Date: Thu, 15 Jun 89 23:19:24 PDT

From: wim
Subject: R7000 Anthology modifications



Newsgroups: rec.ham-radio

RE::Icom R-7000 Anthology

Posted:12 Oct 88 21:52:03 GMT

Organization: AT&T Bell Laboratories - Naperville, Illinois





Here is a repost of just a few of the articles about the Icom R-7000

receiver posted to the net over the past years.  There were

also articles on interfacing Icom equipment with computers, but

I have not included them in this posting.





                                - 1 -







              EXAMINING THE ICOM IC-R7000 RECEIVER



                        Bob Parnass, AJ9S



     The long awaited ICOM R7000 is here.  I bought my R7000

     (S/N  001400)  on  June  14, 1986 from Spectronics, and

     agree with other R7000 owners:ICOM did their  homework

     on this radio.



     I had several questions about the R7000 that  were  not

     answered  in  ICOM's  advertisements, and could only be

     answered by fiddling with the real thing:



       1.  Can one set the R7000 to behave like  a  "normal"

           scanner,  waiting  for a transmission to complete

           before resuming the scan?  Contrary to the review

           in  July  Monitoring  Times,  the  answer is YES.

           There are 4 choices of when  to  resume  scanning

           (or seaching), and this is one of them.



       2.  Does the R7000 have a "search  and  store"  mode,

           like  the  old  Bearcat  250?  Yes, and it's well

           done.  There is a mode which will search  between

           two  frequency  limits, and store the active fre-

           quencies in the top 20 channels.   The  R7000  is

           smart enough not to store duplicate frequencies.



       3.  Does the R7000 use  the  concept  of  a  "channel

           bank"?   Yes,  one can select and deselect any of

           the 99 channels to be in a bank.   This  is  much

           more  flexible  than  traditional  scanners.  For

           example, the user can form  a  bank  composed  of

           channels 2, 5, 31, 48, and 79.



       4.  Does the Priority Scan feature work like a  Bear-

           cat  scanner?   Well,  sort  of.  The best way to

           describe the ICOM R7000 priority algorithm is  to

           say  is  resembles using a Bearcat scanner in the

           manual mode with the priority  feature  selected.

           One  cannot  "scan"  more than one channel on the

           7000 while sampling the priority channel.  On the

           plus side, the priority frequency does not use up

           any of the 99 channels, but  is  programmed  from

           the  keyboard and has its own register.  The user

           can use the "scan speed" control to set how often

           the  priority frequency is sampled, a nice touch.

           In practice, the R7000  dwells  on  the  priority

           frequency  for  a  little  too  long, essentially

           chopping up the signal on the non  priority  fre-

           quency too much.



























                           - 2 -







     Using the internal, top-mounted speaker, the R7000  has

     good audio power and fidelity, better than my R71A.



     The user manual is generally good, and a  schematic  is

     furnished.   Some broken English makes it unclear as to

     whether  the  R7000  battery  backed  up  RAM  contains

     firmware as in the R71A.



     There are provisions for  activating  a  tape  recorder

     when  a  signal  is  received,  but  there is about a 1

     second delay in activation,  causing  the  recorder  to

     miss  the start of the transmission.  I may replace the

     capacitor in that relay circuit when I get the nerve to

     open the cabinet for the first time.



     Another relay is used to switch  in  some  filters  for

     reception  above 512 MHz, so one hears the relay click-

     ing while scanning a mixture of low and  high  frequen-

     cies, a bit unnerving.



     There's a lot of fun to be had with the R7000.  It  was

     interesting  tuning through the link and paging signals

     in the 72-76 MHz band, and listening to  military  air-

     craft in the 200-400 MHz band.



     My UHF antenna system consists of a government  surplus

     FAA  discone,  good  for coverage between 150-1200 MHz.

     Although not as good as a Butternut SC3000  antenna  in

     the 150-174 and 440-512 MHz ranges, the discone has the

     edge in the 225-400 and 512-1200 MHz bands.   At  these

     frequencies, a low loss feedline is very important, and

     I use a Belden 9913 clone made  by  International  Wire

     and Cable.







                                - 3 -







      COOL YOUR ICOM R7000 RECEIVER WITH ANOTHER HEAT SINK



                        Bob Parnass, AJ9S



     The new ICOM R7000 25-2000  MHz  receiver  is  a  super

     radio,  but the power supply tends to run hot.  The two

     biggest heat generators are  the  pass  transistor  and

     bridge  rectifier  module.  The stock heat sink, a flat

     piece of metal bolted to  the  inside  of  the  cabinet

     rear, is inadequate.  After 30 minutes of use, the back

     panel gets very hot, and the entire cabinet warms.



     I added a small heat sink to the outside of  my  radio,

     using  the  screw that holds the bridge rectifer to the

     stock heat sink.  An  application  of  heat  conductive

     grease between the added sink and the cabinet helps the

     heat transfer process.  Now the  rest  of  the  cabinet

     gets barely warm to the touch.







                                - 4 -







         ADD A COOLING FAN TO YOUR ICOM R-7000 RECEIVER



                    by Brian Kantor, WB6CYT1



     In my R-7000, adding a  fan  makes  a  big  difference.

     I've  had  it  on  continuously for three days now, and

     it's still nice and cool.  Turns out most of  the  heat

     comes  from the transformer core in the AC supply.  One

     of those 3-1/2" 12V DC fans fits just nicely -  a  pair

     of 1/4" standoffs screwed through two of the upper back

     panel ventilation slots holds it in  place,  the  power

     leads  snake  through  the lower ventilation slots, and

     some duct tape to form a gasket, and it pulls  the  hot

     air  right out.  If you pick the 12V off the power sup-

     ply regulator board at W3 (orange lead), it  will  even

     work properly when you run the radio off 12 volts.



     [In order to blow hot air out, the  fan  must  suck  in

     cool  air  from  somewhere.  Users are advised to be on

     guard for dust being drawn into fan-equipped R-7000s. -

     Editor]







__________



 1. Brian Kantor, WB6CYT.  University of California San

    Diego.  ARPANET address:brian




                        - 5 -







                     TV INTERFACE FOR R7000



                            John Biro



     I just got the video interface for the R7000, and to my

     surprise it is not an internal option.  It bolts to the

     side of the radio (right side were the rubber feet  use

     to  mount).   It  is  about  1  inch wide, and the same

     height and length as  the  R7000,  and  in  a  matching

     cabinet.



     TV video is taken off the 10.7 MHz IF output jack, this

     presents  a  problem  if  you  are  using it for a Band

     Scope.  It also "steals" the power from the  IF  output

     (the center pin of the IF out carries 12VDC so be care-

     ful not to short it out).



     The interface provides RCA type jacks  for  both  Video

     out  and  Audio  out.  The Video is standard levels and

     the Audio is low level output for input  to  a  typical

     audio  amp (it can not drive a speaker directly).  I am

     not sure why the audio output is there as you can moni-

     tor the audio on the R7000, looking at the circuit they

     do have a sideband filter circuit so I would assume the

     audio  is  cleaner  but  I have not tried it and do not

     have any problem with the R7000  audio  receiving  WBFM

     from the TV stations.



     Results:The TV-R7000 works OK, but I  am  just  disap-

     pointed  in  the fact that it does not mount internally

     in the R7000.  This could also help in its  high  price

     tag  of  $119.  I had a Yaesu FRG9600 with video option

     (only about $30), and it worked about  the  same.   The

     picture  quality  is  good,  and it is very stable.  My

     antenna is vertically polarized, so I am working  cros-

     sed  polarized  for  TV  stations  but  still  get good

     results, strangely better on UHF  then  VHF  freq.   In

     fact,  I  get  UHF  on  this set up better then my late

     model TV upstairs.



     I think that I am most disappointed in  the  fact  that

     the unit mounts on the side of the R7000.  I don't have

     the extra inch of bench space, so I had to  put  rubber

     feet  on  the unit and lay it on its side on top of the

     R7000.  It works fine and I do not see  any  difference

     with the case of each unit tied together or not.



     I made a "T" adapter and ran both the BAND-SCOPE and TV

     on  the  IF  output.   I  have not tried to add a third

     option to the IF output yet but it seems to be buffered

     from the main IF (wide band data 9600 baud).





                                - 6 -







     The unit comes with schematic, installation  info,  and

     cables to hook it up to a video/audio monitor.  Instal-

     lation is 5 minutes or less if you know where  to  find

     your screw driver the only tool required.



     Now to look for some Amateur TV and for Hidden TV  sta-

     tions.  There is more out there then featured in the TV

     Guide.









                                - 7 -







                      198 CHANNELS FOR YOUR

                         R7000 RECEIVER?



                      by Bob Parnass, AJ9S



     The ICOM R7000 appears to use a uPD446C, 16K static RAM

     chip,  for  storing  99 memory channels.  By looking at

     the pinout of this chip (IC8 on the Logic Unit)  in  my

     service  manual, it appears that ICOM is only using 1/2

     its memory capacity.  Address lead A10 (pin 19) is sol-

     dered to a ground pad.



     To double the number of memory channels in the R7000 to

     198,  it looks like one could "lift" pin 19 of IC8, and

     connect it to pin 24 (+Vcc) through a 10,000 ohm resis-

     tor.  A SPST switch could be used to ground pin 19.



     Another challenge would be finding a place on the R7000

     to  put  the  added  "Memory Bank" switch.  Perhaps one

     could use the Noise Blanker switch, and just leave  the

     NB on at all times.



     I don't have time to try this experiment, and would  be

     interested  in  hearing  results  from any enterprising

     hobbyist willing to try this.



     Long live tinkering!





     [PS: Jack Albert, WA9FVP, reports that  he  tried  the

     modification,  and  it  works!   Jack  doesn't have the

     remote control option in his R7000, so  he  elected  to

     use the front panel REMOTE switch as a bank switch.  He

     installed a 48,000 ohm resistor between IC8 pin 19  and

     ground,  and ran a wire from the REMOTE switch, through

     an 82,000 ohm resistor, to pin  19.   When  you  switch

     between  banks, you must also rotate the channel selec-

     tor knob, forcing to the microprocessor  to  read  from

     memory.]





                                - 8 -







        MODIFY YOUR ICOM R7000 TO SCAN AND SEARCH FASTER



                      by Bob Parnass, AJ9S



     This article describes how to  increase  the  scan  and

     search speeds of the ICOM R7000 receiver by 60% without

     noticeable performance degradation.



                           Background



     The  front  panel  SCAN  SPEED  control  on  the  R7000

     receiver  allows  the user to adjust the speed of scan-

     ning and searching operations, as well as the  rate  at

     which  the  priority  channel is sampled.  Rotating the

     control counterclockwise decreases the speed, and rota-

     ting it clockwise increases the speed.



     When the SCAN SPEED control on my R7000 (serial  number

     001400)  was  turned  fully  clockwise, the radio would

     scan a maximum of about 8  channels/second,  or  search

     about  8  increments/second.   As  the  following table

     shows, the stock R7000 can scan  about  as  fast  as  a

     Radio Shack PRO-30 or PRO-2003.



     TABLE 1.  Maximum Scan Rates of Selected Receivers



      _____________________________________________________

     |             Scanner               Maximum Scan Rate|

     |                                |  (channels/second)|

     |________________________________|___________________|

     | Kenwood TR-2600                |         1.2       |

     | Radio Shack PRO-30             |         8         |

     | Radio Shack PRO-2003           |         8         |

     | ICOM R7000 (stock)             |         8         |

     | ICOM R7000 (after modification)|        13         |

     | Regency M400                   |        13         |

     | Bearcat 20/20                  |        15         |

     | Bearcat 300                    |        15         |

     |________________________________|___________________|







                       R7000 Scan Circuits



     The scan rate of the R7000 is determined, in part, by a

     simple  clock  outside  the  microprocessor.  The front

     panel SCAN SPEED rheostat and resistor R18  (and  other

     components in the LOGIC UNIT) control the speed of this

     clock.  The clock output is connected to  what  appears

     to  be an input port on the microprocessor.  The upshot

     is that we can affect the scan rate  without  affecting





                                - 9 -







     the other chores performed by the microprocessor.



     The modification consists simply of soldering a 470,000

     ohm  resistor  across  the leads of resistor R18 on the

     LOGIC UNIT circuit board.



     How was the value of 470,000 ohms chosen?  Experimenta-

     tion  with  different  resistor  values showed that for

     values both above and below  470,000  ohms,  the  R7000

     scan  rate  decreases.   Not  having  the R7000 Service

     Manual, I assume this can be explained by the  firmware

     within the microprocessor associated with the scan rate

     input port.2



     Adding the 470,000 ohm resistor in parallel  with  R18,

     rather than just replacing R18, has a few advantages:



       1.  The modification is easily undone, returning  the

           radio to stock condition.



       2.  The LOGIC UNIT board does not have to be removed,

           as  would  be the case if R18 was unsoldered from

           the foil side.





                     Making the Modification



     Accessing this circuit  board  is  not  difficult,  and

     involves  the  same  steps  used  when  installing  the

     optional Remote Controller or Speech units.



     Use a towel to cover your work area to avoid scratching

     the  R7000 cabinet.  Unplug the R7000 from the AC line,

     and turn the radio  upside  down.   Remove  the  bottom

     cover by removing the 12 screws holding it in place.



     Remove the 4 screws holding what ICOM terms the "parti-

     tion  panel".  Pictures on pages 32 and 34 of the R7000

     Instruction Manual show  the  partition  panel.   After

     removing  this  panel,  the component side of the LOGIC

     UNIT circuit board is accessible.





__________



 2. Perhaps the firmware polls the scan rate input port

    infrequently.  Another possibility is that the scanning

    pulses interrupt the processor, and the interrupt

    firmware is limited in its ability to process frequent

    interrupts.





                                - 10 -







     Locate R18, a 270,000 ohm 1/8 watt resistor, near  con-

     nector J5.  You may wish to remove plug P5 from J5 tem-

     porarily if it gets in your way.   Carefully  solder  a

     470,000  ohm  resistor  in parallel with R18.  I used a

     1/4 watt resistor as it was the smallest on hand.



     Reassemble the  radio,  connect  it  to  AC  power  and

     antenna, and enjoy.



     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.







                        - 11 -







                      A LOW COST PANADAPTOR

                         FOR THE R-7000



                      by 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





__________



 3. Sherwood Communications, 1310 Industrial Highway,

    Southampton, PA 19866.  tel (215)357-9056.



 4. Spectra-Display is sold by GTI Electronics, RD 1 Box

    272, Lehighton, PA 18235.  tel (717)386-4032.







                                - 12 -







           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  genera-

           tor.



       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





                                - 13 -







     you have the BS-5 or BS-8 panadaptor module.





                     Changes for BS-5 Module



     Change the following capacitors:



       1.  C231 from 1000 pf to 68 pf.



       2.  C232 from .01 uf to 1000 pf.  (You  can  use  the

           capacitor which used to be C231.)



       3.  C234 from 100 pf to 22 pf.



       4.  C236 from 47 pf to 22 pf.



       5.  C237 from 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





                                - 14 -







     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





                                - 15 -







     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 proper point in the IF  stage  (before

     filtering  takes place), install a connector, then wire

     a DC blocking capacitor between the IF stage  and  con-

     nector.





===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===

Bob Parnass AJ9S,  AT&T Bell Laboratories  -  att!ihuxz!parnass - (312)979-5414