Hi Tod!
Thanks for the data.
I'd like to build up several toroid chokes for 160, 80 and 40 meter use.
I looked at the Fair-Rite site, no 31 material.
I looked at their vendors and went to Amidon
...amidoncorp.com/items/19
Amidon does have "F Material Ferrite Toroids"
" High Saturation flux density at high temperature.
For power conversion transfomers.
Good noise suppression from 0.5 to 20 MHz."
They offer an "F material" core:
FT-240-FC ( $20.00 ea )
Inner Diameter 1.4
Outer Diameter 2.4
Height 0.5
Al Value 4107
Is this material suitable or am I barking up the wrong tree?
73
Lloyd - N9LB
-------- Begin forwarded message --------
Subject: Topband Digest, Vol 104, Issue 21
Date: 8/29/11 2:00:40 PM
From: topband-request@contesting.com
To: topband@contesting.com
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Today's Topics:
1. Fabricated common mode chokes and their impedances (Tod)
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Message: 1
Date: Sun, 28 Aug 2011 16:51:14 -0600
From: "Tod" <tod@k0to.us>
Subject: Topband: Fabricated common mode chokes and their impedances
To: <topband@contesting.com>, <towertalk@contesting.com>
Message-ID: <0E6261DE04D24FDDA95DBC885D2CE12F@g2>
Content-Type: text/plain; charset="us-ascii"
This probably has a limited audience but I do know that there are some
readers on this list interested in fabrication of high impedance common
mode
chokes for their stations.
I built and measured 18 of this type of choke during the past week.
There is
a write-up on my web site which shows how they were fabricated, how they
were measured and the measurement results. I used Fair-Rite 2.4 inch
diameter type 31 toroidal cores and small diameter [RG 59 size} coax. I
measured the magnitude of the impedance for each of the chokes on the
160,
80, 40, 20, 15 and 10 meter bands. There are also attenuation values for
each choke [specific to the 50 ohm measurement circuit]. The results are
shown as a series of graphs for two cores, three cores and four cores
with
3, 4, 5, 6, 7 and 8 turns on the core bundle.
These graphs should provide guidance to those fabricating their own
common
mode chokes.
The site is
http://www.k0to.us/HAM/ham.htm
The article is under Experiments & Measurements
"Measurement of Chokes made using type 31 material cores"
My work is an extension of material found in the excellent paper on this
subject written by Jim Brown, K9YC, which has been mentioned here
before.
Tod Olson, K0TO
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