications for a product design, and then there are the real requirements. The paper specs are dry, bland, and rigidly numeric, making ...

Special Video Section
The LT8640 is a 42V, 5A synchronous step-down regulator ...
The LTC2000 high-speed DAC has low noise and excellent ...
How do you protect the load and ensure output continues to ...
General-purpose DACs have applications in instrumentation, ...
Linear Technology demonstrates its latest measurement ...
10:29
Demos from Maxim Integrated at Electronica 2014 show ...
Bosch CEO Stefan Finkbeiner shows off latest combo and ...
STMicroelectronics demoed this simple gesture control ...
Keysight shows you what signals lurk in real-time at 510MHz ...
TE Connectivity's clear-plastic, full-size model car shows ...
Why culture makes Linear Tech a winner.
Recently formed Architects of Modern Power consortium ...
Specially modified Corvette C7 Stingray responds to ex Indy ...
Avago’s ACPL-K30T is the first solid-state driver qualified ...
NXP launches its line of multi-gate, multifunction, ...
Doug Bailey, VP of marketing at Power Integrations, gives a ...
See how to ease software bring-up with DesignWare IP ...
DesignWare IP Prototyping Kits enable fast software ...
This video explores the LT3086, a new member of our LDO+ ...
In today’s modern electronic systems, the need for power ...