H/L/DTMF + VFO knob = Change output power (4 power levels when using 13.8 vdc)
The following key combinations selects "power on modes". Start with the radio OFF, then hold down the indicated keys, and continue to hold them while turning the power ON. Some 'modes' override others.
LIGHT + * LIGHT + 0 LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT LIGHT + + + + + + + + + + + + + + + 9 A B C D # B + #
= PTT enable = PTT Disabled (inhibits the transmitter, good security method) = = = = = = = = = = = = = = = 1 MHz digit set (4 digit frequency entry) 10 MHz digit set (5 digit frequency entry) 100 MHz digit set (6 digit frequency entry) Scan pause until signal disappears Scan pause for 10 seconds ???? Unknown action Power Save deactivated (use this for packet operation) Power Save (minimum - 0.125 / 0.5 second) Power Save (maximum - 0.125 / 2.0 seconds) ???? Unknown action ???? Unknown action ???? Unknown action ???? Unknown action ???? Unknown action RX Extended Range enable This requires that diode D13 is removed (left diode on CPU board). Note that this diode has already been removed by ICOM at the factory on many units. Be sure to hold these keys down until the activity display stops and is showing a receive frequency.

FUNC + A

= Reset the CPU (this will clear all the memory channels to the factory defaults)
This modification is read 820 times.
(IC-24) IC-24AT sensitivity
Following the frequency expansion modification (as specified by Icom), a sample IC-24 was recently tested for tuning range and input sensitivity for an S9 signal. While the sensitivity measurements should not be directly compared with the manufacturer's specifications (usually measured reference to a signal-to-noise quieting ratio), this "quick and dirty" data should give you a good idea of the sensitivity to a medium-strength signal.
Tuning Range 310 107.354.995 MHz MHz MHz MHz MHz
Mode (fm) (am) (fm) (am) (fm)
Band VHF VHF VHF VHF VHF range range range range range
Sensitivity for S9 Signal approx 1 mV 10 - 30 V 1 V - 1 mV (1) 50 V - 1 mV (2) 50 V - 3 uV (2) 3 - 10 V 1 V - 100 V (3) 10 - 100 V

355 - - - 955

MHz (fm) MHz (fm) MHz (fm)
UHF range UHF range UHF range
Notes: (1) The sensitivity from 138 - 150 MHz was 1 uV. From 150 - 240, the sensitivity decreased almost linearly from 1 uV to 1 mV (with input voltage plotted logarithmically). (2) The sensitivity increased almost linearly for both these ranges (with input voltage plotted logarithmically). (3) The sensitivity plot looked like a "U" with the bottom of the "U" corresponding to the range 440 - 450 MHz (1 uV). The sensitivity then got worse below 440 and above 450. (Tests courtesy of WB6GTM)

(IC-2410) Cross-band repeat
An edited version from an ICOM info sheet) 1. Set frequencies for both UHF and VHF. If necessary, set transmit offset and tone. 2. Hold the "BAND" switch and the "SET" switch. The memory number display will flash the letter "L". This indicates the 2410 is in the "Mini Repeater" mode. 3. Transmission by PTT is possible. If PTT is operated, the band which is indicated by the flashing decimal point will be transmitted on. This can be done even when in "Mini Repeat" mode. In other words, PTT has priority over the "Mini Repeat" operation. Transmitted band will be switched by the "UP" or "DN" key on the microphone. The flashing decimal point will indicate which band will be transmitted on. 4. Mini Repeater function will remain even when power is turned off. To disable repeater function, hold the "SET" key until the flashing "L" disappears. Remote cross-band activation To activate cross-band repeat remotely: after dialing "B", optional 3 digit code then "#", the command for cross-band repeat on is "B", "D", "*". To turn off repeat, dial "B", optional 3 digit code, then "#".
This modification is read 720 times.
(IC-2410) IC-2410 Dual Band External & Mike Remote Codes

Call 1 VHF 4 Vmoni 7

MR 2 UHF 5 Umoni 8

VFO 3 High 6 Low 9

CLR A Acs B Spch C
Dwn Mute Up Ent Please enter a blank line to continue, anything else to halt output * 0 # D

Other Functions

B# or B???# = External On (?=password) Further protection used Tone/Squelch B* = External Off DB* DB# DC = CrossBand On = CrossBand Off = Speech Transmit Freq.
4,5,7,8,0 Function not available via External Remote Control???? C Function not available when in CrossBand Mode???? Display debate, don't know why the original display was boycotted, but I seen both & had a choice. I preferred the original, lovingly refer to, as stealth. Think twice, before you get the other one.???? There are diodes to be installed for some features, like transmit in Please enter a blank line to continue, anything else to halt output rest of UHF ham band (420-450) and extended receive.etc. Check your local authorities, regarding scanning laws.
This modification is read 709 times.
(IC-2410) IC-2410 Modification area as follows. New and old version
For OLD version 1. Turn on the radio wtih pressing [V/MHz] + [SET] + [DN]on microphone. That's All!!! X-band reperter modification Cut diode [D2] on back side of front panel. Press [BAND] + [SET] more than 1 sec. cancel => press [SET] more than 1 Sec. For NEW version 1. 2. 3. 4. SEE THE BACK SIDE OF FRONT PANEL. YOU CAN FIND Li BATTERY. CUT [W27] or [D10] & [D8] Reset the radio.

28-08-1999

(IC-251) Modifications for the ICOM IC-251
Author: Martin - G1GYC - Martin@g1gyc.demon.co.uk.MODIFICATION.NET 1987
SSB & CW VARIABLE POWER
Place set with the controls towards you and remove lid. If necessary check FM and CW power. Connect set to known good dummy load and power meter.Locate R13 and R14 on the small board behind the front panel RF power control. With RF power control on max, TX on FM and adjust RH pot(R13) for 10-12watts. Turn RF power control fully down and adjust LH pot(R14) for desired low power setting (min 200mw). Short key jack at rear of set, switch to CW, TX and adjust R129 for 10-12watts the same as on FM. Switch off power. Locate the brown wire to the left of the Xtal filter it runs from next to R258 to near R327 its marked with a small b on the main unit board layout diagram. Cut this wire at the front end and solder to the emmiter of Q65 or the purple lead marked I on the main unit layout. Solder the slider of a 4.7k preset to the LH end of the resistor behind R14,then
solder a 3.3k resistor to one leg of the preset, run a wire from this resistor to the top of R272 (scrape the paint off before attempting to solder). Switch on. Switch to CW, TX and with front panel RF power control fully down adjust the(4.7k preset for desired low power level (min 200mw) SSB power is the same as CW. The front panel control now affects both FM,CW & SSB power levels. The following modification was carried out to enable the front panel power control to be used on CW/SSB as well as FM. The modification is in two parts (1) the front panel and (2) the main circuit board. (1) FRONT PANEL i. Remove four retaining screws and top cover. ii. Remove four retaining screws and bottom cover, disconnecting the speaker. iii. If you have a Mutek front end board fitted remove it now. MAKE NOTE OF THE CONNECTIONS TO IT! ***WRITE IT DOWN*** iv. Remove the four front panel frame screws v. disconnect the wiriing harness and remove the front panel. NOTE WHERE ALL THE PLUGS GO! ***WRITE IT DOWN*** vi. Locate the orange wire linking the mode switch and the board behind the power control potentiometer. vii. Desolder it from it's present position on the mode switch and move it to the common side of the switch. That completes the front panel mod. (2) MAIN CIRCUIT BOARD i. Remove the internal PSU if fitted. ii. Remove the VCO and screening plate on the underside of the main circuit board. iii. Now turn the rig over and find the brown wire that places TX9V(FM) on to Q64/Q65. If you look at the board layout in the manual the wire runs from sectors 3F to 4F and is marked "b". iv. Cut this wire where it joins the board, near R327/R46. v. Now find the purple wire marked "k" on the board layout on the edge of sectors 5F/6F, locate this point on the underside of the PCB. I did this by standing the rig on one side panel and shining a light upon the component side of the board. Pointing to the wire with a pencil or radio driver and looking at the track side to see the shadows. vi. Once you have identified the point on the trackside of the PCB desolder the wire and clear the hole that is left. vii. Join the purple and brown wires, then solder them back into the hole from where the purple wire came from. If the brown wire is to short replace it, as I did. I used a purple wire striped from a ribbon cable. This now means that when the radio is switched to transmit TX9V is placed on to Q64/Q65 and not TX9V(FM) as before. That completes the mod. viii. Reassemble the radio in the reverse order to which you disassembled it, leaving the top cover off. ix. The only thing to do now is to check that the rig still works ok and to reset the high and low power levels. This is done by adjusting VR13(high) and VR14(low) with a power meter and dummy load connected to the aerial connector and if possible a two tone audio generator feeding into the microphone socket at around 600mV should de used to set the rig up on SSB. The power reading on the RMS power meter should be approximately half the PEP. When the desired power levels have been set fit the top cover. NOTES: I found that the power control on SSB/CW tends to drop the power off rather quickly but if you use it in conjunction with the mic gain control very low power levels are attainable (milliwatts). Since this mod was done, G8RCF Des Sayer has also completed the same and when we last spoke said he had not experienced any problems. An ALC input is included in the multiway socket on the back apron and if you are going to use the rig with a transverter for 6M, 4M, 70Cm, 23Cm or even HF, I suggest you look at a method of using this input to control the drive to the external equipment and not the modified power control as it is far too easy to forget to lower the power or to catch the control. The afore mentioned note on ALC apart, this mod is useful to run a linear at a lower out put, e.i. I run my MML100s at 40 watts or less as this stops breakthrough to a neighbours television set, yet alowing me to gain a higher ERP than just using the rig to feed in to the aerial. My thanks go to G8RCF who was the second one to modify an IC251 using the method I used to my knowledge. Hope you find

This modification is read 2638 times.

27-01-2001

(IC-2800) DTMF options card
Author: 73 de SM0XKO Peter If you have ICOM IC-2800 + options DTMF card ( CT-91 ) (in sweden UT-49) you can make changes from other radios through DTMF tones. First! Push [DTMF] twice on the radio and its light (REMO) in the display. To make changes press Open = B code # default code = = Call channel 2 = Memory 3 = VFO 6 = High transmit power 9 = Low transmit power * = step down # = step up A = Escape D = Clear only in mode 2 or 3. After that you can enter memory channel number or VFO Mhz DB* = Log out / Cross band repeater ON B* = Log out / Cross band repeater OFF Good luck! / 73 de SM0XKO Peter
This modification is read 2160 times.

20-10-2001

(IC-2800) Screen saver Turn OFF option for IC-2800
Author: Chuck Lynn - stang@tds.net.MODIFICATION.NET
When the unit is turned off, simultaneously depress the "CHANG/L" key and the "POWER" key. Both located on the bottom corners of the control head. Sceen saver mode will be suspended. To reactivate sceen saver mode repeat the above step. 73 KG4FKU Chuck
This modification is read 2132 times.

13-01-2002

(IC-2800) Cross Band Repeat for IC-2800
Author: KC5VCF - KC5VCF@hotmail.com.MODIFICATION.NET
To cross band repeat with the IC2800 Hold down simutanisuly CHG/L and both MAIN/EDIT buttons.
This modification is read 1221 times.

17-02-2002

(IC-2800) Enable crossband function for IC-2800
Author: - helmut.knaak@t-online.de.MODIFICATION.NET
Unsolder or cut D 60 (near W 13) Press "Main UHF,Main VHF,Chg/L" For 2 seconds, crossband will be enabled.
This modification is read 649 times.
(IC-281) Crossband repeat
To enable crossband repeat press and hold the BAND key and the SET key for about a second, a flashing L will appear in the lower right. To turn off hold the SET key. Unfortunately code squelch does not seem to work when crossband repeat is enabled. Don't know about tone squelch.
This modification is read 877 times.
(IC-281) Extended Receive for IC-281
To enable extended receive a jumper has to be removed. To enable extended transmit a diode has to be removed. I have only tested the extended receive which gives you from 118-174.995 and 320-479.995. Open the case by removing all the screws on the top, bottom and left/right sides and separating the top and bottom covers from the chassis. Next remove the plastic front panel that covers the logic circuit board by removing the two top and two bottom screws that attach it to the chassis. Next remove the front panel logic board by taking out the four front screws that attach it to the chassis. Position the logic board so that the side normally near the chassis is on top and a round flat battery attached via leads is visible with the connector near the bottom and the cut out at the bottom right. Below the battery on the lower right there are a number of diodes, most likely surfaced mounted. Look just to the left of the diodes, there will be a very small surface mount jumper at the bottom (-#WW#- on diagram below). There is no silk screen on the board to identify it (on mine at least) but the part itself may have a zero printed on it for zero ohms. Removing this jumper will give you extended receive capability. Diagram (very bad but hopefully you get the idea)

Frequency: 80.00 MHz 90.00 MHz 100.0 MHz 110.0 MHz 140.0 MHz 150.0 MHz 160.0 MHz 170.0 MHz 180.0 MHz 190.0 MHz 191.61MHz V dBm 217 ----101.185 -122.16 -123.3 -117.9 ---74 --- vfo goes unlocked ---
210.0 MHz 590 -50 220.0 MHz 590 -50 230.0 MHz 2000 -40 250.0 MHz 173 -62 260.0 MHz 340 -56 270.0 MHz 27 -78 280.0 MHz 4 -94 290.0 MHz.7 -110 300.0 MHz.38 -115 310.0 MHz.5 -113 320.0 MHz.275 -118 330.0 MHz.23 -120 340.0 MHz.23 -120 350.0 MHz.32 -117 360.0 MHz.4 -115 365.0 MHz.72 -110 -------------------------------vfo goes unlocked-------------------
Transmit Power: Voltage input at Coaxial plug on top of radio versus Power output

15.0V 14.0V 5.3W 5.2W

13.0V 12.0V 11.0V 10.0V 9.0V 8.0V 7.0V Internal HI power LO power LO power LO power
5.0W 5.0W 5.0W 4.5W 3.75W 3.0W 2.3W Battery Pack (7.2V): - 2.5W 0.9A 3 - 2.5W 0.9A 2 - 1.3W 0.68A 1 -.4W 0.43A
13.8V input via Coaxial Plug on top of radio: HI Power - 5W 1.3A LOW power 3 - 3W 1.0A LOW power 2 - 1.4W.76A LOW power 1 - 0.4W.5A
This modification is read 1029 times.
(IC-2SAT) Software coverage mods, IC-2SAT
From: kraft@perdita.gac.edu (Steven Kraft) Modifying the IC2SAT for extended receive is very simple if a certain diode was not installed at the factory, as was the case with my 2SAT. Turn the radio off, simultaneously press [#],[B],[light] and turn it on. (The button is not labeled, it is on the side under the wrist strap.) Release those three buttons after the radio beeps. (I think that mine beeped.) It can now receive over three large frequency ranges and will receive AM aircraft band transmissions acceptably. Experiment to find which frequencies you can get. The memory channel number will display the letter "U" to show that the PLL circuit is unlocked on frequencies that cannot be received. It will tune from 0-1300MHz but the operable ranges are not that big, its highest receiving freq is a little over 300MHz. If that doesn't work, a diode will have to be removed. It is a glass diode mounted on the PTT switch circuit board, and I think it is the only standard component in that area. It is mostly surface mount components. Standard disclaimers apply, since I cannot be responsible for whatever you may do if and when you must remove the front to look for a diode. (The owner's manual explains how to open the 2SAT.) Steven Kraft KRAFT@GAC.EDU KE9RW to other hams

This modification is read 536 times.
(IC-3) Low audio speaker mike on IC2A, 3A, 4A OR 02AT
This modification is read 367 times.
(IC-32) Out of band mod for the IC-32AT
This mod allows the unit to RX-TX outside both ham bands, plus function as a crossband repeater! BE CAREFUL THAT YOU DON'T INADVERTENTLY TRANSMIT! DISASSEMBLY 1. 2. 3. 4. Remove the battery. Loosen but do not remove the two screws holding the PTT switch plate. Remove the 4 screws on the back of the radio. Now remove the front of the HT by carefully lifting the bottom edge and then pulling it down so it clears the top of the HT. Be carefull as there is a ribbon cable attached. 5. Unplug the Speaker/Mic plug from the main chassis to allow the front conver to be fully opened.
MODIFICATION (Refer to figure 1.) 1. 2. 3. 4. Remove D907 Remove D913. Move D912 down to next pad. (D???, bottom location) Add diodes Da and Db (1N914 or Equiv.).
VCO ADJUSTMENT 1. Unplug and remove the PTT/FUNCTION circuit board and lay it aside. 2. Remove the top circuit board by removing the screws located in each corner of the board. These are the ones that are recessed and not the ones on top of the board. 3. Carefully pry up the circuit board until it can be folded out. Plug in the PTT/Function button circuit board cable. 4. Hook up the battery and reset the CPU by holding down the "Function" and "A" buttons and cycling power off and on. 5. On the bottom circuit board are located the two VCO's (refer to figure 2). The left hand VCO is for VHF and the right hand VCO is for UHF. Located just to the left of the UHF VCO is a resistor standing on end. Hook the V. O. M. positive lead to the top of this resistor. The negative lead goes to ground. 6. Under aluminum tape on each VCO is the adjustment point. Normally, the VHF VCO will not require adjustment. The VHF adjustment is L554, the UHF adjustment is C510. Adjust the desired VCO for a +.5vdc reading for the lowest frequency you wish to tune on that band. Don't forget to retape the holes on the VCO's. 7. Disconnect the battery and carefully reassemble the radio. DON'T PINCH ANY WIRES! CROSSBAND REPEATER COMMANDS 1. Enter one VHF and one UHF frequency into each VFO. (Offsets won't work.) 2. To enable crossband repeater, hold down "FUNCTION" buttom and key in, [C] [6] [D]. Then release "FUNCTION" button. 3. To disable crossband repeater, wait until handheld is in receive only and then hold down "FUNCTION" button and key in, [D] [C]. Then release "FUNCTION" button. *** Once handheld retransmits a signal from opposite band you cannot disable crossband function untill squelch closes and handheld quits transmitting! *** Figure 1

Now power on and type in the frequency coverage as request, for the VHF and the UHF. Above I alredy mentioned the sure working frequencies. To power on the transponder old the BAND and SET botton for two seconds. Same operation is required to disable it. 6. Make same operation as point 1 and 2 if not yet ready. 7. Unplug the two flat cables. Be kindly !!! And use appropriate tool to open the plugs. 8. Unscrew the LOGIC UNIT (4 screws) and unplug it. Take off from the back all the screws around the antenna cables Take off the screws on the metal plates to cover the high power section on both sides. 9. Make free the 8 soldered pins with a solder and the tools that you prefer for this operation, located near the VCO Unit on MAIN B. Make free the pin near the power cable (+) and the pin near the antenna cable (hot). Pratically you have 10 pass trought pins to desolder. 10. Unscrew all the screws on the MAIN A and MAIN B boars and remove them from the aluminum block. Unplug the back fan from MAIN A board. EASY ??? Now is all open !!! 11. Solder a shield-cable on PIN 2 of J2 of VCO B for the TX Audio on UHF Solder a shield-cable on PIN 2 of J2 of VCO B for the TX Audio on VHF Choose the smaller cable that you can have for this !!! You just have a little bit of distance. A good idea is to apply a capacitor to filter the signals (100.000 pF usually is good). 12. Place back the MAIN A and MAIN B board. If you're lucky positioning your cables will be easy. But be careful, because you musn't damage the cables. Use teh right screws and solder the 10 PINs. 13. Place back the LOGIC UNIT with the right screws and work on it ! Solder a shield-cable on PIN 11 of J2 for UHF RX Audio Solder a shield-cable on PIN 14 of J3 for VHF RX Audio It's always good place the capicitors on this connections. 14. Place back the front panel flat cables and the panel too. If you like you can place a wire for the PTT signal directly inside your RTX and than follow the hole in the back where you place the 900 MHz antenna to have all the cables outside. Replace the back fan plug. Replace back all the screws on your table and remeber to plug-in the speaker plug before to replace the two covers. EASY !!!! Now if you done a good job all it's running. but check your watch. you spent here one day and your wife is still waiting for you to make shopping. You can test your RIG tommorow !!! Will be better !!! I hope that you'll be lucky. 73'sss de Flavio IK2XYU or KF6EEZ !!! For other infos, send me a message:

(IC-575) General Coverage TX Modification
Author: Adam MAURER, VK4CP - vk4cp@bigpond.com.MODIFICATION.NET
Access to the LOGIC UNIT is required. PREPARATION: 1. Disconnect mains lead and antenna lead. 2. Remove the EIGHT screws from the TOP COVER. 3. Remove the FOUR side screws. (Two left & two right). 4. Remove the top cover. 5. Remove FOUR screws holding the PA/REG UNIT. (Two at top front & two at rear). 6. Carefully hinge PA/REG UNIT back out of the way. 7. Remove shield to LOGIC UNIT. (Unit on right hand side).
MODIFICATION: Refer to diagram above. This modification is done to the LOGIC UNIT in three parts; 1. Cut the red wire to J3 2. Add a diode (small signal type ie; 1N914 etc.) between PIN 18 of IC5 74HC244 [ANODE END OF DIODE] and the CATHODE of D10 [CATHODE END OF DIODE]. The back-up battery may have to be carefully levered out of the way in order to gain better access to PIN 18 of IC5. 3. Add a diode (small signal type ie; 1N914 etc.) between the pad where D25 CATHODE would go [CATHODE END OF DIODE] and the pad just opposite D20 CATHODE [ANODE END OF DIODE]. See diagram for details. (that's coming later) Thanks to http://www.qsl.net/vk4cp/ for the modification.
(IC-575) Pass band Tuning Modification
(for those who have that silly Data Level control)
This article appeared in "Six News" Issue 40
17 June 1993 (Revised 15 October 1996) Although specifically for the IC-575, this modification should apply to both the IC275 and IC-475. The early versions of the Icom IC-x75 rigs had Pass Band Tuning (PBT), a feature left off later models, but with minimal effort this feature can be retrofitted. An improvement in 2nd I.F. selectivity also results. The PBTless models use the PBT potentiometer as a "Data Level" control which adjusts the level of the external audio input from the accessory socket on the back of the rig. The most obvious use for this is for a RTTY/packet modem. In my opinion the "Data Level" control does not need to be on the front panel because once it has been set correctly for a particular TNC etc. it should not require tweaking. Interestingly, the "Data Level" pot is still a centre-detent type like the original PBT control. Examination of the schematic reveals that it's the same value, 10K, as the original. Furthermore, the PBT line from the D.A.S. unit is now connected to a fixed-value resistive divider, made up of two 4k7 resistors. Hmmm! A comparison between the "old" schematic and the "new" schematic also shows that a ceramic filter, FI3, has been deleted from the newer radios, being replaced with a 0.0047uF capacitor. Other than that, everything else is still there. When you think about it, it's the obvious and cheap way out for Icom to remove this feature by making minimal changes to the design and to "hardwire" the PBT to the centre position, rather than making major changes to its production run. The "missing" filter You will need to purchase a Murata CFJ455K5 filter. The specifications of this filter are; Centre frequency: Bandwidth: Passband Ripple: Input Impedance: Output Impedance: 455kHz 2.4kHz @ -6dB 2dB 2k Ohm 2k Ohm

R107 R108 C47 C48 1M 4.7K 2.2uf.022uf -.1uf
.1 reduces the overshoot from 200%+ to 20%,.022 eliminates it almost completely. However, as the value of this capacitor is reduced, I'm concerned that IM products in the audio may start to increase due to syllabic compression of the RF envelope. I had no way to verify this. Perhaps a project for a better equipped workshop! I would think.047 would be fine, though I'm using.022 without any noticeable degradation of audio quality. Mel, VE2DC
This modification is read 908 times.

26-06-1999

(IC-781) Reduce the internal heat by the speaker
If you remove the internal speaker, you can reduce the internal heat generated therein by quite a measure! LEE, KH6BZF
This modification is read 851 times.

19-03-2000

(IC-781) Icom IC-781 filter modification
Author: Adam Farson, VA7OJ/AB4OJ - ab4oj@arrl.net.MODIFICATION.NET Adam Farson, VA7OJ/AB4OJ, August 1999 The stock FL-96 (455 kHz SSB: 2,8 kHz wide @ -6 dB) can be replaced with an FL-44A (2,4 kHz wide @ -6 dB) to improve adjacent-channel selectivity and sharpen Twin PBT operation. In addition, the stock FL-102 (9 MHz, AM) can be replaced with an FL-223 (9 MHz SSB: 1,9 kHz wide @ -6 dB) to provide an SSB-NARROW bandwidth setting. Here is the filter installation procedure: (I would suggest that you purchase an IC-781 service manual from Icom Parts for guidance, if you do not already have one. Icom Parts should also have the FL-44A). 1. Remove the top and bottom case covers. 2. Lay the radio upside down on a towel, with the front panel facing you. 3. Using a magnetic-tip manual screwdriver with a #2 Phillips tip having rounded blade edges, remove all eleven retaining screws from the IF board (the board with all the filters). 4. Unplug the multi-conductor header cables from the board, to allow the board to be moved aside. 5. Grab the inner edge of the board, and swing the board away from the chassis. Do not stress coax cables on board. Rest board on a stand (e.g. 2 phone books) next to radio. 6. Locate FL-96. Using a solder-sucker or wick, and a temperature-controlled pencil iron, desolder 4 filter pins. 7. Remove nuts & washers from filter mounting studs. (I think the nuts are M3 or M4.) 8. Remove FL-96, wiggling it gently to free pins. You may need to re-heat pins quickly to release filter. The board is G-10, and can take reasonable heat. 9. Place FL-44A on board; tighten down studs with nuts & washers. 10. Re-solder pins of FL-44A; clean excess flux with nylon brush & isopropyl alcohol. Also ensure that there are no solder blobs or slashes.

For the R71A to tune above 31 MHz, in addition to editing the RAM module, you will have to make a modification to the Logic Unit. I have included a file which describes how to do this. See the file named "R71MEM.TXT" for instructions. Credit for this part of the mod goes to the author of that file. The software is NOT a polished product. There isn't much in the way of error checking when reading or writing a file to disk. It will however verify writes to the RAM module automatically after writing. I just added an unlisted (V)erify function accessable from the menu and an automatic CPU timing test. The software should work with a standard IBM-PC bi-directional parallel port with base addresses of 3BC, 378 and 278. Most modern computers, including laptops, now have bi-directional parallel ports. You may however need to mess with your parallel port configuration. I have not had any trouble running the software on my IBM Thinkpad 486-25 or on my AMD-K6-III-450 tower. That doesn't mean it will work for everyone though. Bi-directional mode is selected by writing a "one" bit to port base+2.5 and if your port works differently the program will likely fail. I have heard that some of the more advanced parallel port ICs need to have an "unlock" bit set before bi-directional mode can be enabled. If anyone can provide me with the necessary info I will update the software to support these ICs. Note that values stored in the RAM module are big-endian and that the static RAM IC is only 4-bits wide (nibble mode.) Some important memory addresses (in hex) in the RAM module for the R71A are as follows:
10/11 = 12/13 = 14/15 = 16/17 = 18/19 = (FM has LSB offset USB offset AM offset CW offset RTTY offset no offset)
30/31 = lowest frequency (factory is 100kHz) 3B/3C = highest frequency (factory 30MHz)
Example 1 - To change the lower frequency limit to 10kHz:
Original - 000: 00F1FF1FF002FFFF000B59686800032005930005000000000100000030003000 Modified - 000: 00F1FF1FF002FFFF000B59686800032005930005000000001000000030003000
Example 2 - To change the upper frequency limit to 35MHz:
Original - 000: 00F1FF1FF002FFFF000B59686800032005930005000000000100000030003000 Modified - 000: 00F1FF1FF002FFFF000B59686800032005930005000000000100000030053000
I have enclosed the file from my R71A receivers (MY-R71.BIN and the hex dump MY-R71.HEX) as a starting point for offset tweakers. The offsets are big-endian meaning that the first value is the least significant. You can compare these files against the non-tweaked files (ORIG-R71.BIN and the hex dump ORIG-R71.HEX) to see what changes have been made. Download the whole file.
This modification is read 776 times.
(IC-RP3010) IC-RP3010 disable the CTCSS

This modification is read 312 times.
(IC-Z1A) IC-Z1A Extended Receive
Ok, after messing around with the radio on my own and then getting the "official" mod, here's a summary of the various diode mods for the Z1A: Icom Z1A mods
[B]+[#]+[POWER] = Extended Receive. VFO *DISPLAYS* 50-299.900 and 300-999.900. AM Aircraft band enabled. SET mode now has a new "PLACE" function for setting the direct entry starting digit.
There is room for four diodes in the Z1A located on the CPU board to the left of the ribbon cable connector. On a US version, only the bottom two are installed. D15 is just below and to the right of the four diodes. These diodes are bigger than the rest of the surface mounted components and are easy to spot. The official ICOM mod (which I unofficially saw.) is to remove D15 for extended TX and to use the above keyboard mod for extended receive. According to the sheet, the 800-900 band is NOT available in US versions.

+-+ | | +-+ +-+ | | +-+

<---- Installing diodes in either of these seems to do nothing.
+-+ +-+ | | | | <---- IN: +-+ +-+ OUT: ^ | +------------ IN: OUT:
US Version 144-148 TX 440-450 TX Extended 136-174 TX 380-470 TX (Lose auto-repeater and tone encode) US European 144-148 TX 440-450 TX 144-148 TX 430-440 TX

"D15"-->

+-+ | | <---- IN: US Version Stock +-+ OUT: Extended TX 136-174 380-470 (keeps auto-repeater and tone encode)
A word of warning about messing with the four diode pads: If you detach either one of the installed diodes, the CPU will reset and you'll lose ALL of your memories. (found that out the hard way.) D15 doesn't seem to affect the memories at all. Since the 800MHz band is not available in US versions, my guess is that there's a keyboard mod to unlock it instead of a diode. The diodes only seem to control the country versions. If anyone has any more keyboard mods, please post them. Bruce KD6ALI Thanks to Edmund F Leavitt for this photo.
This modification is read 697 times.

04-12-2001

(IC-Z1A) IC-Z1A 800-900 MHz Receive

This modification is read 863 times.
(R-7000) A low cost panadaptor for the R-7000
Author: Bob Parnass, AJ9S A panadaptor, or spectrum display, is a device which portrays visually the signals in a part of the radio spectrum. Panadaptors allow radio listeners to "see" activity on a portion of band without requiring the listener to tune the receiver. They are useful for detecting the presence of spread spectrum signals or "hidden" signals riding on a sub- carrier of a main channel. Panadaptors are invaluable for detecting spurious emissions from transmitters, and unwanted products caused when 2 or more signals mix. Panadaptors most often employ a cathode ray tube (CRT) for the display, and must be connected to the inter- mediate frequency (IF) amplifier stage of a receiver, at a point before filtering takes place. The ICOM R-7000 2-2000 MHz receiver rear panel has a phono jack for wide band 10.7 MHz IF output. A DC vol- tage is also present at this connector and is used to power an ICOM TV accessory. I've seen mention of 3 panadaptors for the R7000: 1. John Biro's article on retuning a Yaesu YO901 Multiscope panadaptor for 10.7 MHz, restricted bandwidth use. Selectable bandwidths of 20, 100, or 200 KHz are available. 2. The Sherwood Communications SCA-7000 signal moni- tor, priced at $1600, and reviewed in May 1987 "Monitoring Times".3 Bandwidth adjustable from 1 KHz - 1 MHz. 3. The Spectra-Display, priced at $350, which requires use of an external scope.4 Bandwidth Sherwood Communications, 1310 Industrial Highway, Southampton, PA 19866. tel (215)357-9056. Spectra-Display is sold by GTI Electronics, RD 1 Box 272, Lehighton, PA 18235. tel (717)386-4032. adjustable from 200 KHz - 10 MHz. Optional preamplifier required for 12 MHz wide sweep. In the past month, several Kenwood SM-220 monitor scope/panadaptors have appeared at hamfests selling in the $200 to $250 range. The Kenwood SM-220 can display transmitted or received signals. To add spectral display capability to the SM-220, one must purchase the optional BS-5 or BS-8 module, which consist of a prin- ted circuit board, a steel enclosure, interconnecting cables, and a new graticule. The panadaptor module mounts inside the SM-220 cabinet. The BS-5 is used with the TS520 and TS530 transceivers, which have an IF of 3.395 MHz. The BS-8 is used with the TS820 and TS830 transceivers, which have an IF of 8.830 MHz. Since the IF of the ICOM R7000 is 10.7 MHz, one must alter the panadaptor circuitry to accept 10.7 MHz input. If you have any choice in the matter, get the BS-8, as it requires fewer changes than the BS-5, and may even require no changes at all! The panadaptor module circuit consists of several stages, but only two are directly related to the IF frequency: 1. A crystal oscillator is used as a marker generator. 2. A voltage tuned oscillator is swept across the IF of the receiver, and employs a varicap diode, an inductor and capacitors. The marker generator is not vital for panadaptor opera- tion. It merely provides a single "pip" that one may use to center the display on the CRT screen, and is similar in purpose to the crystal calibrator in older receivers. The marker generator circuits in the BS-5 and BS-8 are identical except for one crystal. One need only replace the 3.395 MHz crystal (in the BS-5), or 8.830 MHz crystal (in the BS-8) with a 10.7 MHz crystal to adapt the SM-220 marker to 10.7 MHz IF. I did not alter this stage, although I would if I had a 10.7 MHz crystal handy. The voltage tuned oscillator is the stage that deserves our attention. The changes required depend on whether you have the BS5 or BS-8 panadaptor module. Changes for BS-5 Module Change the following capacitors:

This modification is read 1318 times.
(SM-20) Icom SM-20 desktop microphone wiring
Author: Philippe, ON4VP - on4vp@pandora.be.MODIFICATION.NET

1. 2. 3. 4. 5. 6. 7. 8.

microphone output +8 VDC input frequency up/down no connection PTT GND (PTT ground) GND (mic ground) No connection
white red blue yellow black shield
Regards and 73, Philippe, ON4VP
This modification is read 623 times.