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APPENDIX B – RFI Considerations

A few guidelines to eliminate problems caused by RFI:

1.

Proper grounding of all electronic equipment is critical.  A modern station contains many, diverse, types of
interconnected and interrelated equipment: transceiver, power amplifier, computer, control boxes, switch
boxes, and power supplies.  Each of these must be  individually grounded with a separate connection to
a single common ground point, thus forming a star ground connection.

Proper grounding of computers, both "desktop" and laptop is often overlooked.  A separate ground
connection should be run from the computer to the station common ground point.  The best place to
ground a computer is a screw with a good connection to the case.   On a laptop, this is often the retaining
screw on a D-sub connector (e.g, VGA output);  on a "desktop" it is often the screws holding the power
supply.  

It is absolutely important to prevent ground currents from flowing to the common ground point by way of
the signal cable.  If you use a microHAM "keyer," a good test is to remove the DB15/DB37 connector and
USB cable from the keyer and measure the resistance from the shell of the DB15/DB37 to the shell of
the USB cable.  There should be NO MORE than FIVE (5) Ohms (and preferably less than TWO Ohms)
between them.  

Note:  many PC manufacturers fail to provide an adequate connection between the shell of the USB
connector and the PC case.  If this is the case, a connection can be established by bridging a folded
piece of aluminum foil between the shell of the USB connector and the PC case.  

2.

Power all your equipment from a single wall outlet.  The "safety ground" often exhibits excessive noise
between power outlets - sometimes often due to other equipment powered from the same branch circuit.
It is always better to avoid this source of noise/interference.  It is also a good idea to check the power
distribution for loose connections, reversed neutral/ground, open ground and other wiring problems. 

3.

Sometimes, the USB cable can be a source of RF interference - the cable might have inadequate
shielding or the transceivers in PC might be improperly designed causing data flowing inside the cable to
be reflected as a common mode current on the shield of the cable.  This common mode current can
radiate a significant "digital noise."  If this is the source of your problems, it can be significantly reduced
or eliminated using ferrite chokes on both ends of the cable.  Two or three turns through a #31 mix FT240
toroid are better than the common snap-on ferrites of unknown mix.  

4.

Often, another cause of RFI problems is a common mode current flowing along the antenna feedline into
the shack.  It is a common misconception that the only thing required of a feedline is that it have low
SWR.  Unfortunately, a low SWR does not guarantee low common mode current.  These common mode
currents are conducted into the shack where they can radiate from the feedline, induce currents in any
nearby metal object, and/or be conducted into the interconnected equipment.  Common mode currents
on a feedline are indicated by problems that differ in intensity from one band to another or from one end
of the band to another,  by problems that change when a feedline is moved or its length changed,  where
the problem moves from one piece of equipment to another based on band, and/or where the severity
changes with transmit power level.  The solution is to use common mode chokes to prevent the current
from entering the shack. This topic has been given thorough treatment in recent works by W1HIS and
K9YC.

 

W1HIS: 

http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf

K9YC:  

http://www.audiosystemsgroup.com/RFI-Ham.pdf

 

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Содержание Digi Keyer II

Страница 1: ...microHAM 2010 All rights reserved DIGI KEYER II microHAM fax 421 2 4594 5100 e mail support microham com homepage www microham com Version 7 9 5 Decenber 2010 1...

Страница 2: ...oHAM USB DEVICE ROUTER 13 Menu Router 13 Menu Preset 14 Menu Device 15 Menu Virtual Port 16 Menu Help 17 Device Configuration 17 Ports Tab 18 CAT 2nd CAT 19 FSK 2nd FSK 21 CW 23 PTT 2nd PTT 23 Foot Sw...

Страница 3: ...0 FT 5000 FT 2000 FT 1000D MP Mark V Kenwood TS 2000 and Elecraft K3 independent front panel level controls for each receiver Front Panel Level Adjustments Pots for Transmit level Main Receiver level...

Страница 4: ...B port Controller is powered from transceiver or transceiver power supply Strong immunity from RFI integrated chokes and filters for best RFI immunity advanced shielding and circuit design to suppress...

Страница 5: ...TX Transmit Audio Level 6 FSK LED flashes with FSK output On indicates closed regardless of mark space polarity 7 PTT LED lights when PTT is active 8 RX MAIN Adjusts receive audio level from the main...

Страница 6: ...SHELL Ground If the jumper is in the SS position the switching transistor open collector is connected to the PA PTT jack The transistor can switch up to 45V 0 8A This position is appropriate for mode...

Страница 7: ...oftware for your operating system 3 configure the microHAM CODEC and USB Device Router for Windows if applicable Preparing DIGI KEYER II for Use 1 Remove the top cover from DIGI KEYER II and set the C...

Страница 8: ...wer connect these leads to a 12 16V DC power supply Be sure to observe the proper polarity NOTE DO NOT use the same power supply as the transceiver 8 Locate but do not connect the USB cable from DIGI...

Страница 9: ...ou download an updated package click on urouter_release_xx_xx exe xx_xx is version to start the installation The Windows setup utility will start and ask into which folder Router and its supporting fi...

Страница 10: ...ds would be played through DIGI KEYER II and onto the air In Windows XP open Sounds and Audio Devices in the Control Panel or right click on the Speaker icon on the Taskbar and select Adjust Audio Pro...

Страница 11: ...are DIGI KEYER II Status When the USB driver is installed correctly and DK II is powered from a radio or external 12V DC supply Router will show a device tab with a GREEN check beside the device name...

Страница 12: ...creating virtual COM ports attach all external devices you use with the computer and allow them to connect to the system Restart Router and then create the virtual COM ports Virtual ports are created...

Страница 13: ...operation These settings are used for the optional automatic selection of audio switching and PTT mode based on operating frequency Careful selection of the Digital band is necessary for transceivers...

Страница 14: ...ferent configurations can be stored in these presets and recalled almost instantly simply by clicking on the preset button Each preset contains the settings for all devices connected to and controlled...

Страница 15: ...tifiable names as shown here Delete Removes a device from the Router Only disconnected devices those with a RED X on the device tab can be removed To disconnect a device from Router unplug the USB cab...

Страница 16: ...II when the new version of Router connects for the first time you have just to allow the upgrade when prompted VIRTUAL PORT MENU It is necessary to create several virtual serial ports COM ports in ord...

Страница 17: ...Router About Shows the Router s internal version number Change logs Shows the Router and firmware changes DEVICE CONFIGURATION TABS There are nine 9 tabs for configuring DIGI KEYER II Each tab contro...

Страница 18: ...de softwre Read the following information carefully DIGI KEYER II has eleven functions with indication of the state and settings applied by the host application CAT uses RxD and TxD 2nd CAT virtual fo...

Страница 19: ...hing back to receive There is a dedicated T R switching channel for this purpose called PTT NOTE If your radio does not support handshake most do not Configure DTR and RTS settings in your application...

Страница 20: ...n monitor The monitor uses colors and tags to indicate which device is responsible for the data Black queries H1 TX or H2 TX and gray radio responses H1 RX or H2 TX are from the host application e g l...

Страница 21: ...th many transceivers particularly Icom split mode must be initiated and ended by only one application and manual split control from the front panel of the radio should not be used NOTE Despite extensi...

Страница 22: ...no parity 1 5 stop bits The second FSK port is useful when operating split with radios that have two receivers e g FT 1000 FT 2000 FT 9000 K3 Orion or IC 7800 The second instance of the RTTY program s...

Страница 23: ...when the port is properly configured To test CW operation click on the Test button with no port assigned or the port closed PTT 2nd PTT PORTS The PTT channel is used for T R switching of the transcei...

Страница 24: ...foot switch but the application does not support foot switch status or no application is running Router reports the channel as closed When an application opens the COM port usually at start up Router...

Страница 25: ...or closed Mon WinKey Monitor allows capturing communications between Router or the application and WinKey Controls for the monitor include Start Stop Clear and Save WinKey Monitor should not be used u...

Страница 26: ...s are controlled from the Audio tab Use Q CW connects the right channel tone decoder to the CW output to allow audio tones to be used for hard keyed CW This permits CW decoding software that only gene...

Страница 27: ...rating configuration Select microHAM CODEC to use the internal soundcard in DIGI KEYER II Router displays separate controls for the left and right Wave Line Out Volume and Line In channels DIGI KEYER...

Страница 28: ...r This change in power is correct If you do NOT see a 50 or more change you are probably over driving the radio Please note that some radios have inbuilt power meters which give a PEAK reading and the...

Страница 29: ...before the transceiver PTT by the time selected for PTT Lead and and will open after the transceiver PTT by the time selected for LNA PTT Tail PTT output generally folows the PTT inputs PTT port PTT I...

Страница 30: ...ady ended If Restore serial CW is not checked application generated CW will remain suppressed until the application releases PTT Mute serial FSK if checked the FSK ports will be blocked while the foot...

Страница 31: ...ority for dual lever paddles If no priority is selected the keyer works in a last paddle wins mode Paddle set point controls when WinKey begins looking for a new paddle press after sensing the current...

Страница 32: ...eed knob Set Key close CW output for selected time in seconds Set Wait wait selected seconds during playback Jump to used for looping a message or calling another message Delay sets the delay in secon...

Страница 33: ...n a memory are CR LF Insert Carriage Return Line Feed Jump to used for looping a message or calling another message Delay sets the delay in seconds before looping or calling another message Store save...

Страница 34: ...pace word mode or when the buffer has reached its limit 16 characters CW from keyboard Type ahead enables type ahead when using a PS 2 keyboard Characters are transmitted after a space word mode or wh...

Страница 35: ...ustment of the audio from the radio main receiver to the sound card computer left channel The RX SUB Pot provides adjustment of the audio from the radio sub receiver or a second receiver to the sound...

Страница 36: ...TIP When you start to create your own presets always begin by selecting the default preset This will configure the audio levels to the proper state before starting any customization Setting audio lev...

Страница 37: ...DIG or DATA for Yaesu LSB D or USB D for current Icom transceivers RTTY or RTTY R on K2 and USB or LSB for Kenwood TenTec and older Icom transceivers Do not select RTTY or FSK they do not use the audi...

Страница 38: ...e can be aborted with the ESC key or the zero key on the number pad Messages may be made to repeat loop by pressing DEL period on the number pad while the message is playing The default minimum wait t...

Страница 39: ...without transmitting PG DN DN NUM WPM control Decrease CW speed step defined by configuration S N mode Decrement number by one HOME ENTER NUM ENTER WPM control Reset CW speed to pot knob value S N mod...

Страница 40: ...lication programs has not been determined microHAM Router is not supported on any 16 bit version of Windows 95 98 ME SE In order to provide sufficient performance for simultaneous operation of microHA...

Страница 41: ...omputer s 2 damage caused by misuse negligence user modifications or failure to follow the user manual 3 connection to improper or excessive voltage or voltage surges 4 the incorrect installation of a...

Страница 42: ...from the transceiver and transfers it via USB to the computer where the operating system processes that data as a sound card The USB sound processor also receives digital audio from any applications r...

Страница 43: ...vice may not cause harmful interference and 2 this device must accept any interference received including interference that may cause undesired operation European Union Declaration of Conformity micro...

Страница 44: ...signal 6 AUDIO OUT GND Radio AUDIO input ground 14 AUDIO IN MAIN S Radio AUDIO output signal main receiver 7 AUDIO IN MAIN G Radio AUDIO output ground 15 AUDIO IN SUB S Radio AUDIO output signal sub...

Страница 45: ...wered from the same branch circuit It is always better to avoid this source of noise interference It is also a good idea to check the power distribution for loose connections reversed neutral ground o...

Страница 46: ...ture The initial version has been tested with Perseus SDR only PERSEUS Radio PERSEUS Port COM10 Source QRG Defines which frequency will be used for SDR tracking Offset Specifies frequency offset from...

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