This modification is read 1203 times.
(IC-02) Low audio speaker mike on IC2A, 3A, 4A OR 02AT
If you own one of the IC2A, 3A, or O2AT series Hand-helds, you may be interested in reading on. I know my hearing is pretty good, but have you ever tried to listen to the audio coming out of your speaker mike on the above ICOM's? For the most part, it's pretty low. I may be the last guy to figure out a cure for this, but here it is anyway. On the O2AT, etc., there is a groove on the back near the top of the rig that is just the right size to accept the HM9 speaker mike turned 90 degrees so that the mike plug fits in that groove in the rear of the rig. Thus alllowing all the audio to be heard from the internal speaker of the rig, usually much better than the speaker mike. Now, in the case of the 2A series, etc., the fix is more complex. These rigs don't have that handy groove built in, so I decided a groove had to be made to accept this configuration. I thought long and hard about a minute, before getting the "Dremel" out and making my own slot or groove. It works well on both hand-helds I have. In fact, you can hook up an external speaker for even more loudness in the auto. So, give it a try or see me for a demo.
This modification is read 1034 times.
(IC-02) ICOM 02/03/04 & Vox Unit
The ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the many available power supply options. The big problem is getting the PTT to operate " CLEANLY " while not compromising the audio level from the TNC when using the resistor or resistor/capacitor interfaces suggested in some manuals. I am using the ICOM HS10-SA Vox unit to interface the ICOM 02/04 AT here.It has worked somewhat well for some time but I was always plagued with a MINIMUM 200 msec transmit "hang " delay until I tore it apart for examination and correction. The small " delay " pot on the front of the unit is in series with a 2.2 Megohm resistor (R-19 on the board). The adjustable pot is also about 2 megohms as well. This combination allows a MINIMUM VOX "hang" transmit delay of 200 msec. By identifiying the solder connections for R-19 on the back of the PC board and placing a low value resistor ( or jumper ) in parallel.I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the FULL COUNTER-CLOCKWISE position. The minimum 200 msec delay has been defeated.

Here's the mod for the IC-2000H 2-meter transceiver: Using a hex wrench, remove the front of the face plate (NOT the main radio back!!) Turning it over, you will see the PC board. Look for 16 solder dots like this:
O O OxO O O O O O O O O O O O O x = the offending diode that is begging to be destroyed.
Taking a set of needle-nosed pliers (or the equivalent) snip the "x", dust off the PC board, and reassemble the radio. Do a complete memory/factory reset which is described on page #38 of your IC-2000 series instruction manual Here's what's involved in the CPU reset referenced above: 1. Push [POWER] to turn power OFF. 2. While pushing [SET] and [PG/CS-MW}, turn power ON All LCD segments appear momentarily, the initial display appears and the tranceiver's CPU is reset. This modification should take you less than one minute to accomplish. You will find your transmit capabilities expanded to 136174 Mhz. Receive will remain at 118-174Mhz. NOTE: It is strongly recommended that you purchase the following optional units: UT-85 Tone Squelch Unit--allows pocket beep functions and tone-squelch receive operation--a must if one is plagued by stupid paging tower inter-mod (a violation of the harmful interference laws.) UT-101 DTMF Unit--provides pager and code squelch functions for selective call and silent standby, etc. These extras are available for under $100 U.S. dollars. Highly recommended!!
This modification is read 1052 times.
(IC-207) Band expansion for IC-207
Remove the 4 screws ataching the bottom cover and remove the cover. (I had to use a small screwdriver to pry on the cover. It's made to fit tight) with face toward you and belly up look to far right of board and close to you. Locate a row of SMT diodes 3 on top then a shift to right and a few more. The three are in a PERFECT row top to bottom! count from the top of the row 3. Remove the # 2 & 3 diodes. Now continue looking down from there and you will see a resistor sticking up in the air (W14). Clip the lead off of the resistor. Reassemble the radio and preform a CPU reset by holding the Set and S.MW buttons while turning the radio on.(page 69 of manual). You now will have :
118-135 RX (stock) 136-174 TX & RX 320-399 RX (hmmm whats there? I've heard a local radio station DJ at a remote location talking to the station) 400-479 TX & RX 849-950 RX

Note: From Bill K7RIE ICOM has not tried this mod nor have we verified this problem.
This modification is read 724 times.
(IC-275) IC-275 Freq. steps mod.
This modification is read 812 times.
(IC-275) Band Expand for ICOM IC-275E/H and IC-275A/H
To expand RX range delete D 44 To expand TX range delete D 27 install D 43 Range 138-174 MHz TX not in full range PLL lockout
This modification is read 952 times.
(IC-275) IC amplifier oscillates
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. 588-001 If the IC amplifier oscillates when the noise blanker is turned on and the FL-83 CW narrow filter is installed

Bulletin #: Subject:

Procedure
1. Remove the covers to gain access to the main circuit board. 2. Remove R354 (22K) from the main circuit board and replace it with a 10K (ICOM P/N 915-01113) resistor. 3. Re-install the main circuit board and replace the covers on the radio.
This modification is read 702 times.
(IC-275) Prevent PLL unlock at high ambient temperature
1. Change the following parts on the PLL board
Original Value 12 pf 50V CH 22K 3 pf 50V New Value 6 pf 50V CH 35D 45 SN (ICOM P/N 915-04229) 15K 6 pf 50V

Part C101 R137 R133 C191

2. The thermister should be installed in series with R133. Unsolder one end of R133 and solder R137 in series with it.
(IC-275) Improve voice synthesizer and side tone audio
1. Remove C214 (.47 uf capacitor) from the main board. 2. Install a.1 mf 16V barrier layer capacitor in series with a 2.2 K 1/8W resistor from the emitter of Q58 and the base of Q59 on the foil side of the board.
This modification is read 662 times.
(IC-275) Prevention of PLL unlock at 174 MHz
1. Remove and replace the following components on the PLL Board
Original Value 120 Ohm 47 Ohm 120 Ohm 60 pf 50V 43 pf 50V New Value 270 Ohm 18 Ohm 270 Ohm 30 pf 50V 62 pf 50V
Part R130 R131 R132 C42 C47
This modification is read 701 times.
(IC-275) Improve the stability of the center meter
Replace C81 on the main board (currently 120pf 50 CH type capacitor) with a 120 pf 50V SH temperature coefficient capacitor (ICOM P/N 918-05960).
(IC-275) Noise coming from speaker during transmit with audio turned up
Replace R125 (currently a 47K resistor) on the main board with a 10K resistor.
This modification is read 674 times.
(IC-275) Eliminate possible spurious emission when thermal switch has turned on during TX

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)
R O U N D B A T T E R Y ! ! ! # D # ! # D # ! # D # ! # D #

-#WW#-

-#D#-#D#- -#D# ! -#D#- -#D#! ! ! ! -#D#- -***-
This modification is read 932 times.
(IC-281) Extended Transmit for IC-281
By removing one of the diodes in the area mentioned above extended transmit is purported to be possible. I have not verified this since I don't need this capability but it is supposed to significantly extend the transmit capability in the VHF band. To enable extended transmit remove the diode that is most near the right hand bottom part of the board as indicated in the diagram above with -***-. Reassemble and reset CPU per instruction manual. Note:When you reset the CPU you loose all memory and have too re-program all.

Japan Version Europe Version Italy Version D6: D5: D6: D5: D6: D4: D9: D5: D6: D4: DA115 DA115 DA115 DAN202U DA114 DA115 ISS254 DA114 DA115 DA115 from from from from from from from from from from from KEYI2 KEYI0 KEYI2 KEYI1 KEYI0 KEYI0 KEYI2 KEYI1 KEYI1 KEYI2 KEYI2 to to to to to to to to to to to KEYS2 KEYS3 KEYS2 KEYS3 and KEYS3 KEYS2 KEYS3 KEYS2 KEYS3 KEYS2 KEYS3
U.S.A. Version Australia Version Asia Version
Now, can anyone use this to figure out the Icom-Europe memo??? Bob KC9RG cromwell@ecn.purdue.edu top of page
(IC-2SAT) Icom IC-2SAT unpublished Specificatons
I have access to some test equipment at work and did some studies on this little marvel of a transceiver. Here are some of my studies I have found so far: 12 dB SINAD Receiver Sensitivity:
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

end of the 10 seconds whether the signal is present or not. In essence the mod. consists of changing the 'MS' scan regime from the band-scan 'MODE A' regime (permanent stop) to the band-scan 'MODE B' regime (pause). Note: The IC-551D handbook says that the pause in 'MODE B' is sixteen seconds, whereas in my radio it is close to ten seconds. It's possible that ICOM revised the design after the handbook was printed, or perhaps the 10-second characteristic of my particular radio is a result of long-term component drift. Whatever, the point here is that the same pause will be used for the 'MS' scan mode as is already used in the 'B' scan mode. So in your particular radio the pause may be 10-16 seconds. Scan Rate: After modification the scan rate becomes adjustable by the 'SCAN SPEED' control, which was previously rendered non-operative in 'MS' scan mode, although it was operative in the two band-scan modes, A and B. Procedure: Remove the power plug from the rear of the IC-551D. Turn the set upside-down with the rear closest to you. From this point on, all expressions such as 'left', 'right', 'up', 'down', refer to the radio as viewed by you in this orientation. 1. Remove the four bottom cover screws and CAREFULLY remove the bottom cover, disconnecting the speaker plug as you lift it away. 2. If your IC-551D does not have the optional FM board installed, go to Step 3. Remove the FM board by disconnecting the white plug from the left corner and removing four screws (two at each end). Lift the FM board away carefully as it's still attached to the radio by a flying cable, and place it on the front corner of the case. 3. Remove the sub-bracket on which the FM board was mounted by removing the screws at each side (in my radio: 2 on LHS, 1 on RHS). 4. Cut a length of light, flexible wire 50-60mm long and strip 3mm of insulation from each end. Tin both ends of this jumper wire with solder. 5. Observe the printed circuit board mounted vertically about 40mm behind the front-panel controls. This PCB is the 'DRIVER' board. This is a CPU/digital processing board and has nothing to do with the transmit driver stages. Observe the three white plugs/sockets (headers) along the upper edge of this PCB. On the left-most header (closest to the centre of the radio) count the wires from right to left as they exit from the plug. This is a six-wire plug/socket (J2/P11). The second wire from the right is a dark-green wire. This is the 'VFO B' wire. DO NOT cut this wire. At some convenient point, strip about 4mm of insulation from it with a razor blade. Tin the exposed wire and solder one end of your 50-60mm jumper wire to it. Caution: In some photos in the ICOM documentation J2/P11 are shown fitted to the front-panel side of the PCB, rather than the rear side. If J2/P11 have been fitted this way in your radio, you must still use the second wire from the right, since the PCB layout does not change. However, the wire may not be dark-green as the colour sequence may be reversed. 6. Look down the left-hand edge of the same PCB. Observe the white plug/socket header, the first one you come to as you look down the edge of the PCB. The header is J4/P7. Count the wires as they exit plug P7. The third wire (counting downwards) is an orange wire. This is the 'MS' wire. To make this wire accessible, prise P7 off J4 with a screwdriver and pull P7 up towards you. At some convenient point, cut the wire, creating two ends, one going into P7, the other coming from the loom. Ignore the wire going into P7, it will not be used. Instead, take the wire which comes from the loom, strip 3mm or so of insulation from it and tin it with solder. Solder the free end of your 50-60mm jumper wire to this tinned end. 7. Push P7 back down into the wiring and press it back onto J4. This is a little tricky, but is best done with a short, skinny, screw- driver. 8. Re-fit the FM board sub-bracket and re-fit its screws. Re-fit the FM board to the bracket and re-fit its screws. Plug in its header plug. Ensure that both of your soldered connections and the cut-off end of the 'MS' wire are clear of metal framework, shield compartments. The rest of the re-assembly is in reverse order to that described earlier. Testing: Turn on the IC-551D. Program three frequencies into memory positions 1,2,3. Set the 'VFO' switch to 'MS' and initiate scanning by pressing the 'MS/MW' button. When one of those frequencies becomes active, scanning will pause for 10-16 seconds; scanning resumes auto- matically at the end of the pause, whether the signal is present or not. When receiving a prolonged transmission, reception is briefly interrupted every 10-16 seconds as the scanning re-starts. When two or three of the frequencies are active, each transmission is heard in rotation for 10-16 seconds, eg. 1,2,3,1,2,3. Scanning can still be stopped and re-started by pressing the 'MS/MW' button. The rate at which the frequencies are scanned is now adjustable by the 'SCAN SPEED' control, accessible by removing the small cover in the top of the case. It's probably best to set the control at the slowest setting (fully anti-clockwise). If set too fast, scanning may not stop on active frequencies. No other function of the IC-551D is disturbed by this modification. I use my IC-551D in the 'MS' scan mode to monitor my three favourite 2-metre repeaters, using a home-brew 144-50 MHz converter connected to the IC-551D.

(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)
This modification is read 866 times.
(IC-745) ICOM IC-745 Unlocked
Locate the RF board on the side of the radio and cut the light brown wire at jack 7., which is going to pin 1. Your transmitter is now unlocked.
This modification is read 1021 times.
(IC-745) 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. 6. Reinstall the RAM board into the radio. Cautions 1. Do not use an AC powered 3 Volt DC source, your grounded soldering iron tip could short out the battery (+) terminal. Use a 3 Volt battery DC source only (2 alkaline cells for example). 2. Do not solder the external DC wires directly to the lithium battery tab pads. If you do so, you will not be able unsolder the battery without having the wires drop off. 3. If by accident you lose power to the RAM unit it must be sent to Icom America for reprogramming. 4. Be careful not to damage or bend the connector pins on the radio side while removing or reinstalling the RAM card. Pictures There are two versions of the ICOM RAM boards. Both are identical in operation, and they are interchangeable. The differences are in the circuit board layouts only. Note that the black and red wires visible on these images are the suggested way of connecting the external DC backup voltage while the battery is being replaced. The wires are not a part of the RAM card, and should be removed when the battery replacement procedure is complete. Refer to the replacement procedure outlined above. RAM card version A images:

IC 803 CHIP ---------------

[W808]

This info are from ICOM SERVICE INFORMATION sheet.
This modification is read 1928 times.
(IC-756) Spectrum Scope Adjustments
Access to the RF Unit is required. Remove bottom cover and then remove cover to RF Unit - see below.
To increase overall Scope gain: Lower the value of R963 (100k as fitted).
I put a 56k 1/4w through-hole resistor across R963 - see above - making the combined resistance approx 36k. (One resistor leg was soldered to pin 2 of IC-961 and the other leg to the junction of R966 and R964)
To be neater you could remove the small 0603 SMT resistor and replace it with a 39k 0603 part. To adjust Scope base-line: Trimpot R966 will adjust the base-line of the Spectrum Scope. Thanks to http://www.qsl.net/vk4cp/ for the modification.
This modification is read 1768 times.
(IC-756) ACC1 Audio Output Increase
Access to the Main Unit is required. The "Line Level" audio output on pin 5 of Rear panel connector ACC1 is very low, with the manual stating 300mV. Normal Line Level is regarded as about 700mV. Although my MiniDisc Recorder had a gain control for its Analogue I/P it still couldn't make 0 VU. Here, by adding two resistors we can increase the gain of the audio appearing on pin 5 of ACC1.
Remove the bottom cover. Remove 6 screws holding down Main Unit. Remove screw on rear panel inbetween ALC & Send RCA sockets. Remove heatsinking clip holding transistor to chassis. Remove flat ribbon cable to J3 in far right corner. Carefully pry PBA loose and fold over - see at left. (I actually had to remove RF Unit shield and loosen a shielded cable to allow the Main Unit PBA to fold out). Locate IC-503, a NJM2058 OPAMP in an SMT SOIC14 package. Remove WSMT link. Fit an 10k 0603 SMT resistor in W3's place.
Fit a 1/8w 5k6 through hole resistor from IC-503 pin 9 to ground.
We have effectively changed the OPAMP IC-503c from being a unity-gain follower into a non-inverting amplifier with a gain of approx 2.5. Thanks to http://www.qsl.net/vk4cp/ for the modification.
This modification is read 1531 times.
(IC-756) General Coverage H.F. TX Mod (1.6 - 30.0MHz)
VHF remains 50.0 - 54MHz TX only. Modification summary: Remove the W805 jumper chip on MAIN unit by soldering iron. Modification Procedure: 1. Remove bottom cover of IC-756. 2. On MAIN unit board you will see I.F. filters and daughter board (DSP PBA) on the right hand side. 3. W805 jumper and IC803 chip located under DSP PBA. 4. Remove DSP PBA (lift up carefully!) 5. Look for IC803 and line of jumpers (0603 sized SMT links). 6. Remove W805 jumper - as indicated below. 7. Re-install DSP PBA 8. Re-fit bottom cover.

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 :

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

In the modified R7000, the scan and search rates are still adjustable using the SCAN SPEED control. With the control turned fully clockwise (maximum speed), the modified R7000 scans at about 13 channels/second and won't miss weak signals.
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:

2nd IF: FL-70 (2.8 KHz) FL-30 (2.3 KHz) 3rd IF: CFW455IT (6 KHz) CFJ455K5 (2.8 KHz)
While the 2nd IF filters are of reasonable quality, the 3rd IF filters are inexpensive ceramic filters. ICOM offers the FL-44A 2.4 KHz high grade crystal filter as an optional replacement for the 2.8 KHz CFJ455K5. Other filter manufacturers have comparable replacements available too. One of two optional (additional) CW filters may also be installed in the 2nd IF; the FL-32 (500 Hz) or the FL-63 (250 Hz). With only its stock filters, the R71A utilizes the following filter combination in its various modes:

2nd IF 3rd IF

AM wide..(none). AM normal. 2.8 KHz (FL-70). SSB/CW/RTTY wide.. 2.8 KHz (FL-70). SSB/CW/RTTY normal. 2.3 KHz (FL-30).
6 KHz (CFW455IT) 2.8 KHz (CFJ455K5) 6 KHz (CFW455IT) 2.8 KHz (CFJ455K5)
At first glance, one might think that it would have been more logical to use both 2.8 KHz filters in the SSB "wide" position (similar to the AM "normal" position), rather than a 2.8 KHz filter followed by a 6 KHz filter. (Since the narrower of the filters in the IF chain really determines the overall bandwidth, the 6 KHz filter is actually doing nothing.) However, if things had been set up this way, replacement of the 2.8 KHz 3rd IF filter with the optional FL-44A 2.4 KHz high grade crystal filter would have restricted the SSB "wide" bandwidth to 2.4 KHz. The SSB "wide" and "normal" bandwidths would then have been virtually identical. Observe that the installation of the FL-44A does in fact reduce the AM "normal" bandwidth from 2.8 KHz to 2.4 KHz. Here's how the filter chart would look for an R71A with both the optional FL-44A and the optional FL-32 CW narrow filter installed:
2nd IF 3rd IF (none). 6 KHz (CFW455IT) 2.8 KHz (FL-70). 2.4 KHz (FL-44A) 2.8 KHz (FL-70). 6 KHz (CFW455IT) 2.3 KHz (FL-30). 2.4 KHz (FL-44A) 500 Hz (FL-32). 2.4 KHz (FL-44A)
AM wide. AM normal. SSB/CW/RTTY wide. SSB/CW/RTTY normal. Narrow-all modes.
Having the razor sharp 2.4 KHz bandwidth of the FL-44A accessible in the AM mode can sometimes be great for critical DXing, but AM audio at that bandwidth does lack sufficient fidelity for comfortable listening. With some minor rewiring of the filter selection hardware, the 2.8 KHz AM bandwidth can be restored in "FL-44A"-equipped R71A receivers. This is done by making the AM "normal" setting select the same 2.8 KHz (FL-70) / 6 KHz (CFW455IT) filter pair which is used in the SSB "wide" setting. For experimental purposes, I had temporarily configured my R71 to select this filter pair in the AM "wide" setting in order to make direct receive fidelity and skirt selectivity comparisons against the 2.4 KHz AM "normal" setting. My findings revealed that with the receiver tuned directly to a broadcast station, both bandwidths produced very similar sounding audio without much fidelity. But by tuning the R71A's main tuning dial 1.5 KHz away from the AM carrier frequency, the 2.8 KHz filter passed the carrier and enough of one of its sidebands to provide halfway decent fidelity. (It was noticeably less than the 6 KHz bandwidth, but still quite usable.) The same trick was also tried with the narrower, 2.4 KHz passband by tuning the main dial 1 KHz off frequency; but even then the fidelity was still too restricted for comfortable listening. Since the 2.8 KHz bandwidth seemed to isolate noisy AM signals just as well as the 2.4 KHz setting in most of my tests, I had initially considered replacing the 2.4 KHz setting with 2.8 KHz in order to take advantage of the additional fidelity. However, I did encounter some relatively rare instances when trying to tune in a weak AM station adjacent to a strong local broadcaster where the 2.8 KHz/6 KHz filter pair allowed some odd residual noise from the strong adjacent signal to become embedded in the desired signal. The noise was not there when using the 2.8 KHz/2.4 KHz filter pair. This revelation led me instead to devise a way of making both bandwidths available in the AM mode (in addition to the 6 KHz bandwidth). TECHNICAL DISCUSSION: For the following technical discussion of the IF filter selection circuit of the R71, you may wish to refer to your schematic diagram or service manual. The filter select IC is IC3 on the main PC board. It has three input pins (pins 9, 10, and 11); the logic state of which are determined by the operating mode (AM, FM, SSB/CW/RTTY) and by the position of the "wide" and "narrow" filter switches on the front panel. The configuration of these settings determines which IC output pin goes high. (Output pins are pins 1, 2, 4, 5, 12, 14 and 15.) Diodes connected from the output pins to the various filters determine which filters are activated by each specific mode-bandwidth combination. There are two output pins (pins 1 and 4) which are only activated in the FM mode. These outputs are unused (not connected to anything) since the optional FM board has its own IF filter which is automatically selected in the FM mode. The following table from the service manual shows the input-output relationship of IC-3:

Connect the remaining lead of the cap to the centre conductor of your screened cable. The screen of the screened lead can be soldered to the casing of the nearest metal can. There is a suitable can approximately 10mm (3/8") to the rear of the wire link (see diagram). Take care not to overheat the can while doing this. You should be able to get the solder to flow nicely onto the can within two or three seocnds. Exactly how you terminate the other end of the screened lead is up to you but I would suggest that you extend it through a suitably drilled hole in the rear panel of the radio and then terminate it on an in-line mini jack socket or phono connector. That's it! Well, almost. Now you have to reverse the whole process in order to close up the radio again. Be extremely careful not to strain any of the wires and take care to ensure none are pinched between metal chassis parts as you close up the radio. Don't forget to reconnect the coaxial lead at the left rear of the radio once the top chassis is back in place. The new output you have created is basically just "raw audio". It is the point in the circuit before audio filtering, volume and squelch control. This means that it is a fixed level output unaffected by the position of the volume and/or squelch controls. Be aware that while short circuiting this output shouldn't cause any harm at all, it will deprive the radio of an audio output thus muting the internal loudspeaker. The impedance of this output is around 10k which is perfect for driving the circuit supplied with the software PD.EXE (a pager transmission decoding utility) but may require buffering if you plan to use it for other purposes. Anyone requiring further assistance is free to Email me at tim@pixie.co.za. I'll do my best to help. This diagram shows the relative location of various key points within the receiver. Be aware that the points shown are all inside the radio and that some are visible only once the upper chassis has been removed.
--------------------------------------------------------|X - coaxial cable connector | | | | | | | | | | | | | | | | | | | | | | | | | | | | X - metal can | | X - wire link (W100) | | | | | | | | | | | | | | | | | | | | X --- chassis screws --- X | | X --- front panel screws --- X | --------------------------------------------------------| | | | | | | | | | | | -----------Vol Sqlch Tuning
(R-7100) Icom R7100 Discriminator Mod

Author: kc8mzm

WARNING You assume all risks involved with performing this modification I will not be held responsible if you destroy your scanner