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

Reviews Summary for NEScaf Audio Filter
NEScaf Audio Filter Reviews: 34 Average rating: 4.8/5 MSRP: $29.00
Description: The NEScaf is a switched capacitive audio filter based on the MF10 chip. It is
designed to be simple to build and use.

It is more flexible than previous filters for QRP rigs. It has two panel-mounted
controls -- a single center-detent potentiometer that sets the center
frequency of the filter's bandpass (default value settable between ~415Hz and
~1kHz), and a dual-ganged potentiometer that provides a continuously
variable bandwidth control (from ~60Hz to ~1500Hz). This ability to smoothly
vary the bandwidth is very useful.

The NEScaf is designed to be driven with a phones or speaker level signal.
Product is in production.
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AD5IW Rating: 5/5 Dec 1, 2011 20:46 Send this review to a friend
Insanely good  Time owned: 3 to 6 months
Been a ham forever (since 1966) and have used audio filters of all kinds. Nothing comes close to this one. It is simply amazing when dialing a narrower bandwidth - the noise and qrm just disappear while the signal stays at the same volume.

The k2 audio filter is joke next to this $29 wonder. Just get one.
PC5F Rating: 5/5 Nov 30, 2011 00:57 Send this review to a friend
Weak Signals Stand Out  Time owned: 0 to 3 months
The NEScaf audio peak filter is not only useable for CW but also for other modes of the digital persuasion, such as PSK and RTTY, where you need to get the weaker signals in the waterfall to stand out from the qrm.
Plus it's very affordable (even with shipping to Europe). You have to put it together yourself, but for me that's an enjoyable extra and easy to do.
The bandwidth gets a bit wider moving to higher audio frequencies, i.e. the right hand side of the waterfall in digital modes. That doesn't really matter for getting results tho.
W8VZM Rating: 5/5 Sep 9, 2011 13:53 Send this review to a friend
Easy Kit Great Filter  Time owned: 0 to 3 months
The kit was easy to complete with minimal tools. Directions are complete and well detailed. Parts were all there when I opened the kit. Is as narrow as I need and a whole lot cheaper than the built in filter. Look for my detailed write up on the filter at
AE4GM Rating: 5/5 Jul 27, 2011 09:13 Send this review to a friend
Great Filter  Time owned: 0 to 3 months
I am building my 2nd Nescaf filter now. The first one I'm using mobile on my Tentec Triton 4 with the rig set at wide cw. I'm hearing complaints from other hams in qso's about qrn and qrm being terrible. All I'm hearing on the Nescaf filter is pure quality CW tone with nothing else. No ringing, no noise, no qrm. I've never purchased a 2nd kit of anything before the Nescaf filter. I just know I'll want to use it in the other vehicle or the house. I enclosed mine in a round cat food can with a regular tin can lid put in place for the opening with Goop glue. I use it with the bottom up for cosmetic purposes. I labeled it by printing out the words on typing paper, cutting them out, and Elmer gluing them in place. I may get a 3rd Nescaf kit someday. We'll see.
K3RLL Rating: 5/5 Jul 13, 2011 17:59 Send this review to a friend
Very Effective  Time owned: more than 12 months
My second NEScaf Audio Filter from NEQRP Club has just recently "followed me home", as they say. The first one was built some time ago and augments a variety of small QRP rigs for portable use.
However, this second one was needed for my summer home and performs even better. Although my FT-817 has a crystal CW filter, the broadbanded receiver is really not up to the crowded band conditions of contesting and Sprints. The NEScaf filter resolves that deficiency nicely at at very modest cost.

There has been a logic chip change in the newer models of the NEScaf Filter which seems to have improved performance a great deal, not that the earlier one was lacking.

My first NEScaf lives in an Altoids tin, but now knowing just what a good piece of equipment it is, the new one has been treated to a 'real' plastic project box that also accommodates an internal 9 volt battery that is eliminated from the circuit when an external 12 volt source is connected.

In my opinion, the NEQRP Club NEScaf Audio Filter is an extremely useful and helpful accessory that vastly improves performance of otherwise marginal receivers.
K4FH Rating: 5/5 Mar 16, 2011 18:49 Send this review to a friend
Great  Time owned: 0 to 3 months
So far a full 5. Build instructions are well written that any novice builder can make this filter. Each stage has test instructions. I took my time and built mine over a couple days buy spending a little time each day on each stage.

It needs to be in a metal box and I'll install it in one as soon as I can get to the store.

I will be building one for portable use. This one for the shack.
KB4MB Rating: 5/5 Aug 31, 2010 07:29 Send this review to a friend
Works Perfectly  Time owned: 0 to 3 months
I didn't have much money, but as a CW newbie, I can't concentrate when there is more than one signal in the passband.

Scraping together the thirty bucks, I put the kit together quickly, and it worked right from the start. I used an old 15pin switch box that I had collecting dust, and used that as my enclosure, combining my K1EL keyer that I had but never finished and this in the same enclosure.

The only problem I had was that I thought RF was getting into the headphones during transmit, but that actually was an artifact of insufficient drive of the chip - turning up the volume on the rig the artifact is gone.

I have decided to live with the non-pure tone then to either blow out my ears or try to pad down the output... I reserve the right to change my mind later on.

The nice thing about the narrow bandwith is it acts as a crude zero-beat indicator until I get my rigs pitch memorized (doing pretty good with that!)... I am amazed how off so many people are!

It does a fair job with SSB as well, but as most people indicated - it is meant for CW primarily. How nice to be able to filter out the QRN on 40m at night with this little guy.

The kit came with a broken DPDT switch and Bruce sent out a replacement very quickly upon hearing it.

Very pleased with the filter, and I highly recommend it to anyone who doesn't have a CW filter (or who wants a nice variable control on a knob in front of them)!
IZ4KBS Rating: 5/5 Jul 21, 2010 09:02 Send this review to a friend
Works really well  Time owned: 0 to 3 months
The NEScaf works as advertized, the kit went together easily and worked out of the box. Unless you enclose it inside your radio (like I did), it needs a metallic case and shielded outside cabling, or it will happily act as an AM broadcast receiver. Also, I wanted it mostly for /P ops and to try and fit it into my portable QRP rigs. The NEScaf is stated to require not much less than 12 volts to work properly. Many portable QRP rigs, TFR etc. are still happy at 9 volts, so this may have been a more appropriate minimum voltage requirement for the NEScaf. Anyway, I managed to squeeze the filter inside my Wilderness Radio SST-20, with excellent results, as you can see from the last three pics at . To make that possible I replaced the 10 Kohm R10 pot with a fixed value 4.7 Kohm resistor, and the dual-gang 50 Kohm R7 A/B pot with two 1 Kohm fixed resistors, so that when I switch the filter in I get an audio bandwidth of about 90 Hz. By choosing different (equal) values for R7 A/B a wider bandwidth can be obtained, within the 60-1600 Hz range of the filter. Squeezing the NEScaf (and a PK4 keyer) inside the tight internal space of the SST was not easy, but I managed by replacing the stock SST PA heathsink with a lower-profile one, and then resting the filter board on top of the underlying components, with a thin layer of insulating material in between. All this, along with built-in paddles and battery pack, makes my SST a truly amazing TFR!

P.S.: in the pics at the above link you'll see also other mods that I tried on that radio, some of which were then removed because rather useless or not working well. The current (and I believe final) look of my SST-20 is this:
KC1JB Rating: 5/5 Jun 22, 2010 09:26 Send this review to a friend
An indispensable gem  Time owned: 0 to 3 months
Just a quick note to say how impressively this filter works. I built mine in April 2010, but I didn't finish it off (packaging) until mid May. I've played with it a bit since then and finally put it to serious use during a recent SKCC Weekend Sprint.

The NEScaf filter is a gem. During the weekend, band conditions weren't great, so I used it to dig relatively weak signals out of the noise, rather than filter out adjacent stations (there weren't many of those). After applying the filter and playing with my rig's volume control, I could easily fool myself into thinking a signal just above the noise floor was an s5 or 6.

I have a budget HF rig (Yaesu FT-450) with DSP and a few other signal-tweaking bells and whistles. And I operate virtually all CW all the time. The NEScaf filter turned an already satisfying CW radio into an even better one. Next: Applying it to my KX-1.

Thanks for an outstanding bit of tech for the shack!
N6MUK Rating: 5/5 Dec 28, 2009 14:05 Send this review to a friend
Great cw Filter and cheap/ easy to build  Time owned: 0 to 3 months
I built it in 1 evening and it worked perfectly upon powering it up the first time. The instructions are easy to follow and very well written!

I use this fine filter with my Yaesu FT-450 during cw operation and it is a great complement to the rig's built in DSP functions. DSP is great but when the going gets tough with cw, nothing works like a good extra narrow cw filter.

The complete lack of ringing with the SCAF technology is remarkable.

For $30 it's an amazing filter. I would have been happy even if I had paid a hundred bucks.
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