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
SOURCE: The QRZ Windows Ham Radio CDROM |
