It would be awesome if someone with the proper equipment would invest some time
to build and test a choke with material 52.
Rudy N2WQ
From: Jeff AC0C <keepwalking188@ac0c.com>
To: towertalk@contesting.com
Sent: Monday, July 4, 2016 3:01 PM
Subject: Re: [TowerTalk] Fair rite materials for choke baluns
The G3 data on the type 52 looks pretty good. It sure seems like a side by
side bench test of the two materials would prove to be very interesting.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Jim Brown
Sent: Monday, July 04, 2016 12:02 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Fair rite materials for choke baluns
On Sun,7/3/2016 11:08 PM, Jim Thomson wrote:
> ## Ok, Im lost. I thought we wanted Z > RS > XS .
> Put another way, RS ideally should be the same as Z... or as close as
> you can get to Z. And RS should definitely be > than XS.
>
> What is RP ??
You really are resistant to studying what I've written. :)
Rp is the resistance in the parallel (RLC) equivalent circuit of the
choke. Rp is the Z at resonance (the peak value), L is the value
computed from Z at frequencies below about half of the resonant
frequency, C is the capacitance that resonates with L. This is nothing
more than the classic curve-fitting that I learned in EE classes in
college 50+ years ago.
I put my measured Z data (magnitude only) into a spreadsheet (I use an
ancient version of Quattro Pro because it is FAR better at producing
engineering plots of data than Excel), and plot that measured data on a
log-scaled graph of Z vs log-scaled of frequency. On another page of the
spreadsheet, I compute and plot the equation for parallel resonance, and
tweak the values of R, L, and C that most closely fits the measured data.
The parallel equivalent circuit is important for at least two reasons.
First, it helps us understand the choke as a component -- as hams, we
understand that any coil has stray R and C, and it will resonate. We
also know that we put a coil into a circuit, resonate it with C, and
control the resonance by the number of turns and by squeezing or
spreading turns to control both L and stray C.
Second, knowing the values for parallel R, L, and C, we can insert them
into an NEC model of our antenna system and find the common mode current
and the common mode power dissipated in the choke (by setting power in
to model to the TX output power).
73, Jim K9YC
On Sun,7/3/2016 11:20 PM, Jim Thomson wrote:
> ## Ok, so the type 31 2.4 core we should be using for CM chokes is the
> toroid controlled for impedance... PN 2643803802 ??
In Fair-Rite's part numbering system, the 26 indicates a cylindrical
core (NOT a clamp-on) controlled for impedance, the following two
digits 43 indicates #43 material, and the remaining digits indicate the
physical dimensions (I haven't figured out that code). So a #31
material in a cylindrical shape would have a part number that begins
with 2631.
> ## Good thing u mentioned the type 31 core comes in 2 x versions. I
> wonder
> how many folks have ordered the wrong part number in error ?
#31 material is NOT sold in two versions -- it's designed ONLY for
suppression.
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