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Icom IC-740


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Comments to date: 7. Page 1 of 1. Average Rating:
eesti1 8:26am on Saturday, September 18th, 2010 
The only issue that I have found is that the rubber ear buds can compress at times - I simply pull them back out, but it can be anoying at times.
tangocontact 6:17am on Wednesday, September 8th, 2010 
My first IEM were "Koss Spark Plug" ( 2 pairs ) and I thought they were good, but after trying EP-630 I forgot "Plugs" like a horrible nightmare.
GuyR 8:03pm on Wednesday, August 18th, 2010 
Very good....when they work! Bought my 2nd pair of these in February. Great value, and a decent sound... Headphones Arrived quickly. Earphones work very well but no good if your lug holes are smaller than the average person.
Quiet_Type 1:49pm on Tuesday, July 13th, 2010 
I use this in my 1998 car with a tape deck to connect my ipod. I find the fm transmitters annoying, and unreliable. This is much simpler.
lsi 6:48am on Monday, June 28th, 2010 
Heralded by the headphone enthusiast community as the KSC75 of ear buds. Creative EP-830 Noise Isolating Earphones Very disappointed with these earphones, i bought them off the back of very good reviews i had read.
sf_zk 9:04pm on Tuesday, June 22nd, 2010 
Hello Bargain Hunters! lightweight, great sound, wide range, comfy none Placement of the headset in the ear of the Creative EP630 with coverage from rubber provide a fantastic experience audio in MP3 format.
akloeckner 6:22pm on Monday, June 21st, 2010 
Sound quality??? After reading other review I am extremely surprised at what I am listening to. Amazing Creative EP-630 In-Ear Noise-Isolating Headphones (Black) I got a pair of these when I ordered my XPS computer system back in 2008. For this great price, not bad So I ordered these on Monday, early morning and after the item was finally shipped.

Comments posted on are solely the views and opinions of the people posting them and do not necessarily reflect the views or opinions of us.




cut. I'm guessing, but it could be that the rest of the diode changes are for the 10 MHz & 100 MHz digit entry (which I'd like but could live without) or out-of-band TX, or the like. If anyone has tried only cutting D13 and resetting? Did it work? What is your serial number? Please post to the net! Mike Pflueger Packet: WD8KPZ @ W1FJI Transmit range doesn't appear to be affected unfortunately. I was at least hoping for 420-450 coverage. BTW, I tried each amateur band from 6m to 23cm. The PLL doesn't lock up at either end. Another negative is the frequency step on 220 doesn't allow one to hit each possible repeater slot. 73 de Gene WA1UXA
This modification is read 871 times.
(IC-24) IC-24AT Keyboard command summary
This is an attempt to document all of the known key sequences for the ICO IC24AT (144/440MHz dual band hand held). Some key sequences may be common with the IC[2,3,4]SAT, therefore a fewkey seqences fr thoseradios re also on this list. Some ke sequenes requre optins (such as the PL encode/decode board). This is not designed to replace the owners manual, but to summarize the information in one place. Note: Many controls vary depending on the current mode, i.e.: Scan up/down will search frequencies when in VFO mode, and will scan meory channels when in Memory mode. Consult the owners guide for complete iformation.
KEY/COMBINATION = Result, action ---------------- ------------------------------------------------------------0-9,A,B,C,D,#,* 0-9 A B C D * # MONI H/L/DTMF FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC FUNC + + + + + + + + + + + + + + + + + A B C D * # 5 + D = = = = = = = = = = = = = = = = = = = = = = = = = = = note: when transmitting these will generate DTMF tones Enter frequency (can also use the VFO knob) VFO mode / clear incomplete entry Memory mode VHF / UHF change Call channel Step frequency down/scan down Step frequency up/scan up Open squelch and change to input frequency (if not simplex) while button is depressed Select High/Low power, or (while transmitting) send preprogrammed DTMF codes Dial set PL enable (when option is installed) Code squelch [NOT for the IC24AT, IC[2,3,4]SAT option only] Skip memory Duplexoperatin Code [NOT for the IC24AT, IC[2,3,4]SAT option only] Mask freuency Priority mode on/off (operation dependent on current mode) Set mode (several different functions, press A to exit) Real time clock and timer functions (press PTT to exit) Memory to VFO transfer Memory Write Split operation (cross band full duplex) Lock mode / Cross Band Repeat disable Scan programmed limits (down) Scan programmed limits (up) Cross Band Repeat enable (split mode must be on!) Diode D14 (right diode on CPU board) must be removed to enable the use of this function) RX/TX light enable / disable Select DTMF Autodialer memory Change frequency/memory channel (according to dial set, see FUNC+0) Lock light on (don't time out)

This modification is read 725 times.
(IC-2410) Expansion of receive range
The following diodes are located on the Logic Unit circuit board. The Logic Unit circuit board sits behind the front panel of the radio. To get to the board remove the top and bottom of the case. Now notice that the front section of the radio is a separate unit from the main body of the radio. Remove the 4 screws holding the sections together but do not yet separate the sections. Place the radio on a table so that it is right side up. Carefully start to separate the sections being careful of ribbon cables that connect the front section of the radio to the rear. If you look at the back of the circuit board on the front section towards the lower part of the radio, you will clearly see three glass diodes labeled D8, D9 and D10. You will know this is the right circuit board because a lithium battery will be taped to it. These are the diodes to cut to get extended receive range as follows: D8 320-399, 830-Mhz coverage requires new antenna input D9 118-135 D10 400-479
This modification is read 760 times.
(IC-2410) 800 MHz antenna input
To receive 800 Mhz you need to add a new antenna input to connector J2 on the MAIN-B unit (UHF unit) which is the large circuit board on the bottom of the radio. J2 connects to a the B-band board which is a very small daughterboard, that is connected to the MAIN-B board. The service manual offers no description of this board but it apparently is the 800 Mhz front end. Two parts are needed: One 5 3/4" grey coax jumper (this is available from ICOM but it doesn't have a part number) Either: One OPC223 pigtail with UHF connector or One OPC166 pigtail with N connector The grey coax jumper has a plug on one end that mates with J2 and bare leads on the other. The pigtail also has two bare leads on one end. This same end also has a metal flange thats designed to screw onto the back panel of the radio after removing one of the dummy caps on either side of the existing antenna pigtail. Without going into too much detail, you must: Remove the small metal cap nearest the bottom of the radio and next to the existing pigtail. Remove the metal shield at the back section of the Main-B unit. Solder the two pieces of coax together, shield to shield, center to center and screw this assembly on to the back panel. Plug the grey cable into J2 and then reassemble the radio.
(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 834 times.
(IC-2GAT) IC-2GAT to packet
For those of you who are trying to interface something to a rig which has a single two-conductor plug for both microphone input and push-to-talk connections, such as many of the handheld rigs including the Icom IC-2AT and IC-02AT, here are three circuits that may be useful to you: ::: Electret condenser microphone to radio: Radio Shack #270-092 mic element?
MIC--------------+--------------------O------------> Mic/PTT on radio | | | | | | <-- Shield +------///----+ | | (20-30K) / <-- PTT | | / switch | +--------------------+ +-----------+------------> Ground on radio ::: Dynamic microphone to radio: MIC +-----------------------O----------> Mic/PTT on radio COIL C | C | C / | <-- Shield | / | +-----------+ +-------+----------> Ground on radio ::: High-level input (such as from tape recorder, RTTY AFSK generator, or Packet TNC output) to radio: HIGH LEVEL OUTPUT: RADIO INPUT: (0.47 uf) Audio to transmitter -------||-------+----O------> Mic/PTT on radio (25K) | | Push-to-talk -------///------------+ | <-- Shield
| Ground -----------------------------------+------> Ground on radio
I made a big mistake in the previously-posted schematic of the connection between an Icom IC-2A, 2AT, or 02AT and a packet radio TNC, RTTY afsk unit, or another microphone. The resistor and capacitor were backwards. The correct schematic follows:
Audio from TNC* PTT | | --/ (C1) --(R1) | / | | Icom HT | | mic input------+-------------+
Ground | | | | | | | | ground--------------------------------+
C1 - 0.47 uf capacitor R1 - 25K resistor
* TNC or RTTY afsk or another microphone or whatever you are interfacing to your Icom HT.
This modification is read 780 times.
(IC-2GAT) ICOM IC-A20 alkaline headset-adapter lost-in-the-soup (Sir Matthew G. Dralle)
> > > > > > > > > >
>.I paid $449 + sales tax for a new IC-A20, $26 for the ICOM >alkaline battery pack, and $50 (arrgghhh) for the headset adapter >(Sigtronics, with a yoke mounted PTT switch). If you can find >the aviation-standard connectors, it would be easy to fabricate >a headset adaptor and save a few dollars. Be careful - There is a LOT more to the ICOM PTT switch than meets the eye. There is no easy way to match up an external mic and the ICOM with out the PTT unit from ICOM. A couple of jacks and a switch or two isn't gonna do it. Icom uses a wierd wiring scheem in the mic jack so that if you were to plug a mic into the Icom directly, you would have to use the PTT *ON* the radio. I..[ stuff deleted some where in here ] can't remember the exact wiring now, but without extensive modification and an additional relay *ADDED* to the PTT cicuit from Icom, you won't be able to use your standard PTT that you got with your headphones. I hate to be a downer, but those are the facts.

.-------------------------------------------------------------------l.------------DIODE-Da--------. l l D915 +-+ ['] D909 : l l.------------DIODE-Db--------+ l l D916 [ ] ['] D910 : l l. : l l D917 +-+ +-+ D911 : l l.----------------------------------------. : l l l.-----------. l : l l l.' '; l : l l l.' '; l : l l l : BACK OF : l : l l l : SPEAKER : l +--+ +-:+ l l l '.' l : : : ': l l l '.' l +--+ +--+ l l l ------------l l l l l +--+ +--+ l l l Removing this diode results in -----> l : --REMOVE-- : l l l expanded UHF coverage from l +--+ +--+ l '--------' 400 - 479 MHZ. l l l +--+ +--+ l l : : : : l l +--+ +--+ l l l l l l +--+ +--+ l Removing this diode results in -----> l : --REMOVE-- : l enabling the unit as a crossl +--+ +--+ l band repeater. l l l +--+ +--+ l l : --DIODE--- : l l +--+ +--+ l l l ------------------'


.------------------------------------. l.----------. l l : : l l : : l l : PA CHIP : l l : : l l : : l l '----------' l l.----. Attach V.O.M.----. l l : : meter lead --> O : : l l : () : : () : l l : : : : l l : : : : l l '----' '----' l l VHF VCO UHF VCO l '------------------------------------' Bottom
This modification is read 987 times.

(IC-32) IC-32E auf 9k6

Hallo, habe mein IC 32E erfolgreich umgebaut auf 9600BD. NF Ausgang vom IC 32E zum TNC an MAIN UNIT an IC707 TK1042M Pin 11. NF Eingang vom TNC zum IC 32E andie Leitung R779 nach R781 Signale UMOD VMOD. PTT an Stecker J710 Signal PTT. Fragen ueber Box DB0IZ oder Digi DB0END in 1200BD oder 0202/521349. Sowie ueber DB0IZ-9 in 9600BD Joerg aus Wuppertal DD8JM. PS: UMOD VMOD sind auch auf MAIN UNIT.
This modification is read 786 times.
(IC-32) IC-32AT Elimination of possible faint pulse noise
IC-32AT Amateur This service bulletin is meant for technical personnel with experience working on solid state communications equipment. Damage caused by improperly installing this modification may cause ICOM to charge for subsequent repairs to the product. ICOM does not warrant this modification. 13889-004 May 1, 1989 Elimination of possible faint pulse noise from speaker when radio is in power save mode The power save mode employs a circuit which creates a high level square wave signal used in the power save function. This modification alters the square wave characteristic to eliminate the noise.

This modification is read 542 times.
(IC-475) Prevent a decrease in RF power output in high ambient temperatures
Note: This service bulletin is meant for technical personnel with experience working on solid state communications equipment. Damage caused by improperly installing this modification may cause ICOM to charge for subsequent repairs to the product. ICOM does not warrant this modification. Bulletin #: 24487-001 Procedure Replace R55 on the RFYGR board (currently 22 ohm 1/8 watt) with a 33 ohm 1/8 watt resistor.
This modification is read 517 times.
(IC-475) IC-475 Freq. steps mod
This modification is read 545 times.
(IC-475) Power control modification
replace R87 (470k) with 100k cut "POCO" wire (pin 3, P1/J1, MAIN, orange) at the plug (P1) connect the "POCO" wire to gate 2 of Q13 (e.g. via top of R87)
adjust R250 (SWR protection), R256 (low power level) & R259 (high power level) fully counter-clockwise. (this will give you full SWR protection, but cancels the ALC in normal operation). put the front plate RF PWR in full output position (clockwise) and adjust R82 (Q13 output attenuator) until you have the nominal output power (initially the output power will be higher because you removed the regulation, but the PA will be saturated). the balance between FM, CW & SSB output can be adjusted with R137 (CW carrier level) & R105 (FM carrier level). other interesting adjustments: R135 (mixer balance i.e. SSB carrier suppression), R133 (TX BFO output level).
This modification is read 534 times.
(IC-475) Restoration of pass band tuning
This modification is read 525 times.
(IC-475) Splitting into RX- and TX paths
(IC-475) Modification of cw pass band (BFO)
For readjusting the BFO you need another transceiver (TRX2) with correct tracking. 1. Receive on TRX2 and transmit in CW. Adjust the VFO (with the RIT off !) of TRX2 until you have the desired side tone in CW mode. (e.g. 800 Hz - can be found by beating the tone with the side tone oscillator). 2. Transmit on TRX2 and adjust Ly (CW-R) until you have the desired side tone in CW mode. (you are setting the ~800Hz
difference between CW-R & CW-T). 3. Adjust Lx (CW-T) for preferred USB/CW receive passband. You might have to repeat the tuning once again, as there is some interaction between the adjustments (diode switching for high impedance RF circuits are not perfect !). If you would like to adjust the LSB passband, this should be done by adjusting the capacitor C, before adjusting the coils.
This modification is read 512 times.
(IC-475) Disabling of SBB squelch

New component values:

C334 82pF L101 180nH C332 10pF C333 1.2pF L100 100nH C331 2.7pF L99 180nH C329 3.9pF C330 10pF
Caps in 0603 size, Farnell or Johanson. Inductors in 1008CS size, Coilcraft. The result is given in plottxnew.pdf. The measured filter response was even better; there was a resonance bump at 120 MHz and 150 MHz. The power levelling did not work so good outside of the ham bands. This is due to the frequency dependent detection circuit on the PA board. The Tx power was +2dB at 120 MHz and +8.5dB at 165 MHz. Spurious emission increases at the Tx band edges, 120 and 170 MHz, to about -30 dB. The VCO1 to VCO0 switch, below 120 MHz for my 706, increases the problem since the doubler output power is a bit low at the band edge.
This modification is read 4213 times.


(IC-706) Adding an extra RX-only port in the Icom IC706
Author: Jaap van oosten -
This is usefull when using a big PA and or for RF bandpass filters. My FT102 + transverter recently broke down So i now use the IC706. The sensitivity of the IC706 is not what I was used with the transverter. There is raise of noise when connecting the antenna so in fact it is just sufficint. Using the IC706 with an external PA you might need a lownoise preamp. But it is not so easy to use because without extra protection relays it can, and sure will be destroyed by the driving power of the IC706. The best solution is having an extra RXonly input like most bigger tranceivers have. This way the preamp can be placed direct behind the first antenna relay and the output of it Goes to the RX-only port. The best place for this antenne relay of course is as close as possible to the antenne to avoid extra cable loss however not so practical. Adding a separate RX port is an easy and clean modification. There is a spare opening in the backpannel where an extra BNC connector can be placed. Extra rings are used to fit because the hole is to big for the BNC. Then this BNC must be connected to J1 (rx) point found at the back of the filterunit. The filterunit is situated top-backside. After removing 5 screws the board can be moved up at the backside Just enough to mount the BNC underneath it. It is not needed to remove it completely that would be a problem because of all connections to it.
This modification is read 411 times.


(IC-706mkii) ICOM 706 MKII Extended transmit mod
From: "Len SantaMaria, KC2ADV" This file may be freely distributed as long as it remains intact, with no modifications, additions, or deletions. DISCLAIMER: I assume no responsibility for damage or inaccuracies contained in this document. In other words, USE THIS AT YOUR OWN RISK. It worked for me, however I don't know if it will work for you. WARNING #1: This mod requires the ability to remove surface mount diodes. Only those who are qualified to do this should attempt this mod. WARNING #2: This mod seems to erase all memory channels, etc. You may want to save this info for reprogramming. Disassembly: 1. 2. 3. 4. 5. Face the front of the radio towards you. Remove the three screws in a row across the middle of the top of the radio. Remove the two screws at the top rear (on the sides) of the radio. Pry the top cover off from the back. Disconnect the speaker at the connector. Modification: 6. Near the top rear of the main circuit board, there is an small, oblong metal can. Directly below the right side of this can is two surface mount diodes with a white silk-screened box around them. There is also what appears to be a circuit board part number just to the left of it (mine says B4916D). Remove the LEFT diode in the box. 7. To the left of this, there is a test point marked CP3. Just to the left and above this test point is another box with two *vertically* mounted surface-mount diodes (Note: there is also a place for 5 more *horizontally* mounted diodes, with 3 installed). Remove the LEFT vertically oriented diode. Reassembly: 8. Reconnect the speaker. 9. Put the top cover back on. Insert the top cover tabs into the slots and lower into position. 10. Replace all of the screws. My radio did not require a reset, however I did lose all of my channel memories. It seems to be able to transmit everywhere except below.5 Mhz. I have not tested the power output at all frequencies yet.

Pin 7 of J3 _________ |ooooooooo| | ____________ |_ | F13 | | |____________| | | ____________ | | CW FILTER | | |____________| | | | | | | -----------| - | CW | New wire >| R-323 | | | FILTER | | -----------+--------| ------------------------------------------------------------------------FRONT


(IC-738) Extended TX modification for Icom IC-738
1. 2. 3. 4. Remove power & antenna. Remove screws & rmove top & bottom covers. Swing PA Block saide & fold down the front panel ( you may need to unplug the Q1 Cable. Note connector orientation ) Locate D15 and move it over one position to the right ( of its original position )
This modification is read 518 times.
(IC-740) Display/distortion problems ICOM IC-740 HF rig
Also probably would apply to IC 735 and IC 745 as well. The symptoms were distortion on transmit, a very unstable display, often tuning dial would not move frequency, display would give all kinds of random numbers, sometimes no numbers at all on sections of display readout. This appeared to be a mechanical problem, as a sharp "rap" on the case would change things, sometimes curing it temporarily. We pulled off the covers of the set, and gently tapped each board. The PLL board appeared to be the culprit. This is the small covered board to the rear left on the underside of the 740. We popped off the little cover over the board, loosened the 4 mounting screws and took out the board. Everything looked good, but the points on the board that contacted the metal standoffs were corroded and dirty. We flowed fresh solder around the screw holes on the board (underside), cleaned the standoffs and cleaned the chassis where they connected to it. This cured the problem. Interestingly enough, we did the same fix to an Icom 22S 2 mtr rig several years ago that would keep going out of "lock". It cured that problem as well. The bottom line is, make sure all your board to ground/chassis connections are real clean. Just a thin film of crud can cause all kinds of problems on a unit that uses the mounting screws as the ground return. Sometimes (but not always!) just loosening and retightening the mounting screws will help the problem.
This modification is read 503 times.
(IC-745) IC-745 - PROBLEM: Tuning counts slowly down
I have a problem with my 745. When I rang Bellevue, WA, they said: Never heard of it. My friend in LA who has the same pronlem got the same anser. The problem is as follows: The tuning counts slowly DOWN whether it's memory or VFO. I temporarily used the set by turning the dial in the UP direction faster than the countdown and then used the lock button when the set arrived on the desired frequency. The XIT?RIT can be used for small corrections. My friend who has a complete professional lab at his disposal found a temporary fix. He grounded pin 40 of the I/O IC which steers the CPU. Everything workds fine except that you miss the slowest tuning speed and that the UP/DOWN button on the mic does not work. I did the same and my set work the same. The tuning is a little bit coarse now but usable except you have to be careful especially with RTTY or AMTOR. The local ICOM repair shop is too busy at the moment with their normal work, and I don't like to be without this set for too ong a time. I can't use the 730 to drive my linear at least not without a lot of trouble. I suspect thqt one of the two transisstors has gone but which? I just wonder if any of your readers has had the same problem and fixed it. (ED Note: Anyone have the solution?) (Thanks, Bob Bartelings, VE6CBN, 170 Haysboro Crescent, Calgary, Alberta Canada T2V 3G3)

R107 R108 C47 C48 1M 100 2.2uf.47uf
Values as per Production ser # 2589:
R107 R108 C47 1M 100.47uf
Note that C47 and C48 have been swapped. a step in the right direction. Values that work:
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.


(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.


(IC-781) Icom IC-781 filter modification
Author: Adam Farson, VA7OJ/AB4OJ - 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.

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.
The receive audio (RXAudio) also passes through the PACT/AMOD slider switch:
In the AMOD position, RXAudio is picked up from either the Main or Sub receiver, according to the setting of another internal slider switch marked MAAF/SAAF, and is squelched. In the PACT position the audio is collected directly from the discriminator of the Main FM circuit, via a 4k7 resistor and 100nf coupling capacitor. It's unsquelched of course.
These switches are not accessible without removing the bottom cover. An access hole could surely have been placed next to the accessory socket, which would allow these switches to be tickled with a small screwdriver. Users will probably drill a couple of holes in the bottom, or cut away some of the underside ventilation grille. But why should you need to touch them at all? Read on. 1200 bps PSK Satellites FO-20, PacSat, Lusat and Weber require an FM uplink, to which is applied audio PSK. The downlink is conventional carrier PSK, and the system is full duplex. Therefore the internal switches must be set to AMOD and SAAF (see above). The uplink "eye" as received at the satellite is OK; it's pinched about 4 db. Remember the TXAudio has been through the regular FM modulator circuits. It's a good idea not to yell into the microphone at this time, unless the Mic gain pot is at minimum, since both signals are added. If you flip the MOD switch to PACT the uplink modulation is text-book perfect, but then you lose your
Sub band PSK receive audio! You get Main FM. Grrr! Downlink 1200 bps PSK reception from the Sub band receiver is excellent, as too is Oscar-13's 400 bps telemetry signal. The only snag with these PacSats is doppler tracking the PSK signal. (See later). 9600 bps DFM Satellites Uosat-22, KitSat-23 etc require the TXAudio to be applied direct to the transmit FM varactor. RXAudio must be picked off directly from the FM discriminator, and the system is full duplex. Thus the internal MOD slider switch needs to be set to PACT. But that immediately picks up the wrong RX audio - from FM Main's discriminator. For satellites we need FM Sub's discriminator output. Consequently you CANNOT operate the 9600 bps satellites with an Icom IC-820H "straight out of the box". There is a solution, but we're back to modifications I'm afraid. What you do is locate the Sub receiver discriminator IC20, pin 9 and fly that signal out on your own lead. This requires you to remove the big PCB called Main Unit, turn it over and do some fine re-work among the Sea of SMD. Alternatively you can pick up a downstream version of the signal without removing the PCB at the optional tone-squelch unit-B socket J20, third pin from the "J". Incidentally this signal is DC coupled to the discriminator chip, so you can implement closed-loop AFC externally using one of the many published circuits. The source impedance is 47K (R329). I checked Uosat-22 and KitSat-23 on Sub-band using this modification. The UO-22 "eye" is poor when it leaves the satellite, with a lot of LF flutter which has always made decoding difficult. But the 9600 bps performance of the Sub band receiver is so good it adds little extra aberration and data decoding was quite satisfactory. The KitSat-23 "eye" was wide open, and data detection perfect. Since there is no AFC indication for Sub band, tracking the changing doppler shift unaided requires either very good judgement, an external system as above, or computer control. Oh, and once again set the mic gain to zero, or microphone sounds will be added to your transmission. 9600 bps DFM Terrestrial Terrestrial 9600 bps packet works perfectly, "right outa the box". Over the last six years I've tested innumerable radios for 9600 bps operation. The Icom IC-820H now shares top place with Kantronics' D4-10. (The latter is however 2-channel, crystal controlled and UHF only). 9600 bps packet requires the TXAudio to be applied direct to the transmit FM varactor. RXAudio must be picked off directly from the FM discriminator, and the system is simplex. Thus the internal MOD slider switch needs to be set to PACT, which also selects RXAudio from FM Main's discriminator. The transmitter circuit's frequency response is from about 15 Hz to well beyond 6 kHz, so the outgoing signal has superb fidelity. If the drive signal exceeds 1.6 volts pk-pk, corresponding to about +/- 5 kHz deviation, modulation is switched off abruptly and stays off until you reduce the drive. A nice touch. The correct drive level is 1 volt pk-pk for +/- 3 kHz deviation and I confirmed this by measurement. The FM Main and Sub receive circuits are similar. Main uses a pair of Icom part no. FL-211 crystal roofing filters (no spec) and a muRata SFH455E ceramic final filter; Sub uses a pair of FL-212 and the muRata CFW455E. The "E" suffix means 15 kHz bandwidth. The SFH types have particularly flat delay characteristics, and are pin compatible with the more common general purpose CFW series. Main's fidelity is outstanding, with a flat frequency and delay response to over 6 kHz. The "eye" was essentially perfect. You can be mistuned by up to +/- 4 kHz before the "eye" starts to look mangled, and +/- 5 kHz if the packets are short. The Sub receiver is almost equally good, but you can't get at it without modifying the radio as described earlier. No quibble with Icom's claims here; 9600 bps simplex works 101%. PSK Satellite Doppler Tracking When using a 1200 bps PSK digital satellite such as FO-20, PacSat, Lusat or Weber it is essential that the PSK modem can control the radio receive frequency in a closed loop fashion, preferably in small steps. The universal means of doing this is via the Up/Down buttons of the microphone socket. The smallest step from the mic Up/Down buttons of the IC-820H is 100 Hz. This really is too big, as the sudden lurch from one frequency to the next will invariably cause momentary loss of demodulator lock, with attendant corrupted characters. The Up/Down line is also accessible from the accessory socket, but it shares a pin with the ALC control. You select which from an internal slide switch.

This modification is read 491 times.
(IC-DELTA1) Band expansion modification for IC-Delta1A
Remove diode D14 Replace diode D13 with a MA132HK (icom part#1790000830) Replace diode D15 with a MA132WK (icom part#1790000850) Reset Radio

After mod, you get:

118-136 MHz AM RX 136-174 MHz RX/TX
350-470 MHz RX/TX 800-950 MHz RX 1240-1300 MHz RX/TX
IC-Delta1A Logic Unit: /---------| | \___________________________ | D D D D D | <-Matrix D14 D13 D15 Q21 Q22 | D D D R | D11 D12 D10 R78 R79 | | | | | | \_____________________________________/ ____ Replacement of D13 =| | MA132HK | /|=k a=|/_| Replacement of D15 ____ a=| | | >|=k a=|/_| MA132WK
1N916 or 1N914 can be used too. Reset The Radio When Finished
Cool radio, too bad its so big and doesn't tx on 800mhz.
This modification is read 575 times.


(IC-DELTA1) IC-Delta 1E repeater mode
Author: Walter, DH0KAR You can change the delta 1 E to -repeater mode- while two of three modules are switched on and squelch is on. You have to press and hold -func, moni and ent- keys, then two blinking -Ls- will show up on the bottom off the display. When one of the two modules receives a signal strong enough to open the squelch this signal is immediately transmitted on the other module and vice versa. You stop the mode by pressing the buttons in the same manner as above and see the blinking -Ls- going away. 73 Walter, DH0KAR
This modification is read 540 times.


(IC-F3/4) Icom F3/4 extended RX & TX
Author: Jonathan Davis -
While holding down the [C] + [Monitor] button turn on radio. Dealer will appear on LCD. Imput 159357. You can ch up or down and you will see the freq corresponding with each ch. Radio will promp to enter RX. Do so and push [#] to enter or again to del.
Push the [left arrow] button to enter TX freq. I have not been able to get ctcss entered this way yet, I'll keep trying. This will only work if Dealer set mode is enabled in the common screen in software. I think enable is by defalt anyhow. Jon.
This modification is read 1362 times.


(IC-M100) Icom IC-M56, M58, M59, M100 - M125 Additional frq. range
Author: Honico -
Power off radio. Unplug. Inside, under the cover, all have a switch labeled PRV. Centrally located in the small radios; and on circuitry -inside the face, bottom-end - Toggle it to enable *to be released* channels.

This modification is read 775 times.
(IC-W31) IC-W31 RX mod part 2.
Author: vu3vtk - Hello Folks. The mods for W 31 IS NOT AVAILABLE OR DOES NOT WORK WITH ALL THE RADIOS. The Rx MODS IS IN THE KEYBOARD.NO hardware change is required. 1. Note all memories. 2. HOLD VFO and POWER ON. 3. This will give a partial reset. 4. Now the Rx is open from 50Mhz to 299.99Mhz in VHF. 301Mhz to 999.99 Mhz in UHF 5. The mod can be confirmed. check if you have "PLACE" ON THE - set- menu. AS USUAL WITH THE DISCLAIMER. GOOD LUCK vu3vtk
This modification is read 696 times.


(IC-W31) Cross Band Repeating with the Icom IC-W31A
Author: Kevin Luker -
1. Select the two frequencies you want to crossband on. 2. Press the function button and then the call button. This will place the radio in locked mode. The radio will indicate this by putting a black L in the lower right of the screen. 3. Turn the radio off. 4. While turning the radio back on press and hold the "MONI", the "#", and "RPT" buttons simultaniously. The black L in the lower right corner should be flashing. Youare now crossband repeating!!! To return the radio to regular operations. 1. Turn the radio off again. 2. While turning the radio back on press and hold the "MONI", "#", and "RPT" buttons again. 3. The black L should not be flashing anymore. 4. Press thr "FUNC" key then the "CALL" key again and the L should disappear. You are now back in Regular radio mode. Take care and enjoy. 73's Kevin Luker
This modification is read 687 times.


(IC-W32) Expanded Frequency Coverage on TX/RX for the Icom IC-W32A/E
9-5-97 NOTICE: We can not guarantee specifications beyond the amateur bands. Not responsible for any damages incurred in attempting this proceedure. This modification may void all warranties. 1. Remove the battery. 2. Remove the 4 screws holding the rear cover and the 2 lower screws holding the shield in place in the battery compartment. 3. Carefully lift the rear cover with the battery comparment shield away from the front cover. 4. The front and rear sections are connected together with a flex strip connector. Carefully lay the rear section aside by lifting upward, turning and laying the rear section over away from the front cover leaving the flex strip connected. 5. With the front cover section in front of you, antenna connector to your left, locate the notch at the right side of the exposed PC board. Next locate the three, 3 terminal diodes near the lower corner of the notch. Two are in line from left to right, with the third below the diode to the right. This last diode (the one below the right one) is diode D523. Very carefully remove D523. Use ca 6. Reassemble the radio in reverse order. 7. Perform a system reset by holding down the Squelch button (on the side) and the Band button while turning the radio on. Note that all memories will be erased, so write down anything you want to save and reprogram. VHF coverage will be from 140 to 170 (plus or minus a bit) on Tx/RX UHF coverage will be from 430 to 470 (plus or minus a bit) on TX/RX

C231 C232 C234 C236 C237

from from from from from
1000 pf to 68 pf.01 uf to 1000 pf. (You can use the capacitor which used to be C231.) 100 pf to 22 pf. 47 pf to 22 pf. 680 pf to 100 pf. (You can use the capacitor which used to be C234.)
Solder a 10 microhenry inductor in parallel with L204, a 20 microhenry inductor. Changes for BS-8 Module I haven't tried the BS-8 module, but encourage you to try using it as is, without modification unless neces- sary. These steps are needed only if you cannot find settings of the side mounted aligment controls that get the display to behave as specified in the owner's manual: 1. Remove C233, the 33 pf disc capacitor, from the printed circuit board. 2. Replace coil L204, the 4.7 microhenry inductor, with a 6 or 7 microhenry inductor. Alignment Follow the alignment procedure in the SM-220 owner's manual to adjust the panadaptor. This consists of adjusting 2 potentiometers and 1 trimmer capacitor through holes thoughtfully provided in the side of the cabinet. The alignment instructions rely on the use of the internal Marker Generator to generate a signal at the center of the passband. If you haven't converted the Marker Generator circuit, you can tune your receiver to a frequency with a signal present at a known frequency (like 162.550 MHz - the National Weather Service), and use that as a frequency standard. Most of the time spent in aligment will be in alternate adjustments between the trimmer capacitor and the wide band sweep potentiometer, which interact with each other. Wider Bandwidth The SCAN WIDTH switch on the stock SM-220 can be set to display a 40 KHz or a 200 KHz wide picture. I adjusted my modified SM-220 to display a 100 KHz or a 500 KHz wide picture. By adjusting the controls on the side of the SM-220, wider bandwidths are possible, but wider bandwidths make it more difficult to resolve individual signals close to each other in frequency. As the bandwidth gets wider, the horizontal sweep loses linearity, causing the graticule calibration lines to be inaccurate. Connection to R-7000 As mentioned earlier, a DC voltage is present at the R-7000 IF output connector and is used to power an ICOM TV accessory. A direct connection between the R-7000 IF output connector and SM-220 would damage at least one of these units. To block the DC voltage, a 0.1 microfarad capacitor was soldered inside the R-7000, between the IF output jack and the adjacent jack labeled "spare". Connection between the R-7000 and SM-220 is then made using a short length of RG-58/U coaxial cable, with one end plugged into the R-7000 "spare" jack, and the other end plugged into the rear of the SM-220. This leaves the original IF output jack undisturbed so it can be used with the TV adaptor accessory. Vertical Sensitivity When I connected my modified SM-220 to my R7000, the SM-220 would display only the strongest of signals. To improve the display sensitivity, I inserted a 20 dB gain RF amplifier between the R7000 and SM-220. The amplifier was a spare Ameco PLF2 FET receiver preamp, adjusted for 10.7 MHz, but other amplifiers can be used, provided they have at least a 500 KHz bandwidth, and sufficient gain, at 10.7 MHz. False Readings - Images The SM-220 circuit is like a superheterodyne receiver. The panadaptor itself has a 455 KHz IF, and like other superheterodyne receivers with a low IF frequency, is prone to images. An image is manifested as a false pip, which moves across the screen as the receiver is tuned, and is 910 KHz (twice the IF) away from the actual signal. The images discussed here are in the SM-220, not in the receiver. Images are bothersome on the strongest sig- nals, like those 300 watt paging transmitters that saturate the county with RF, belching out out strange digital noises or voices (now illegal to monitor). Use With Other Receivers The modified SM-220 can be used with other receivers having a 10.7 MHz IF. In other receivers, one would need to find the

A. Remove the top cover of the receiver. B. Turn ON the filter switch (S1) on the main PC board. S1 is a small slide switch not far from the center of the board. C. Locate D37 on the main PC board right next to IC3 near the center of the board. Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D37 to the cathode (top) lead of D39 (located on the opposite side of IC3). D. PERFORM THIS STEP ONLY IF YOU WISH TO MAKE THE "IF-SHIFT" MODIFICATION FOR THE SSB/CW/RTTY "BOTH SWITCHES OUT" POSITION, AS DISCUSSED IN THE PREVIOUS TEXT. IF YOU ONLY WANT THE EXTRA AM BANDWIDTH, SKIP TO STEP "E." Cut the top (cathode) lead of D44, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up and solder a jumper wire from it to the top (cathode) lead of D42 (located near filter switch S1). E. Cut the top (cathode) lead of D46 (located a little toward the front of the main PC board). Make sure the two clipped leads are not touching. F. Locate D45 on the main PC board (near IC3). Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D45 to the lead sticking out of the PC board which was clipped from D44. If step D was not performed, then solder the jumper to the cathode (top) lead of D44. G. Inspect your work and verify all steps were done properly. Make sure all tools are out of harm's way. Reconnect power, antenna and an external speaker, and test the modification. You should now have the following bandwidth settings:
AM wide. AM normal. SSB/CW/RTTY wide. SSB/CW/RTTY normal.. or SSB/CW/RTTY normal.. 6 KHz 2.8 KHz 2.8 KHz 2.4 KHz 2.3 KHz (CFW455IT) [no change] (FL-70/CFW455IT) (FL-70/CFW455IT) [no change] (FL-44A) [IF-shift, if step D was performed] (FL-30/FL-44A) [no change, if step D was not performed] (FL-30/FL-44A)
Narrow, all modes. 2.3 KHz
If everything works OK. reassemble the receiver.
OPTION 3 REPLACE THE 2.4 KHz AM "NORMAL" BANDWIDTH WITH 2.8 KHz. MAKE NO OTHER CHANGES TO THE FILTER SELECT CIRCUIT. A. Remove the top cover of the receiver. B. Locate D37 on the main PC board right next to IC3 near the center of the board. Cut the top (cathode) lead of the diode, leaving enough wire on both sides of the cut to make connections to. Bend the wire lead on the diode up. Solder a jumper wire from the cathode lead of D37 to the cathode (top) lead of D39 (located on the opposite side of IC3). C. Inspect your work and verify it was done properly. Make sure all tools are out of harm's way. Reconnect power, antenna and an external speaker and test the modification. Your AM "normal" bandwidth will now be 2.8 KHz (FL-70/CFW455IT) instead of 2.4 KHz (FL-70/FL-44A) If everything works OK, reassemble the receiver.



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