[Boatanchors] QEX Dec 1988 Article

[hwhall at compuserve.com]

Re: making your own. There are also "cup cores" with plastic bobbins you can chuck into a drillmotor or other winding device. Far easier than shoving wire through a toroid. Though I admit I don't know what cores you'd want to choose for the same or better operation as the traditional telco 88mH coils.
Pic of what I'm talking about:
https://www.picclickimg.com/d/l400/pict/261585024927_/Pot-Core-18x11-Bobbin-2x-Set-Kit.jpg
Wayne
WB4OGM
-----Original Message-----
From: McDonald, J Douglas <jdmcdona at illinois.edu>
Cc: boatanchors at mailman.qth.net <boatanchors at mailman.qth.net>
Sent: Sun, Jul 12, 2020 9:33 am
Subject: Re: [Boatanchors] QEX Dec 1988 Article

...  It’s
too bad that 88/44/22 mH coils have become so seemingly scarce. ...

Its not hard to make your own, if you don't mind them being
a bit larger than the originals.  The large toroid cores are readily available
and being large, require fewer turns, and make it easier to get the bobbin through.

I can look up the specs of the cores I used. They are expensive but cheaper
than ePay prices for the old original these days.

I've made medium impedance (500-5000 ohms) audio filters
with excellent response for CW with these, similar to the audio filter
in the R-390A, and used them with good effect with my SX-88,
NC-400, and BC-453.

I tried cores the size of the original 88 mH ones and gave up from bobbin frustration.

Doug McDonald
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