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


Reviews Summary for W3NQN Passive Audio Filter
Reviews: 31 Average rating: 4.9/5 MSRP: $70 USD $75 Cdn $90. overseas
Description: Passive audio bandpass filter, center frequency 800Hz eMail: faye.ed@comcast.net
Product is in production.
More info: http://W3nqn.com
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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
 
KI0Z Rating: 5/5 Apr 11, 2012 18:36 Send this review to a friend
AWSOME  Time owned: 0 to 3 months
ANYTHING THAT CAN HELP THE TS-590 & IC-7800 is worth looking at!! this is an amazing design .. I have had a lot of filters but this Active filter Is a big help WOW ........!!!!!!oN THE ts-590 NR-2 WHEN LISTENING TO cw YOU GET THE POT HOLES OF REMOVED BAND NOISE SPACES AND THE cw SIGNAL. turn on the W3NQN filter and it's just CW signals only !!! even on wide filter settings of the xcvr it has a lot of selectivity. just set it up for stereo plug and jack.Don't short out 1/2 of the signal out of the xcvr with a mono plug!!tye both hot of plug to input wire and have full output at filter.same as at xcvr.use the filter on the IC-7800 snd hesr both rcvrs in both ears at once with stereo setup. . GL 73 DX Dave KI0Z..
 
W8FA Rating: 5/5 Mar 7, 2012 16:21 Send this review to a friend
Save your ears, get this filter.  Time owned: more than 12 months
I can't say enough about this simple PASSIVE audio filter for CW. I use it every day. There is no ringing, echo, hiss or roar. It is so much more pleasant to listen to the band background noise using this filter compared to others I've used, which are either built into the rig (crystal or mechanical), DSP, or, are an outboard accessory, for which I have a box full, with some costing $500. THIS FILTER DOES NOT ADD DISTORTION TO THE RECEIVED AUDIO like typical active filters, DSP, etc. It also makes it easier to dig weak signals out of the noise level. The kit was easy to build. I did add extra output connections and switches on the filter box in order to direct the output audio to other pieces of equipment, speakers, and multiple headphones. The only problem I had was with two inductor wires broken at their solder connection point. I quickly found this problem after checking with an ohmmeter, but could have seen the bad connection if I had opened my eyes. You do not have to be a homebuilder to build this filter. It's simple point-to-point soldering at about two dozen points. There is even step-by-step pictures of construction on the website which you can click-on and enlarge. If you operate CW, save your ears and get this filter. Does it work miracles? No. The band noise is still there, although at a reduced level. But most important, the noise is less tiring. And without distortion. I plan on using this filter for life. This is one of the few accessories I've used in the last 40+ years that really works. Considering what a simple passive filter like this costs, I can't figure out why the big transceiver manufacturers don't build these into their multi-thousand dollar rigs. Oh wait, maybe I can figure that out.
 
G3LGR Rating: 5/5 Mar 7, 2012 07:51 Send this review to a friend
Excellent non rringing filter  Time owned: 3 to 6 months
Recently purchased a 600Hz version of the filter from Ed to carry out some very low signal to noise tests.
before starting the tests I tried the filter on my IC 706 and FT 897. The filter has been a pleasure to use, no ringing, just an absence of noise and reduction of nearby signals. I've not bothered using my 599ZX on the HF and found that the filter when combined with the BHI DSP unit at a low setting has provided a very nice relaxing way of sorting out weak Cw stations, especially on my favourite band, 40 metres.
Ed produces the kits at various frequencies from 500 Hz upwards
 
N7AG Rating: 5/5 Apr 5, 2011 00:31 Send this review to a friend
THE CW FILTER  Time owned: more than 12 months
If I could have but one cw filter, this is it. His website is most useful for construction. Filter is not tiring to listen to. Have tried numerous DSP, low-pass filters.
 
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