Although the ICOM FL222 (1.8khz –6db), when using with FL223, will greatly improve the selectivity, the sound is too harsh. In the 6 m DX hunting, signal is always weak (often 42 or 53), using FL222 will make you lose your RX signal entirely.

I understand that some of the hams simply like myself – not a radioman by profession- find difficulties in doing the modification. Therefore, I would take this chance to detail the steps:

1. With the LCD front panel facing yourself and bottom facing upwards (the carrying handle is now at your right hand side, this will be the referencing position in the following steps), remove the bottom cover;
   
    
2. Remove total 6 screws holding the main unit – 4 at the corners, 1 near the middle and the remaining 1 near the voice synthesizer socket;
   
    
3. Remove the screw on rear panel in between ALC & send RCA sockets;
   
    
4. Remove heating sinking clip holding transistor to chassis (left hand side of the main unit PCB);
   
    
5. Remove all the flat ribbon cables (white in colour) by holding the cables (not the socket) and carefully pull them up. Do not bend or fold them!! Also no excessive force;
   
    
6. Watch out the small flat cable at the lower left corner towards the front panel; gently pull it out towards right. Be careful, this small flat cable is very delicate and is fixed by a piece of adhesive tape. Remove the adhesive tape first before pull it out;
   
    
7. Remove the RF Unit metal shield and loosen 2 (or 3 as appropriate) shielded cables to allow the main unit PCB to fold out to a workable position;
   
    
8. Fold out the main unit PCB, loosen the two hexa nuts & washers holding the FL96;
   
    
9. Desolder the filter pins of FL96 using solder sucker and a 20 to 25 watt soldering iron;
   
    
10. Remove FL-96 by wiggling it gently to free pins. You may need to re-heat pins quickly to release filter;
    
     
11. Replace with FL44A; tighten down studs with nuts and washers (do not screw too tight);
    
     
12. Re-solder pins of FL-44A; clean excess flux and make sure good solder join;
    
     
13. If you have already installed a FL223 (9mhz narrow IF filter), you may wish to take this chance to solder the studs of the metal case to the PCB. This will hold the filter to the PCB firmly – better contact and hence less noise. Clearly, you should only do that if you do not want to remove the FL223 in the nearest future.
    
     
14. Re-install the board and all cables unplugged in previous steps. When re-install the flat ribbon cables, make sure you use the minimum force and only when the pin positions are correct. Re-instate the adhesive tapes, heat sink clips removed earlier;
    
     
15. Test the radio and replace covers. I now have 4 IF filters namely FL80 (original stock) and FL223; FL44A and FL222 – a great varieties.
    
     
16. If you do not like FL44A, you may consider using INRAD # 109, which will give you a slightly better shape factor.

Clearly, any modification to the radio is at your own risks and I will not take up any responsibility on the above.

Open de bottom side off the radio and turn it so you can read the text on de 455kc standard wide ssb filter. Next to te right down side off the filter you will find a tiny smd switch with W-N printed on de pcb. Change the switch position to wide.

Make sure you use a good mike! A bad one will sound even wourse!

And be carefull not overload the ALC. Otherwise you might splatter!!!

BTW Early numbers (below 01900) do not have this secret option!

Remove bottom cover and then remove cover to RF Unit - see below.

To increase overall Scope gain:

Lower the value of R963 (100k as fitted).

I put a 56k 1/4w through-hole resistor across R963 - see above - making the combined resistance approx 36k.
(One resistor leg was soldered to pin 2 of IC-961 and the other leg to the junction of R966 and R964)

To be neater you could remove the small 0603 SMT resistor and replace it with a 39k 0603 part.

To adjust Scope base-line:

Trimpot R966 will adjust the base-line of the Spectrum Scope.

The "Line Level" audio output on pin 5 of Rear panel connector ACC1 is very low, with the manual stating 300mV. Normal Line Level is regarded as about 700mV. Although my MiniDisc Recorder had a gain control for its Analogue I/P it still couldn't make 0 VU. Here, by adding two resistors we can increase the gain of the audio appearing on pin 5 of ACC1.

• Remove the bottom cover.
  
   
• Remove 6 screws holding down Main Unit.
  
   
• Remove screw on rear panel inbetween ALC & Send RCA sockets.
  
   
• Remove heatsinking clip holding transistor to chassis.
  
   
• Remove flat ribbon cable to J3 in far right corner.
  
   
• Carefully pry PBA loose and fold over - see at left.
  (I actually had to remove RF Unit shield and loosen a shielded cable to allow the Main Unit PBA to fold out).
  
   
• Locate IC-503, a NJM2058 OPAMP in an SMT SOIC14 package.
  
   
• Remove W3 0603 SMT link.
  
   
• Fit an 10k 0603 SMT resistor in W3's place.
  
   
• Fit a 1/8w 5k6 through hole resistor from IC-503 pin 9 to ground.

We have effectively changed the OPAMP IC-503c from being a unity-gain follower into a non-inverting amplifier with a gain of approx 2.5.

Modification summary:

Remove the W805 jumper chip on MAIN unit by soldering iron.

Modification Procedure:

1. Remove bottom cover of IC-756.
   On MAIN unit board you will see I.F. filters and daughter board (DSP PBA) on the right hand side.
   W805 jumper and IC803 chip located under DSP PBA.
   
   Remove DSP PBA (lift up carefully!)
   
   Look for IC803 and line of jumpers (0603 sized SMT links).
   
   Remove W805 jumper - as indicated below.
   
   Re-install DSP PBA
   
   Re-fit bottom cover.

                    ---------------
           [W801] |               |
           [W802] |               |
           [W803] |    IC 803     |
           [W804] |               |
   Remove=>[W805] |     CHIP      |
           [W806] |               |
           [W807]  ---------------
           [W808]