Elad Fdm77 Hf Receiver Operating Manual

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step. A shortcut for changing a single digit can be activated through the “Q”, “W”,”E”, “R”, 
“T”,  “Y”,  “U”,  “I”  keys  (increment)  and  “A”,  “S”,”D”,  “F”,  “G”,  “H”,  “J”,  “K”  (decreas e). 
The  “I”  and  “K”  keys  move  1  Hz  digit  and  up  to  10  MHz  the  “Q”  and  “A ”.     Note  that  the 
arrows on the PC keyboard control the frequency only if the window of the coc kpit is active (i.e. the 
upper bar of the window must be blue and not gray).  
Any frequencies outside the receiver limits ( 10 KHz – 65 MHz) will  be ignored and reverted 
to the limit frequency.  
  
2.3.4 Selection of the frequency through the Keyboard.  
When the control of the operating frequency through the VFO is selected, you can choose to input 
the tuning frequency directly through the PC keyboard. To input directly the operating frequency 
through  the PC  keyboard, just click on the KEY button and a new window will open. Type on the 
keyboard of your PC the frequency  ( the selected frequency will appear in the lower l eft side of the 
windows) and confirm with   8  key.  If a keyboard is not available you can input the frequency also   
Clicking with your mouse the button on the TUNING window.  
 
2.3.5 Selection of the frequency’s unit of measure.  
The default setting of the unit of measure is KHz, but the user can change the unit to  MHz or Hz 
simply clicking with the mouse over the unit at the right side of the frequency rea d out. This is a 
toggle control allowing to pass from KHz to MHz and Hz.  
  
2.4 Tuning Steps  
The  default  tuning  step  is  set  to  1  Hz,  but  other  steps  can  be  sele cted  to  match  the  operator’s 
preferences. Simply click on one of the digit of the frequency display or on the 5 KHz / 9KHz la bels 
to select the desired step or use the    arrows on the PC keyboard. The selected digit will change 
colour to show the selection and all the frequency control ( shuttle  knob, up and down buttons, #   $ 
arrows of  the PC keyboard) will work with the new selected step.     
 
 
   
						

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2.5 Mode Selection 
Conventional  modes  (  CW,  LSB,USB,AM,FM)  are  simply  selected  by  clic king  on  the  relevant 
buttons in the MODE window of the cockpit.  
DRM  mode  is  selected  through  the  DRM  SET  button.  By  clicking  on  the  DRM   SET  button  a  new 
DRM  Setting  window  will  open  allowing  to  choose  the  preferred  DRM   application    to  be  used  to 
decode the digital signal. There are two options:  
If  DRN  Int.  is  selected  the  DRM  signal  is  processed  through  the   optional  Channel  Decoder  and 
Audio Decoder integrated in the ELAD FDM -77 Software Radio.  
If  DRM  Ext.  is  selected  the  DRM  signal  is  processed  through  the   DRM  software  preferred  by  the 
operator.  The  complete  path  of  the  directory  where  this  software   is  installed    must  be  specified  on 
the application path windows through the browse button.  
After having done the selection close the window with OK.  
  
2.5.1 DRM reception status window.  
After having completed the main setup you can access the DRM mode by clicking the DRM but ton 
in the “MODE” window. Doing so a new window will popup allowing the monitoring of the  
decoding status of the DRM channel with all the relevant parameters.  The decoding proc ess can be 
observed through the SYNC ; FAC ; SDC and MSC sequence. Only when all the labels (incl uding 
MSC) will lite -on,  the voice and/or sound will be decoded and reproduced by the PC loudspeakers.  
 
 
  
Example of DRM signal reception.
   
						

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2.6 Band Selection. 
  
No  band  selection  is  required  to  explore  the  whole  range  of  frequencies .  Simply  select,  with  the 
VFO, Keyboard and/or Memory the desired frequency.   
The internal pre -selector filter will be automatically activated in the RF Hardware fr ont-end.  
  
3 Operation of the receiver – Advanced  
  
The  set  up  of  the  RF  front -end  input  has  a  strong  impact  on    the  quality  of  the  reception.  In 
particular the use of the preamplifier and of the attenuator should be used in the prope r way. 
  
3.1 Preamplifier  
  
Operating  your  FDM -77  with  the  “Pre”  activated  while  receiving  strong  in -channel  or  adiacent 
channel signals, as in the very crowded HF bands, can leads to severe  distortions of the audio due to 
interfering  signals    or  clipping  and  inter -modulation  caused  by  input  levels  out  of  the  linear 
dynamic  range  of  the  RF  front -end.  Therefore  the  use  of  the  “Pre”  is  recommended  with  weeks 
signals in the upper HF bands.  
  
3.2 Attenuator  
  
While receiving in low HF bands, where very strong signals are possible operating with bi g external 
antennas, the use of the attenuator could 
bring best performances.                                                                                                                                                                                                                                        
 
 
   
						

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3.3 Frequency scanning 
  
By clicking the SCAN button the scan panel will popup . Before starting the scan Start  and Stop 
frequencies must be selected together with the Time hold ( 200 mS is the default ) , Step frequency 
and Step X (of the frequency axis).   
 
 
   
At the end of the scanning process a diagram with S -meter level and frequencies will be displayed.  
Passing with the mouse over the diagram the relevant frequencies will be displa yed on the 
frequency windows located on the left bottom side. Left clicking with the mouse on a point in t he 
diagram a red mark can be inserted and the relevant frequency  will be tuned and displ ayed on the 
cockpit.  
           
						

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3.4 Memories  
  
3.4.1 Saving a station/frequency in the memory.  
  
When the desired station/frequency is tuned simply click the memory button to open the MEMO RY 
file. Click on the “Save in Mem” Button and the data will be inserted in the ta ble. Click Close to 
exit.  
 
 
      
3.4.2 Recalling a station/frequency from the memory.  
  
Open the MEMORY table and then double click on the row with the station/frequency you want  to 
recall and the new frequency will appear on the display . Exit with close button.  
   
						

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3.5 Advanced controls. 
  
In the TUNING window an ADV button is included.   
  
Clicking  on  this  button  a  new  ADVANCED  window  will  pop -up  showing  the  DSP  function  and 
controls.  The  advanced  window  includes:  Input  Spectrum,  Audio  Spectrum,  Audio  Oscilloscope, 
DSP Filter BW, IF SHIFT, CW MODE and AGC CONTROL.   
 
 
 
   
						

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3.5.1 Input Spectrum.  
  
A Low Frequency real time spectrum diagram is available in the uppe r left side of the window . In 
the  diagram  the  12  KHz  signal  level  at  the  input  of  the  soundcard  i s  displayed    in  dB    and  the 
frequency in KHz. Zoon function is also available for both the level and frequency.   
The signal pass -band is showed with black/dashed area together with two notch filters if enabled.  
Once  the  ADVANCED  window  is  made  active  (eventually  by  clicking  on  the  upper  bar)  the  PB 
filter width can be varied also with the  


  and   


 arrows on the PC keyboard.   
   A facility to help the operator to fast tuning a signal displayed on the spectrum i s provided.  
   To use it simply move the cursor over the signal and hold  Shift  + left click mouse.  
   Moreover the operator is allowed to choose the input rough signal display or the DSP post -
processed  signal.  
  
3.5.2 Band Pass & Selectivity selection     
  
In the upper right side of the ADVANCED window the filter control section is avai lable, where 
DSP filters Bandwidth can be selected  from  250 Hz  up to 10.00 KHz. Use the proper BW that  
best match the mode and channel to be received. The default BW is: CW = 100Hz; SSB =2750HZ;  
AM/FM=4000Hz; DRM=10000Hz.   
 
 
      USB signal received with 2.5 KHz BW DSP filter  
   
						

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                LSB signal received with 2.5 KHz BW DSP filter  
 
 
              AM signal received with 4.0 KHz BW DSP filter  
      
						

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                FM signal received with 5.0 KHz BW DSP filter.  
  
3.5.3 IF Shift control.  
This control allow the operator to move the 455 IF band pass filter with reference t o the tuned 
signal in order to attenuate an on band interfering signal.    
 
 
                 Display of the tuned AM signal together with a CW interfering signal.   
(Interfering signal 1Khz down of  the carrier frequency)     
						

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               IF band pass filter shifted 500 Hz up to attenuate the CW interfering signal.  
 
3.5.4 CW MODE  
  
In the middle right side a CW mode filter control is available with seve ral operative mode. 
  
Mode A  : This operative mode is very similar to old style radio recei vers provided with the BFO 
control.  Move  the  frequency  slide  to  choose    the  tone  of  CW  signal  that   best  conform  to  your 
preferences.  In  this  way  you  don’t  need  to  move  the  main  tuning  to  change  the  tone.  The 
frequency of the decoded tone can be observed on the spectrum scope. The de fault of this mode is 
800  Hz  tone.  Note  that  in  this  mode  the  filter  PB  is  kept  fixed  and  the  decoded  tone  is  varied 
through the BFO frequency.  
 
Mode  B  :  In  this  mode  the  FIR  CW  filter  centre  frequency  is  moved  from   0  to  1200  Hz    while 
keeping fixed the BFO frequency.   
The down conversion from 12KHz  to 0 - 1.200 Hz is made variable.  
 It’s  expected  that  the  operator    choose  the  centre  frequency  of  t he  filter  and  then  to  tune  the 
receiver with the VFO to have the tone down -converted inside the PB of the filter.   
 
When  a  slow  speed  CW  signal  is  being  received  the  Dit  and  Dash  co de  can  be  displayed  in  the 
Audio Oscilloscope to help the decoding.