Testimonials and Comments
About the W3NQN CW Filter

Steve - K0SR, DXCC Honor Roll
I still use my w3nqn filter almost daily.

Rich - K7SZ
One thing I noticed is the lack of background hiss that is prevalent in active AF filters. Ed's filter is quiet. Another thing I noticed is the "mellow" sound of this filter. It is definitely easy on the ears.

Ken - WB2ART
When I hooked it up to my Kenwood TS-570D(g), the background noise almost disappeared. When you hear a signal of interest, switch it in. The signal will stand out and all you hear is that signal. It is remarkable.

Dick - AA6EZ
...DSP drastically alters the audio waveform which I really don't care for. That seems to be one of the drawbacks of DSP. I tend to be somewhat of a purist when it comes to audio quality. The W3NQN passive audio cw filter wins my vote, hands down, for good audio quality. The sharp selectivity does alter the audio path slightly, wow, no ringing either, however when you give just a touch more audio gain the sound is great. If there is insertion loss, and I suspect there is, it isn't a factor. With careful manipulation of the RF and AF gain controls, and switching in the filter, I am able to copy signals that are practically buried in the noise. The analog brain is a wonderful filter in its own right !!

Theo - PA3GHJ
Because I’m a fan of CW operation and live in a noisy suburban area in the western part of the Netherlands I’m always looking for ways to filter out noise and QRM when listening to CW signals.

The kit was received only a couple of days after ordering and assembling the filter proved very easy since Ed made a very clear step by step assembly manual and all parts were clearly marked.

The filter was build in a couple of hours, most time was needed for the glue to dry.

On the first try was the filter successful, I hooked up an old FT 200 rig and was surprised with the result; clear CW signals without noise or ringing. Then I tried my FT 2K and there the same effect is present, the filter removes the annoying audio hiss coming from the sets audio amp that is very present with high quality headphones and for me it sounds better than the digital audio filtering in the set itself. I also tried the filter with my 2N 22 XX Norcal QRP TRX for 40M, there the effect was very good; a pity though that the filter weighs more than the QRP rig itself!

Marty - W4MBW
73's Ed....
I tried several different, both current and vintage, "active" type audio filters and found them to be uncomfortable to listen to due to ringing and distortion on strong signals. I have a Ten Tec Jupiter with the 150 Hz DSP filters and was skeptical if Ed's "passive" 250 Hz filter would even help copy weak CW. But his very reasonable price was worth trying.

Wow, was I ever surprised! I tried it on a weak 40 CW signal and as soon as I switched the filter into my headphone circuit the code almost seemed to jump out of the background and was much clearer to copy...Also absent was a lot of background atmospheric hiss, even with my DSP filters, and there is absolutely no ringing. Very pleasant to listen to. With strong signals the CW was clear with no distortion. Strong nearby signals 200 Hz away were noticeably diminished and signals 500 Hz away disappeared entirely. The skirts appear to be very steep but in the bandpass it is easy to tune in signals.

Ed's instructions are also extremely well written and clear. The assembly took me about 4 hours and Ed's drawings and schematics were very easy to understand. The filter worked perfectly the first time.

Great job Ed....thank you! Marty W4MBW

Craig - AC0WQ
Testimonial Sept. 16, 2011
I am so impressed with this filter! I installed it in a Lowe SP-150 Audio Processor that is the companion to the Lowe HF-150 general coverage receiver (made in the UK). I use these two with my 6 band homebrew QRP transmitter. The audio quality is outstanding! I pay a lot of attention to audio quality having spent most of my life in professional audio applications (AM/FM broadcast engineering and recording studios). What I hear is the lack of ringing and the harshness you always hear with narrow bandwidth crystal filters. The purity of tone cuts through the noise when the signal is fading down to the noise floor. The leading edge of each dit and dah is well defined and not smeared like you find with the "expensive" filters! It is a pleasure to listen to.

In addition to the Lowe/ W3NQN CW Filter combination (the Lowe HF150 also has excellent audio), I use a companion 3 inch pvc pipe speaker where the speaker is mounted on the back side and the length of the pvc pipe has been precisely cut to resonate at the same frequency of the CW filter (600 Hz). The combination of the filter and pipe speaker makes the signals jump out "in your face" when you hit that sweet spot of 600 Hz. Any signals above or below 600 Hz just disappear. I might add that the filter is switched in at the input of the audio power amplifier that drives the pvc pipe speaker. If you pay attention to good audio, this is a welcome tool for good sounding CW.
Craig AC0WQ

Steve - W7SRM
I could not be more delighted in your filter. I am running it with my Ten Tec Omni 7. I am cw only and use headphones about 99% of the time. The Ten Tec rig has both the 500 and 300 hz Collins filters installed and a great dsp. Its the best rig I have owned in 21 years of being a ham. Your filter makes it better. Even with the 300 hz filter engaged and the dsp cranked down to 200 hz I see a benefit with your filter. It takes that band roar background away. I find I am setting the rig a tad wider at about 400 hz and then using your filter. That way I keep the audio more alive and less digital.

The kit was easy to build - just point to point wiring essentially. I followed your directions and the ones linked to from your site by AK3W. Having just gone through cataract surgery I used the computer to zoom in on the diagrams to be sure I was seeing correctly. One other hint is that after cutting off every other wire on the inductor stack I used a fine tip sharpie pen to draw the connections between terminals. That really helped to keep it all straight. I may change the input to the back end of the box from the switch due to my shack set up, but for now I too busy using the filter.
73
Steve Miller W7SRM

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