MORSE is NOT dead!!!

A $1.00 Noise Reducing Speaker

Many a good QSO has been wrecked by that high pitched crackling noise that is common on weak
signals. Sometimes it comes in louder than the voice and makes it impossible for you to hear your
partner. It’s called “Bacon Frying” or “Spike Noise” and it’s the enemy of every ham.

Spike noise is a high frequency pulse that rides on top of the voice on weak signals. It is usually the
highest pitched sound coming from your speaker and sometimes it’s the loudest. Traditionally this
has been handled by add on filtering systems using either analog or digital signal processing
methods. Only high end (i.e. expensive) rigs have had these devices built in. Whether analog or
digital, many low end and mobile radios don’t include them.
Fear not! There is a perfectly workable solution to the problem using nothing more than a couple of
cheap parts…

The circuit, pictured below, is a simple low pass filter that can be added to any speaker and uses
only a pair of 50 cent parts.

noise reduction speaker 300x109 A $1.00 Noise Reducing Speaker

Despite the unusual electronic symbol, C1 is a common non-polarized electrolytic capacitor used
mostly in speaker crossover networks. It has to be non-polarized because the speaker is working on
alternating current. You cannot use a polarized electrolytic capacitor here because under reverse
voltage it acts like a short and would cause considerable distortion.
The resistor, R1, is also a common part you can get at any electronics supply house. There is some
volume loss due to the resistor being in series with one of the speaker leads but it is barely
noticeable and given the benefits, it’s a good trade off.
Human speech doesn’t require full fidelity audio. Most voice energy is concentrated in the range of
400 to 3000 hz. Most of the really annoying noise is in the range of 2500 to 10,000 hz. Since these
two ranges don’t overlap very much we can effectively reduce the audible noise on a signal using a
low pass filter to remove the portion of the audio spectrum above 3,000hz. This effectively takes off
the noise and leaves the voice alone.
The combination of series resistor and shunt capacitor forms our low pass filter. At low frequencies
the capacitor appears as an open circuit and all the audio goes to the speaker. At higher frequencies
it acts as a short across the speaker, causing this energy to be dissipated across the resistor where
we don’t hear it.
The part values for noise canceling with minimal impact on voice quality are on the right. The
resistor should be 2 watts or better. The capacitor should be a non-polarized electrolytic type rated
for at least 16 volts.
There is no harm in experimenting with different capacitor values to get a tonality you like.
Increasing the capacitor’s value will increase the noise reduction but will also make voices sound
more bassy. Go too far and everything will sound muffled. To avoid excessive losses you should
always match the resistor with the impedance of your speaker.

Wire wound resistors work better in that situation than carbon ones… the inductance of the wire coil helps the curve of the filter.

noise reduction speaker values 300x209 A $1.00 Noise Reducing Speaker

Ok, a $1.00 circuit isn’t going to replace a $100.00 DSP unit but it can bring about considerable
relief from that nasty crackling noise and it might save you a couple of headaches when trying to
work that rare signal. So there you have it… less than a dollar for a noise reducing speaker that will
turn your station into a headache free zone!

An article by L.D. Blake – VE3VDC

Ham radio logger program for linux

The world best Linux ham radio logger program

Ham radio maps

romania ham radio prefix map 300x203 Ham radio maps

Read the rest of this entry »


Amateur radio list of HF Beacons

Amateur radio wire antenna SWR table

Amateur radio wire antenna SWR table

Use this balun for the antenna:
balun1 9 Amateur radio wire antenna SWR table

Ham radio KITS

Ham radio electronic kits

Amateur radio kits

Ham radio links related to kit building projects. Many ham radio operators enjoy building transceivers, tuners, keyers, and other kits and homebrew projects.

K1EL Systems – Amateur Radio Kits and Projects

  • K12 Keyer IC and Kit – The K12 replaces the very popular K10 and K10+ keyers which have been shipping for almost ten years now.
  • K10+ Keyer IC – The K10+ is a Morse keyer I.C. with lots of built in features only found in high end keyer I.C.s.
  • K-ID and K-ID2 – This chip is designed expressly for dedicated beacon or CW identifier applications. It is very flexible and has the advantage of a very large message storage bank (512 bytes) which is non-volatile.

HamSphere 2.0 virtual transceiver

HamSphere 2.0 beta should be release today.
Hamsphere Virtual Transceiver
Kelly Lindman announced on his website that we’ve to wait some more days to get the latest HamSphere 2.0
Hamsphere virtual transceiver features going to be:

  • Brand new appealing Radio skin with true VFO.
  • Multiple skin options. Currently two skins available. (See Bill Walch HS 2.0 version here)
  • Improved DX cluster
  • Simulation on/off switch
  • Improved warning system / Ban / Kick
  • Dual filters
  • Monitor
  • Memory channel / VFO operation
  • Fast direct frequency to band setting.
  • Realistic VFO with 10 hz resolution.
  • Progressive VFO for fast and reliable tuning.
  • Fully implemented jitter buffer to minimize audio latency. Can be switched off for fully reliable audio stream.
  • TCP protocol transport. Will work through most firewalls (unless it’s blocking outbound traffic)
  • Single channel NAT-friendly TCP/IP operation.
  • All HAM bands included: 10, 15, 20, 40, 80, 160, WARC bands + BC band.
  • Better audio compressor.
  • Better audio bandwidth (up to 4 kHz).
  • 32kbit audio codecs (Application will require 32kbit up and down stream).
  • Fully realistic analogue S-meter with dB scale.
  • Instant band shifting
  • Improved bandscope.
  • Improved Ionospheric simulation.
  • Same modulation technique as before. Hamsphere uses Digital Local Oscillators and true DSB modulation.
  • Limited tranceiver for guests (Limited band, power and filters)
  • Subscribers enjoy; DxCluster, Full power, unlimited bands, audio codecs, noise free bands if needed.
  • Subscriptions only for real hams and serious “11 meter DX ers” that have to pass a test and a user agreement.
  • Broadcast band for broadcast people. Will not interfere with QSO bands.
  • Robots will be on demo and DX bands only. No QRM on rag chew bands.

Virtual ham radio transceiver

Don’t you have a transceiver?
WebSDR is an online virtual transceiver. You can listen the traffic on 20m, 40m and 80m.

websdr virtual transceiver

Another WebSDR transceiver can be found at w4mq. It supports 160m and 40m amateur band.

Have fun!