Review of Minicom 0D23008 KVM extender
In this article we review the KVM extender 0D23008 made by Minicom. For a general discussion about using KVM extenders see our other article Using KVM extensions to reduce electromagnetic exposure .
Product description
This KVM extender is composed by a Transmitter and a Receiver which have to be connected by means of a CAT5 network cable or superior category.
It provides the basic channels only, i.e. keyboard, video and mouse.
The video channel is of VGA type and it supports a screen resolution up to 1600 x 1200 pixels, furthermore the device supports the DDC subsystem of VGA displays which allow the display to communicate its native resolution to the system, and so even older display standards like 1440 x 900 works smoothly.
The mouse and keyboard channels are PS2, but it is possible to use also USB mouse or keyboards with a small USB to PS2 adapter ( female USB to male PS2 ).
Positive aspects
This KVM extender is very easy to install, following the few steps of the setup manual.
The video quality, once that the receiver has been tuned a little by turning its recessed screw with the small screwdriver included, is very good, it is almost impossible to tell the difference respect to when the monitor was connected directly to the computer by means of a high quality VGA cable.
The transmitter and receiver devices do not heat up at all , at least when used with a 10 meters cable as our test. This means that they don't consume almost any electric power. probably the power consuption is greater if the cable used is longer, but the power is very small anyway.
Limits
This KVM extender does not have audio channels, so if you need to use headphones or a microphone connected to the computer you have to lay another cable, possibly two, for that.
Negative aspects
The biggest problem of this product in terms of electromagnetic emissions is the receiver's small power supply.
This small power supply takes the mains voltage ( 120 V or 230 V ) as input and gives an allegedly direct voltage of 5 V as output, but like any power supply of this kind, it works by means of high frequency switching circuits, which create a huge amount of electromagnetic radiation.
The electromagnetic emissions created by this power supply not only radiate from the small power supply box, but are carried along the wire to the KVM receiver little box, from which they are radiated much more. Part of this electromagnetic radiation goes also to the mouse, keyboard and monitor connectors which become additional emitters.
In few words, the product with its original small power supply is an electromagnetic disaster for the user that sits near the receiver.
Possible improvement
We have tried to use this KVM extender with another, low EMF, power supply. Using the same 5V stabilized voltage from the low EMF power supply of our modified LCD monitor, we have been able to use the KVM extender.
We have used the KVM extender for some time with our smooth DC voltage source, and we conclude that in these conditions, and only in these conditions, the results are good.
With the original power supply the product cannot be used, it creates a mess of electromagnetic radiation at the receiver side, that vanishes completely the advantages of having a KVM extension. The electromagnetic environment around the desk with the original power supply is worse than having the computer box on the table.
Conclusions
In conclusion we can say that this product is a starting point to make a KVM extension with really low electromagnetic radiation in the user zone, but to really obtain this result you have to replace the original small power supply with a low EMF source of DC voltage of adequate power.
Of course the manufacturers of this product did not face the problem of electromagnetic emissions from the power supply, because they are an industry of components for computer networks and data centers.
We are satisfied by the functions and quality of the KVM extension provided by this product, but we can't validate this product as a good solution for having low EMF in the computer workplace, because of the extremely strong emissions of the power supply included in this product.