RCS-5A (& RCS-5B) Chirp Sounder Receivers

Brooke Clarke 2000 - 2018

BR Communications RCS-5A Chirp Sounder Receiver
Chirp Sounder Basics - Purpose - Operation - Background
Antennas - Wide Band Folded Dipole - Loop - Wide Band Vertical - NVIS - TCI-545
Listening with RCS-5A Chirpsounder Receiver -Chirpcom MessageStation Log as seperate web page-
HF Radio & Motorola 56002 DSP Method seperate web page - Station Log in Comma, Seperated, Format
Doppler HF Radar - Using a PC audio card as a spectrogram to see the doppler shift
Remote Programming of the RCS-5A/B -
Listening to Chrip Transmissions with a Shortwave Radio
RSS-5 Spectrum Monitor
RCS-5B Reveiver Chirp Sounder "B" version coming soon

Chirp Sounder Basics

July 2018 Update

There are now many Digital Radio Modes that allow testing antennas-propagation, see for example WSPR. using a 200 mW signal and a message frame time just under 2 minutes a 30 dB improvement in s/n can be obtained.

Oct 2006 Update

PA1ARE - Chirp Software to step the frequency of  Kenwood radios to get ionogram and Chirp overview.

State of Chirp Receiving as of Jan 2004

In the beginning the only way for a hobbyist to receive chirps was by using their ears and a short wave receiver tuned to a fixed frequency or manually tuning the receiver or use a commercial chirp receiver like the RCS-5().

Next came the Motorola 56000 DSP Evaluation kit based chirp sounder receiving method.  With this method the DSP time stamps, using a GPS locked 1 PPS, each sounder as it passes through a fixed frequency. This is a great method of finding sounders and of determining where they are by triangulation.

Next came the PC sound card version of the DSP method called Chirp View. by Andrew Senior.  In this method the 1 PPS from a GPS goes into one of the audio channels of the sound card and the other channel gets the chirp from a fixed tuned receiver.  Generates a log that's in the same format as the 56000 DSP method.

Currently (Jan 2004) there is work on a new method based on the Software Defined Radio which will use a swept Local Oscillator and produce an ionogram, just like the RCS-5.  There is a possibility that this type of chirp receiver can also decode the chirpcom message that contains up to 40 characters repeated 63 times in a 2 to 30 MHz sweep.
20 Oct 2004 - G4ZFQ Combining ChirpView & HRD to get ionogram.

2017 Aug 4 - gcs GNU Chirp Sounder - uses a pair of loop antennas and a pair of SDR radios.

Mailing List

Chirps   - Mostly log files from either the 56000 based or PC based single frequency methods and info on new sounders.  Includes both BR and other sounders. Some infoo n the SDR based method.
To subscribe send a request to   mailman-owner<at>aintel.bi.ehu.es

Yahoo Group

Chirpsounders    Mostly propagation info and BR sounder status.

Types of Chirp Transmitters

Antenna Pattern

Note that although older transmitters had their clocks manually set (to better than 1/4 second) most have now been retrofitted with GPS timing receivers so that the start time is exactly on the UTC second.

At the receiving station (at a known location) you can determine the apparent start time of the received signal.  The apparent start time will be later than the actual start time as a function of the distance between your location and the transmitter location.  Since these measurements are absolute it's good to have a local clock that's good to a small fraction of the earth's circumference expressed in time.

12,756 km dia => 40, 074 km circumference => 40.074E6 meters => 133 ms
Allowing for the height of the ionosphere the time is 138.5 ms.
So you can see it would be good to know the time to 0.1 ms or better.

Unfortunately most GPS receivers have been optimized for position determination and may have gross errors in their 1 PPS outputs.  Motorola specialized in GPS timing receivers (used in many cell phone sites for timing) and they are very good.  The long obsolete 6 and 8 channel receivers are reasonably priced now.


To determine what the actual path conditions are between one of the chirp sounder transmitters and the receiver. This is used to choose the best frequency for that path.  There are about 130 chirp sounder transmitters located all over the word.  In addition a 40 character message can be sent very reliably during a single sweep.  This can be used for order wire type information or by special forces sending a message to a military installation that is near a sounder transmitter.   BR Communications now part of TCI in Fremont (just moved from Sunnyvale), CA has been making chirpsounders for many years.  Some have been adapted as military units with the nomenclature: AN/TRQ-35(V) consists of the T-1373 transmitter, R-2081 receiver, and  R2093 spectrum monitor.  The BR 4280 is a man portable chirpcom transceiver and chirpsounder receiver.  See the September '93 issue of Popular Communications article "Monitoring the World's ionosounds" by Andrew W. Clegg for an introductory article.

When BR Communications (before they were bought by TCI) first worked on chirp equipment they used the HP 5110 synthesizer.  This does NOT have any phase lock loops, it works with arithmitic (add, multiply, subtract) and is phase coherent through frequency changes that happen a in a few microseconds.  The remote programming is with a wire for each button on the front panel.  See photo of my unit (two upper instruments).  I first learned about these signals from the September '93 issue of Popular Communications article "Monitoring the World's ionosounds" by Andrew W. Clegg.

RCS-5A/B Data sheet at BR communications - Fixed 6 Jan 2001
FM 24-18 - Appendix B Ionospheric Sounder AN/TRQ-35(V) -
FM 24-24 - AN/TRQ 35(V) Tactical Frequency Sounding System -
RCS-4B (R-2081/TRQ-35(V)) NSN 5820-01-005-4247  - TM 11-5820-917-13 (368 pg pdf file REQUIRES 128 bit Netscape, no others)

5943629  Method and apparatus for real-time ionospheric mapping and dynamic forecasting - A TCI patent that contains some info on the BR chirpsounder and the Maritime ARCS (Automatic Radio Calling System).
5230076 Ionospheric sounding, Wilkinson; Robert G. (Portsmouth, GB2), 455/62 ; 375/133; 375/150; 455/226.1; 455/226.2; 455/226.3; 455/63.1; 455/67.13 - uses a much more complex modulation than the simple sweep.  Has a long list of referenced patents
6822574 Ionosonde, Nakamura; Yoshikatsu (Koganei, JP), Nov 23, 2004, 340/601 ; 342/460; 702/2 - X, Y and Z components are measured
 ALE-systems, tone calls,  ionosondes & chirpsounders - example sound files IONOSONDE (STANDARD) is the BR chirp
FAS - AN/TRQ-35 High Frequency Radio Chirpsounder -
Photo of: Front, Back,


Suppose that a transmitter sweeps from 2 MHz to 30 MHz at a rate of 100 kHz/second. (or optionally 2 to 16 MHz at 50 kHz/s)
The sweep will take 280 seconds or 4 minutes and 40 seconds.
Since all the chirp sounders transmit on the same frequencies they can not be specified by their transmit frequency.
The start time can be unique for each station.  There are 12 five minute frames in each hour. (i.e. 00, 05, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 minutes past the hour)  Most sounder transmitters operate either "evey 5" or on 4 frames seperated by 15 minutes.  Some only transmitt for testing or on demand.
There are many non BR sounders that are on periods other than 300 or 900 seconds.
The transmitter carrier and receiver local oscillator (at a remote location) both start sweeping at the exact same time (GPS based timing can  do this).
For a fixed length path between the transmitter and receiver the receiver will output a constant frequency audio tone proportional to the distance from transmitter to receiver which is also proportional to the time delay between the transmitter and receiver.
Example 1:
a 3,000 km path length
will cause a  time delay of  (path length km) / (speed of light)  = 3,000 km / 300,000 km/sec = 0.01 sec = 10 mS
the audio tone frequency that  will be caused by the difference between the transmitter carrier and the receiver LO is: 0.01 S * 100 kHz/S = 1,000 Hz
This tone will be the same audio frequency for all received RF frequencies if the path length is constant.
That is because both the transmitter and receiver oscillators are sweeping at the same rate.
Now suppose that there are two different paths from transmitter to receiver, one a surface wave and another that is a single hop to one of the ionosphere layers.  The receiver will hear two simultaneous audio tones that will be fixed in frequency if both paths are of constant length.  In the real world the path(s) are changing constantly as a function of frequency then the result of a chirp sounder sweep is a plot of the layers -vs.- frequency and also a plot of received signal strength-vs.- the same frequency x-axis.

The chirp sounder receiver uses an audio spectrum analyzer to look at what frequencies are present.  Each frequency represents a path delay and a different type of propagation.

A Scale drawing showing propagation.  This gives some idea of the minimum and maximum single hop distances.

Background on BR Chirp Sounders

I was with BR Communications since 1968 and before that at Stanford  University Radioscience Laboratory. Bob Fenwick and George Barry developed  chirpsounding at Stanford and Barry Research (later BR Communications) took over  manufacturing Chirpsounders for practical use by HF communicators. In 1960 the only  oblique HF ionospheric sounder was a pulse sounder made by Granger Associates.   The signal to noise ratio of the pulse ionograms was terrible. This is why  Barry and Fenwick decided to develop Chirpsounding. The average chirp power  received from a 100 W chirp transmitter was much greater than the pulse power from a 100 kW pulse transmitter, and chirp is coherent.

 The basic BR sweep was 100 kHz/second. We used the first HP synthesizers to get sweeps linear enough to make Chirpsounding practical. The sweep linearity  was coherent over 1 MHz thus giving 1 microsecond time delay resolution.

 The receiver used the same synthesizer as a local oscillator (offset by the  IF frequency). Thus we could get coherent analysis over 1 MHz, or down to 1 microsecond resolution.

 The sweeping receiver bandwidth was chosen to be 500 Hz. At 100 kHz/sec this  gives a 5 mS delay window. Early spectrum analyzers analyzed this bandwidth to  2.5 Hz (200 lines) resolution. This is equivalent to 25 microsecond cells.   The spectrum analyzers were digital speedup design. We had to develop a spectrum  analyzer ourselves as there was nothing available for this use in the late 1960s.

 Today the BR RCS-7 Chirpsounder receiver uses DSP at the second IF frequency.  We use a standard IF of 42 MHz and a 1 kHz wide mechanical filter. This goes  directly into a DSP where we use the center 500 Hz bandwidth for analysis.  The RCS-7 is calibrated in amplitude. Besides a color display the data cells are available as a file. [8-bit amplitude and nearly 1 microsecond time resolution]

 BR/TCI now make HR receivers for spectrum monitoring purposes that DSP very large chunks of the HF spectrum at once. But no Chirpsounder yet.

Clint Gilliland


Also see the Antenna Theory section of my Electronics page, my Antennas and HF Propagation web pages.

In Feb. 2000 I installed the B&W (BWD 1.8 - 30).  The high end is up about 85' and the low end about 40' and at least 25 feet from the trees.
Listening to WWV I can see a 10 dB increase in signal strength.  In some cases this makes the difference between hearing a station and not hearing that station!
Using this antenna with the NRD-545 and going through the Passport to World Radio book, where I mark stations that I can hear, I marked 2 or 3 times as many stations as I had using the McKay-Dymec DA100 active whip. DA-100 Board Layout & Circuit Diagram.

With the RCS-5A the B&W antenna is a great improvement!

Wide Band Folded Dipole

I was using an old McKay-Dymec DA100 active whip.  I was hearing what BR/TCI hears with their massive 2 - 30 MHz log periodic.
The B&W Broadband Folded Dipole Antennas (ASW-90) U.S. Patent 4423423  are a better choice.  I saw one today at the Santa Rosa National Guard on highway 101.  This antenna is designed to have continuous coverage for both transmit and receive, although the transmit performance is poor on the lower frequencies.
T2FD - is another name for the B&W 2-30 antenna.
T2FD Antenna - Terminated, Tilted, Folded Dipole by David Gordon KB4LCI - T2FD dimensions - says good for a 6 to 1 bandwidth
Modeling the T2FD - by L. B. Cebik, W4RNL - in an amateur TRANSMITTING application
How To Build the TTFD-2 - Diagram - at Radio Habana Cuba
Codan Pty Ltd - Code 411 Terminated Folded Dipole -
KIWA - Shortwave PreAmp - provision for use with T2FD
June 1949 issue of QST, May 1984 73 Magazine, 1989 WRTH,  "Practical Antenna Handbook, 2nd Ed.", by Joseph J. Carr
Nordic Shortwave Center - Comments under "Special" -  T2FD - The Forgotten Antenna - T2FD design -T2FD vs Other antennas - excellent receiving antenna -
Spi-Ro Manufacturing - all band - amateur 70' overall (uses loading coils) or 135' dipole no coils
Loos & Co - Tension Gauges -
Antenna Products Corp HT20-B - this was mentioned on a newsgroup
T2FD -- The Forgotten Antenna
Bushcom - BBA-100 -  looks interesting, but pricey
Array Solutions USA disty for the BBA-100 with data on it.


K9AY Loop - QST 9/97 pg 43-46 & QST 5/98 pg. 73
A Compact Directional Receiving Antenna by K9AY -
Al - K4GLU - comments and improvements -
TopBand: K9AY 's Loop & ICE - Would the ICE Beverage Matching Assy, Model 181A (DC Passive) work with the circuit used by K9AY for his switchable EWE array?
Industrial Communication Engineers Inc. (ICE) - model 180 matching transformer (web page not complete)- Nordic Review -
Wellbrook Communications - makes the K9AY loop - BDXC Review of Wellbrook Communications K9AY Antenna System - also has conventional ALA 1530 loop.  These may provide a way to get DF bearings on chirp transmissions.
Nordic Comments QST 9/95 -
ARRL - Receiving Wire Antennas -

Wide Band Vertical

Sommer Antennas
model T-25 - (1.5) 3.5 - 60 MHz - Principles of operation - $260
model T-50 - 1.0 - >30 MHz - Principles of operation -  $540


Near Vertical Incident Scattering Antenna -
TCI/BR - AS-2259 -
WB5UDE - NVIS: Near Vertical Incidence Skywave -
AN/TRC-510(V) - with photo of AS-2259/GR NVIS antenna & fast tune ant. tuner
Fort Gordon - Single Channel Radio Operator/Maintainer - I02-LP2: Construct NVIS Antenna AS-2259/GR. (2 Hrs) - FM24-1  Appendix M Near-Vertical ncidence Sky-Wave Propagation Concept -
Book  "Near Vertical Incidence Skywave Communications--Theory, Techniques and Validation" by David M. Fiedler and Edward J. Farmer.  It's published by Worldradio books, Bos 189490 Sacramento, CA 95818
Tactical Link Systems - Mobile NVIS - details on a mobile NVIS antenna system
EYRING CORPORATION - ELPA Model 302 A -5.3 Lbs,  2 to 65 MHz.

TCI - 545

Both NVIS and low angle (switchable) 40' mast - very interesting - is 4 seperate wires wound around the guys.
This antenna can be fed for either vertical or HORIZONTAL polarization!  When in horizontal mode it is more like a wide band dipole.
My Sketch of a possible 545 antenna using logrithmic spacing along guy, 16 wires per side, k=1.1 and a=16"
 TCI_545.dwf you need WHIP! or Volo to view this drawing.

Antenna Transformers

SWL Longwire Impedance Matching by John Doty -
Boston Area DXers (BADX) - Low Noise Antenna Connection -
ICE Matching Transformer - ICE -


dressler - various models 40 kHz - 2,000 MHz


Listening with RCS-5A Chirpsounder Receiver

The 4 Letter ID is my input for the RCS-5A screen label.  The last twelve columns are minutes past the hour.  To get the actual start time add the minutes past the hour to the start time (offset).  For example CHEL starts at 1 min 12.1880 seconds past the hour. RICO starts at 10 min 59.8185 seconds past the hour.  All sweeps start at 2 MHz and take 280 seconds.  Here is a screen shot of the Scan.vi LabVIEW program.  I have scrolled up the output so that 4:02 and 4:04 are not all seen.

Chirp is not a magic mode and for some paths you can only hear anything at certain times of the day/night.  The station in Reykjavik can not be heard around 00:00 UTC but can be heard around 17:00 UTC.

I have found that if you set the RCS-5 in manual mode, and put it into autosync with a new start time ending with .0000 seconds.  After a day or so you may find it in normal sweep mode and the start time will not have changed.  This indicates that autosync was fooled by some signal.

Remote Programming of the RCS-5A/B

 There are two serial ports in the J4 connector.  RS-422 or RS-423 is supported so that a number of receivers can be controlled from a single computer and to increase the distance between the computer and the receivers.  These ports can be wired to communicate using RS-232.Drawing for the J4 cable with both Port 1 and Port 2)  RCS-RS232.dwf - (Get Whip!, Volo, etc ).  This cable has been used for Port 1 and 2, it works.  I made up the printer cable but it did not work with my HP LaserJet 4 printer.  The manual mentiones "ESC L" command sequence for double density (72 x 120 DPI) used by Epson and Okidata printers.  I think this is a format that predates Postscript and HP PCL.

Note that the check sum on transmitted data does NOT include the single command letter!

Port 1

 Port 1 is a bi-directional port for all commands and responses except the raw data which is sent over the one way port 2.  To use the port 1 commands and data outputs: Now it will process commands on port 1.  The "Read Chirp Data" command returns a graphic data set that matches the CRT on the RCS-5A, that is to say it is 1 bit per pixel data.  The AGC, Signal Strength and Path Quality data is also returned from this command.

Port 2

Port 2 is constantly outputting data and the "mode" switch has no effect on this. There are 3 different data blocks:

Path Programmer

I think of this as "time slot" programmer.  There are 12 lines (one for each 5 minute time slot) and you can assign one of the 4 paths to a time slot or if zero is set then the time slot is not used.  Remember that the paths are defined by the start time ( zero to 4:59 minutes) and upper frequency limit (either 16 or 30 MHz).  When the mode switch is in ANY position other than "monitor" the RCS-5 will be looking for the start time for the current time slot and will start a sweep.  When the computer program finishes, if there are valid paths and slot assignments the receiver will continue to sweep.

Path Overlap

For example suppose that paths 1,2 and 3 are set for start times of 0:32, 0:35 and 0:45 and "auto-sync" is enabled for all these because we are just getting started.  Also suppose that the time slots for these are:
slot  path  (minutes past hour) Start time  +4:40 =  end time  +  pause = next start time
0    1            0                            0:32                    5:12            0:23
1    2            5                            5:35                   10:15           0:30
2    3            10                         10:45                   15:25           0:07
3    1            15
4    2            20
5    3            25
6    1            30
7    2            35
8    3            40
9    1            45
10  2            50
11  3            55

Now the receiver will try to sync on the first path starting at 32 seconds past the hour.  That sweep will end 4:40 (all sweeps take 4 min and 40 seconds) later at 5:12 past the hour.  There will be a 23 second pause while the receiver waits until 5:35 for the second path to start.  The second path will end at 10:15 past the hour and will pause for 30 seconds waiting for the third path to start at 10:45 past the hour.  It will finish at 15:25 past the hour.  The first path will start at 15:32 so there will be a 7 second pause.  In this example there is not any problem because there always is a pause between paths.

If the third path in the above example is now changed to start at 0:55 there will be a problem because the third path will now start at 10:55 and end at 15:35 or 2 seconds AFTER the first path was supposed to start. If path 3 is in auto-sync mode then path 1 will NOT start, path 3 will finish and there will be a pause of about 5 minutes then path 2 will start.  So the sequence will be path 2, path 3, long pause, path 2, etc.

It is important how the start times and time slots are assigned.  When searching the next start time can be 1 or two seconds later than the prior path thus not wasting time pausing, making the search more time efficient.

Sync Range

The RCS-5A will sync at least over a 1 second range but not 2 seconds.  This means that there can not be two separate transmitting stations with start times 1 second apart and have the same time slot assignment.  If you look at a Start-Time List you will see that there must be at least a 2 second separation between start times.  In the log above there are a couple of cases where I am showing start times less then 2 seconds apart and the same time slot.  These must be some kind of error in the scan program and will be resolved.

LabVIEW Code

For those who would like to use a computer to capture data from an RCS-5 I am posting some 32 bit Windows LabVIEW 5.1 software.  This is NOT a finished product, but does work.  I use this software while manually setting the receiver for the stations that I want to capture.  The output is a color intensity graph, even though the screen on the RCS-5A is black and white.

The P2-Raw_data.vi needs to be loaded and running in the background.  It can be minimized down to the task bar.  It listens to the RCS-5 port 2 data stream that is coming from the receiver in all positions of the "Mode" control except for "monitor" during each sweep.  It is separating the data stream into three different packet types (2, 86 and 107 bytes long) and sending them to a global variable that can be read by other programs.  This VI calls Read_N.vi that gets the data from the LabVIEW serial port buffer.  It also calls P2_Status.vi that decodes the Port 2 status byte.

Int_Gph4.vi is the program that I have open and manually start about 1 second after a sweep starts that has already been synchronized, or if the receiver is in auto-sync mode and I hear it sync I start the program.  In a  future improved version this VI could be called by the computer for each receiver sweep and the result automatically saved to disk.  I have not yet decided on what data to save to disk and in what format.  This VI calls Chirp_Gph.vi  that breaks apart the 107 byte packet into data ready to graph.  When the sweep stops I currently just <alt><print screen> and paste into Windows Paint then save as a jpeg image.  There is a stock vi that will convert a graph into a jpeg file, but I have not been able to get it to work properly.  If anyone gets it working, let me know.

Chirpcom Message

A TCS-5 transmitter (or the TCS-4 with the BR 3050 adapter) can send a 40 character message.  The message is repeated 63 times during the 280 second long sweep.
The modulation is similar to 250 Hz FSK at 55 bits per second.  If a chirpcom message is present then there will be a ghost image above the actual path image.  The longer the message the more the ghosting.

The first 2 characters of the message are reserved for the ID of the transmitting station.

There is also provision for either a general alarm or a selective call alarm where the 2 character receiver ID must match the Selcal characters. Inchon is the only station that I know of that is sending a general alarm,  I have not tried to search for a selective alarm.

See patent 4244053 below.  The Air Force liked it for long range bomber coms.

Listening to Chrip Transmissions with a Shortwave Radio

By tuning to a fixed frequency in the CW mode (BFO turned on) and listening you will hear a "chirp" as the transmitter sweeps through your tuned frequency. Note the clock time that the "chirp" occurs.  The clock needs to be accurate to better than one second.  Since all start frequencies are 2 MHz the start time can be computed if the sweep rate is known.  To check the sweep rate tune up in frequency and note the chirp time, tune up again and note the time again.  You will soon know if it is a 100 kHz per second or 50 kHz per second sweep.

Using this method I found the BR Utah station in the first line of the logging table above.

Example 2:
tuned to 9.000 MHz
hear chirp at 07:09 (mm:ss) local time
know the sweep rate is 50 kHz/sec. = 20 sec / MHz
delta frequency since start is 9 MHz - 2 MHz = 7 MHz
time since start was 7E6 MHz / 50E3 kHz/sec = 140 seconds prior to hearing the chirp at 9 MHz
7:09 = 6:69 = 5:129 = 4:189
4:189 - 140 = 4:49

G3PLX Chirp Project - http://www.qsl.net/zl1bpu/chirp/chirps.html -

Note that "chrip time" in the G3PLX system is at zero frequency.  This makes the math much easier, but you need to add 20 seconds for BR start times.
Power Supply Problem  - was fixed by - as far as I can remember - an office of Reasonat Power Technology in Milpitas, California.  But their web page only shows South Dakota.  The interactions between the different switching mode supplies makes troubleshooting very difficult.

RSS-5 Spectrum Monitor

This is a spectrum monitor based on the RCS-5 Receiver Chirp Sounder.  It covers 2 to 30 MHz in 3 kHz cells with a sweep taking about 12 seconds.  Unlike a spectrum analyzer the RSS-5 stores channel use history for 30 minutes.  You can have it just scan channels (frequiencies) that you are interested in.  The purpose is to see if a channel is being used.  The RCS-5 can show at the top of the CRT the receiver AGC, signal strength or signal quality.  I think that these are the basis of the RSS-5.  If you have a chirp sounder receiver that will tell you what frequencies will propagate and a RSS-5 to tell you what channels are not being used, then you can make a selection of the frequency that has the best propagation and the lowest usage giving you the highest probablity of making contact.
Photo1 , Photo 2, Screen Shot

RCS-5B Receiver Chirp Sounder


BR Communications
        RCS-5B Chirp ReceiverTop Inside


BR Communications
        RCS-5B Chirp ReceiverRear Panel


The UPS store that packaged the unit did a very poor job and the "used only a couple of hours" receiver arrived DOA.  When the power switch is turned on nothing happens.  The line voltage (124 VAC RMS) is being switched into the Resonant Power Technology A18 power supply, but the supply appears dead.  The F1 (top) and F2 (bottom) fuses are both OK.  There are no fuses on the rear panel.
RCS-5B Power
                Supply Top
F1  is just below the toroid and
connector at the right center.
RCS-5B Power Supply Bottom
F2 is in upper right corner.

TCI/BR RCS-5B Chirp Receiver Power Supply Troubleshooting

                RCS-5B Chirp Receiver Power Supply Troubleshooting
The A18 power supply can be removed from the receiver (4 screws on side panel) and then opened up (4 screws on PS) and then folded open to allow troubleshooting.  The top has the input and output connectors and all of the HV related circuitry.  There is a 2 wire (wh/red, grn/brn) cable that feeds +300 and 300R to the +24 Volt supply in the bottom.  The key test points are 300, 300R, U17-7 in the top part.  The problem seems to be in the area of U17 (CS2842A) and Q42 (BUZ50B).  The breaker trip signal is in the large J2 mil connector and the line inputs are in the smaller J1 connector so it may be a troubleshooting technique to disconnect J2 for troubleshooting.  I'm trying to confirm that before trying it.

The +24 V supply feeds the +5 and +12 VDC supplies all of which are in the bottom part.
TCI/BR RCS-5B Power Supply Top HV PCB
                RCS-5B Power Supply Top HV PCB
The top PCB removed from it's metal housing to get access to the back side.
There is a switch on the rear panel for 115 or 230 VAC.  The supply rectifies the input AC into HV DC that then drives everything.  There are multiple interconnected switch mode power supplies that probably use a resonant mode of operation (based on the company name).  Resonant Power Technology used to be in Santa Clara, California, but their web site and phone seem to have been disconnected.  If you know of someone who has the very specialized knowledge to repair this power supply please let me know.

9 Jan 2010 - When U17 is replaced and the front panel switch turned ON, the LED light up of a fraction of a second then the breaker trips.  Probably one of the safety circuits in the power supply is forcing the breaker to trip.  If the switch is turned back on a few times the unit goes back to being completely dead.  This implies there's something else wrong that's both causing the breaker trip signal AND is burning out U17.

19 Jan 2010 - With the new U17 IC installed the breaker is being set to off, so in order to measure voltages related to R126 I've removed U17 and discovered that Z9 appears to be a short.  But after removing it seems OK on the Fluke 87 diode test, so U14 the LM339 quad comparator is suspect.  Removing U14 allows running a good diode check on the empty Z9 PCB contacts.

11 Mar 2010 - Removed the(Output & Trip) connector from power supply and with the circuit breaker/power switch on get the following voltages on the power supply test points:
to gnd (J6)
No Load
Adj R111
was: 6.0 V
now: 6.2 V
to gnd (J6)
? Pwr Det +3.0 +5.1
J4 -12
R111 (not R110 which is a fixed resistor) adjusts the -12 V current trip point.  It's the same problem that John R. had on his RCS-5 receiver.  The wiper voltage appears on U13 at pin 8 with U13 pin 12 as ground.

The problem relates to the -12 supply being overloaded.  Removing the large output connector on the power supply disconnects both the loads and the circuit breaker trip signal.  A good thing to do when troubleshooting the power supply.  Next to study the manual to see what plug-in boards use the -12V supply rail and unplug them to see which is loading the rail.  I'm expecting a bad cap on the -12V rail, a good test for the ESR Micro tester.\\
Disconnecting the power plug to A4 RF Front End, A5 2nd IF, A6 Synth and A7 Programmer/Audio boards did not restore the -12 V rail.  The A4 RF Front end power disconnect did bring the rail up from -6.4 to -7.0.  That leaves the mother board connection A3A1 which needs to be found.

When powered up the front panel LEDs work properly and the Function swithc functions.  But the CRT is has three copies of the text, like the time instead on just one.


3331035 Frequency Synthesizer, G.E. Strickholm (Sanders Assoc), Jly 11 1967 - 
3493865 Frequency Encoded Digital with each encoded frequency swept over a band of frequencies, R.L. Miller (Bell Labs), Feb 3 1970
4037159 Chirp communication system, A.R. Martin (Harris), Jly 19 1977, - Pseudo Random start and short constant slope chirp
4244053 Privacy communication method and system, M.R. Clinch, C.R. Graf, P.E. Martin, R.B. Fenwick (Air Force), Jan 6 1981, 380/34 - Chirpcom
1571005 Secret Signaling, R.V.L. Hartley (WE), Jan 26 1926, 380/39 ; 370/295 - Single Side Band, made more secure by varying the carrier frequency
2448055 Wobbled Frequency Carrier Wave Communication System, M.Silver, C.A. Segerstrom, R.B Reade (Fed Tel & Radio), Aug 31 1948, 380/32 ; 346/37 -
 provides anti jam and multiplex capability, like the modern SINCGARS radios.
2998573 Signal Generator having an Output Linerly Related to an Input Function, R. Beagles (RCA), Aug 29 1961, 331/37 ; 327/105; 331/178; 331/179; 331/180 -
 maybe for sweeping 10.7 MHz IF strips?
3124748 Secret Signalling Systems, E.Y. Webb, Mar 10 1964, - replaces the balanced modulator with a filter in the inverted speech scrambler
2206590 Portable Transmission System, E.Y. Webb, Jly 2 1940, 380/33 ; 332/171; 332/176; 380/38 - voice inversion voice scrambler
1227113 Electronic Wave-Filter, G.A. Campbell (AT&T), - LC band pass and band stop filters
3155908 Electronic Coding Device for Radio-Electronic or Telephone Links, L Berman (Compagnie Ind), Nov 3 1964, - SSB w/highly stable carrier
3204034 Orthogonal Polynomial Multiplex Transmission Systems, A.H Ballard & B.R. Boymel, Aug 31 1965, - complex mux system
3283254 Control system Imploying Counter to Generate Signals for Changing Output, Linearly or Non-Linearly, of Frequency synthesizer, G.D. Haynie (Bell Labs) Nov 1966, -digital swept frequency generator
3331035  <see above>
3493865  <see above>
3619802 Frequency synthesizer, D.R. Lohrmann (Army), Nov 9 1971 - instead of varing the division ratio this one chooses the harmonic comb
3681708 Pseudo-Random Frequency Generator, M.E. Olmstead (Bendix), Aug 1 1972, - used in PLL to modulate an RF carrier
4066964 Communication system, S.T. Costanza, P.G. Franklin, F.L. Gebhardt, J.D. Isreal, C.R.Moore, C.E. Wheatley (Rockwell), Jan 3, 1978 -
police, fire, etc radio system with confrerence call, command override
5943629 Method and apparatus for real-time ionospheric mapping and dynamic forecasting, J.W. Ballard, J.M. Goodman (TCI Intl), Aug 24 1999 -
4980924 HF radio communication systems with frequency management, A.P.C. Reed et al (Plessey), Dec 25, 1990 - models ionosphere
5230076 Ionospheric sounding, R.G. Wilkinson (HM UK), Jul 20, 1993 - bi-static hi power pulse system (chirp works much better)
5428358 Apparatus and method for ionospheric mapping, S.B. Gardner (Navy), Jun 27, 1995 - single site GPS receiver
5585800 Location-corrector for removing sun-induced effects in the global positioning system, S.R. ChubbDec 17, 1996 - Sun and theory of relativity
5990845 Broadband fan cone direction finding antenna and array, E.D. Sharp, S.W. Hsi (TCI Intl), Nov 23, 1999, - bi-conical or disk-cone vertical polarization, but directional
6150988 Wideband slot antenna with low VSWR, G. Sinclair & Po-shin Cheng (TCI Intl), Nov 21 2000, - cellphone 470 - 870 MHz
application 11490249 Apparatus and method for local broadcasting in the twenty-six megahertz short wave band, Po-Shin Cheng, G. Sinclair (TCI Intl), Jan 25 2007, -
DRM antenna that supresses sky wave. i.e. is a local only antenna.
4965607  Antenna coupler, M.L. WIlkins & A.O. Wong (BR Com) October 23, 1990 343/861; 333/17.3; 343/860; 455/123
An automatic antenna coupler is disclosed. The antenna coupler automatically matches the output impedance of a 50-ohm transmitter to the input impedance of a non-broad-band antenna, such as a whip, dipole or long wire. The resulting increase in transmit coupling efficiency provides greater radiative power than that available from an unmatched antenna.

Learns and remembers all the matching for 2 to 30 MHz then can tune ant in about 20 ms (time to set relays).  So probably would work with frequency hopping radios if the time on each frequency was longer than 20 ms.

Can be used for receive by sending the coupler the frequency as a digital word.

Patent Class 343 is Antennas


Oregon Hardware-Software Factory - DSP & HF digital comms
ZL1BPU  Fuzzy modes -
Audio Spectrum Analysis -
TAPR - Digital Signal Processing - EVM Radio Interface Kit - Using the Motorola DSP56002EVM for Amateur Radio DSP Projects -
dsp overviews - DSP links
Motorola - Evaluation Module Kits - DSP56002EVM: DSP56002 Evaluation Module - IS BECOMING OBSOLETE the 56303EVM or 56307EVM may be replacements that will need code conversion
Flash EPROM is Atmel  AT29C256
NA1DB formerly N1OWU - much older software for the EVM
TCI/BR Data Sheets: RCS-5A/B - RCS-6A - RCS-6B - RCS-7A/B/C -
Oblique HF Sounder Homepage at LANL -

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