[AMRadio] How to ID a swinging choke?

John Coleman jc at pctechref.com
Sat Dec 8 18:14:05 EST 2007

Yep, I see your dilemma Carl, Maybe I am wrong but I don't think there is
any difference other than the amount of magnetic gap.  

Sorry about my ramblings, HIHI  

Perhaps if the inductance, as measured with a bridge measuring device, shows
to be quite high for the chokes physical size, this might be a clue that it
is a swinger.  I measure inductance of unknown chokes by placing a variable
resistance in series with the choke.  Then placing the circuit across a 12
Volt XFMR or some other low voltage source, I adjust the resistance until
the voltage drop across the inductor and the resistor are equal.  The value
of the resistor is then measured and this is the inductive reactance of the
choke at 60HZ.  The actual inductance in Henrys can then be calculated.
Where H = R/376.8 (formula good for 60HZ only)

John, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of jeremy-ca
Sent: Saturday, December 08, 2007 3:54 PM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] How to ID a swinging choke?

John, the theory is explained in detail in a series of articles in 1932 
QST's. It even includes an elaborate test setup with AC and DC voltage and 
current meters ( 7 in all) and discussions on setting the gap for different 

At this point all I wanted was a way to tell the two types apart and a very 
simple test setup.

Im afraid it wont be that easy although the reply earlier and yours gives me

a few ideas.

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