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Reviews Categories | Filters, RF: bandpass, duplexer, lowpass, highpass, RFI/EMI | Alden McDuffie CW filter Help

Reviews Summary for Alden McDuffie CW filter
Alden McDuffie CW filter Reviews: 1 Average rating: 5.0/5 MSRP: $62.90 kit; $72.90 assembled
Description: A 500 Hz outboard filter powered by internal 9-volt battery or external 12-volt supply.
Product is in production.
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KC0MAX Rating: 5/5 Dec 19, 2004 20:38 Send this review to a friend
Fun and useful kit  Time owned: 3 to 6 months
The Alden McDuffie 500 Hz CW outboard filter goes between the radio and your headphones and does a great job, at about half the price of the Icom CW filters. It is a great companion to radios such as the Icom 703 and works very well, particularly with use of the 703's IF shift. It also has the advantage of being able to be used with other radios, and is particularly suited for field use, because it is powered by an internal 9-volt battery (or 13.8 volt external supply). The filter is an 8-pole Chebyshev, 500 Hz bandwidth, centered at 750 Hz. The battery draws just 10 ma with no signal, and ~ 12 ma with average signal. There is also an audio pass-through.

The filter does a great job of filtering out noise and competing signals. My experience has been that peak audio response on this filter is around 850 or 900 Hz. Also, the audio output is mono, so a pair of headphones that has a mono/stereo switch and perhaps a volume control will enhance one's listening enjoyment. I found that the very inexpensive Coby DV-130 phones, which have both of these features, is an outstanding value at less than $6 at Big Lots.

While many argue that outboard filters do not compare to IF filters, the AM filter is certainly convenient, and I use it every day. I also have friends who have had good luck with it. The kit takes about an hour or so to build, the manual is clear, and the case is well-made and very professional. The filter was designed by Phil Anderson, W0XI, who does terrific work and provides outstanding support. This was the first Alden McDuffie kit I built, and I have ordered several more since. The manual for the filter and other AM products is available for download from the Alden McDuffie website.


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