Audio filter for CW

[Dave Edwards]

Mike....I think the audio response is typical for Heath. My SB301, and SB303 
are also lacking in low frequency response. As I recall...so was the SB102 
and HW101.
Perhaps someone else can chime in, but I think that is the way the rig is 
designed.
...Dave
----- Original Message ----- 
From: "Michael Waldrop" <w5rkl at YAHOO.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Sunday, September 24, 2006 9:56 PM
Subject: Audio filter for CW


> Hello everyone,
>
> I work alot of CW using either an SB-300 or SB-303 receiver. Although the 
> Heath CW filter does a good job, the audio output to either a speaker or 
> headphones is a bit high in frequency for my taste.
>
> The idea of using an outboard filter came about while looking for an 
> alternative to the Heath filters. The cost for a replacement IF CW filter 
> was $100 or more.
>
> The filter is built around the popular LM-741 op amp in a high Q bandpass 
> configuration  Using the High Q bandpass configuration, the filter is 
> capable of providing an adjustable resonate frequency between 50Hz to 1KHz 
> with an overall bandwidth of 500Hz, perfect for CW work. The filter runs 
> on a single supply, a 9 volt battery, and draws no more than 3.5ma. I 
> tested the filter using a dual supply but I could not see any difference 
> in performance between single versus dual supplies. The battery supply 
> eliminates the need for a seperate power supply.
>
> A great cost savings that provides great filtering for CW work.
>
> 73's,
>
> Mike
> W5RKL
>
>
>
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