THE HI-PER-MITE ACTIVE AUDIO CW BANDPASS FILTER IS AWESOME

[Chuck aa0hw]

I recently finished building my HI-PER-MITE cw filter.  I am very impressed at how well this filter performs  It may be one of the best active cw bandpass filters I have every used.   Here are my results from testing this awesome filter:

Here is a picture of my build

Here is a picture and audio file of an audio frequency sweep through the filter from 300 hertz to 1200 hertz

Here is what the sweep sounds like through the filter

 

Here is a good example of how well the HI-PER-MITE does at filtering a harsh square wave sidetone

 

Here are some spectrum views from AUDACITY

The original spectrum of the harsh square wave sidetone

Here is the spectrum after the HI-PER-MITE cleans up this sidetone

Even the edges of the cw waveform get cleaned up with the HI-PER-MITE

Here is the view of the end of a cw note without filtering

Here is what the cw note edge looks like after the HI-PER-MITE filtering

HERE IS A TEST SENDING A QRQ DIT STREAM AT 75wpm FROM FLdigi

FLdigi set to standard parameters, rise/fall time = 5ms, 3/1 dash/dot ratio, 75 wpm sending the number "5"

HERE IS A PICTURE OF FLDIGI WITHOUT FILTER [ 5 dits ]

HERE IS A PICTURE OF FLDIGI WITH HI-PER-MITE FILTER [ 5 dits ]

HERE IS A BLENDED VIEW OF THE 2 PICTURES ABOVE

HERE IS A PICTURE OF A CLOSEUP OF ONE DIT FROM FLDIGI - NO FILTER -

HERE IS A PICTURE OF CLOSE UP, OF ONE DIT - WITH - THE HI-PER-MITE FILTER

HERE IS A BLENDED VIEW OF THE 2 PICTURES ABOVE

FLDIGI 3 TONE TEST FOR HI-PER-MITE

FLdigi is sending three different cw characters at three different cw pitches; 400 hertz, 700 hertz, and 1000 hertz at equal volume. The HI-PER-MITE filter is used in the second half of the file as a narrow active bandpass filter centered at 700 hertz and does a great job of reducing (@-30db) the other two cw signals of 400 hertz and 1000 hertz. This test was setup to closely represent a typical nearby interfering signal(s) that you might hear when on the air with other cw signals that are nearby your own frequency. The HI-PER-MITE proves itself very useful to be able to successfully filter out the other signals and still be able to continue on with your own qso.

SPECTRUM of 3 tones before filter at equal volume

SPECTRUM OF 3 TONES after the HI-PER-MITE FILTER

[Chuck aa0hw]

Here is another example of using the HIPER MITE CW FILTER to clean up a 555 square wave that connects to the MIC JACK INPUT of your computer sound card, and how to listen to that sidetone in low latency using a pulseaudio command on a LINUX COMPUTER:

this video demo's a way of creating a pulseaudio loopback to be able to monitor in real time, your cw morse code sidetone audio that is connected to your sound card's MICROPHONE or LINE INPUT...the audio will go from the SOUND CARD INPUT directly to the SPEAKER OUTPUT...through a virtual audio loopback cable created by pulseaudio with the command listed below..

many modern computers do not have a way to directly monitor the input of your soundcard...pulseaudio can provide a way to do so....

pacmd load-module module-loopback latency_msec=1

normally the 555 puts out a harsh square wave with tons of harmonics, which will sound very raspy....However, by using a HIPERMITE CW AUDIO BANDPASS filter between the output of the 555 and the input of the computer sound card input , the HIPERMITE will FILTER OUT the harsh harmonics very well...and even smooth out the cw element edges from "zero" rise & fall time to around "5 or 6 milliseconds" of rise/fall time
http://www.4sqrp.com/hipermite.php

NOTE: this video recording has a small amount of static hiss and distortion that was not present while i was listening during the original setup...the recording setup introduced some slight distortion that is not present during a "LIVE" session...

[Chuck aa0hw]

Here is another example using the HIPERMITE CW AUDIO BANDPASS FILTER used with the JACK AUDIO CONNECTION KIT ENGINE...for lower audio latency and higher performance and more functions:

this video demo's a way of monitoring in real time, your cw morse code sidetone audio that is connected to your sound card's MICROPHONE or LINE INPUT...using the JACK AUDIO CONNECTION KIT(works on WINDOWS, MAC and LINUX)
the audio will go directly from the SOUND CARD INPUT directly to the SPEAKER OUTPUT...and with VERY low latency due to the JACK AUDIO CONNECTION KIT's audio engine features and ability...

many modern computers do not have a way to directly monitor the input of your soundcard...JACK AUDIO CONNECTION KIT can provide a way to do so....http://jackaudio.org/
J.A.C.K. has versions for WINDOWS, MAC and LINUX..and even the Raspberry PI

normally the 555 puts out a harsh square wave with tons of harmonics, which will sound very raspy....However, by using a HIPERMITE CW AUDIO BANDPASS filter between the output of the 555 and the input of the computer sound card input , the HIPERMITE will FILTER OUT the harsh harmonics very well...and even smooth out the cw element edges from "zero" rise & fall time to around "5 or 6 milliseconds" of rise/fall time
http://www.4sqrp.com/hipermite.php

NOTE: compared to the previous video using PULSEAUDIO
https://youtu.be/fqqqUCLLg8E
JACK AUDIO does an even better job...
- there are many more audio functions available with J.A.C.K.
- there is lower audio latency with J.A.C.K. than pulseaudio