2 Meter
Synthesized / Portable Receiver
By: Steve
Hageman
The 2 meter receiver shown
built in both desktop and hand-held versions
As seen on
the cover of QST
magazine,
February 1999.
Thanks to the
courtesy of the ARRL and QST you may now read the entire article on
line (To Online
Article)
Great News: As of
June 1, 2005 Lansdale Electronics has announced that they are making
the MC13135 and MC145170 replacement parts for Motorola. So this
project is alive again! Please contact Lansdale at www.lansdale.com
for price and availability.
The receiver is built from a Motorola single chip receiver IC, driven
by a Motorola single loop PLL (1st LO drive). The receiver operation
is controlled by a Microchip PIC16C73 uP (Source code available
here). The PIC controls
the LCD display, PLL and all the user interface including the rotary
encoder used for tuning. The LCD displays the tuned frequency and
signal strength in a bar graph format.
The receiver can tune the
entire 144-148 MHz band with tuning steps of 5, 10, 100 and 1000 kHz
steps (switch selectable). Scanning the entire band for signals can
also be done in less than 4 seconds. The scanning mode works like
most commercial scanners, that is it stops on any signal and only
continues the scan after 2 seconds of silence.
In RS232 mode the scanner can
be controlled by an RS232 link to any Windows 95 computer. The PC
program can completely control the receiver (example screen
shot) and adds memory
functions and also allows computer controlled scanning. The PC
program also has the capability of acting like a spectrum analyzer by
continually scanning the entire band and displaying the strength of
any signals found (example screen
shot) .
The receiver can be built in
the Handheld version or the Desktop version (minus the display,
computer control only) using the same PCB by simply deciding which
parts to include during assembly. Both versions can be built for
RS232 control. A preprogrammed PIC16C73 is available from
me, see below.
Specifications of the receiver
are:
- Double tuned input
filter
- 144-148 MHz tuning
range
- LCD display of frequency
and signal strength
- Rotary encoder for
tuning
- Selectable tuning step size
(5, 10, 100 kHz and 1 MHz)
- PLL synthesized
tuning
- Full microprocessor
controlled band scanning capability
- RS232 link for PC control
(PC program is a Visual Basic, 32 bit application that adds memory
tuning/scanning and spectrum display features).
- Dual conversion
superhetrodyne (10.7 MHz and 455 kHz) with Crystal and Ceramic IF
filtering
- Squelch function entirely
controlled by the 16C73 uP (no extra OPAMP's!)
- Volume control and audio
amplifier / speaker built in
- 8-10 Hours operation on
internal NiMh batteries (rechargeable in place)
2 Meter
Receiver Project FAQ's
Please e-mail with your questions and if
you have found parts anywhere. That's how this all works, you share
with me, I'll post it so everyone knows -- and I'll give you credit
too!
Documentation:
Thanks to the
generosity of the ARRL and QST, they now allow me to post the entire
article, schematics, etc. You may now download the Schematic and
parts list, along with the assembly information for the PCB here.
Download
2_rx_article.zip
Parts Issues:
As with the
Personal Network Analyzer
Project, I
will be keeping folks abreast of where to get parts for the project
here.
1) A PCB is available
for the project from FAR
Circuits.
Check with FAR directly please, as they supply the PCB's, not
me.
2) A preprogrammed
16C73 PIC is available from me for $30 US Dollars. Shipping
to the US of A (and Canada, Eh?) is FREE. Shipping to Europe is $5.00
(Via US Post Office Global Priority Mail). Shipping to South America
is $10 US Dollars (Via anyway I think it will get there!). Sorry
South America, the postal system down there just looses too much of
what I send.
3) DC Kits lists the
MC13135 on their web site. Try them at
www.dckits.com. You might also ask about the MC145170 and the
MPSH10 transistors.
4) Future (a big
Canadian distributor, eh?) is not on the WEB (i.e. no search engine),
but they do supply a lot of Motorola parts to the world. Give them a
call at 1-800-655-0006 and see if they have the Motorola
parts.
5)
A free
program called PartMiner is available from partminer.com. This nifty
program will search a dozen sites for parts that you may need. Try
it, it's how I keep up to date on what is available
where. -
Sorry they went belly up!
6) Newark has the
MC13135P and MC145170D1 parts as of Mid January 1999. They have a $5
service charge for orders under $25. You can buy many of the other
parts needed for the receiver from Newark also, such as Capacitors,
Pac-Tec Case, Transistors, LM386, Speaker, 10 MHz crystal, Display
etc. So if you shop carefully you should be able to 'Bundle' enough
business with Newark to get over the minimum with no extra
charges.
7) Well, it turns out
that Digi-Key is no longer supplying the Toko TKS2715CT-ND SMT
inductors that were used in the input filter (L1 and L2). Not to
worry, the solution is to buy the exact same inductor (4 1/2 turn
MC152 type) without the tuning slug, the part number for this core is
TKS2709CT-ND. You will need two of these, one for L1 and one for L2.
Then when you are buying the other inductor (L3) buy three of them
(TKS2714CT-ND). When you get the inductors, take the brass tuning
slugs from two of the TKS2714CT's and place the slugs in the
TKS2709CT coils that do not have slugs. Viola... You just made (in a
round about way) some TKS2715CT inductors exactly as specified in the
article.
8) I slipped a digit!
All Mouser capacitors listed that are 20 pF and under should have the
prefix 141-100N2-XXXX, not 141-100N5-XXXX as printed in the article (cripes, it's
February and already I've made my one mistake for the year!).
Additionally, C3 was listed as 5 pF, this part has been discontinued
by Mouser. An equivalent replacement is the 141-100N2-4R7D (4.7 pF,
close enough for this application). Thanks Doug for pointing this out
to me.
9) Bill found some
reasonable sources for the 10.245 MHz, 2nd LO crystals (thanks for
the help Bill!)
Crystek
Crystals, 12730 Commonwealth Drive, Unit 6&7, Ft. Myers, FL
33913, 1-800-237-3061
They stock 10.245MHz
xtals in HC49 holders for 32pFd load, 50 PPM at, 25deg. C. Price is
$7.50 ea. with $25 min for out of town. If you want a custom ground
crystal they are @12-$13 each.
JAN Crystals, 2341
Crystal Drive, PO Box 06017, Ft. Myers, FL 33906-6017,
1-800-526-9825
They do not stock
10.245MHz, but are ground to order. Price is $11.00ea. plus $3.00
S&H
Hardware FAQ's:
Here are the FAQ's as
they relate to the hardware portion of the project.
1) Very detail
oriented persons may notice that my article's parts list calls out
for a specific values of inductance for L1, L2 and L3. Then they
might notice that the TOKO description of these parts is always
higher. What Gives? Well TOKO lists their inductance for the coil
with no brass tuning slug, but they are sold with a slug. I listed
the actual value of the inductance that the circuit was designed for
(and what the specified coils are). The part numbers listed in the
article are correct, the TOKO description is incorrect! They should
really get a Agilent Technologies
(Formerly Hewlett-Packard) LCR meter so they would know what their actual
inductance values are!
2) Unfortunately at
the last minute QST changed the schematic and swapped the labels for
L3(VCO Coil) and L4 (Quadrature coil). The QST schematic and parts
list agree, but not the PCB that I laid out for FAR Circuits. On the
FAR PCB, please note that L3 is the Quadrature coil (a large shielded
package). L4 on the FAR PCB is the VCO tuning coil (a small SMT
package). This should not pose much of a problem as there is no way
that you can confuse the parts, the Quadrature coil is 5 times the
size of the VCO oscillator coil.
3) The MC145170 is
available in many varieties. First are the package types: P is a
leaded plastic part, D is a surface mount version (Don't buy the DT
part, it's really small). The surface mount versions can be used in
the FAR circuit board with the use of an Aries SMT to DIP adaptor
socket that is available from Mouser (Aries # 535-16-350000-10).
Motorola also makes a -1 (dash 1) version of this part. The dash 1 is
a slightly higher frequency version of the part, an associate of mine
tried this part on the FAR PCB and reported no problems with it.
Motorola also advises me that dash 1 is backwards compatible with the
non dash 1 parts and should be a drop in replacement. The exact part
numbers that should work are: MC145170P, MC145170D, MC145170P1 and
MC145170D1.
4) The MC13135 is
also available in many varieties. First are the package types: P is a
leaded plastic part, DW is a surface mount version. Unfortunately
Aries does not make an adaptor for the DW package. If you find only
DW parts the only option today is to use wire wrap wire to extend the
leads to the leaded pattern on the PCB (keep the wires as short as
possible). FLASH:
The MC13135 just showed up on Motorola's discontinuance list, this
means that by the end of 1999 the leaded plastic parts will no longer
be available. Thank's loads Motorola :( If anyone knows of an adapter
socket please let me know so I can post it here for everyone to see!
Thank you.....
5) Where do the
jumpers on the FAR PCB go? Click here to download a nice Acrobat
file that shows the locations.
6) The battery in the
portable unit could probably use more clarification as to charging.
The battery specified is a 550 milliamp hour (i.e. the one 'C' rate
is 550 mA) Nickel Metal Hydride type (in AAA format cells). Each cell
has a nominal voltage of 1.2 volts, so 5 cells produce 6 volts.
During charge, the battery will rise to about 1.4 volts per cell (or
8.4 volts) when fully charged. The 36 ohm / 12 volt charge I
specified in the article produces a full charge in around 4 to 5
hours. The wall wart I used dips to about 11 volts at 100 mA so the
setup I used trickle charged the batteries at about 140 mA when the
charge starts, then drops to about 72 mA at the end of charge. These
cells may be charged with up to 110 mA continuously without damage
(C/5 rate). The setup I used 'taper' charges the batteries safely
limiting the fully charged current to around 72 mA. At any rate the
batteries should never be charged so fast that they get hot to the
touch as heat will greatly reduce their life. If you are using a 12
volt wall wart and want a 12-14 hour charge instead, then limit the
charging current to 55 mA (C/10) average. Probably a 100 to 150 ohm,
1/2 watt resistor will suffice for 12-14 hour charging .
7) It was brought to
my attention that the speaker symbol was dropped from the QST
published schematic. The parts list lists LS1 as a part and a really
nifty Panasonic speaker, but no LS1 on the schematic. The speaker
connects to the output (labeled "Audio Output") of the LM386
amplifier. You can also use any small 8 ohm speaker for audio that
you may have in your *junk box* if you like.
8) In the articles
conclusion I wrote that it is possible to add transmit operation by
using a cell phone output stage. This is possible as mentioned, but I
have no plans right now to implement this feature. If you are
interested in doing this yourself, you will need to reprogram the PIC
to change to the PLL to the transmit frequency, add a T/R switch to
the antenna, squelch the receiver, rework the PLL some, etc. This is
not difficult, but it will require some knowledge of PIC's, PLL's,
Impedance matching, etc. If you want more information on cell phone
output amplifiers, check the following manufacturers: Anadigics,
Connexant, Triquint, Motorola, ITT or go to www.rfglobalnet.com to find an excellent industry
resource for all kinds of wireless parts.
9) Bill reports: C32
(the PLL 10 MHz crystal oscillator frequency adjustment), Digi-Key
part number SG10016-ND, is a bottom adjust trimmer. I drilled a hole
in the PC board to gain access to the adjusting slot. Another choice
would be the SG10015-ND, same value but top adjust. Center for the
mounting holes is 1.27mm different but tabs may bend a bit to
accommodate the difference. Thanks for the information Bill.
10) Bill asked about
noise pickup, here is what I know from my prototypes:
A) I
found that my display would cause some noise when placed really close
to the receiver board. This noise was strongest around 145 MHz, and
was not really apparent on all channels (kinda like you would expect
from digital noise). I mounted the LCD in the portable case with an
aluminum strap. When I grounded the strap to the receiver board
topside ground plane with a short wire, the problem went away. Copper
tape applied to the back of the display and grounded in the same
manner would probably work as well, just be sure not to short out the
display!
B) The other noise
problem I discovered was pickup with the RS232 lines. This sounds
more like a 'thump-thump' sound (i.e. you can hear the RS232
'polling' from the computer). This noise was audible on all channels,
like you would expect from low frequency audio coupling. This turned
out to be audio pickup. When I re-routed the audio volume control
away from the RS232 cable this problem was eliminated. Another
possibility is to shield the audio leads to the volume
control.
Software FAQ's:
Here are the FAQ's as
they relate to the Software (Firmware or PC Program) portion of the
project.
1) The associated
software (yes, and source code) is available free as HAG2MRX.ZIP at
the ARRL
Files Site.
The program runs on Windows 95, 98 and NT and requires a standard
RS232 port driven by a 16550 UART for proper operation (all name
brand computers of 486DX and better should have this type of UART).
The PIC Source code is available here also. The download from the ARRL
includes the executable program, the Visual Basic 5.0 Source, The PIC
source and the PIC HEX programming file (Useful if you can program a
16C73 from a HEX file).
2) If you unzipped
the package with a DOS version of PKUNZIP (like version 2.04g), you
may get the message that the install program can't find the file
"two_meter.ini". This is because the DOS PKUNZIP truncated the file
name on disk 3 to "two_mete.in_" (only 8.3 characters allowed). To
fix this simply, rename the file on disk 3 to "two_meter.in_". Notice
the trailing 'r', and install the program again. You must use the -D
option when unzipping to recreate the directory structure.
3) Sometimes, it is
reported, the install may take two tries to get the program installed
(especially if the program updated any system files and rebooted the
PC). Keep at it!
4) Overwriting of
outdated files during install the should be safe as these files are
all genuine, Microsoft files. If you don't feel safe about this, note
the name of the file name(s) the install program want's to update,
respond NO to the prompt(s). Then find these file(s), copy them to a
floppy and reinstall the program. This way if anything goes wrong,
you can recover from the problem.
5) You can uninstall
the program by going to -> Control Panel -> Add/Remove
programs.
6) Wouldn't you know
it - I found two minor errors in the PC control program nanoseconds
after I sent it to the ARRL :( #1 If you start a memory scan with no
memory channels loaded the PC program will hang (to recover - do a
CTL-ALT-DEL and end the task). #2 The lower left hand corner of the
program window was supposed to show what COM port the receiver was
found on. In version 1.0.0 it always says COM 1, even if the hardware
was actually found on some other port. If you want a 90 k update to
version 1.0.1 that fixes both these problems, then CLICK
HERE TO DOWNLOAD. This is an update to the PC control program only,
the PIC Firmware is OK. To use the update you still need to download
and install the files from the ARRL (see direct link above). Then
replace the TwoMeter.exe downloaded above with the one that the ARRL
download installed.
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Updated -
1Jun05