You might find the GenRad (GR) Yahoo Group useful.

HP also made some RF bridges in their early days.

Best,

-John

==============

Fred wrote:

Instruments of that type are known as "impedance bridges,"
"admittance bridges," or "immittance bridges."  If they are designed
to be used at RF frequencies, they may be called "RF bridges."  So,
the first thing to figure out is what frequencies you want/need to
use (for example, if you want to measure the driving point impedance
of an AM radio antenna array for a station on 680 kHz, you need to
measure at 680 kHz +/-).  To measure the S-parameters of a 440 MHz
matching network, you need to measure at 440 MHz +/-.  Some
general-purpose bridges work with (or are calibrated only for)
excitation at audio frequencies.

The most often encountered quality general-purpose impedance bridges
are the GR 650, 1608, and 1650-A.  The 916-A was GR's RF impedance
bridge.  The Boonton 250-A has a built-in oscillator and detector,
and covers from 0.5 to 250 MHz.  Here are some references to get you started:

http://www.jamminpower.com/main/GR%20Bridge.html

http://www.radiomuseum.org/r/gener_raco_impedance_bridge_1650_a16.html

http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/RFBridges.htm

These bridges will generally measure the loss (real part) of a
reactance (ESR, dissipation, Q).  They will not measure the
dielectric absorption of capacitors.

Best regards,

Charles

Hi Fred:

In HP speak "meters" have numerical readouts and "analyzers" have graphical readouts.
So the 4-terminal pair LCR meters are good, but the 4-terminal pair LCR analyzers are better.
You can substitute "Impedance" for LCR in the above.
I say better because the you can get an equivalent circuit from an analyzer that has more than two components, which is
the limit of the meters.
Some analyzers can fit complex models automatically, for example Impedance Analyzers and Crystal Impedance meters (which
use swept frequency but only have numerical readouts).

The bible for impedance measurement is HP's "The Impedance Measurement Handbook", see my Related paragraph on the
Impedance web page:
http://www.prc68.com/I/Z.shtml#Rel
This is a MUST READ if you're into precision LCR type measurements.
There's also the issue of compensation and correction of fixture parasitics.  For more on fixtures see the HP
Accessories Selection Guide for Impedance Measurements.

The key idea is that there's a contour plot of accuracy vs impedance and frequency for the different measurement
methods, with the 4-terminal pair method giving the most accurate results.  http://www.prc68.com/I/HP4274_4275_LCR.shtml#4TP
A lot of that is because of canceling magnetic coupling between the 4 coax cables (note that not all the coax shields
are are at ground).
The earlier instruments that used 4 each 5-way binding posts are not anywhere as accurate.

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Clarke4Congress.html

Fred Schneider wrote:

Thanks for the info, the HP impedance measurement handbook is a bit my bible so I know it.

About analysers, i know a modern impedance analyser, be it a vna, IV, or just a LCR meter can be more accurate and has more possibilities.
I have two digital vna's  ( DG8SAQ VNWA) one that has the RF-IV test head designed by Paul and an analog one from HP. The latter I yesterday used to make RF-IV measurements as an experiment. A tek CT currentprobe from splitter to reference and the other output via a shunt fixture to the test port. The result was above wat I expected,  a nice impedance curve that has a resolution of 40 dB under 1 ohm.
I am most time busy doing network analysing, component research, most of them involve capacitors and parasitic behaviour of components. And playing with calibrators.

But I teached my self everything and i have no math education so I always avoided that ( i have discalculus too) but I like it a lot and the lat time I try to get back to the basics for deeper understanding about what I am meaduring and for most practice and learn some math. The result is new ( that is for me) ways to measure things. I ( re ?)invented a CF converter, build snd designed a IV-meter like fF meter, did coulomb and C ( under 10pF) measurements with a O plugin in an old Tek 547 ( after that i found out it was, in a different form, described in the manual). Did tek-130 style C measements like described by Terman. Measured capacitanceusing DC, tryed about 10 ways to measure ESR, recently tried to measure the parasitics of 10 m bare wire. Things like inductance, resistance, skineffect, Q, capacitance ect. Very intresting, the meaurements worked, grapical it made sense and gave an idea, but the math was to complex for me to extract it to numbers, gave the data ( thoughstone files) and graphs to a friend who is a math , RF engineer and RF guru but he had to admit it was even to complex for him. He could probably do it but it would take to much time. I could not anlyse the data my self.  This is pure hobby, I do not even have an electronic education.

I have a marconi TF1313A, 0,1% bridge and a HP ( the same, like the damaged one you have)
I builded a simpke complex measurement bridge based on the arrl antenna handbook. Also made a poor mans wobbulator based on a noise source, external signal generator and audio SA software ( involved mixing so it could be used for the whole HF band)

But it would be great to have an old bridge like the GR ones. With lots of knobs and after that calculate from there, to the corrections ect. Mostly to measure capacitove stuff.

I'm offered a GR1620 from a list member that I will buy, i read the manual and I allready love it.
With the info gathered I also would like to have a passive RF type bridge. I know I can easy use a vna but I like to measure the basics and try to extract the other parametrs from there as a learning experience. I am now doing some 3 voltmeter experiments. It is nice to compare results from this experiments to my vna. Some times I'm way of but it feels good if it worked out well. Like meauring capacitance and esr on a curvtracer, that was fun. Or the RI-IV meaurement of a cap. After that I had calculated esr capacitance and esl from that I did a simulation and that gave the same SRF. That gives me a kick.

So to be short ( very difficult for me ;-) ) , i do not have a need for a frequency or so, i adjust/ make up my experiments around an instrument.

Thanks to the answers from you and the others and your link i now know were to look for and use the right search terms. First wait for answer from the seller of the GR about transport and hopr we find a way abd then play with that nice instrument and then look for a RF admitance/impedance bridge.

Short question, keithley makes source meters, They are in the micromeasurements handbook but I can not really place this. It sounds like a sort of IV meter, or coulomb meter but for DC. Not planning to buy one, just curious.

Thanks,

Fred PA4TIM

Op 25 mei 2012 om 22:41 heeft Brooke Clarke brooke@pacific.net het volgende geschreven:

Hi Fred:

Here's my page on transmission line Zo and how it's not a constant impedance:
http://www.prc68.com/I/Zo.shtml
I've added a list of impedance equipment on the Impedance web page:
http://www.prc68.com/I/Z.shtml#Rel

I've used a number of the Keithley DC boxes for automated testing of semiconductors.
http://www.prc68.com/I/RASS_PP.html#D
http://www.prc68.com/I/RASS_PP.html#TD
They are great where you need a current source in the nano or femto amp range or higher.

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Clarke4Congress.html

Fred Schneider wrote:

Look for the website from G3YNH, some very excellent stuff about bridges and AC theory regarding impedance and admittance.
www,g3ynh.info/zdocs/AC_theory/index.html
I have bought the GR1620 and I love it. Found info about the hatfield LE300, that looks just what I was looking for as a generl RF admitance bridge. But i do not search for equivalents yet. To late now, i go to bed.

Fred PA4TIM

Op 26 mei 2012 om 22:16 heeft Brooke Clarke brooke@pacific.net het volgende geschreven:

On 9/14/2012 8:04 PM, Fred Schneider wrote:

just building a refrence with it and If it is not regulated i want

The datasheet shows heater current to be inversely proportional to
ambient temperature, so there's some level of regulation. I'd think that
trying to force a constant current wouldn't be significantly different
than not driving the heater at all (which is just the special case of
constant current = 0).

On 09/14/2012 07:04 PM, Fred Schneider wrote:

It is regulated to a nominal 90C.  When power is first applied heater current
spikes to typically above 120 mA.  After a few seconds it drops to a 10 - 40 mA
(depends on heater voltage level and environment).

--
Bob Smither, PhD                                  Circuit Concepts, Inc.

---=======
"The beauty of the second amendment is that it will not be needed until
they try to take it." --Thomas Jefferson

---=======
Smither@C-C-I.Com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)

Hello Fred,

the heater is regulated to 90 degrees centigrade as is stated in the data
sheet.
A current source for the heater would lead to a instable regulation.
Instead it is essential to supply the heater from a well regulated voltage
source.
The output voltage of the zener changes with the heater voltage (or
current?)
by up to 2ppm/Volt at low heater voltages (around 10V).
Higher heater voltages are more stable.

The LM399 is also sensitive to orientation.
The output voltage changes if you put the LM399 up side down to the sides or
in normal orientation.
(needs 1-2 minutes for stabilization)

For the LTZ1000 try Arrow (USA) they usually have some from time to time.
(today: 13 pieces if you are fast)
http://components.arrow.com/part/search/ltz1000

with best regards

Andreas

----- Original Message -----
From: "Fred Schneider" pa4tim@gmail.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Saturday, September 15, 2012 2:04 AM
Subject: [volt-nuts] Lm399 heater

Fine Standard,
btw. where did you get all those hermetically sealed resistors?

best regards

Andreas

----- Original Message -----
From: "Михаил (Mickle)" timka2k@yandex.ru
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Saturday, September 15, 2012 8:52 AM
Subject: Re: [volt-nuts] Lm399 heater

Hi Mickle ( and the rest )

Thank for the answers. I only looked LM399 but looking for LM199 gives more info.
The LM399 is now running, just on its own without the buffer as test to know the excact voltage. It started after a few minutes at 7.031,321 and after an hour it was 7.031,345V. I must go on a visit now so it is turned off for now.

Allmost killed it. I'm glad I used my PM2811 psu with the max current set at 160 mA. The layout is very confusing. The plus fom the heater is at the anode side of the housing. I only looked at cathode and anode and because in all the schematics the plus and kathode are drawn on the same side i overlooked it. After this I was afraid I killed it but it looks OK. Draws around 140 mA during the first seconds and a few mA ( 30 or 40 i think, but I gave not calibrated the current reading of the psu yet) after this time.

Tommow I get in the garage and part out an old realy defect Fluke 8500. There are WW precision card types and other precision resistors in there. Maybe I'm lucky and some paralleled resitors, and one from them in series together with a 10 turn potentiometer , brings me to 10V plus/min 20 to 50 uV, so a full turn of the pot is 2 to 5  uV for finetuning. In that case the tempco and mechanical construction of the 10K or 2K pot will not give much deviation ( I think) and in that case I can skip one KV and a buffer) I can do that with the ( green vishay) resistors I have but those WW card types have lower tempco I think. I also have a few WW precision potentiometers like those used in lcr bridges. Are they a good choise ( awfull big alltough)

But I do not mind ordering resistors for this but there is so much choise I do not know what to choose and real low tempco ones are over 15 euro a piece. If I make a refrence using a LTZ1000 I will buy them.

Fred PA4TIM

Op 15 sep. 2012 om 08:52 heeft Михаил (Mickle) timka2k@yandex.ru het volgende geschreven:

On 09/15/2012 08:54 AM, Fred Schneider wrote:

Unless you want to track the first few days of stability, why not just leave it
on?  I have a Traveling Standard (see: http://www.c-c-i.com/ts ) that has made
the round trip to some of us volt nuts.  When I get it back I leave it on 24/7
to get it along towards its ultimate stability.

--
Bob Smither                                              Smither@c-c-i.com

---========
The powers not delegated to the United States by the Constitution, nor
prohibited by it to the States, are reserved to the States respectively, or
to the people.
-- Tenth amendment to the Constitution of the united States

---========
Circuit Concepts, Inc.                                        281-331-2744

Hi Bob,
It will be on 24/7 but this was the first test on a lab-psu. I have about 50 wall contacts. About 10 are 24/7 on, they feed my guildline cabinet, timestandard ect ( there is also an UPS in between). When I leave my lab all other contacts are switched off at once for safety. So if I wanted to let it powered I had to do a lot of work to put the psu on a permanent contact ( the psu is under pile of other gear and the mains wires are all behind the shelfs. The permanent contacts are not near the bench. All ovenised and other 24/7 powered stuff is in one corner.

Fred PA4TIM

Op 15 sep. 2012 om 19:08 heeft Bob Smither smither@c-c-i.com het volgende geschreven:

On 09/15/2012 01:38 PM, Fred Schneider wrote:

Hi Fred,

Sounds like a great setup.

Expanding on my first comment, it is pretty interesting looking at an LM399 when
first 'activated.'  I recently brought up a second LM199 that I have had for
decades and never powered.  I charted the difference between the new one and one
that has thousands of hours on it.  Interesting to watch it settle in over a few
days.

Best regards,

Bob Smither, PhD                                    Circuit Concepts, Inc.

---========
"I cannot undertake to lay my finger on that article of the Constitution
which granted a right to Congress of expending, on objects of benevolence,
the money of their constituents"
-James Madison, author of the Constitution

---========
Smither@C-C-I.Com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)