Quick Review of Malahit DSP2

[JustGreg]

I now have the new version Malahit DSP2 receiver.  Here are my first impressions of it.

It is nice made with a nice aluminum case.  The speaker (two) are facing front. This allows one to hear them better.  One no
longer has to connect another set of computer speakers to the headphone jack.  The audio is good.  My estimation for the power
is about 1 watt.  Enough to fill a room, but, not too loud.

The two (2) sma jacks are close together on the top.  This makes connecting an antenna a bit difficult if you have fat fingers. I
used a 45 degree adapter to connect the antenna.  The adapter is a help.

The biggest improvement is the user interface.  I had used the previous firmware 1.10c and 1.10d versions.  Both could be an
exercise in frustration to do certain functions.  Sometimes, a fat finger would work and for others, one needed a stylus. 

My unit came with version 2.40.  There is an older version 2.30.  I like the 2.40 version.  It works fine with either the fat finger
or stylus.  I prefer the stylus.  The screen does not quickly get dirty with the stylus.  The stylus that comes with the unit is double ended.  One end is a pen and the other end is pen with a plastic pad.  The plastic pad looks like it could come off.  I am using a regular tablet stylus.

The other improvement, there is a manual for the firmware functions.  This is a major help on what the functions do and how to use them.  The manual is not complete.  There is no mention on how to set the clock.  It has not changed.  One needs to do touch the Radio Menu key until it beeps.  The the clock setting menu is shown, then clock setting is easy. 

The RF performance has been improved.  There are not as much aliasing and spurious mixer products shown on the screen.  One radio setting that needs to be turn on is PGA BST.  This helps to reduce the spurious signals.  Where I live, I can see the transmit towers for a local FM station and the NOAA weather station.  The PGA BST ON setting helps.  I also found sometimes that it was needed to turn ON the MIXER GR setting to keep the receiver from overloading.  With the MIXER GR ON, the demodulated audio is reduced.  One needs to turn up the volume.

This is not the receiver to use for long wave stations.  There were many spurious signals from local medium wave stations.  I could not improve the performance.

I did find the NOISE REDUCTION work well.  It does not work for FM (wide and narrow).  But, for AM and sideband signals, it is a help.  It works nicely for listening to HF Pirate broadcasts.

It can also be controlled by a computer.  The manual gives brief instructions on how to do it with a Windows computer.  I tried it with my Raspberry PI Linux computer for the WSJTX.  I was able to do the Malahit configuration to recieve both FT8 and WSPR digital modes.

Final thoughts, this is nice receiver with good improvements.  However, I paid $359.  To me, this is a bit high for a specialize portable receiver.  One can get a higher end Tecsun radio for less money and have less overload issues.  The spectrum display to me is the feature that makes it "keeper" for me.

[JustGreg]

An update, now that I had it for awhile.  I use it for medium wave, shortwave and VHF FM broadcasts.

It does work better than the previous versions.  During the day, I have no problems with spurious signals.  However, at night, when 40 meters goes long, then spurious signals (images, aliasing, etc) show up.  I found the settings that minimize spurious signals on medium wave and shortwave.  One has to enable:  PGA BST, MIX GR (this reduces audio levels) and RF Gain = 10 to compensate for loss in audio.  Long wave does not work.  There is aliasing of medium wave broadcasts into the long wave band.  This is a lack of anti-aliasing filters.  I guess the designers have decided the extra effort for long wave is not worth it. 

I have found no problems with FM broadcasts showing up in the shortwave bands.  Broadcast FM performance is good. 

In general, it is nice to see the what is on without needing to start up a computer.  This is an addition to my listening post and not a replacement of the Air Spy HF + Discovery Raspberry PI combination.

[JustGreg]

After using this some more until different propagation and noise conditions, I find this more like some of the old vacuum tube receivers.  One has to play with the RF GAIN setting.  Sometimes RF GAIN = 10 works and other times the RF GAIN = 16 is best.  The AGC seems not work the way one thinks it should.  The processing gain between the analog RF and digital processing  seems to be skewed to too much digital gain and not enough RF gain.  One has to play with the settings.  There does not seem to be no magic settings for the controls.   PGA BST and MIX GR definitely need to be enabled.    I also found the S meter reads much to high.  I had to reduce Sm correct (S meter correct) setting by -26 dB.  Another indicator that gain distribution is wrong.  I hope this helps someone else with one of these.