31-01-2000

(AH-4) Icom, AH-4, AH-3 ( automatic antenna tuner ) connection to any radio.
Author: AA7OL Niko Takahashi - aa7ol@hotmail.com.MODIFICATION.NET
Icom AH-4 and AH-3 ( automatic antenna tuner ) connection to any radio
Both AH-3 and AH-4 are similar Here is a redesign of connection digram of the ICOM IC-AH3 and IC-AH4 by 5B4AEZ.
There is four wire control cable coming out beside coax cable. Control cable has White: Start tuning Green: Tuning in process RED: 12 V DC input Black: GND
Tuning Process 1. Put about 10 watts of power into tuner. ( CW )
2. After about 0.5 second, press start switch for a moment. ( use momentary contact switch ) 3. LED start blinking , which indicate tuning is in process. 4. After about 3 seconds or so, LED shut off, and tuning is completed, If tuning is successful SWR should be less than 1.2
Some radio start to reduce the power when SWR is high, this tuner takes at least 10 watts of power for tuner to work properly. Most of the 100 watts radio should not have any problem, since they still put out 10 watts or so, even with high SWR. But, it does not work with some QRP radio ( 5 watts or less ). Adjust power level, if necessary. You may extend control cable to 100 feet , it still work fine, you can put this tuner on top of tower. Let me know , how it worked aa7ol@hotmail.com.MODIFICATION.NET
This modification is read 1503 times.

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07-06-2001
(AT-160) Using the AT-160 with the IC-706MKII
Author: Dave Abshire Sr. - KG4KOX - KG4KOX@aol.com.MODIFICATION.NET
ICOM's IC-706MKII transceiver and AT-180 antenna tuner are designed to work together. However, ICOM's AT-160 is a very popular antenna tuner. Originally designed to work with the IC-728 and IC-729 transceivers (now out of production), the AT-160 will work with the IC-706MKII if the following instructions are followed: 1. (IC-706MKII only, not IC-706) The IC-706MKII will transmit on VHF constantly when connected to the AT-160. To stop this, remove the wire attached to pin 6 of the DIN connector within the OPC-104 cable. 2. Open the AT-160 and make sure the switch labelled "S1" on the circuit board is switched to the bottom, shown as "IC725/726" in the AT-160 instructions. 3. Make sure that the connections to the AT-160, using the OPC-319, OPC-104, or OPC-125C cables, are according to the AT160 instruction manual. ICOM America suggests using the OPC-599 adapter cable for connection of the OPC-104 to the IC706MKII. 4. Connect the radio to the transmitter terminal and connect an antenna to the ANT terminal. Make sure the antenna has less than a 3:1 SWR. Place the radio in FM, AM or RTTY mode and key the mic. The AT-160 will now tune properly. 5. The tuning button on the front of the IC-706MKII will not operate when using the AT-160 antenna tuner. This feature was designed to work with the AT-180. 6. Check the SWR presented to the radio. It should be less than 1.5:1. The AT-160 operates with the IC-706MKII as it would with the IC-725 or 726 transceivers. Included with the AT-160 instructions is a page dedicated to the antenna tuner's operation with an IC-725 and IC-726 transceiver. This is not the way the AT-160 operates with the IC-706MKII. 7. There is no way to turn the AT-160 off or place it into "thru" mode when operating with the IC-706MKII.

ADD D4 I--+ V D4 I + + REMOVE D2 --+-ID2 I I I +---+

--+-ID3 I I I +---+

+ D1 + +
6. Install radio chassis back into front cover. Leave back off temporarily. 7. Carefully apply power to radio and enter the lowest desired frequency. 8. Adjust slug through bottom hole on VCO corr for.5 VDC at VCO test point (just below VCO shield) at lowest desired operating frequency. 9. This completes the modification. A few words of caution: 1. The radio is not type accepted for use in the commercial band. 2. Make sure you reinstall the battery latch correctly on bottom of radio or battery will become permanently locked onto radio. 3. Tighten screws on bottom of radio snuggly. If they loosen while battery is connected you cannot remove the battery. (This has happened to any units and it would be prudent to periodically check these screws to assure their tightness.)
This modification is read 1612 times.
(IC-02) Audio modification for IC-02 AND IC-04
This audio mod works on the 02 and 04AT. It increases the level of audio, as well as rolling off some of the lows. Sounds real nice. It involves the circuit around Q105. 1. Replace C119 with a.01 uF cap (disc ceramic is fine). 2. Parallel R131 with a 1 uF cap (use a tantalum cap). 3. Parallel R132 with a.01 uF cap (disc ceramic is fine). This is not the same mod as the one International Radio is advertising, which involves changing C117. I tried an AB-1 Audiolaster from Engineering Consulting, and was very unhappy with the results. I am very pleased with the audio given by this mod (much cheaper too!).
This modification is read 1146 times.
(IC-02) IC-02A Modified PLL rigs
The modification to the IC-02A to increase the receiver is fairly straight forward although a little delicate. The programming diodes are located on the board directly behind the front panel, and are located in the corner of the board. They are little rectangular black three leaded devices. The proceedure to modify the radio is as follows: 1. Remove diode D2 - use a very small iron and solder wick to remove most of the solder, then lift the diode GENTLY while heating the single tab side. After getting the first tab free, proceed to the other two tabs, lifting them one at a time. Do NOT use a large iron or too much heat. 2. Take the diode and locate in the position labled D5. Carefully solder the diode in place. 3. Reassemble the radio except for the back.
4. Program the radio to the local weather channel (162.400 or 162.550) in the following manner: 0 or 0 NOTE: the programming proceedure now requires that you enter the ten's of Mhz when entering a frequency. 5. Look at the back of the radio. In approximately the center of the exposed board is a metal can with two adjustments. The top adjustment is a metal screw (actually a trimmer capacitor) while the bottom adjustment is a black slug with a small rectangular adjusting slot 6. With the squelch open, adjust the lower black core counterclockwise approximately 1 1/4 turns until you receive the weather station. As soon as you receive the weather, STOP turning the adjustment. 7. Replace the back on the radio and you are in business. With this modification, the radio will tune from 140.000 Mhz to something over 162.550 without difficulty. Just remember that you must enter the ten's of Mhz when entering a frequency. This modification does not affect the transmitter which still covers 140.000 to 151.995 Mhz. Please note: This mod does not retune any of the RF stages of the receiver so the sensitivity is down some at the weather frequency, however, I have no difficulty receiving it at thirty to forty miles. I do have the ICOM service manual on the IC-02A. I purchased it from Delaware Amateur Supply at a local hamfest several weeks ago. According to the manual, the VCO on the PLL should cover 25 Mhz. minimum.

This modification is read 353 times.
(IC-1271) VOX of an IC-271,471,1271 usable for FM
How to make the VOX of an IC-271,471,1271 usable for FM : 1'st type of "main-board" : The only thing to be done is to add a diode such as 1n4148 or bax13 on the MAIN board on the position D74 When D74 is inserted. the vox works in FM also. The diode is on the shematic diagram of the Main board but is not mounted on the pcb in the factory. 73's de stefaan ON4BY @ ON4HU 16/03/1990 18.31 h 2'nd type : (On this board a D74 is present (near PA- and RF-YGR- Unit)) (It might be not present in the plans !) Disconnect the cathode of D69 from it's old postition. It's new position is the cathode of D50 or D51

name D69 D50 D51

! ! ! !
position on main board near "CW-DELAY". near "RF-YGR-Unit" near "RF-YGR-Unit"
(old) function "FM -VOX-OFF" "USB-VOX-ON" "LSB-VOX-ON"
! ! FM 8V ! USB8V ! LSB8V

20/03/1990 16.52 h

This modification is read 572 times.

30-03-2001

(IC-1271) RAM Card Backup Battery Replacement Instructions
Author: ICOM In the early 1980s Icom America marketed a group of transceivers and radios that utilized the latest state-of-the-art computer technology to enhance the operation of the radios. This technology improvement allowed hams to afford a reasonably priced high performance transceiver which until then was only available on units costing much more. Features now available to the hams included: higher frequency stability, better frequency resolution, digital frequency display, almost instant recall of saved frequencies (memory channels), quick mode signal processing and built in tones and offsets for the rapidly emerging repeater operation. Implementation of all these features required a CPU with associated logic circuitry. In the early 80s, the most cost effective way to implement data processing and memory functions was through a DRAM (Dynamic Random Access Memory) to control the CPU. This DRAM was a volatile memory integrated circuit which required a lithium battery to retain its instruction set. The following receivers and transceivers had such RAM units: IC-271 ; IC-471 ; IC-1271 ; IC-745 ; IC-751/A ; IC-R71A The lithium batteries in these units typically lasted about 5 to 7 years before replacement was required. This was specifically noted in each of the Owners Manuals for the products. This lithium battery can be replaced by the radio owner if care is used. The following is a recommended procedure to accomplish this: Procedure 1. Disconnect the power cable from the radio, and take the cover off. 2. Unplug the RAM board and remove it from the radio. 3. Temporarily solder a 3 Volt DC battery source across the existing battery terminals (see suggested connection points on the circuit board pictures). 4. Unsolder the old lithium battery and replace it with a new one. (BR2325 1HC, ICOM stock number 945 03112) 5. Unsolder your temporary 3 Volt DC source.

This modification is read 790 times.
(IC-24) Out of band modification of the ICOM IC-24AT
The Icom IC-24AT is truly a remarkable unit. Having it's genesis in the IC-R1, Icom's extremely wide band Hand Held Receiver, it is capable of receiving a wide range of frequencies, as well as being able to transmit on short excursions, outside of the amateur two meter and 440 MHZ. bands. The more current models can be modified to receive out of band, by a simple software (not necessary to physically open the transceiver) procedure as follows; Turn the power switch off. While simultaneously holding the "light" button, the "B" button, and the "#" button, turn the radio on. All elements of the display will light up. Continue holding the buttons until the display goes out. It may be helpful to have a buddy give you an extra hand during this procedure.Your unit will now receive out of band. The older models of this transceiver, require the removal of diode D13, before performing the above procedure. D13 is on the main logic board and is a discreet diode near the center of the board. It is the diode on the left of the two on the board when the radio is open and held with the controls away from you. The "stock" transceiver, was also not designed, to provide full direct keyboard entry of the operating frequency. This can also be modified by one or both of the two procedures below; To directly key in the 10Mhz. frequency, simultaneously hold the "light" button and the "2" button, while turning the radio on. To directly key in the 100Mhz. frequency, simultaneously hold the "light" button and the "3" button, while turning the radio on. The modification of the unit to enable it to transmit out of the amateur bands is a fairly simple procedure. It is however, complicated by the fact that the construction technique used in this transceiver is "Surface Mounted Technology." If you have no experience dealing with this technology, you may well be better advised to defer this procedure to someone who has. It is extremely small and delicate, and is best done with specialized equipment. Also, because the unit may not be FCC type accepted for all the frequencies on which it can then transmit, it may not be legal for you to use it, despite the fact you may be licensed to transmit on those frequencies. This information is provided only for those who are licensed for and want to use the unit on MARS and CAP frequencies, where there are no type acceptance restrictions. The procedure is as follows; Order a couple of DA204u diodes from Icom or your Icom dealer. These are a special three terminal device with two diode in one package. They are very very small, about half the size of one of the key buttons on the touch tone pad. Locate and remove the diode device in position D8 Locate the vacant position of diode D7 and attach one of the DA204u diodes at that location. Locate the vacant position of diode D12 and attach the other DA204u diode at that position. If diode D13 (procedure above) has not been removed, remove it.

The IC-2SRA appears to be very similar to the IC-W2A, with a Wideband Receiver unit replacing the UHF RF unit. Not having an IC-W2A or the service manual for it, I can't be sure. This mod is very much like the IC-W2A mod by AA7BQ, which I used as a starting point. Extended Receive Right out of the box, the IC-2SRA Ham Band will tune 136-174 MHZ, and transmit 140-150 MHZ. Although the Receiver Band will tune 25-950 MHZ, sensitivity is better on the Ham Band side. Direct entry of frequencies outside of the amateur band is not as convenient as it could be. But there is an undocumented (by Icom) feature which makes it easier. Enable extended receive by holding down the 3, B, and # keys while turning on the power. Keep your fingers on the B and # keys for a minute, and you can see the full LCD function display. Besides what is normally seen, there are also VOX, TOT, RIT, and VXO displays. Makes one wonder if there are additional undocumented features? I haven't a clue! There are other key combinations which will do the same thing. With this done, the dial select step can be set to 10 MHZ, and the first digit for frequency input can be selected as 100 MHZ in SET mode. The display will now go from 50-500 MHZ, but don't think that you can receive in that range. You can believe signals in the 136-174 MHZ range, but outside of that you are most probably hearing images. Extended Transmit This is the fun part. The radio is designed to allow a wide range of applications, meeting amateur band requirements all over the world. This is accomplished with a diode matrix on the Logic unit. For the US, this involves diodes between lines D2 and 10 (D16), and between lines D3 and 11 (D22), on the Main CPU (IC2). To open up the full 136-174 MHZ range for transmit, diode D22 is removed, and diode D19 is instaled between IC2 lines D0 and 11. The diodes are very small three legged surface mount components. Icom doesn't publish any information on the CPU logic (that I know of), so I'm not sure just why any of this works. But it does work! Start by ordering one MA133 diode, order number 1790000860, from Icom America customer service in Bellevue, WA, at (206) 454-7619. Don't bother trying to order through one of the regional service centers, as they normally just forward part orders back to the corporate headquarters anyway. Cost in March 92 was $2.43, plus $1.75 handling. I don't know if they have a minimum; I ordered four diodes which brought the Visa charge to a litle over $10.00. When the diode arrives, it's time to open up your radio. You need a set of small Phillips head screwdrivers which can be found at any Radio Shack. Remove the five screws on the back, and two smaller screws on the side of the case under the PTT switch. Don't worry about the screw for the handstrap, it is screwed into the metal back and comes off with the back. With the screws removed, the back is easily lifted off. This much is shown pretty well on page 57 of the instruction manual where it talks about installation of the UT-63 (which is already installed in the US version of the IC-2SRA). Now remove the UT-63, and the PTT rubber. In front of you is the Receiver unit, stacked on top of the VHF RF unit, which is on top of the Logic unit. That is where we need to end up, so start disassembling. The Receiver unit is held to the VHF RF unit by a small screw on each side. You won't have any trouble figuring out which ones they are. There is also a small screw at the bottom of the Receiver unit, which fastens a spring clip holding the two units together. Remove the screws, and keep track of them. Both units are then individually removed by gently unplugging them from the Connector unit with a down and out movement. At this point you should be impressed by the well thought out design of the radio, and the ease with which it can be taken apart. In front of you now is the Logic unit, but there is a plastic encased metal foil, the CPU shield, still in the way. This shield is under the wiring harness between the Logic unit and the Connector unit. It isn't attached to anything, and can be gently curled and slipped out to the right. Here's kind of what you'll see under the CPU shield:

This modification is read 919 times.

From: Geoffrey Dann

(IC-32) Cross-band repeater (Icom)
Icom Service Bulletin #13889-005 The IC-32AT has the capability of being used as a cross-band repeater. This function is not enabled as the unit is shipped from the factory. To enable this function perform the following steps: 1. 2. 3. 4. 5. 6. Cut D912 on LOGIC UNIT. (see above figure) Push and hold the (FUNCTION) switch. Push the (C) key. Push the (6) key. Push the (D) key. Release the (FUNCTION) switch.
To cancel "MINI REPEATER" perform the following steps: 1. 2. 3. 4. Push and hold the (FUNCTION) switch. Push the (D) key. Push the (C) key. Release the (FUNCTION) switch.
This modification is read 837 times.
(IC-32) Receive coverage for VHF & UHF and enable keyboard entry
Remove battery and antenna. Loosen two screws on top of unit as much as possible without removing them. Loosen 4 flat head screws on bottom of unit 1 turn. Loosen 2 screws near PTT switch 1 turn. Remove 4 black screws on back of unit. Lift bottom of front cover.25 inch, slide it down.25 inch, then lift front cover up 1 inch. Disconnect plug on 4 wires coming from the speaker. Lay front panel on table up-side down being careful of the flex circuit. All mods are done to the back of the front panel. Notice places for 5 axial diodes, which I will call 1 through 5, 1 being nearest the display. Add/remove diodes so there are diodes in positions 3 and 5. This will open up receive coverage for VHF & UHF and enable keyboard entry of the 10 MHz digit. 10. Notice 4 surface mount resistors slightly left of center directly above the speaker, lined up in a row. Solder the anode (the side without the bar) of two diodes to the right side of the lower of the four caps. Now find the CPU. It's the PGA under the shield near the top of the board. Find the row of pins on the CPU nearest the speaker. Notice the the 8th pin from the right has a thicker trace coming from it. Now notice that there are small solder pads about.25 inch toward the speaker on both the fat trace and the two traces to the right of it. Solder one each of the cathodes of the 2 diodes to the solder pads on the two smaller traces. This will open up the transmit for VHF & UHF. 11. Put unit back together in reverse order. This procedure worked for my unit (and many others), but I can't guarantee it will work for yours. Bill Pherigo WR0Y

(IC-3220) ICOM IC-3220A/H Frequency expansion
To extend the receiver range on VHF: 118.000mhz (AM) to 174.000mhz (FM) Cut D6 on the LOGIC board (located on the front of the radio) To extend the receiver range on UHF: 400.000mhz to 479.000mhz Cut D4 on the LOGIC board. To extend transmitter range on VHF: 136.000mhz to 174.000 Solder a bridge between the solder pads next to D9 To extend transmitter range on UHF: 400.000mhz to 479.000mhz Install 1SS190 (diode) at D9 position on the LOGIC board.
This modification is read 799 times.
(IC-3220) ICOM IC-3220A/H mini repeater function
1. Set rig to "DUAL" by using the BAND switch. 2. Set frequencies in VHF and UHF. You may set in offset on either band. You may also set it up in VFO or MEMORY. 3. Simultaneously hold BAND and SET key. The memory number will display a flashing "L". It will be in repeater mode To disable repeater mode, depress and hold "SET" key until the flashing "L" goes to a memory number or VFO mode. The repeater mode will not be disabled by turning the rig off and on.
This modification is read 897 times.
(IC-3230) ICOM IC-3230 Mods for 9k6
by IK2XYU/KF6EEZ Hi to all, here you have a step to step way to modify your IC3230 to enhance it with frequency coverage,transponder function and 9k6 Baud packet use. Is not easy make changes inside this tranceiver, so if you've not skill ask to another ham to help you !!! A good range of the frequencies are 120 - 175 MHz and 400 - 500 Mhz and 850 - 950 Mhz. Your RIG can surely handle more frequency but not with a big success on sensibility. If you make this, you'll be the responsible of your RIG. Make it just if your law permit this to you !!! 1. Take off the screws of the two covers (6+6) and remove them unplugging the speaker plug. 2. Take off the 4 screws of the front panel (2 for each side) and be careful removing it because you have a couple of flat cables. 3. Open the diodes,with a cutter, located under the front panel. They look as 1N4148 kind and you cannot make mistakes. More cuts it's meaning more new function, so you must cut all the available diodes. The diodes are located on the board called LOGIC UNIT. 4. Replace the front panel with the four screws. Connect a shield-cable (RG-58) on the small coaxial plug on the MAIN-B board and make this cable able to go outside of your RIG when you replace the two covers. To do this you can remove the small cover in the back of the RTX, the one just above the original antenna cable. This new coax-cable will be to apply the 900 MHz antenna. If you're not interested to listen to this band, you have just to replace the front panel and jump to point 5. 5. Plug in the speaker and replace the covers. If you like to make the 9k6 mod jump to point 6.

The smallest HF rig on the market (similar in size to the Kenwood TS-50) Detachable face plate with a jack for a speaker or headphone. The mic plugs into the face plate using a plug similar to a modular telephone plug. (A spare plug is included.) The cable to allow for this detachment costs extra.
Full HF/VHF transmit coverage from 1.6 to 54 MHz and 144-148 MHz (the rig transmits only on the ham bands out of the box, but an easy modification unlocks the transmitter, see below) General coverage receive from 50 KHz to 163 MHz (requires modification, see below) Rig receives up to 200 MHz but with poor sensitivity above 162 MHz even with the modification. You will be able to receive: longwave, AM broadcast band, shortwave broadcast, all amateur bands in all modes from 160m to 2m, FM broadcast band (wide FM), aircraft (118-136 MHz AM), VHF from 30 MHz to about 162 MHz, US TV channels 2 through 6, NOAA weather at 162 MHZ. 6 meters and 2 meters, all-mode 100 watts on HF and 6 meters (10 watts on 2 meters) Innovative, easy-to-operate menu system. It becomes quite easy and natural to use after reading the well-written manual for about an hour. (In contrast to my Yaesu FT-470 HT, which I still cannot figure out.) The manual is very well written, with lots of easy-to-understand diagrams. Simple, but useful and configurable band scope. (Previously available only on very expensive rigs like the Icom 781.) This allows you to examine nearby frequencies for activity. Split frequency operation appears complicated at first, but the rig's "quick split" mode makes it fast and easy. Built-in electronic keyer at no extra charge. The Up/Down buttons on the mic can be used as a paddle. This has rejuvenated by interest in CW. I worked a couple of slow CW stations on the novice portion of 80m, which made me remember how fun CW is. FSK (Nice feature for this price range) DTMF and programmable offset for repeaters and split frequency work Good audio reports from contacted stations. A station on 3.85 MHz reported "a very good signal for a mobile". A 2m FM station reported "very good audio. so that's the 706 I've been hearing about." Works very well with the AH-3 antenna tuner. This is the Icom HF (1.8-30 MHz) random wire tuner that worked with the 725. The tuner is mounted under the trunk lid of my car with cable ties. It can also be mounted outdoors. It will tune any 8foot whip or wire for any HF band. (You need 40 feet for it to tune to 160m.) You can press a button to enable the tuner, or the tuner can fire off automatically if your SWR is too high. With my 7-foot 6-meter whip, I can tune to any HF band above 3.5 MHz. That means I need only one simple antenna for HF and 6m. 100 memories that store frequency, split offset, mode, and FM tone. Two antenna connectors: one for HF/6m and one for 2m. The connectors are switched at 60 MHz. Jacks for remote speaker and/or headphones on both the face plate and the back of the rig. Multifunction meter: S meter, SWR, relative power output, ALC.

This modification is read 903 times.
(IC-737) Icom IC-737 general coverange in transmission
1. Remove the top and bottom covers of the transceiver. 2. Remove the final power amplifier module. 3. Locate the LOGIC-UNIT on witch there is a back-up lithium battery for the RAM memory. 4. On the LOGIC-UNIT, near the chip called IC6 (TMP82C265BF-2),between the output pin PC06 and the imput pin PA15, find the diode D3. 5. This diode is not an SMD component. 6. Cut the diode D3.Now the ICOM IC-737 will transmit from 1,6 to 30 Mhz !!!. 73's de IW3BKW Riccardo @OE7XCI. ***
(IC-737) CW Filter Switching Modification for the Icom 737
The Icom 737 is a wonderful radio for CW operation, but I did not like the filtering switching options offered in normal operation of the radio when you have installed BOTH the 9 Mhz and 455 Khz optional CW filters. The default option is to use the SSB filter for CW in the CW mode, and then switch in BOTH the 9 Mhz and 455 Khz optional IF filters in the CW-N mode. This provides too broad a filter for general tuning in CW, and the CW-N mode (with the two filters in) is far too sharp for just tuning around. I felt that it would be better to allow the 455 Khz filter to be functioning full time in the CW mode, and then switch in the 9 Mhz CW filter in the CW-N mode. The following simple modification only requires a single wire to added to the radio. MODIFICATION 1. Remove the top/bottom cover of the radio as per the manual.
2. Position the radio facing you and locate the resistor R-323 which is simply labeled "323" on the PC board just to the left of the opional 455 Khz CW filter. Solder a wire to the end of R-323 which is closest to the front pannel. 3. Locate J-3 just above and to the right of the 9 Mhz filter F-13. Attach a wire to the connector or wire going to pin 7. Pin 7 is the third pin from the right. (The pins are numbered 1-9 from left to right) You may carefully tack solder a wire to the plug by removing it first. I used a solid 28 gauge wire and just pushed it into the connector without soldering. 4. Replace the top and bottom covers. I'm happy with the function of this modified switching arrangement. The CW-N function is now the mode of last resort when going after the weak ones, or when the QRM gets out of control, and tuning with just the 455 Khz filter is a better than using the SSB filter. Good luck! 73's Greg Chartrand WA9EYY

The Yaesu FT726R first appeared ten years ago, the FT736R six, so the operational needs of satellite operators are well established. Why have Icom made such heavy weather of it? Preamplifiers & Linear Amps You can send +10v up either, both or neither of the VHF/UHF antenna sockets. This supply is removed from the relevant socket on transmit. The manual does not specify a maximum loading; I tried 100 ma and 200 ma and the voltage remained steady; at 330 ma it began to droop. The limit is set by dissipation in a PQ20VZ51 regulator on the display unit. Other than this 10v supply, there is no provision for hard switching of pre-amplifiers or linear amplifiers unless you confine yourself to one band, when you can of course use the PTT line via the accessory socket. Serious operators will regret this omission. In contrast, the Yaesu FT736R has four control lines, one for each band. Internal TX/RX changeover is by PIN diodes, so it's fast and silent. RF Power Control The front panel sports a high/low power control button. Low power is 4-5 watts. If you have an external linear amplifier or a transverter you need to be able to vary the output power continuously. There is no knob provided for this. There is instead an ALC facility on the accessory socket. The control voltage is -4 to 0 volts into "more than 10K", but you must provide a supply and a pot to do this. And a box, and a place to put it. Tacky. There's some free space on the rear panel though. There are several ways to key this transmitter; there's the Tone button, mixed in with other frequently used buttons and easily hit. Then there's the bigger Transmit button, and the normal PTT (mic or TNC). More than once I accidentally hit the Tone button, sending a minimum of 4 watts skywards. That would have wiped out my S-band converter had it been connected. RF Attenuators You can attenuate the RF input of either or both receivers, by 15db, from a front panel button. This is in lieu of a (big) RF Gain knob, and an is excellent feature. Many preamplifiers have far too much gain; an S-band pre-amp plus converter most certainly does. Being able to cut the signal down to size prevents cross modulation and overloading. Digital Satellite/Terrestrial Operation Before describing this, it's necessary to tell you how the data input and output audio is routed, because it is not unconditional. You might like to draw yourself a little sketch. Both signals are presented to the 8-pin DIN Accessory socket on the rear panel. The incoming transmit audio (TXAudio) passes though a slider switch marked PACT/AMOD :
In the AMOD position the TXAudio passes to the Main subsystem where it meets up with the regular pre-amplified microphone sound for use in FM or SSB modes, and then through some audio processing. In the PACT position the audio goes directly to the varactor diode of Main's FM section.

Click for big view

This is a colour photo were the diodes can be found , D108 is on the left, D101 is on the right
After soldering D108 into place you will have to do the following to get the x-band repeater to work: 1. Turn ON the power switch. 2. Set the both band desire frequency at dial 3. Set [LOCK] function (see instruction manual) 4. Turn OFF the the power switch 5. Push [M/S] key and turn on power switch. 6. You can stop pushing the [M/S] key now (LOL) This enabels the x-band repeater
To disable the x-band repeater just push [LOCK] to release lock function.
(IC-821) Icom IC-821H mods
On this page is the rx/tx modification discribed for the ICOM IC-821h allmode dualband tranciever with photo's. You can also find this modification on www.qsl.net/pe3hmp. I have done this mod myselve but If You do annything wrong I'm not responseble !! You need to locate the row of diodes on the display board, for that You need to remove top and bottom covers of the 821 (discribed in Your owners manual on page 50 and remove two screws witch hold the front of the 821 and turn the 2 other screws 1/4 loose so You can pull the front towards You (about 5cm) Now You have enough space to carefully remove the diodes.
can You find them ? (they are SMD diodes) Removing D101 gives You 136 - 174 Mhz (RX) Removing D103 gives You 420 - 460 Mhz (RX) Removing D105 gives You 136 - 174 Mhz (TX) Removing D107 gives You 420 - 460 Mhz (TX) And then You will have to make a choice: leaving the D102 diode in place for 1750Hz tone when You press the tone button on the front, or if You remove D102 You can use the subaudio tones (like the ones used at some european repeaters) but no 1750Hz tone. If this is Your first attempt to solder annything I would suggest to leave it untill You have alot of practice, make sure You have a small soldering tip and some pliers then gently heat one side of the diode and lift that side up, I would suggest leaving the diod hanging there (only connected to one side) in case You want to restore the 821h to its original state. I removed ALL diodes so now I have RX/TX 136 - 174 Mhz and RX/TX 420 - 460 Mhz and subaudio tones.
On this photo You can see were the diodes used to be.
After I had done the mod there occured a problem, the subtone's deviation was too high because the same pot is used for the deviation of the 1750Hz burst tone in the european models, the deviation should be about 1/3 of that of the 1750Hz tone (about 0.6Khz). If You have a second reciever just connect a voltmeter over the speaker of Your second reviever (not the 821) and note the meter readout then adjust R64 for 1/3 of the first signal (after the mod You now have a usa+ version). Were can You find R64 ? well just look at the following photo's and You will find the R64. Thanks to Amanda G7TUA / M0DZO for giving me the info about the subtones (I do not have the service manual yet).

*** WARNING *** The SMA Antenna ferrule is held on with some kind of super glue in the threads so you will need to
work this nut loose ever so carefully. Just a piece of information that you may find useful, all the ferrules on the radio rotate clockwise to tighten and counterclockwise to loosen. Thus the old saying (Righitie tightie, leftie loosie). I used a jewlers screwdriver and a pair of needle nose pliers and placed the tip of the screwdriver into one of the notches of the SMA ferrule and "TAPPED" ever so lightly until it began to move. This requires time so take as much of it as you need, no sense screwing up this mod before you begin. It will work loose so take your time. You might also want to remember that you will be taking out the RF module board later and the SMA connector must come out of the case so you will need to remove the nut SORRY. The SMA connector is also glued to the case but using the same "TAPPING" method above, you will work it loose (more on that subject later) STEP 4 Once you have removed the ferrules in step 3, you can remove the battery cover and batteries from the radio to reveal two screws in the compartment. Remove these screws and place them in your box. Just a note, I taped the screws to a post-it paper and labeled them so I knew where the went when I was re-assembling the radio. Next lift off the rear cover by prying the cover from the front at the rear then up and towards you (keeping in mind the orientation of your radio as described). STEP 5
You should now see the RF board (daughter board) on top of the main board inside your Q7A. WHEW! STEP 6 On the RF BOARD! there is one visible screw located on the right side, see figure 1.4 below:
STEP 7 There are three points where the shielding for the RF board has been soldered to the lower board. One is in the lower left corner just above the ferrite inductor figure 1.5 and along the right side of the RF board next to the PTT button figure 1.6 and in the upper left corner near the blue assembly of the dial figure 1.7 Figure 1.5 Figure 1.6 Figure 1.7
Unsolder Figures 1.5, 1.6, and 1.7 with the solder sucker and desoldering braid to wick up any left over solder. Be careful not to melt the plastic case in the procedure in figure 1.7.
*** WARNING *** ONLY, do a small spot at a time. DO NOT OVERHEAT sections. If you don't get all the solder in one time, don't worry, let things cool down a bit and go back for more later when it cools.
STEP 8 Once you have removed all the solder from the above steps, lift gently with your FINGERS ONLY, the rear of the RF board until the connector on the RF board figure 1.8 dislodges from its counter part on the main board, figure 1.9, use your fingers only because of the surface mount components which are located near the edge of the circuit board, you don't want to pry off any of them with the blade of a screw driver. Figure 1.8 Figure 1.9

Disclaimers: Be sure to have the proper permits for out of band operations. And, do this mod at your own risk!
This modification is read 424 times.

08-01-2002

(IC-V8) IC-V8 MOD for expanded RX/TX range. (136 174MHz)
Author: Scott KD4CWB - kd4cwb@aol.com.MODIFICATION.NET
1. Remove the battery pack. 2. Peel off the black plastic panel on the bottom. (it will re-stick in place). 3. With the white expansion connector on your left side, locate the series of diodes in the upper right side of the opening. Remove the diode located on the far left side on the lower row. (see photo or text diagram).
------------------------------------------------------_--------_-------_----|o| o |o| o |o| | | | | | | | | Option Connector |o| o |o| o |o| | ____ | | ^ | | - - | | | | - - | Remove this | | | - - | diode ONLY! | | | - - | --------------+ | | - - | | | - - | | | - - | | | - - | | | - - | | | - - | | |____/ | | ----------------------------------------------------------------------------Mod by: Scott KD4CWB@AOL.COM
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21-03-2002

(IC-V8000) v8000 gne caper

Author: spritsan

v8000 mod for genral coverage tx (makes a good marine tx.er) On the front panel there are 4 diodes side by side thay have white cups drawn around them remove all and of you go(go baby go). The diodes are on the top of the pcb very clandestine looking ones the unit will produce at leat 31 watts on the marine band bye form spritsan. Date: 22-03-2002 Subject: Power Output You say at least 31 watt's on the marine band;do you know how stable the the power is elsewhere? Also,is the removal of these four diods confined to just the marine band,or 136-174?
This modification is read 108 times.

From: KG6FPC

(IC-W21) Receive only expansion for IC-W21
1. Turn radio off 2. Press [B]+[#] switch and turn ON radio. Depress [B] and [#] only when the display shows all functions and the radio emits a beep. 3. Go to SET mode and a new function will appear after TONE selection.The new function is designed by PL. Set PL to "1"for 1 MHz frqcy. enter, to 10 for 10 MHz frqcy. enter and to 100 for 100 MHz frqcy. enter resolution. Note1: This modification does not reset information saved on the CPU. Note2:
Frequency range is 50,0-107,995 MHz FM 108,0-135,995 MHz AM (aviation band) 136,0-299,900 MHz FM for the VHF portion; 300,0-999,900 MHz FM for the UHF portion.
This modification is read 948 times.
(IC-W21) Transmit expansion for IC-W21
1. Call Icom Parts Dept. and order one diode MA132WK (D.23) for IC-W21AT, Symbol: MU; 2. Open radio and localize the logic unit; The logic unit is the half portion of the radio that contains the CPU, display, keyboard, etc.; 3. Localize some orange colour components in the lowset right part of the portion, below the CPU shield plate. Localize the smallest orange colour component. Note a empty place for a surface mount diode (3 dots) near this orange component (see draw below);

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