[ICOM] Microham Keyer or RigExpert Plus?

[Joe Subich, W4TV]

Howard White writes: 

> I ran a parallel test bed for a while.. RigExpert on one Computer,
> RigBlaster on a second computer both connected to the same radio... 
> IC-756 Pro2, PW-1, SteppIR MonstIR... the RigExpert would decode 
> digital signals about 10db better than the RigBlaster...and would 
> still give 100% copy when the RigBlaster gave none...
> 
> The reason was that the RigExpert had its own built in sound card
> ...which was external to the sound card inside the computers... 
> hence it was not subject to the internal computer noise and 
> aliasing that the internal sound card generates...
> 
> USING THE INTERNAL PC SOUND CARD WOULD BE A MAJOR WEAKNESS IN THE
> MICROHAM KEYER


I wish Howard would refrain from making blanket statements on 
products with which he has no first hand knowledge.  In this 
case he is making a freshman mistake by confusing the effect 
and the cause. 

Our experience (and my own measurements) indicates that while the 
noise floor may be somewhat lower with an external codec (also 
known as external sound card or USB sound card) the difference 
is completely masked by "background" noise (sky/atmospheric noise) 
on an HF channel.  There is no sound card, internal or external, 
that can withstand the full dynamic range (130+ dB) of a receiver 
without AGC.  As soon as AGC comes into play, weak signals will 
be masked by nearby stronger signals (gain compression in the 
receiver).  If the weak signal is on a "clear" channel, simply 
increasing drive to the sound card to the point that the 
background noise masks the sound card noise floor results in 
equivalent performance in internal and external sound cards. 

The degraded performance that some experience with internal 
sound cards is generally due to external factors like improper 
grounding, lack of isolation ("ground loops"), improper levels. 
etc.  Both the computer's case (desktop) and the radio are 
connected to a common power system "safety" ground through the 
third wire of the power cord.  The radio is generally tied 
to a separate ground via the shield of the coax, many computer 
sound cards and most radio designers make the mistake of tying 
the audio return of unbalanced inputs and outputs to chassis 
ground.  

microKEYER avoids these problems by providing complete transformer 
isolation of the line in/line out connections to the computer,  
optically isolating the data between the USB interface and 
internal microcontroller, a split power system which takes 
power for the USB interface from the USB line while 
powering the radio functions from the radio or external 
power supply (Kenwood) and providing effective level controls 
on the front panel.  The device tested by Dr. White provides no 
isolation or level control for received audio!  His "test" is 
of absolutely no value in comparing the real performance of  
internal and external codecs.  

Further, I know of no external sound card that provides 
both simultaneous microphone level and stereo line input and 
full duplex operation.  Our designers have looked for codec 
chips with available, standard windows compliant drivers that 
provide those functions for possible use in future product 
designs without success.  While we could certainly "write our 
own" sound drivers, that would restrict the full capability of 
our products to software that was written specifically to our 
specifications (e.g. MixW and RigExpert) or expose the user 
to significant problems in dealing with hardware/operating 
system/software conflicts.  

If all one is interested in is rig control and WinLink/AFSK/etc. 
the microHAM USB Interface II excels as a "Go-Kit" with a    
radio like the IC-706/FT-857/etc.  A USB and two audio cables 
connect to the laptop and a single cable (CAT, Accessory and CW 
connectors) to the radio.  USB II will also do "software CW" 
(DTR) or FSK (with MMTTY/EXTFSK) in a pinch.  It does not impact 
mic audio and provides complete isolation and level control 
between the computer and radio.  

73, 

    ... Joe Subich, W4TV 
        microHAM America, LLC. 
        www.microHAM-USA.com