[Amps] LCR Meter

[Jim Thomson]

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

On Sat, 3 Apr 2010 06:02:15 -0700, "Jim Thomson" <Jim.thom at telus.net>
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