I was looking through a book I bought about 15 years ago that was a
compilation of QST reviews called "The Arrl Radio Buyer's Sourcebook".
In it is a copy of the review for the 544. There really was not much
to say about it, and the review as published in the book, had a full
schematic of the audio filter and a discussion of components used to
If you have access to the QST review, it would pay to read it. If the
review is different than the one in the book, let me know and I can
send you a copy.
BTW, it was a simple 4 stage active audio filter, using IC's common 20
years ago. Almost anything similar would do. For example I used to
have an MFJ 9020 QRP transceiver with a plug in audio filter. If you
can get one from MFJ, it would be IMHO a suitable replacement.
The TenTec filter had 4 bandwiths, the MFJ has one, but the 544 only
used the last, i.e. all four cascaded.
Geoffrey S. Mendelson, N3OWJ/4X1GM
To help restaurants, as part of the "stimulus package", everyone must
order dessert. As part of the socialized health plan, you are
forbidden to eat it. :-)
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