Date: Sat, 27 Mar 2010 16:02:13 -0800
From: "Zeitler, Lane LT, FST-1" <zeitlel*******>
Subject: [Amps] L and C "meter"

I am curious as to what you guys are using to measure the L and C of
your circuits/components. I looked at the B & K 875-B and it can be had
for $192.00 on Amazon dot com. I do not know if this is reasonable but
the meter seems to offer quite a bit and the accuracy according to the
specs seems pretty good.



Lane

Ku7i

##  I bought a new  B+k 875-A  back in 1992.  Still  works superb.
## last year, I bought a new 875-B. Both units  are an industry
standard, and just don't crap out.   The 875-B comes with a
3 yr warranty.  They both use  1 khz  square wave for the measurement
freq.

## The newer 875-B  will measure  lytics up to  20,000 uf. [875-A will
only measure up to 2000 uf]    875-A measures DC resistance.  The
875-B measures AC resistance.. and now has a 2 ohm scale.. and measures
down to .001 ohm.   Both of em will measure  down to .1uh  and .1pf

##  Both will measure  uh  up to  200 Henries !    We have used the 875's
at work for measuring huge chokes, etc.   The 875-B  has a front panel
adjustable  zero set.. which is a big bonus.  The older 875-A  didn't... and I always
had to remember  to subtract .66 uh  for the  2 x 12"  long test leads.   The B
model comes with  2 x  6"  test leads.  

## The  AS   Aim  4170 is even better, but requires a PC.  

##  Bottom line is, I require  something that will  accurately  [1%]   measure typ stuff
,like a 2.2 uh  tank coil, or measure the stray C  of cab side walls  [typ 1-2 pf] ,
big and small chokes, and also audio chokes and xfmr's.  The 875-B  will also measure
the ESR  on HV lytics..down to .001 ohm.    You can spot a bad cap asap.
Both will also measure D on caps.
Being able to now measure up to 20,000 uf  [ instead of 2000 uf]  is a big bonus these days.
All my hv lytics  are >  2000 uf.    B4  I had  to put 2 x in series.

## the real bottom line is.. with out some kind of lcr meter, or similar device, you are dead
in the water, when playing with amps.   A  YC-156 has 35 pf C.. between anode and grid flange
on the wooden test bench.. which rises to aprx 53 pf.. when bolted to chassis.   A  3CX-3000A7
is 24 pf.. and rises to 33 pf, when inserted into socket and grid ring.   A  YU-148 is 24.5 pf.... and
rises to 39.6 pf  when  installed in socket.

Think abt it.  For amps,[ and ham radio in general].. all you are playing with is pf and uh.....
and stray pf and stray uh.  Not having a LCR meter is like not owning a screw driver !
It's the number 1 tool.   Want to know how long that coil of  213 is ?   Just measure the C  between
braid and center conductor... then divide by XXX .
I measure all the C  on control cables, coax etc.. and document it.  Very useful  when it comes to
trbl shooting.   We  started using lcr meters a few yrs ago on new ADSL  equipment /turn ups
in the local telco I worked at.   Once C readings  were taken on known  good cable assy's, and esp
pot's  splitter/filter assys...  finding a bad one was real easy. Get  2 x rings crossed.. or 2 x tips crossed
in a factory splice, or a contractor splice..and the  C readings instantly change.. dead give away.

Later...... Jim  VE7RF

  
F  

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I have used an HP LCR meter at work but never paid any attention to the
frequency at which the measurement is made. I wonder what discrepancies in
measurement values of L and C could be encountered if one measured at
various RF frequencies, and why they might occur. I have seen such
discrepancies, using a popular antenna analyzer, even though I was careful
not to introduce sources of error, like lead lengths.

Thanks,

--
Jack, W6NF
Silver Springs, NV
DM09ji

If the coil has a ferrite or iron core of any kind, the inductance varies a lot with
frequency. Inductors with cores must be measured near the operating frequency. And in
general, as you raise the frequency the various stray capacitances and inductances in the
device under test become more significant.
--
Vic, K2VCO
Fresno CA http://www.qsl.net/k2vco/

Here are some real numbers I just measured on a network analyzer
calibrated at the plane of the core being measured.

Core = T94-2 powdered iron u=10, 22 turns #18 occupying about 80% of core

Msmt. freq.     L(measured)

50KHz           3.06uH
100KHz          3.86uH
200KHz          4.53uH
500KHz          4.51uH
1MHz            4.50uH
5MHz            4.50uH
10MHz           4.58uH
20MHz           4.89uH
30MHz           5.52uH
40MHz           6.80uH
68.1MHz         parallel resonant freq.

As can be seen frequencies above 10MHz show the beginning effects of the
parallel resonance and low measurement frequencies underestimate the
inductance by a significant amount.  Also mounting the inductor in a
metal box will reduce the inductance. I suspect if the measurement freq.
was 1KHz the values would be even lower.  I always measure near the
frequency I intend to use the inductor at and if possible with the
inductor mounted in the enclosure.  Then calibrating to the inductor
plane gives the "real" inductance and filters and matching networks come
out as predicted.

73,
Larry, W0QE

It would be interesting to see what a 1kHz instrument would read with that
same core.

A 2 mix is a poor performer at 50kHz and you might be reading true
inductance.

Also at 30 mHz it only takes a few turns in the typical input network. At 6M
the 6 mix is the core of choice.

Carl
KM1H

D'OH...of course, I should have thought of that with the inductors.

However, I am seeing discrepancies on capacitors, as well. For example, a
good quality 5kv mica, rescued from a salvaged broadcast transmitter, has
measured 2200pf (it's rated value) at 500kHz, about 1900pf at 1MHz and 1700
pf at 1.8MHz. That certainly has me puzzled.

Let's see if there's a response that rates another D'OH :>)

--
Jack, W6NF
Silver Springs, NV
DM09ji

Its been my experience at places Ive worked is that incoming inspection tests L and C at 1kHz using HP equipment.

I suspect that 1 kHz is an industry standard going back to the 1 kc days. What the part does at another frequency is up to the engineer using it to determine. Back in the days of the black arts and slide rules it was called the fudge factor.

Carl
KM1H

  From: Jack/W6NF
  To: Carl
  Cc: Larry Benko ; amps*******
  Sent: Tuesday, March 30, 2010 10:21 PM
  Subject: Re: [Amps] LCR meter

  D'OH...of course, I should have thought of that with the inductors.

  However, I am seeing discrepancies on capacitors, as well. For example, a good quality 5kv mica, rescued from a salvaged broadcast transmitter, has measured 2200pf (it's rated value) at 500kHz, about 1900pf at 1MHz and 1700 pf at 1.8MHz. That certainly has me puzzled.

  Let's see if there's a response that rates another D'OH :>)

    It would be interesting to see what a 1kHz instrument would read with that
    same core.

    A 2 mix is a poor performer at 50kHz and you might be reading true
    inductance.

    Also at 30 mHz it only takes a few turns in the typical input network. At 6M
    the 6 mix is the core of choice.

    Carl
    KM1H

    From: "Larry Benko" <xxw0qe*******>
    To: <amps*******>
    Sent: Tuesday, March 30, 2010 1:30 PM
    Subject: Re: [Amps] LCR meter

    > Here are some real numbers I just measured on a network analyzer
    > calibrated at the plane of the core being measured.
    >
    > Core = T94-2 powdered iron u=10, 22 turns #18 occupying about 80% of core
    >
    > Msmt. freq.     L(measured)
    >
    > 50KHz           3.06uH
    > 100KHz          3.86uH
    > 200KHz          4.53uH
    > 500KHz          4.51uH
    > 1MHz            4.50uH
    > 5MHz            4.50uH
    > 10MHz           4.58uH
    > 20MHz           4.89uH
    > 30MHz           5.52uH
    > 40MHz           6.80uH
    > 68.1MHz         parallel resonant freq.
    >
    > As can be seen frequencies above 10MHz show the beginning effects of the
    > parallel resonance and low measurement frequencies underestimate the
    > inductance by a significant amount.  Also mounting the inductor in a
    > metal box will reduce the inductance. I suspect if the measurement freq.
    > was 1KHz the values would be even lower.  I always measure near the
    > frequency I intend to use the inductor at and if possible with the
    > inductor mounted in the enclosure.  Then calibrating to the inductor
    > plane gives the "real" inductance and filters and matching networks come
    > out as predicted.
    >
    > 73,
    > Larry, W0QE
    >
    >
    >
    >
    >>
    >>> I have used an HP LCR meter at work but never paid any attention to the
    >>> frequency at which the measurement is made. I wonder what discrepancies
    >>> in
    >>> measurement values of L and C could be encountered if one measured at
    >>> various RF frequencies, and why they might occur. I have seen such
    >>> discrepancies, using a popular antenna analyzer, even though I was
    >>> careful
    >>> not to introduce sources of error, like lead lengths.
    >>>
    >>
    >> If the coil has a ferrite or iron core of any kind, the inductance varies
    >> a lot with
    >> frequency. Inductors with cores must be measured near the operating
    >> frequency. And in
    >> general, as you raise the frequency the various stray capacitances and
    >> inductances in the
    >> device under test become more significant.
    >>
    > _______________________________________________
    > Amps mailing list
    > Amps*******
    >  http://lists.contesting.com/mailman/listinfo/amps

When measuring inductance or capacitance with the MFJ-259b readings vary, epending on the frequency.  I usually run a part through a 10mhz sweep  There will be an area in the "middle" where the calculated value changs much slower than at the extremes, and the measured values will correlatenicely with the AADE LC meter.  This happens between 6 to 9 mhz; I've "sandardized" on 7mhz for measurement.  Correlation to parts previously mesured on the AADE meter is within 2 or 3 percent, and often closer.

The measuring of L and C values for the 259b is stated as a reactance rang, that being between 7 and 650 ohms.  So, working backwards from 7mhz, is measurement range is

Inductors = 0.15uh to 15uh   and  Capacitors = 35pf to 3200pf

I've taken some license in those end points to make it easier to remember,but they're close, reactance wise.  Also, its easy to see we shouldn't b throwing away our AADE, BK, or HP LC meters because the MFJ range is veryrestricted.

The mfj has a 259 connector output, so you need an adapter to measure part values.  I've found the type used can be critical to the ability to repat value determination.  Leads longer than 1 to 2 inches need not apply,and that includes coax with alligator clips on the end.  The best I've fund is to to use a banana plug, without its insulator, in the 259 center cnnector with a nut screwed over the post, and another nut screwed over thenearby ground connector.  Parts connected directly between them.

I'm going to copy this post over to the 259b's yahoo forum.

73 - Jim - K9JFK

Message: 9

Date: Thu, 1 Apr 2010 09:32:42 +0300
From: "Alex Eban" <alexeban*******>
Subject: Re: [Amps] LCR meter.

The AADE instrument is more than adequate for all practical purposes. It's
nice to have variable frequency option, but in any case, at the higher
frequencies, the influence of unpredictable strays in the circuit becomes so
strong, that frequency dependent variables in the component cease to be
relevant. These unpredictables strays make any accuracy over a few percents
superfluous.
BTW, another very adequate instrument is the Autek RFxx series at half the
price of an MFJ, with variable frequency AND reactance sign.
Alex 4Z5KS

##  bottom line is.. when a 10 uh coil measures anything other than
10 uh, you will screw up  your pi-net, LC networks etc, guaranteed.

##  rauch claims the stray C  [Xc] between turns of a coil will negate
from the coil itself   [Xl].   If that's the case, then why is it, that when I compress
the turns  together  on any tubing coil, the uh  goes WAY up ?

##  as  a  side note, that's  what F-12 uses on their infamous tornado drive,
to get their 80m rotary dipole's and  80m yagi's, from  ssb  band.. to the cw band,
and no rolling contacts, like in a roller inductor.  

Jim,

My question is to the fundamental accuracy of the MFJ vs. the effects on
calibration variation.  Is the MFJ really this inaccurate, or is the
accuracy in your case atypical.  It would be interesting if someone else
could do a controlled test with the MFJ vs. a lab type unit (well, a unit of
known capability).

##  IF  I use a MFJ-259  to tap a tank  coil, at say 4 uh... and the same tap shows
as 6 uh on my 875B,  now I have a discrepancy.  The  GM3SEK  PI  spreadsheet
will  depict values  for C1, L,  C2.   IF  the spread sheet  wants  4 uh, and XXX  for
C1.... and YYY  for C2..... and the mfj is used  to tap the  coil at 4uh.... then what happens
is the  C1 and C2 values [after tweaking for resonance on the standard test jig]  are  way on
the LOW side.    The coil is in reality 6 uh.. and not 4 uh !

##  Now if the 875 is used to tap the coil  to 4 uh, then both the C1  and C2  caps [ both
jennings ceramic vac caps]   come out  dead on  VS  the Pi spread sheet.   The point here is,
sure, there might be  variations in measuring uh on your favorite test gear, but  the  giveaway
is when the same coil is used in a tuned circuit, like a PI  net..... or in a LC network.  IF I use the
MFJ  to tweak the tubing coil  in the LC network, used  for  50 ohms in.. and  25 ohms out [ to handle
2 x 40m yagi's]  the LC network is a mile off.  [ caps used are paralleled  HT-50/58 doorknobs]...
and  ditto  with the  50 ohm in, 16.66 ohm  out  LC  network, [used  for  3 x 20m yagis].

##  I can't rely, or use the MFJ  to design any of these networks, it doesn't work, plane and simple !
I also used the B+K  875  to  wind the  tubing  coils used for making hairpins  for  the 160 vertical,
80m rotary dipole, 40m yagi, and 20m yagi.   When  I require precisely, a  say .8 uh  coil  for a hairpin
tubing coil,  I don't want  a ,9uh.. or a .6 uh..... none of which will work anyway.    I use  stokes  book to get
the tubing coil winding [L to diam ratio I'm using]  into the ballpark.   Then  tweak with the 875....  then install it,
then flat swr right off the bat.   Plan B is.. the  coil is compressed /expanded till  flat swr results.  Coil is then
measured on the  875... and it'  measured value is dead on VS   Bings  RF  software  network analyzer
spreadsheet I use to design  LC networks.    The hairpins also come out dead on.

Nothing more frustrating than tearing your hair out with a mfj, that flat out can't measure pf and uh.
I also bought the pair of  mating 'grid dip coils' for the mfj-259b.   Totally useless as  a grid dip meter.
I can't grid dip anything with them, even simple 10uh  coil and parallel  cap on the bench.... and neither
can any of my associates.   Even rauch sez they don't work....  so don't waste your money.

The  259 is a glorified swr meter, that's  handy on top of a tower.. and that's  about it.

Jim   VE7RF

I only have the AADE meter here in are the Fo there is variable; as well as
the MFJ.

73/jeff/ac0c

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1)Yeah, if you call 9.99 to  10.09 anything ! And then you DON'T even guess
how much stray inductance you added when you soldered it in with unknown
length pigtails!!

2) Rauch is right! That , when you hit series resonance, reactances add in
series opposing and cancel. that how you get a trap. The effect , though, is
pronounced only close to resonance.

3) when you compress a coil you increase the self inductance, but also the
self resonant frequency.

3) could you please explain to us munchkins what you mean by the last
statement?

Alex        4Z5KS

)Yeah, if you call 9.99 to  10.09 anything ! And then you DON'T even guess
how much stray inductance you added when you soldered it in with unknown
length pigtails!!

## Now u know why I never, EVERr use  wire  to connect caps, coils, or anything else.
##  it's always super wide cu strap... like  1-1.5" wide, or for tuned inputs, 3/8" wide.
##  If making a plate block assy, I'll use  AL plate on both sides of 6-9 x HT-57's.

##  If u don't like the stray L from say .01uf  disc caps.. I solder strap to the wire leads
dead center, down the middle.. and stray uh  drops to nil.

## If I do a temp hook up  with wire, say for tank coil temp taps,  then wire is
replaced with wide strap,  the tune and load caps  are outa whack.  If wire is
used for interconnecting relays on a remote ant switchbox, the Z is screwed
up.  It's  strap or nothing.  Braid doesn't work either.    we ran outa  strap
one night.. and used  some 1"  wide  tinned braid  for a tank coil tap.. and
it just abt exploded, sparks everywhere.  

2) Rauch is right! That , when you hit series resonance, reactances add in
series opposing and cancel. that how you get a trap. The effect , though, is
pronounced only close to resonance.

3) when you compress a coil you increase the self inductance, but also the
self resonant frequency.

3) could you please explain to us munchkins what you mean by the last
statement?

## exactly what it sez... the mfj 259 is a glorified swr meter.  Don't even
think abt using it to set taps on a tank coil, or winding coils  for  hairpins
LC networks  or anything else, ur wasting ur time with it.  Either that, or
both my  259's and all 4  of my friends 259's  are all out to lunch.  If u
want a real piece of  test gear.... buy something else.

Jim   VE7RF

Alex 4Z5KS

ORIGINAL MESSAGE:

REPLY:

I have to disagree on not using it to set taps on a tank coil. When
connected in reverse, i.e. connecting it to the output of a pi-net,
with a non-inductive resistor of the appropriate value from plate to
ground, it does an excellent job of helping you find the right tap.

For all the other purposes that MJF claims (grid-dipper, etc, etc) I
agree it's junk.

73, Bill W6WRT

ORIGINAL MESSAGE:

REPLY:

Simple. In an air core solenoid-wound coil, any given turn is coupled
tightest to adjacent turns, then less and less to each turn as you
move away from that turn. When you compress the coil, you increase the
coupling between all the turns. On a long, skinny coil, the turns at
the very ends barely "see" each other.

By comparison, when you add an iron core you are creating a magnetic
conductor, so to speak, that couples all the turns tightly to each
other. That's why an iron core increases inductance so dramatically.

73, Bill W6WRT

It's one of the greatest gadgets for setting an antenna tuner you'll
find.  Hooked in the line with a switch to select either the input to
the tuner, or 259 you can adjust the tuner of 52 ohms X=0, tune the amp
into a 50 ohm dummy load, switch amp to the tuner and you are set to go
without ever putting a signal on the air.

73

Roger (K8RI)

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And for tweaking antennas for best match; I use it to determine best
whip length on my Anttron HamWhips. But that's one of the things it was
designed to do, and so may not belong in this thread.

--
Mike Andrews, W5EGO
mikea*******
Tired old sysadmin

Date: Fri, 02 Apr 2010 09:53:35 -0700
From: "Bill, W6WRT" <dezrat1242*******>
Subject: Re: [Amps] LCR mteter.

On Fri, 2 Apr 2010 00:23:16 -0700, "Jim Thomson" <Jim.thom*******>
wrote:

>## Not a chance Bill.   Sure  Myself, and everybody else  does the
>same trick u do,,,, put a non inductive Resistor, between  anode and chassis
>and the put the MFJ  on the output, and activate the T/R  relays.
>
>## Tune and load caps  are then tweaked for  flat swr on the MFJ. This
>procedure alone, doesn't help  FINDING correct  coil  taps  one bit !
>EG:  I could easily have almost double the  uh  required  for say 40m....
>and simply REDUCE the tune + load cap values.. till  swr on mfj  reads 1:1.

REPLY:

You say "not a chance Bill" and then you say you do exactly what I do.
What do you mean by "not a chance Bill"?

###  I mean  I wouldn't use the MFJ  to measure the uh.. and
select taps based on uh readings  from any mfj, when  mfj used
to measure uh.

Second, when using the MFJ for this, the way I prefer is to preset the
tune cap for the value shown in the spreadsheets and then DO NOT TOUCH
it during the rest of the procedure. Adjust the load cap and change
the tap on the coil until you have the SWR 1:1. That way you end up
with the correct value of tune C and Q. Can't miss.

##  sure, this method works good too.   What  do u use  to measure the tune
cap ??     If the  mfj is used to measure the tune cap, you will be out to lunch.
If your AADE unit is used to measure the tune cap,  all is well.

##  I found that if  I measured the taps  with the b+K  875.. and tapped the coil
using the spread sheet results..... everything came out just fine.  When the Tune cap
was checked [ after resonating the  tune + load caps.. with mfj on the output]  after
the fact, it was dead on  VS  the  spreadsheet. [ or extremely close]    

Also, when pre-setting the tune cap, be sure to have the tube anode connected so
it's capacitance is included too.

##   agreed.   The tube C  will add another  33 pf on a 3CX-3000A7.  That tube
C  has already been factored in on the spread sheet.   When the spreadsheet  wants
say  270pf  for tune cap, it actually wants  303 pf..... but  33 pf  comes  from the  tube,
the C1  cap provides the balance...270pf.

If you are using a low frequency C-meter such as the AADE unit, disconnect the plate
choke lest it throw the C measurement off.

##  here I disagree.  The  effect of the plate choke is ALREADY factored in ..on the
spread sheet.   My 200 uh plate choke  will..'eat'  40  pf  from my Tune cap on 160m.
That effect can be seen right away, when plate choke removed.  With  choke removed,
the tune cap has to be REDUCED in value by exactly 40 pf.  Change the value of the
plate choke on the spread sheet, and you will see the effects on the value of the
tune cap asap.   Huge difference  between 20uh, 200 uh.. and 99999 uh. [ 160m]

##  to recap... the  tube adds  another  33 pf..... but the 200 uh plate choke  'eats'
40 pf.  [160m]   On the  higher bands, the  plate choke has a small effect.

##  if the LCR meter. or what ever u use.. is more accurate  measuring caps...  yes,
I would  tweak the tune cap with it [ including tube and plate choke].    Then use the same
lcr meter  to get the coil tap in the ballpark.  Then tweak the coil tap and load cap  to resonate.
I used to use a loaded Q of 12  [ = 10 using the old arrl/orr/eimac method.. which is just input
Q and not total Q] ,  I now use  a loaded  Q  of  8-10.  Eff improves, less coil  and band switch
heating, amp requires less adjustment, once tweaked at  14.200..... it's good from  14.100  to
14.300 .  Harmonic suppression  might drop a bit,  but the ant's are monobanders, and swr on
the 2nd harmonic is sky high.... or is not inside a ham band.  My 40 m yagi does not resonate
on either  20m or  15m.  I still use a LP filter.. with a 33 mhz  cut off.

later........ Jim   VE7RF    

73, Bill W6WRT

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You are not going to read anything with a low frequency C meter such as the
AADE, trying to measure the plate tune cap with the plate choke in the
circuit. The choke will look like a short at the low frequency.

The only way to measure plate tune C with the plate choke in circuit is to
use a C meter that does it "on frequency of interest". Otherwise you must
disconnect the plate choke.

73
Gary  K4FMX

ORIGINAL MESSAGE:

REPLY:

I use the AADE.

73, Bill W6WRT

ORIGINAL MESSAGE:

REPLY:

Good enough.

73, Bill W6WRT

ORIGINAL MESSAGE:

REPLY:

If you are using a low frequency C meter, the plate choke will be
pretty close to a short and will not contribute the reactance it will
at the operating frequency. If you are doing the procedure at the
operating frequency, no problem. In fact, better.

73, Bill W6WRT

Date: Sat, 03 Apr 2010 14:42:16 -0700
From: "Bill, W6WRT" <dezrat1242*******>
Subject: Re: [Amps] LCR Meter

On Sat, 3 Apr 2010 06:02:15 -0700, "Jim Thomson" <Jim.thom*******>
wrote:

>
> If you are using a low frequency C-meter such as the AADE unit, disconnect the plate
>choke lest it throw the C measurement off.
>
>##  here I disagree.  The  effect of the plate choke is ALREADY factored in ..on the
>spread sheet.   My 200 uh plate choke  will..'eat'  40  pf  from my Tune cap on 160m.
>That effect can be seen right away, when plate choke removed.  With  choke removed,
>the tune cap has to be REDUCED in value by exactly 40 pf.  Change the value of the
>plate choke on the spread sheet, and you will see the effects on the value of the
>tune cap asap.   Huge difference  between 20uh, 200 uh.. and 99999 uh. [ 160m]

REPLY:

If you are using a low frequency C meter, the plate choke will be
pretty close to a short and will not contribute the reactance it will
at the operating frequency. If you are doing the procedure at the
operating frequency, no problem. In fact, better.

73, Bill W6WRT

##  Both the  875A  and  875B     operate  at  1 khz  square wave.  What freq does the
AADE operate at ??     I rechecked my notes  from yrs ago... and don't know if the  choke
was in the circuit or not.[ when measuring tune cap C.. after the fact].     I do know  that
when the mfj in rvs test was done... that I chassis grnded the cold end of the plate choke.
IE: bypass capS  at base of plate choke was shorted out.

## The notes say, that with choke removed... and mfj in rvs test was conducted, that everything
resonated  just fine.  LCR meter  used to tap the coils initially.   When  plate choke was  added back
into the circuit, the TUNE  C  had to be INCREASED  by 40 pf.  [160m only] ..and 10 pf on 80m.

##  with choke removed,  and tune C  checked.[ tune re-tweaked 1st].. it was 40 pf LESS  than
spread sheet depicted,which is normal,  since the choke... 'eats  40 pf '  on  160m.   So as long as
u know what the effect of the choke is on 160 + 80m... u are ok.. and can factor it in.   That's  easy
to do... just toggle between  200 uh [what ever ur choke is].... and  9999 uh.    Then u can see the effect
of the choke right away... and can compensate any tune C  readings....  with choke removed from circuit.  

##  here's  one thing u  can't  do with the newer  875-B.. and that's  try and  measure the dc resistance
of the primary /sec of any plate xfmr.    The 875-B  measures  ac resistance.. and also  fires a tone out at
1 khz  square wave.   The plate xfmr now thinks its' an audio xfmr.... and flat out  won't pass a 1 khz square wave.
The  ac resistance  measurement does work  superb on hv lytics  though.

later.......... Jim   VE7RF

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ORIGINAL MESSAGE:

REPLY:

The AADE changes frequency automatically depending on the value being
measured, but I think the max is 100 kHz. If this is incorrect,
someone please correct me.

The nifty part about doing this procedure is that when the RF choke
"eats" some C, it really doesn't matter as long as you have enough
spare C in the tune cap. When you re-connect the RF choke and re-tune
the tune cap, you end up with exactly the same net value of C anyway.

73, Bill W6WRT

The link was published here a few days ago but here it is again http://www.cliftonlaboratories.com/aade_l_c_iib_meter_review[..]  and in
the 3rd paragraph is a button to download a pdf file of the review.  
Page 13 of the review has a detailed graph of test frequency vs
capacitance or inductance.  The highest test freq. is about 750KHz and
the lowest is about 10KHz.

Larry Benko,. W0QE

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Date: Sun, 04 Apr 2010 07:42:21 -0600
From: Larry Benko <xxw0qe*******>
Subject: Re: [Amps] LCR Meter

Jack, K8ZOA wrote a very in depth review of the AADE L/C IIB recently.  
The link was published here a few days ago but here it is again http://www.cliftonlaboratories.com/aade_l_c_iib_meter_review[..]  and in
the 3rd paragraph is a button to download a pdf file of the review.  
Page 13 of the review has a detailed graph of test frequency vs
capacitance or inductance.  The highest test freq. is about 750KHz and
the lowest is about 10KHz.

Larry Benko,. W0QE

##  here's  what it WON'T  do... which sucks.  It won't measure  caps  bigger
than 1.5 uf.    It won't measure polarized caps.. like lytics.   It won't measure
'D'  of caps.    It won't measure higher than 1.5 Milli Henry.  It doesn't have
spring loaded slots  to get rid of excess L and C.     It won't measure  resistance
at all....so it's not really a LCR meter... but a LC meter.

##  it's good for small value coils and caps, for amp building, and that's good.
Not being able to measure chokes up to 200 Henries, or polarized lytics up to
20,000uf  really stings.  And ditto,not being able to measure resistance  down
to .001 ohm.  Not being able to measure 'D'  of caps is another negative.

##  Once in a while I have to be able to measure  chokes up to 5 Henries.
I measure Hv  lytics  all the time.   For the small diff in price  between the
AADE  unit.. and a new  B+K  875B, I really don't think you are saving a great deal.
With the AADE unit,   I'd have to buy more test gear,  to measure chokes and hv lytics.
Even my fluke 87  won't read down to .001 ohm.  The  AADE  won't measure resistance
at all, but that's not it's  pri function.

Later.... Jim   VE7RF
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