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Reviews Categories | Filters, Audio: (DSP and others) | W3NQN Passive Audio Filter Help


Reviews Summary for W3NQN Passive Audio Filter
Reviews: 35 Average rating: 4.9/5 MSRP: $70 USD $75 Cdn $90. overseas
Description: Passive audio bandpass filter for CW Ed.W3NQN@comcast.net
Product is not in production.
More info: http://W3nqn.com
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K5SBR Rating: 5/5 Jan 25, 2015 22:40 Send this review to a friend
Terrific device  Time owned: 0 to 3 months
Ed's latest passive filter is terrific. 200 hz. bandwidth centered on 600 hz. Knocks out all the DSP "artifacts", QRM, etc. and leaves nice clean CW. No ringing. No batteries required. It just works. Since the in/out is 8 ohms, it may be used with a speaker, too.
 
WC3N Rating: 5/5 Dec 10, 2014 09:45 Send this review to a friend
An excellent product!  Time owned: 0 to 3 months
This review is for the passive LC 600-Hz CW filter. This filter was designed by Jim Tonne, W4ENE, to provide an Arithmetical Symmetry response for optimum reception of CW signals while using only four surplus potted toroidal inductors.

I wanted a better CW filtering option on my 2 older rigs, an Icom 751a and an Yaesu FT 990. The Yaesu FT 990 has DSP filtering but I was never happy with the hollow ringing sound it produces. I found it very fatiguing listening to this for any period of time. I had never heard of a passive CW filter before. But I must say it is very impressive. This filter works. It minimizes both the noise and distortion that I hear when using the DSP filter. It is much more enjoyable listening to CW using the passive filter and the fatigue factor is greatly reduced. I was using a Radio Sport headset which I can switch from stereo to mono. When using the filter you need to be in a mono headset.

On the Icom 751a it was equally impressive. I love switching into the CW mode and after switching on the passive filter just to get rid of the noise and start hearing clean, crisp CW signals. It really does reduce the fatigue factor. Anyone having an older radio with or without DSP and who loves CW should seriously consider this filter.

This unit comes with an internal 1K potentiometer to equalize the audio headset levels. If your receiver needs an adjustment just remove the cover and turn the pot shaft with the filter either in or out.

Ed, W3NQN, does the assembly work and I contacted him directly via email. It is a very well assembled product. From start to finish his service was top notch.
 
HS0ZFQ Rating: 5/5 Oct 19, 2014 05:45 Send this review to a friend
best purchase ever made  Time owned: 0 to 3 months
I live in Thailand and ordered the kit from Ed
Wetherhold.I took it down to my radio man in Chiangrai with misgivings.After two weeks I was getting ready to take it to another guy when lo and behold he had finished it.I waited until the Worked All Germany contest this weekend and installed it between my headphones and my trusty Kenwood TS-830S which has never seen a filter.I found three stations close together and then turned the filter on. When I turned the dial on my rig it was like being in a tunnel with just one signal coming at me.I did not hear anybody on the sides. It was just plain incredible.Later that night I picked up a weak KP4CPC in Puerto Rico ( I had never heard Puerto Rico ) in ten years in Thailand.That did it. I needed to tell some people to quit wasting their money on expensive contraptions and just try the passive audio filter by Jim
Tonne and assembled by Ed Wetherhold. They won't be disappointed.
Richard
HS0ZFQ

 
WA2DFP Rating: 5/5 Oct 5, 2014 05:29 Send this review to a friend
Outstanding with CW Skimmer  Time owned: 0 to 3 months
I like to use CW Skimmer software to monitor a 2 kHz pass band; but, I don't like to listen to all of the output. Placing the W3NQN filter between the transceiver and the speaker allows me to have it both ways - I see the whole 2 kHz on my computer screen, and hear only the 600 Hz note of the CW station I am copying. The output tone is clear, a real listening pleasure. I couldn't be more pleased with it. Other filters I tried, one active and one a simpler passive design (no input and output impedance transformers), did not produce the pure tones of this device.
 
W9FR Rating: 5/5 Sep 8, 2014 08:43 Send this review to a friend
Fantastic filter  Time owned: 0 to 3 months
I recently evaluated and purchased a W3NQN 200 Hz audio bandpass filter using four potted inductors. This is the Jim Tonne, W4ENE, arithmetrical symmetry 600 Hz filter design.

The filter provides excellent rejection of band noise and adjacent signals. It dramatically improved the cw response of my IC756 pro 2 DSP based filtering. In all cases, it was not necessary to use the narrow DSP filter with its watery sound and ringing. I could leave the radio at 850 or 500Hz and switching in the passive filter would completely eliminate the background noise and only allow great clean reception of cw.
signals.

In the recent NA cw contest with strong signals on my non DSP IC737A. the passive filter would eliminate all of the signals that were present within the 500Hz crystal filter but outside of the 200 Hz audio filter bandwidth. Reception was fantastic with the background noise totally eliminated. Switching back and forth between the filter and radio clearly showed the elimination of signals that were within the 500 Hz crystal filter but were more than 200 Hz away.

In my non DSP based K2/100, the passive filter eliminated the hiss from the 700/400/200 filters when selected. It made the normally quiet K2/100 a real dream machine.

I also evaluated the filter at QRQ speeds at 70 wpm. While softening up the rise and fall times, it still allowed perfect copy without any ringing.

I highly recomment this filter and I should have purchased one of the Ed Wetherhold passive filters years ago.

Noel, W9FR
 
W7BGO Rating: 5/5 Jul 29, 2014 19:59 Send this review to a friend
Excellent filter  Time owned: 0 to 3 months
A good CW filter is an essential tool to any amateur radio station. The standard 500-Hz CW filter found in most rigs doesn’t have the selectivity to operate under difficult conditions when DX’ing amidst DX pileups or Field Day where the CW portion of the band can be wall to wall signals, a bandwidth closer to 250 Hz is required.

A nice complement to the standard 500-Hz IF filter is an outboard audio filter. Nearly all available designs are active, using IC’s, transistors and DC power. These introduce noise or hiss and often distortion of some type to a degree. A new CW filter designed by Jim Tonne, W4ENE is in a different class by itself as it is passive. No power supply, or IC’s are required. Just plug your headphones or earbuds in and go. Since it is passive there is no added noise or hiss.

I used the Tonne passive 4-resonator CW filter along with W3NQN Ed Wetherhold’s passive 5-resonator CW filter featured in QST, CQ, Rad Com and many issues of the ARRL Handbook during the 2014 Field Day. I have always considered W3NQN’s filter the “gold standard” in passive designs. This is a superb filter that was available for 30 years but unfortunately is unavailable. The source of surplus toroids from old analog telephone equipment has dried up. I was glad to hear Jim Tonne’s design also uses surplus telephone toroids (a different value) but in a novel new approach called “arithmetical symmetry attenuation” The end result is excellent.

Both filters are centered at 600 Hz and both exhibit a high degree of sideband attenuation. The measured insertion loss and measured -6 dB bandwidth of 265 Hz were identical. There was nearly no difference between the two filters in the high frequency response where the measured attenuation was 40 to 70 dB between 1 kHz and 1.5 kHz. However, the low frequency response does show a difference where W4ENE Jim Tonne’s filter attenuation measured 18 to 35 dB between 350 Hz to 200 Hz and W3NQN’s filter attenuation measured 35 to 70 dB between the same frequencies. The difference was noticeable during Field Day where the interfering signal was a couple hundred Hz lower. Switching to W3NQN’s filter made a noticeable difference.

I have owned several active CW filters over the years using both Hi-Q opamp circuitry and SCAF (Switched Capacitor Audio Filter) designs. One thing I have noticed, is that when they are adjusted to the same bandwidth or Hi-Q setting as the passive filters they often exhibit a ringing/hollow sound when listening to the background noise. The passive filters are cleaner as the background noise sounds more natural. The passive filters in general exhibit the best ultimate attenuation often exceeding 70 dB. A popular SCAF CW filter currently being sold has an ultimate rejection of just over 50 dB when measured at the 200-Hz and 1.5-kHz points. When comparing the sound quality of a passive filter to a 250 Hz crystal filter, the passive filter doesn’t exhibit the harshness of sound. There is less listening fatigue using a passive filter.

I really enjoy using these passive filters. I found it absolutely essential to use a filter like Jim’s during Field Day. The 20m CW band was mayhem and the 265 Hz bandwidth allowed QSO copy that otherwise would have been impossible.
If you enjoy good CW audio and need an extra boost to capture that elusive signal, you might consider a passive CW filter like W4ENE Jim Tonne’s. You won’t be disappointed!

W3NQN will offer the filter components for this Passive 600-Hz CW Filter in the form of two options:
a. Kit Form. The four matched potted inductors will include the schematic and pictorial diagrams, a Bill of Materials giving a distributor stock number. Cost is $15 postpaid for the USA and $20 for Canada and Europe.
b. Assembled filter with a 600-Hz center frequency. $70 postpaid for the USA.
c. For details please send an email to: Ed Wetherhold ed.w3nqn@comcast.net
 
VE7HS Rating: 5/5 Jul 24, 2014 11:36 Send this review to a friend
Works very well!  Time owned: 0 to 3 months
Some time ago, Ed sent us a passive 600 Hz audio CW filter that we evaluated - first at the VE7NA Club Station, where we tried it with three different transceivers, including a Kenwood TS590, a Yaesu FT897D, and a Yaesu FT101Z, and then during our Field Day operation. All those who used the filter have been very pleased - sharp bandwidth, an noticeable lack of noise and hiss, just signals popping out of the noise. The lack of hiss and noise makes it quite comfortable to copy even for long periods of time.

The 600-Hz center frequency filter consists of four potted inductors having an arithmetically symmetrical response in a design by Jim Tonne, W4ENE. This attenuation response is intended to optimize the clarity of CW signals because of its superior envelope delay as compared to the more common Cauer and Chebyshev responses. Bandwidth of the filter is 200 Hz.

When we first began to use the filter, all that was required to equalize the sound level whether the filter was in or out was a small adjustment of a variable resistor. The quality of sound was also impressive, especially on strong signals, with no distortion noticed.

And because it's a passive filter, we didn't need to find a power supply, either - just plug it into the audio jack and turn it on, with the headphones plugged into the filter.

If you want your own filter, for $15 US, Ed will mail four matched potted inductors having the two internal toroidal windings wired in series-aiding to provide an inductance of 70 to 80 mH, including a pictorial diagram showing the filter wiring with a listing of the capacitor values, a schematic diagram of the filter, and a bill of materials with recommended distributors and stock numbers so any interested user can conveniently obtain the necessary parts; or for $80 US, Ed will provide, postpaid, a fully assembled and tested 600-Hz center-frequency filter to any US or Canadian hams interested  in obtaining an assembled filter. The filter is intended for a mono-two-wire headset.

After Field Day, I put the filter in my own shack, where I got similar results with my old TS-820S which came with a 500Hz CW filter. Filter out, noise and signals, filter in, just signals. I'm very pleased with this filter, and it will be a mainstay in my radio room for years to come.

Bob Smits, VE7HS
 
VE7HS Rating: 5/5 Jul 8, 2014 15:59 Send this review to a friend
Works very well!  Time owned: 0 to 3 months
Some time ago, Ed sent us a passive audio CW filter that we evaluated - first at the VE7NA Club Station, where we tried it with three different transceivers, including a Kenwood TS590, a Yaesu FT897D, and a Yaesu FT101Z, and then during our Field Day operation.

All those who used the filter have been very pleased - sharp bandwidth, an noticeable lack of noise and hiss, just signals popping out of the noise. The lack of hiss and noise makes it quite comfortable to copy even for long periods of time.

When we first began to use the filter, all that was required to equalize the sound level whether the filter was in or out was a small adjustment of a variable resistor.

The quality of sound was also impressive, especially on strong signals, with no distortion noticed.

And because it's a passive filter, we didn't need to find a power supply, either - just plug it into the audio jack and turn it on, with the headphones plugged into the filter.

In the tradition of ham radio, you get this as a kit, with all the parts including the case. No running around trying to find all the bits, it's all there.

After Field Day, I put the filter in my own shack, where I got similar results with my old TS-820S which came with a 500Hz CW filter. Filter out, noise and signals, filter in, just signals.

I'm very pleased with this filter, and it will be a mainstay in my radio room for years to come.

Bob Smits, VE7HS
 
KA5QQA Rating: 5/5 May 3, 2014 18:56 Send this review to a friend
An effective audio filter with no ringing!  Time owned: 3 to 6 months

I have been pleased to have the opportunity to evaluate a new cw filter designed by Jim Tonne and produced by W3NQN. I have been searching for additional filtering for my Elecraft K2 including it’s useful KAF2 active audio filter. My major difficulty has been filter ringing and QRN that gives the crystal filter fits when trying to copy “weak” or “just in the noise” cw signals with or without QSB. Also the hiss of the AF1 and the Ringing of the AF2 filter in the K2 audio filter hinders some weak signal work.

My main antenna is a full sized 40 meter delta loop supported by a 38ft. Maxgain fiberglass mast, fed with 20 feet of ladder line to a MFJ 998b auto tuner housed in a weather sealed box near the feed point of the loop. I live in the Houston metro area with its many noise sources. I feel this is a relatively quiet choice and works well on 10-40m and will just work on 160-80m. Because of some unresolved noise sources at my operating position at our family computer desk, I have successfully reduced some of the noise at times by setting up my rigs near the tuner in the back yard, weather permitting.

My main pursuits are QRP DX, QFox hunts, SOTA chasing, and portable operating such as Field day and QRP to the field events and contests.

The filter arrived well protected in a “beta” enclosure labeled as : A 4 inductor, 7 capacitor passive cw filter using 4 potted inductors, 7 capacitors. The only control consists of a single toggle switch for bypass and filter selection, a headphone jack, and a mono audio jack to bring the rigs Ext. speaker or headphone output to the filter. No power required.

After the simple connections were made to my K2, I mainly used a K-251/U, Astrocom Army communication headset and occasionally my Scullcandy cellphone earbud that I already alternately use with the rig and use as a comparison and control with the filter out of line.

First impression with minimal QRN is the passive filter has a sweet, sound that doesn’t cause the fatigue that, at least my KAF2 generates over time, I think due to its hiss and ringing. None of my filters nor this passive filter deals well alone with high QRN in conjunction with a signal at the noise level. Luckily the KNB2 noise blanker does deal with many of my static issues. But this filter does add another layer of filtering that helps my crystal filters separate weak cw signals from the QRN/static. Also this passive filter sounds great with stronger signals, narrowing the bandwidth without ringing for signal reception with a great tone and no hiss! Now this is an audio filter so, strong adjacent signals can splatter, requiring the use of my 700, 400, and 200hz crystal filters in the K2. And the great tone and lack of hiss help the crystal filter in the K2 sound even better.

So… no single filter is a solution to every situation, but this is a great tool used alone or in combination with other filters in many common situations on our hf bands. I also used the filter with my other rigs including an Icom 751a, Elecraft KX1 and K1 with similar results in each. I even tried it on PSK with some very positive results keeping the signal within the bandwidth of my waterfall. Would really enjoy trying one with a center of 1000hz for digital and a wider version for SSB. Bet they would be real winners too. Hint hint…

Rob, KA5QQA
 
W4OP Rating: 5/5 Dec 31, 2012 13:04 Send this review to a friend
Fantastic CW Filter  Time owned: 3 to 6 months
I just recently installed this filter in a station accessory I built for my Hallicrafters FPM-300 MK II transceiver. Totally different sound than SCAF or op-amp active filters- and perhaps the best part is that you do not need to be concerned with keeping the input AF level within a certain range in order to not overload active devices.
Exceeds my expectations and Ed's customer service is excellent


Dale W4OP
 
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