Newsgroup: it.hobby.radioamatori
Titolo: Allargamento banda IC-706

Ciao a tutti, sapete dirmi come abilitare la trasmissione dell' apparato 
in topic anche su bande esterne a quelle ufficiali??
Ringrazio per l'aiuto...sono gradite risposte anche in e-mail.
-- 
	co...@XnoSPAMXquackquack.com
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Subject: ICOM IC-706 Yellow Wire Mod Details?
Questo e' quanto ho trovato in rete, spero che l'iglese non sia per te
un problema.
Ciao...
============================================
Can someone point me to specific info on the details of the (in)famous
yellow wire mod for the IC-706 which opens up Receive above 129MHz?
Remove the radio top cover. With the radio faceplate facing you,
you'll see a multiconductor plug near the middle of the radio.
The fourth wire from the *left* is yellow. Remove this wire from
the connector and tape it off, or cut it, and you've done the
yellow wire mod (type 1). Be careful, there's also a yellow
wire fourth from the *right*, that's not the one you want.
What this mod does is force the radio to use the 2m bandpass
filter all the time rather than just in the range 144-148 MHz.
The "wideband" filter that would normally be selected outside
the 2m band actually cuts off at about 140 MHz, so you can't
receive signals above the 2m band (such as national wx at
162.55 MHz) with the stock radio. After the mod, the 2m BP
filter has wide enough skirts to allow you to receive national
wx, but peters out above that.
There's a downside to this (type 1) yellow wire mod. After
the mod, signals in the aircraft band will be greatly 
attenuated. That's because the lower skirt of the 2m BP
filter (now used all the time) peters out at about 130 MHz.
To avoid this problem, there is a type 2 yellow wire mod.
In this latter mod, you take the yellow wire you disconnected
in the type 1 mod and extend it to the bottom of the radio
and connect it to a switching transistor there. Remove the
radio bottom cover. You'll see 5 SMD transistors just behind
the front panel menu key. The center transistor has a trace
going over to a feedthru hole near a coax connector on the
right side of the board. Solder the extended yellow wire
to this feedthru hole. Now when you tune *below* 2m, the
original "wideband" receiving filter will be switched in
and you'll have restored aircraft band sensitivity. Above
2m, the 2m BP filter is still used, so you'll still be able
to pick up national wx.
There is a different solution, other than messing with yellow
wires, to the problem which can give you coverage all the way 
to the 200 MHz upper tuning limit of the radio. This mod requires 
you to modify the "wideband" filter so that it actually cuts off 
above 200 MHz as it should. This mod requires removing two SMD 
capacitors in the filter (and optionally piggybacking one of them 
back on top of another capacitor). The former mod is simpler since 
you don't have to worry about damaging the removed capacitors, but 
can cause image problems. To do either version of this mod, you 
really need the service manual's parts layout diagram. It is 
difficult to explain exactly where these capacitors are without 
a drawing. (Needless to say, you should also have some SMD rework
experience to perform this mod.)
==========================================
MARS/CAP Modification for ICOM IC-706:
Tools required:
1) #0 Philips head screwdriver
2) 10 - 15 watt pencil tip soldering iron
3) Magnifying glass
4) Tweezers
Remove the TOP cover by removing three philips head screws on the top
and one on each side. Move the speaker bracket out of the way. Locate
D-59, this is a three terminal SMD diode in an SOT package, about
1 x 3 mm (with the radio front panel oriented towards you, D-59 is
located in a row of SMD diodes just to the right of the ribbon cbale
header above the 9 MHz SSB filter FL-30. There are pads for 5 diodes
with only three installed. D-59 is the second from the left).
Useing tweezers and a low-wattage soldering iron (and magnifying
glass, if necessary) remove D-59 by appplying some heat to the single
leg side of the device while lifting gently, then apply heat to the
other two legs and removing the device. Be careful not to apply too
much heat, not to rip or burn any traces or not to leave excess solder
on the PCB.
Replace the speaker bracket and top cover. Apply power and reset the
microprocessor.
TX = 1600 kHz - 54.00 MHz and 118.000 - 174.000 MHz
=========================================

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HO trovato anche queste info sulla radio in questione...
              ICOM IC-706 HF/VHF AMATEUR RADIO TRANSCEIVER
           Product Review, Hints and Tips, and Modifications
                        As Of: December 28, 1995
                         by Randall Rhea, KG0HW
                           OVERALL IMPRESSION
  "Too good to be true".  This was my understandable reaction to
  Icom's announcement of the IC-706 amateur radio transceiver last
  summer.  It looked like my dream mobile rig: very small size,
  detachable face plate, all HF bands, FSK, 6 meters with 100 watts
  ... AND 2 meters, all in one rig? It sounds too good to be true, but
  after using this radio in my car for about a month, I can tell you
  that this radio is real.  Although the rig is not without its
  faults, Icom has produced an innovative masterpiece.  The rig does
  just about everything as advertised.  It is an easy-to-use radio
  that replaces several other radios that I was operating in my car.
  Over the Christmas holidays, I took a couple of long car trips here
  in Texas.  The 706 was installed under a car seat, leaving plenty of
  room for luggage and packages.  (Do NOT block the top of the rig.
  Leave room for air circulation.  The rig gets VERY hot when
  transmitting!)  The face plate was installed just below the dash
  within easy sight when driving.  I used headphones, so my wife and
  daughter could listen to CDs while I was working DX.  The headphone
  plugged into the face plate.  I used a 7-foot whip mounted on the
  trunk of the car tuned for the SSB portion of 6 meters, my favorite
  band.  The radio was a pleasure to use, even while driving.
  During a nice opening on 6 meters on the evening of December 27, I
  worked several new grid squares in the midwest and Arizona.  I also
  worked North Dakota for the first time.  I was able to work a
  station in Mexico City quite easily, despite the pileup.  That 100
  watts sure helps.  (I previously used a 10-watt rig.)  The
  sensitivity of the receiver, although not quite what the "pros"
  would want, was quite adequate.  Noise from the car engine was only
  a minor problem; the noise blanker was effective for SSB.
  During the trip I also listened to a football game on TV channel 2,
  listened to truckers' traffic reports on CB channel 19 (27.185 MHz),
  worked a couple of 10m stations during the sporadic E opening on
  December 27, worked a couple of 20m stations, listened to WWV on
  2.5, 5, and 10 MHz, eavesdropped on some interesting baby monitors
  and cordless phones on 49 MHz, listened to NOAA weather forecasts on
  162.55 MHz, monitored some aircraft traffic, and did some ragchewing
  on 2-meter repeaters.  Not bad for ONE radio!
  PRICE
  I paid $1249 for mine at Tucker Electronics in Dallas.  They told me
  that they have sold about 200 of them in six weeks, making the IC-
  706 their best selling rig of all time.  They are getting them from
  Icom in lots of 20 and are having trouble keeping them in stock.
  Prices for accessories are pretty high.  There is little profit
  margin in the box, so they make up for it with high accessory
  prices.  The cable to allow for front-panel detachment is $48.
  UNIQUE FEATURES AND INNOVATIONS
     See
 
http://www.icomamerica.com/icom/amateur/hf/#IC-706
     for a list of features.
  * 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 8-foot 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.
  DRAWBACKS/FLAWS
  * Extended VHF receive requires modification (see below).
  * Poor sensitivity above 162 MHz.
  * Noise blanker does not work on AM.  Very irritating pulse noise on
  AM while the car's engine is on.  The blanker works well on other
  modes (except FM, where it is not needed).  Not good for listening
  to AM while driving.  A rather serious flaw in my opinion, since my
  $40 CB has a noise blanker that works well.
  * Poor QSK (full break-in) capability.  Not recommended for high-
  speed CW operators who want QSK.  Use semi-break-in instead.
  * No CW narrow filter.  You can install one as an extra-cost option
  or use an external CW filter or DSP unit.
  * The built-in speaker provides surprisingly good audio for its
  size, but you will probably want to use an external speaker.  The
  speaker can be connected to the face plate or to the rig itself.
  * Automatic repeater offset is not programmed into the rig.  You
  need to program -600 or +600 yourself through the menu system.  This
  is not a problem if you store your favorite repeaters into one of
  the 100 memories.
  * The S-meter is inaccurate below S9.  Above S9, it is quite
  accurate.
  * High prices for accessories (typical of just about all other
  vendors)
  * The AH-3 antenna tuner is shipped with an unshielded cable, which
  picks up a lot of auto engine noise.  You need to make your own
  shielded 4-wire cable.  The AH-3 also blocks signals above 54 MHz.
  It also only works for HF, not for 6m or 2m.
  * Expect performance and receiver sensitivity similar to other rigs
  in this price range.  This is a low-end rig in terms of price.  For
  price vs. performance, this is probably the best amateur radio of
  all time.  However, it will not outperform your $4000 rig.  You
  probably won't win contests with it.  You will have a lot of fun and
  own a nearly ideal rig for mobile work.
  HINTS AND TIPS
  1) Take time to read the manual.  The menu system will be
  bewildering unless you read the manual.  One you get used to it, you
  will find the rig to be amazingly easy and fun to use.
  2) You need to set the mode to wide FM to receive FM or TV
  broadcasts.  Tune to the station, press the MODE key until the front
  display shows FM, then press and hold the MODE key for 2 seconds.
  WFM will appear in the display, and you will hear the station with
  nice audio.
  3) Don't use the noise blanker on AM.  It will not be effective and
  may distort your audio.
  4) Don't use the QSK feature.
  5) The rig gets very hot while transmitting.  Keep the top of the
  radio clear to allow air circulation.
                             MODIFICATIONS
  WARNING: Improperly performed modifications can severely damage your
  radio.  I have performed these modifications successfully, but I
  offer no guarantee or warranty for them.  Proceed at your own risk.
  TOOLS NEEDED:
  1) Small philips-head screwdriver 2) Tweezers 3) Magnifying glass 4)
  Low-wattage (15 watt) soldering iron 5) Long-nosed pliers
  MODIFICATION 1: Enables out-of-band transmit for 1.6 MHz to 54 MHz.
  This does not enable extended VHF transmit; a modification for this
  may be available soon.  This does not enable AM or FM broadcast band
  transmit.  Your memories will be cleared after this modification,
  since you need to reset the CPU.
  1) Open the top of the radio by removing the 3 top screws and 2 side
  screws. Look at the radio from the with the front panel facing you.
  screws.
  2) Gently pull up the speaker and set is aside without damaging the
  speaker or the wires that attach it to the rig.
  3) Note the silver rectangular box near the middle of the PCB marked
  something like "9 MHz SSB Filter".
  4) Move your eyes up from this filter toward the back of the radio.
  Just before you get to the "D 108" marking, you will see two tiny
  diodes, two blank spaces, and one additional diode.  They look
  something like this:
                     D108
                        [XX] [XX] [  ] [  ] [XX]
           Remove this diode ^^^^
  5) The second diode from the left needs to be removed.  I did this
  by crushing it with long-nosed pliers.  You can also heat it with a
  low-wattage soldering iron and pull it up with tweezers.  Be sure
  not to damage the other diodes or the PCB.  Be sure that you don't
  apply too much heat, since the heat can damage the PCB and the other
  diodes.
  6) Re-assemble the radio.  Reset the CPU by pressing and holding
  down the UP and DOWN buttons on the front panel and pressing POWER.
  MODIFICATION 2: Enables more sensitive transmit above the 2 meter
  band.  (148 to about 162 MHz; after that, sensitivity drops off.)
  Keeps sensitivity for the FM broadcast band.
  1) Open the top of the radio by removing the 3 top screws and 2 side
  screws. Look at the radio from the with the front panel facing you.
  2) Note the silver rectangular box near the middle of the PCB marked
  something like "9 MHz SSB Filter".
  3) Move your eyes up from this filter toward the back of the radio.
  Follow the ribbon cable up.  Notice a wide white connector with
  several colored wires in it on the back of the PCB.
  4) The fourth wire from the left is a yellow wire.  Cut this wire.
  Rather than cutting it, you can remove the connector, stick a paper
  clip in the side of the connector under the wire, push it in, and
  pull the wire out.  Be careful not to remove the other yellow wire.
  5) Re-insert the connector back to its original place on the PCB.
  6) Open the bottom of the radio.  You will again need to remove 5
  screws.
  7) Look at the radio with the front panel facing you.  Note 5 tiny
  transistors behind the MENU button.  Follow the trace from the
  middle transistor to a hole just to the left of jack J8.
                           +------------------------+
                           |                        |      *
               [XX] [XX] [XX] [XX] [XX]             +-O   ***  J8
                                                           *
                           Solder wire into this hole ^
  8) Solder a small wire into this hole.  Be careful not to apply too
  much heat; use a low-wattage soldering iron.  Be careful not to
  damage the PCB or the grey cable coming out of J8.  Use a magnifying
  glass.
  9) Run the other end of the wire you just soldered to the front of
  the radio and attach it to the yellow wire you just cut.
  10) Re-assemble the radio.
====================================
Ok, here's the computer simulation info I promised. I modeled
the 60 MHz to 200 MHz bandpass response. To say the least, it
sucked rocks. There are two poles, one at about 136 MHz and the 
other at about 160.5 MHz. Response is nice and flat from 60 MHz 
to 120 MHz with less than 4 db of ripple, but it takes a dive from 
there. In the 130 MHz to 170 MHz range, the loss is at least 36 db,
rising back to only 30 db at 200 MHz. Image rejection at 280 MHz
is only 26 db.
Now the ideal fix is to change the inductors so that L49 is 27nH,
L40 is 22 nH, and change C152 to 30pF. That gives a lovely passband
across 60 MHz to 200 MHz, and gives strong image rejection at 280 MHz 
and up, with one of the nulls falling right on that frequency. The 
factory ought to do that.
Unfortunately, examination shows these coils aren't easy to modify. 
So there's another way that still gives a pretty good response. If 
you remove C53 and C153, you'll get full response, though with a dip 
of 4 db in the 160 MHz to 180 MHz range, and only 26 db of image 
rejection at 280 MHz. But if you increase the value of C152 to 32pF 
by tacking the removed C153 across it, response flattens and tightens 
in the upper VHF range, and image rejection improves to 31 db at 280
MHz. 
That's about as good as we're going to get without replacing L49 and L40 
and C152 with the recomended values. 
Here's the ARRL Radio Designer file for the filter.
**************************************************
*ARRL Radio Designer v1.0
*IC-706 60 MHz to 200 MHz bandpass filter
* Gary Coffman KE4ZV 1/18/96
**************************************************
Blk
**Component data inductors
L22:1.2uH       
L49:82nH        ;ideal 27nH
L40:68nH        ;ideal 22nH
L25:0.15uH
L26:0.18uH
L27:1.2uH
**Component data capacitors
C51:.001uF
C154:20pF
C153:0pF        ;was 12pF       
C152:32pF       ;was 20pF
C53:0pF         ;was 20pF
C151:24pF
C52:18pF        
C54:220pF
C55:22pF
C56:82pF
C57:27pF
**Node list
IND 1 0 L=L22
CAP 1 2 C=C51
CAP 2 0 C=C154
IND 2 3 L=L49
CAP 2 3 C=C153
CAP 3 0 C=C152
IND 3 4 L=L40
CAP 3 4 C=C53
CAP 4 0 C=C52
CAP 4 5 C=C151
CAP 5 6 C=C54
IND 6 0 L=L25
CAP 5 7 C=C55
CAP 7 8 C=C56
IND 8 0 L=L26
CAP 7 9 C=C57
IND 9 0 L=L27
BPF:2POR 1 9
END
**Frequency block
FREQ
ESTP 50MHz 300MHz 511
END
=====================================
Icom 706 doesn't out of stock listen to frequencies over 148MHz,
although
that is advertised. At Least mine didn't.
Studying the schematics I noticed a front-end filter, that should be
operating in the range of 60MHz - 200MHz. I studied the filter with a
program and noticed, that the passband was 60MHz - 140MHz !! The upper
end
was blocked out.
I changed the circuit in a way that enables the radio to work as
advertised
by removing Capacitors C53 and C153. Now the filters upper edge is
around
230MHz.
This modification doesn't affect 2m RX in anyway, because 2m has its'
own,
thight front-end, that is used instead of the modified filter, when in
2m
band. HF and 6m aren't affected either.
The Capacitors are found in the PA UNIT board, behind the external
speaker
connector in a relatively easy place.
The job requires cautiousness because the components dislike static and
excessive heat.
This modification works, if the radio isn't already modified with the
modification, which puts 2m front-end in use in frequencies above
144MHz.
At Least My unit worked well with this modification.
Measured from my IC-706:
Frequency                Sensitivity (microvolts /20dB SINAD)
60-140                   0.14
144-148                  0.12
150                      0.18
155                      0.15
160                      0.2
165                      0.3
170                      0.4
175                      0.6
180                      1.5
185                      1.5
190                      >100mV -- deaf!
195                      5
200                      29
=====================================
Non ho ovviamente testato nulla di quanto sopra.
Cordiali saluti, Angelo IK1QLD

 
La configurazione iniziale della matrice a diodi del mio 706 non era 
quella presentata nel post di IK1QLD (che ringrazio moltissimo), ma 
quella finale si!
Quindi per l'allargamento di banda e' necessario lasciare solamente il 1° 
ed il 5° diodo (e se non ci sono bisogna metterceli...)
Provato e testato, funziona al 100%
Ciao e grazie.
