Date: Sat, 03 Apr 2010 14:42:16 -0700
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
Subject: Re: [Amps] LCR Meter
On Sat, 3 Apr 2010 06:02:15 -0700, "Jim Thomson" <Jim.thom@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
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