For Improved hearing above 148Mhz for the ICOM IC-706: Tools required: 1) #0 Philips head screwdriver 2) 10 - 15 watt pencil tip soldering iron 3) Magnifying glass 4) Tweezers Remove the TOP cover by removing three philips head screws on the top and one on each side. The fourth yellow wire from the right on the header, should be cut open. just above the 9 MHz SSB filter FL-30. This controls a low pass filter at 120MHz which remains in service when above 148MHz and make the IC-706 very deaf above 148MHz. Note: Be careful, another yellow wire exists on the same header. Above is the new official Mod from Icom USA !!! This increades sensitiivity avove 148MHz, but degrades sensititivity in the 88-108 FM Broadcast portion. *************************************************************************** Below is a mod that takes the yellow wire mod one step further, to restore FM broadcast sensitivity and keep reception above 148MHz. Connecting open yellow wire to J8 VCO transistor switch bank. I tried this mod and it works, If I just did the yellow wire mod, I noted RF images from the 144-148MHz, falling in the 82-84MHz region, by reconnecting it to the VCO switch bank, no more images, and FM broadcat restored, with good sensitivity above 148MHz. Only noted that FM broadcast FM band can overload aircraft band betwwen 118-129Mhz, I switch the preamp off(green to black) and the problem goes away and still can hear aircraft. 73 Mike WB6DJI I suggest that a pin with a plug be done for this J8 mod for future Icom 706's radios to implement this in a production environment. Date: 16 Nov 95 15:12:30 EET From: harjula@ntc01.tele.nokia.fi Subject: Icom 706 - modified In article <4884r9$14to@chnews.ch.intel.com>, cmoore@vegas.ch.intel.com (Cecil A. Moore~) writes: > In article <1995Nov8.090310.1@ntc01.tele.nokia.fi>, > wrote: > >>The fourth yellow wire seems to control >>a lowpass/highpass 120 MHz filter. In the standard configuration the highpass >>filter is used only on 144-148 MHz, every other frequency uses the lowpass. >>Anyway, if you want to listen to frequencies above 120 MHz this mod is >>very useful. It does even remove most of the FM band intermodulation. >>I just don't understand why Icom has not put the switching limit on >>120 MHz instead of 144/148. > > Does this mod affect HF or 6m? After the mod, what frequencies use the LP and > what frequencies use the HP filter? The mod affects only frequencies above 60 MHz. If you just cut or remove the yellow wire, the HP or actually 2m bandpass filter is used all the time. Last night I took the loose yellow wire and connected it to a VCO control switch transistor (?) on the lower PC board. Now I have the LP filter in use between 60 and 129 MHz and the 2m bandpass between 129 and 200 MHz. There are five SMD transistors on the lower PC board just behind the "MENU" button. The one in the middle controls the VCO that is in use from 60 to 129 MHz. The single pin has 5V when within this range. The mod affects only frequencies above 60 MHz. If you just cut or remove the yellow wire, the HP or actually 2m bandpass filter is used all the time. Last night I took the loose yellow wire and connected it to a VCO control switch transistor (?) on the lower PC board. Now I have the LP filter in use between 60 and 129 MHz and the 2m bandpass between 129 and 200 MHz. There are five SMD transistors on the lower PC board just behind the "MENU" button. The one in the middle controls the VCO that is in use from 60 to 129 MHz. The single pin has 5V when within this range. There is a trace from this pin to a plated-through hole near J8. This is a good place to connect the wire. (I haven't even seen the schematic so cannot say if this is the best way to do it. But it works for me.) ***************************************************************************** (Notes: de WB6DJI) found this point with a DVM to identify right plated thru hole(Just to to left of J8 marking on board on bottom side of radio) I put a 3/8" wire, reheated it and got it to say in in the plated thru hole next to J8, the attached the open ended yellow wire to it. Careful not to damage the gray cable with your soldering iron, its pretty tight, small area in there!! **************************************************************************** 129 MHz seems to be quite close to the cross-over point of the LP and 2m BP filters. Here is a listing of the (NBFM) signal strength needed to "light" the first segment on the S-meter on each frequency: MHz uV/LP uV/BP 125 .8 2 135 12 .5 145 .15 155 30 .5 165 3 175 11 185 140 After the mod I can listen to the Helsinki airport on 134 MHz but the Meteo on 128.4 is still drowned in intermod from the FM BC band. > thanks and 73, Cecil, KG7BK, OOTC (not speaking for my employer) Neither am I. Proceed at your own risk etc. And have more fun with the 706 ! 73 de Arto, OH2BGN -- Arto Harjula tel +358-0-5112 8308 fax +358-0-5112 8299 Nokia Telecommunications / PMR arto.harjula@ntc.nokia.com This is the 50Mhz and down mod. I myself need the above 50 mod. All those alergic to surface mount quit now. The 706 has five diodes on the main board (just to the right of the orange ribbon cable connection and to the left of part R-198) in a row, unmarked. The one you need to remove is D-59, second from the left (with the speaker side up and tuning knob facing you.) in that left to right row. Caution: removing this diode might disable further mod's (unless you can remove it whole and reuse it.) and WILL void the warranty. Mail me any further mod's you find. This mod. came from a trusted dealer in LA. I have not done it yet myself. Good luck. M. Davies -- There are men whom one hates until a certain moment when one sees, through a chink in their armor, the writhing of something nailed down and in torment. Kersh ICOM-706 MODIFICATIONS As of Dec. 9, 1995 SUMMARY ------- MODIFICATION 1: Enables extended transmit from 1.6 to 54 MHz inclusive. MODIFICATION 2: Enables extended receive from .05 to about 165 MHz inclusive. CAUTION ------- Improperly performed modifications can severely damage your radio. Use extreme caution. Proceed at your own risk. Transmitting on frequencies other than those assigned to the amateur radio service may be illegal. TOOLS RECOMMENDED ----------------- 1) Small philips-head screwdriver 2) Magnifying glass 3) Small wattage (15 watt) soldering iron with a small tip 4) Long-nosed pliers 5) Paper clip 6) Tweezers MODIFICATION 1 -------------- Result of modification: The IC-706 transmits only on the ham bands. This modification allows for transmit on any frequency from 1.6 to 54 MHz. The radio will also continue to transmit on 2 meters (144 to 148 MHz in the United States) at 10 watts output. This modification will NOT allow for transmit on the AM or FM broadcast bands. The radio will appear to transmit on most frequencies above 54 MHz, but the power output will be a milliwatt or less. The highest power output will be 100 watts from 1.6 to 54 MHz (SSB, FM, CW; 40 watts AM) and 10 watts on 2 meters. (SSB, FM, CW; 4 watts AM) Note: This modification requires that you reset the CPU. All memory information will be erased. 1) Disconnect the power cable. Open the TOP cover of the radio. You will need to remove only 5 screws: three on the top of the radio and one screw on each side. Pull up the speaker carefully and set it aside. Look at the radio from the front; the speaker area should be in front. 2) Locate the rectangular, silver 9 MHz SSB filter. This is clearly marked on the top of it. Now look to the right. Note the "D 108" marking. Below this marking, there are three tiny black diodes. There are two diodes, followed by two blank sockets, followed by another diode. 3) The second diode from the left (the middle diode) is diode D-59. This diode needs to be removed. There are many ways to remove this diode. The easiest way is to crush it with long-nosed pliers. Another way is to use a low-wattage soldering iron and tweezers and carefully heat the diode, then pull with the tweezers. Be extremely careful not to apply too much heat. 4) Re-assemble the radio. Press and hold the UP and DOWN buttons on the right side of the front panel, and while holding them down, turn on the power. This resets the CPU. MODIFICATION 2 -------------- Result of modification: The bandpass filters on the IC-706 are improperly wired. As a result, the radio does not receive any stations above 129 MHz, except in the 2-meter band. This modification allows for reception up to about 165 MHz. (Note: If your radio receives the FM broadcast band (88-108 MHz), the aircraft band (108-136 MHz), 2 meters, and stations above 148 MHz, it is possible that the modification has already been performed by Icom; you may have a later model.) 1) Open the TOP cover of the radio. You will need to remove only 5 screws: three on the back of the radio and one screw on each side. Pull up the speaker carefully and set it aside. Look at the radio from the front; the speaker area should be in front. 2) Locate the rectangular, silver 9 MHz SSB filter. This is clearly marked on the top of it. Now move your eyes toward the back of the radio until you notice a long white connector with several colored wires on it. 3) The 4th wire from the left, a yellow wire, needs to be removed from the connector. You can cut this wire carefully if you wish. Or, another alternaive is to remove it from the connector. Stick a paper clip or perhaps a pin into the side of the connector under the yellow wire. Pull the wire with tweezers and remove it. There are two yellow wires; be sure to remove the 4th wire from the left, not the other one. 4) Open the BOTTOM of the radio, removing similar screws as you did when you removed the TOP. 5) Look at the PC board just behind the MENU button. You will notice a jack marked "J8" with a grey cable coming out of it. 6) To the left of jack J8, you will see five tiny transistors. Look at the middle transistor. Follow the light green circuit board trace from the middle transistor to a tiny hole just to the left of J9. 7) The yellow wire from the top of the radio needs to be connected to this transistor. The easiest way is to solder a small insulated wire to the yellow wire you just removed, run this new wire underneath the radio to the hole you found in #6 above, put the wire into the hole, and solder the wire into the hole with a low-wattage soldering iron. Use caution not to damage the grey cable or to apply too much heat. This could damage the PCB and seriously affect the radio. If you perform only steps 1 through 3, you will be able to hear stations above 148 MHz, but you will not be able to hear FM broadcast stations on the 88-108 MHz band. RECEPTION SUGGESTIONS --------------------- 1) You need to use wide FM to receive FM broadcast signals on the 88-108 MHz band, or TV sound signals between 59 and 87 MHz. To receive wide FM, press the MODE button until "FM" or "FM-T" appears on the display, then press and hold the MODE button for two seconds. "WFM" should now appear on the display, and you should be able to hear the FM broadcast stations. Reception quality is quite good if you use a decent external speaker. 2) Aircraft (118-136 MHz) uses AM. You will need to set the radio to AM to receive aircraft. 3) The sensitivity of the radio diminishes rapidly after about 165 MHz. NOAA weather stations (162.40 to 162.55) are clearly audible, however. 4) If you find the FM broadcast signals overload the aircraft portion of the bands, disable the preampifier by pressing PREAMP (the green light should go out.)