[Amps] Measuring tank coil inductance

[Bill Turner]

ORIGINAL MESSAGE (may be snipped): 
On Thu, 25 Apr 2013 20:04:11 -0700, VE7RF wrote:

>
>##  whoa.  A typ 90 uh plate choke on a  80-10m amp will  eat 10 pf  from the C1 tune cap on 80m..
>A typ 180 uh plate choke will eat 40 pf  from the C1 tune cap on 160m band. 

REPLY: 
Whoa yourself.

My comment to disconnect the plate choke was IF YOU ARE USING THE AADE UNIT
to measure in-circuit capacitance. Why? The AADE unit uses a very low
frequency relative to the tank operating frequency, and the plate choke is
almost a dead short down there. As a result, you will be measuring right
through the choke, which will include the bypass cap at the base of the
choke and on into the power supply. 

In contrast, when you are using the MFJ SWR analyzer, you are measuring AT
THE OPERATING FREQUENCY and so the plate choke should remain in circuit. 

Electronics 101. 

Bill, W6WRT