﻿			sudd



			Spectrum

			UoSAT

			Data

			Demodulator



			User's Guide





N.P. Taylor (G4HLX)

46 Hunters Field				SOFTWARE BY

Stanford in the Vale

Faringdon

Oxon.  SN7 8LX					G4HLX



		Program and explanatory material Copyright (C) 1985,87 N.P. Taylor



			Users Guide revised for SUDD version 3.1  February 1987



1.  INTRODUCTION



The two University of Surrey satellites, UoSAT-1/OSCAR-9 and

UoSAT-2/OSCAR-11 (abreviated here as UO-9 and UO-11) are capable

of transmitting data in a variety of formats.  The most commonly

used is the synchronous 1200 baud ASCII data transmission, using

1200 Hz and 2400 Hz tones (in UO-9 data, the 1200 Hz tone

represents "space" and 2400 Hz "mark"; in Uo-11 these are 

reversed).



Transmissions include news bulletins and general satellite

information sent as text, and telemetry data which, after

decoding, provides the output from a number of sensors around

the spacecraft.  Also sent is the output from experiemental

modules on-board the satellites.  These transmissions are carried

on the beacons in the 145 MHz and 435 MHz bands, the general

beacon on 145.825 MHz carrying the information on more general

interest.  The modulation is AFSK using narrow band frequency

modulation.



The received audio has to be decoded to recover the ASCII text

characters, and the conventional means of doing this is with a

hardware demodulator (essentially the receive part of a

specialized modem), feeding the serial data input of a computer

or VDU, etc.  In the case of the ZX Spectrum, an additional

serial interface woould also be required to accomplish this.  The

SUDD program performs the functions of both the demodulator and

serial interface using software, the only connection to the

Spectrum being the receiving audio to the "EAR" socket (or via

the datacorder in the Plus 2 model).



After demodulating the signal, the text is stored in a buffer

within the Spectrum RAM, from where the SUDD program will

process it to display the vallues of all the telemetry channels,

performing a validation test on the checksum digit.  Alter-

natively, the data in the buffer may be displayed on the screen

or printed as text.  Another option enables the demodulated text

to be saved on cassette or microdrive, from where your own

programs can read it, enabling you to experiment with the

various data sent by the satellite.



2.  RECEIVING UoSAT



The general beacon of both UO-9 and UO-11 is on 145.825 MHz.  This

signal may be readily received with a suitable narrow-band FM

receiver.  This may be a dedicated unit such as the ASTRID, or an

FM receiver for the 2m amateur band.  A VHF scanning receiver may

also be suitable.  Good signals can be obtained with a simple

antenna such as crossed dipoles, provided these are mounted in

an elevated position with a clear view of the sky.  If you use a

directional antenna such as a yaggl array, this should be rotated

(and, ideally, elevated) to track the satellite, but such

sophistication is not generally necessary to get signals of

adequate strength.  Your success will depend on the level of

noise on 145 Hz at your location.



Of course, you will need to know when to listen for the UoSATs.

There will be several orbits each day which are in range of your

station (typically, in the UK, 5 orbits of each satellite

provide a "pass" of 8 or more minutes ) - if you're using a

simple antenna you should aim to receive the near overhead

passes.  The timing of these orbits can be obtained from a number



			-1-	



of sources.  One option is to run a satellite tracking program,

using basic orbital data (either as EQX data or Keplerian

elements, depending on the complexity of the program): this data

is sent by the UoSATs and published in Oscar News, the AMSAT-UK

journal (see section 9), and in various other magazines.

AMSAT-UK also have available to members a detailed orbital

calendar which gives times for all orbits in range of the UK.

Another method is to use the "Oscarlocator", a simple chart

system, also available from AMSAT-UK.



The University of Surrey recorded telephone message (see section

9) also gives basic orbital data.  The announcements give the

times and longitudes at which the satellites will cross the

equator (travelling North) for selected orbits.  Times and long-

itudes for other orbits may be calculated by repeatedly adding

the period and longitude increment which are also given.  In the 

UK, the satellite comes into range typically 8-10 minutes after

an equator crossing at around 350 degrees W.



For minimum error rate the audio signal from the receiver should 

be as noise-free as possible.  It is not difficult to receive

strong, fully-quieting signals from UO-9 and UO-11, but if

signals are noisy, attention should be given to the receiving

system and antenna.  The use of a filter in the audio can help in

difficult cases.  By far the most efficient is the G3RUR UoSAT

Decoder, the current version of which produces re-generated

tones as an output option, so the unit acts as a highly

optimized filter.  Details can be obtained from AMSAT-UK (see

section 9), who also produce a printed circuit board.  If you

build this unit, note that the sense of the tones produced are

such that for SUDD the selector switch should be permanently set

to "UoSAT-2", whicheer satellite is being received.



3.  GENERAL PRINCIPLES OF DECODING



If using s Spectrum 48K, Spectrum Plus, or Spectrum 128, the

audio signal derived from a suitable FM receiver must be conn-

ected into the "ear" socket of the computer using a standard

3.5mm jack plug.  The level of signal required will be roughly

that used when loading programs from cassette tape.  This can be

provided directly from the loudspeaker output of the receiver,

or from a cassette recorder on which the signals have been

recorded.  If you are using a Spectrum 128K Plus 2, which does

not have an "ear" socket, the signals should be recorded on

cassette tape, and then replayed on the Plus 2's internal

Datacorder.



There are a number of advantages in recording the UoSAT signals

onto cassette as they are received rather than decoding them

"live".  Firstly the buffer which stores the demodulated data in

SUDD is long enough to store only about 90 seconds of data as

transmitted (this is actually a lot of text at 1200 baud!).  If a

tape recording of one pass of the satellite is made, it can be

processed in several sections if desired.  Secondly you may find

that the 145 MHz receiver experiences considerable interference

from the Spectrum computer if it is running whilst receiving.

Thirdly, during the pass you will be free to concentrate on jobs

such as tuning the receiver, rotating the antenna, if necessary,

whilst the signal goes onto the tape.  Finally, using the same

cassette recorder as usually used for loading programs

simplifies connections to the computer (and of course, this

becomes essential if using a Spectrum 128K Plus 2).



		-2-



To summarize the receiving - demodulating - decoding procedure:



(i)	Signals from the satellite are received on suitable

	equipment and recorded on cassette (or if you prefer, fed

	directly into the Spectrum)



(ii)	The received audio is replayed into the Spectrum "ear"

	socket (or through the Datacorder in Plus 2 models), with

	SUDD in its "demodulate" mode.  It will demodulate the

	signals and fill a buffer with the data recovered (up to

	a maximum of 9450 characters).



(iii)	The data in the buffer is displayed, printed or processed

	by SUDD to decode the telemetry data.  Or the data may be

	saved on tape or microdrive for use by other programs.



4.  DETAILED INSTRUCTIONS



All the options in SUDD are selected from menus.  After loading

the program (using LOAD "SUDD" or just LOAD "", having selected 48

BASIC mode if using a 128K machine), you will see the main menu.

To pick an option just press the key indicated alongside your

choice on the menu.  In some cases this will bring up a further

menu which should be used in a similar way.



The "break" key remains active in SUDD, i.e. you can abort the

process at any time by pressing it.  The program can then be

simply restarted without loss of data (see section 4.4).



The options of the main menu and sub-menus are described below

in the order in which they occur, which is also the order in

which they will be used in many cases.



4.1 Main Menu



4.1.1 "S" - Select satellite



It is essential that the correct satellite is selected here

before demodulating, due to numerous differences in data formats

between UO-9 and UO-11.  When loaded, UoSAT-1/OSCAR-9 is selec-

ted.  Each press of the "S" key will flip the selection between

this and UoSAT-2/OSCAR-11, as shown on the display.



4.1.2 "C" - parity Check select



Usually, the even parity check performed during demodulation

should be on, so that errors in received data can be spotted.

However, some of the data from experimental modules in the

U0SATs are sent as 8-bit data with no parity bit (this is true,

for example, of the Digital Communications Experiment in UO-11).

To demodulate this data, the parity check in SUDD must be first

disabled by the "C" option.  Each press of C will toggle the

parity check between ON and OFF, as shown on the display.



The normal telemetry frames and news bulletins always use 7-bit

data with an even parity bit, so the parity check should be left

ON for reception of these.



4.1.3 "D" - Demodulate signal



This option will display the demodulator "front panel", and the



		-3-



audio signal fed into the ear socket is demodulated.



As this is being done, you will see a number of things on the

display :



(i)	The border shows a pattern similar to that obtained when

	loading programs, except the colours are magenta and

	green.



(ii)	The green "mark" and "space" lights illuminate as valid

	tones are recognised; these should be flickering on and

	off during demodulation.



(iii)	The red "parity" and "framing" error lights illuminate

	when an error is detected in the incoming data.  The parity

	error light shows that a byte has failed the even-parity

	check; the framing error light shows that valid stop bits

	were not found in the expected position.  During normal

	demodulation of a clean signal, these lights should rarely

	flash.  If the signal is noisy, or if the data format is

	not as expected (e.g. you've selected the wrong satellite,

	or the satellite is sending experimental data in an

	unusual or non-parity-checked format) one or both lights

	will flicker continually.



(iv)	A graphic indication of how full the data buffer has be-

	come is shown at the bottom of the display.  About 9.2

	Kbytes can be accomodated, and as the buffer is filled the

	yellow line extends across the tick marks to give you some

	idea of the space used.  Each tick represents 1 Kbyte of

	buffer, except the rightmost one which is the buffer end.



The demodulation process will end in one of two ways.  Either the

buffer will become full, or you can halt the process by pressing

the break key (once).  In either case the display will show the

total number of bytes of data (i.e. no. of characters) received,

and the total number of parity and framing errors.  For reliable

reception these error counts should be small.



4.1.4 "P" - Process/display/print options



This option brings up the process etc. options menu to determine

what to do with the data in the buffer.  This is fully described

in section 4.2.



4.1.5 "E" - Erase buffer contents



If, after demodulating one section of data, option "D" is sub-

sequently invoked to receive some further data, this will be

appended to that already in the buffer.  If you wish to clear the

buffer of the earlier data before proceding (which will be

essential if the buffer has already been filled), option "E"

should be used.



You will be asked to confirm your intention to erase the con-

tents of the buffer (respond by pressing "Y" to confirm, or "N"

if you've changed your mind), and the "number of bytes in

buffer" value displayed will be seen to change to zero.



4.1.6 "T" - save data to Tape, etc.



This option brings up the menu for saving demodulated data/text

to tape or microdrive, or loading previously saved data.  This is



		-4-



described in section 4.3.



4.2. Process/Display/Print Options



The menu offering these options is reached via the "P" option on

the main menu, which can be used only after data has been read

into the buffer by the demodulation step.  Any of the following

options can be repeatedly used in any order to process the same

section of data in different ways.



4.2.1 "T" - Telemetry decoding



The basic telemetry data sent by both UoSATs are in the form of 

60 analogue values ("channels").  In addition to these, UO-11

(but not UO-9) sends 96 "status points" (basically on/off

values).  When the satellite is sending this telemetry data a

complete set of these values (a "frame") is sent approvimately

every 5 seconds.  With experience you will be able to recognize

the repetitive sound of the telemetry frames.



Using the "T" option, SUDD will decode the telemetry data to

provide the analogue results, applying the calibration formula

published by the University of Surrey.  Due to differences in

data formats, it is, of course, essential that the correct sat-

allite has been selected on the main menu.  If the data is from

UO-11, after selecting the "T" option, a further short menu

offers either analogue channels or status points.



SUDD searches the buffer for a valid sequence of characters rep-

resenting the start of a telemetry frame.  If there are no

telemetry frames in the buffer (i.e. the satellite was not sen-

ding data of this type), the outcome will be rather un-

predictable, but no valid data will follow.  This will be evident

from the top line of the display, which shows the 7 characters

which head each telemetry frame; these should be "UOSAT-1" or

"UOSAT-2".



Assuming that valid telemetry data is present, the position

within the buffer of the start of the first frame will be dis-

played at the foot of the screen as a "byte no.".  The UOSAT-1 or

UOSAT-2 heading is displayed, followed by the date and time

decoded from the frame heading.  As there is no error-checking of

this heading and date/time, odd results may sometimes occur.



Each analogue channel (or status point) is then checked and

converted in turn.  The checksum is tested, and the channel is

rejected if the checksum fails, or if any of its component

characters failed the parity check during demodulation.  During

this process, the number of the channel or status point being

checked is shown at the foot of the screen.  These digits will

change rapidly, unless the data is highly corrupted when the

time taken to find valid data will increase.  For any channel

which is rejected, the number is shown on a red background.

After a rejection, the subsequent characters in the buffer are

tested to find the next valid chabel, subject to certain rules

to ensure that the date is correctly interpreted.  In this way

loss of information due to erroneous or missing characters is

minimized.



The results for the first 20 analogue channels or status points

are then displayed on the screen.  If a particular channel was

not found in the frame (due, for example, to a data error

corrupting the channel number), the position for that result is



		-5-



left blank.  If the channel was identified, but was rejected due

to a checksum or parity error, as error code "c" or "p", re-

spectively, is shown.  For status points the errors are not

distinguished, and "e" is shown for either condition, which will

always affect groups of 12 status points together.



Several options are then displayed at the foot of the screen.

The "down" cursor key (or "6" key on older keyboards" can be

used to display the next 20 channels or status points.  The up

and down cursor keys (or "7" and "6") may be used repeatedly to

browse up and down through the results.



The "P" option will print all the analogue channels or status

points in the currently analyzed frame (not just the 20 being

displayed), to a connected printer (see section 6).



Pressing ENTER will cause SUDD to jump forward to the next

telemetry frame in the buffer, and repeat the checking and

display of results, the screen display always initially showing

the same channel numbers as when the ENTER key was pressed.  This

may be done repeatedly to see all the telemetry frames in the

buffer in turn, until the message "No further frames in buffer"

is given.



The "E" key can be used to end the processing of telemetry

frames and return to the previous menu.  All menus contain an "R"

option to return to the next highest level menu, and thence back

to the main menu.



4.2.2. "D" - Display text



This option displays on the screen the contents of the buffer as

text, at 32 or 64 characters per line according to the use of

the "C" option (see below).  Any character in which a parity

error was detected during demodulation is replaced by a "_" in

the display.  If the parity check was switched off, this same

character is shown in place of any non-ASCII character received.



At the end of each screen-full of text, three options are shown

at the foot of the screen, as well as the range of byte numbers

for the displayed data (i.e. the address within the buffer) so

that you know where in the buffer you are viewing.



The options are the ENTER key to scroll down and display the

next 22 lines, "E" to end the display and return to the previous

menu, and "C" to copy the screen image to a ZX, Alphacom, or

similar printer (must be able to respond to the COPY command).

If using 64 character/line display, this option is useful way of

printing at this density on these simple printers, otherwise

printing is normally done by the "P" option (see section 4.2.4).



Note that any line of text which is longer than the currently

selected line length (64 or 32 characters), will "wrap-round" at

the end of the display.



4.2.3 "C" - Characters per line select



Each press of the "C" key on the process/display/print menu

flips the character per line setting between 32 and 64.  This

affects only the format of the text display described in section

4.2.2.  The 32 chars/line selection gives the normal Spectrum

character set, while the 64 chars/line set is highly compressed.

The advantage of this option is that the news bulletins sent by



		-6-



the UoSATs are generally up to 62 characters in each line, so

that they are displayed more naturllay at this pitch without

splitting each line in half, particularly if tables of data are

included.  On the other hand, on some TV monitors it may prove

difficult to read the tiny characters, and you may prefer to 

return to the standard set.



4.2.4 "P" - Print text



Provided a suitable printer is connected, this option is uded to 

print the buffer contents as text in the normal.  The maximum

line length is set by the characteristics of the printer.  For

advice on connection of printers, see section 6.



4.2.5 "S" - set Start point



The processing, printing and display of buffer contents as de-

scribed in the above sections will normally start at the first

byte in the buffer (known as "byte no." 1).  The "S" option can

be used to set the starting byte to some other point.  After

pressing "S", SUDD will ask you to enter the byte no. of the new

start point.



This can be useful for jumping through the buffer to a desired

point, particularly when used in conjunction with the display of

byte number shown during the other displays.  For example, if the

telemetry displays shows the start of a certain frame as byte no.

967 and you wish to look at the raw data which comprises that

frame, you can use the "S" option to  set the start point to 967

and then use "D" to display.



4.3 Save/Load Data to/from Tape, Microdrive or Opus Disc



This menu is reached by the "T" option on the main menu.  It

enables data which has been demodulated and stored in the buffer

to be saved on tape, microdrive or Opus disc, as a conventional

CODE file.  This can then be loaded back in by your own program

for processing in some way, for example to use some of the other

experimental data sent by the UoSATs.  Furthermore, there are

options for loading previously saved data back into the buffer.



Use of the four options is straightforward - just follow the

instructions displayed on the screen.  All four options will ask

for a file name (this may be null for the "L" tape load options,

whereupon the next file on the tape will be loaded); the

microdrive options "M" and "D", which are also used for Opus

disc, will always save or load using drive number 1.



The two save options "S" and "M", will display the absolute

address of the start and end of the data block to be saved, as

well as the number of bytes of data (including the two initial

bytes - see below).  Note that only that part of the buffer which

is currently filled will be saved.  When loading the data back

into your own program, it is, of course possible to re-locate

the data anywhere you like in the address map (having reset

RAMTOP appropriately).



The number of bytes actually saved is two more that the number

of bytes of data.  The first two bytes give, in the usual Z80 low

byte - high byte format, the number of data bytes which follow.



An example of a program segment which might be used to load in a 



		-7-



saved file is given here:

		CLEAR 49999

		LOAD "FRED" CODE 50000

		LET N = PEEK 50000 + 256 * PEEK 50001

		PRINT "There are ";N;" bytes starting at 50002"



The data bytes contain the ASCII codes as received from UoSAT

during demodulation.  If the parity check is switched on, these

are 7-bit values (i.e. decimal 0 - 127), with the most sig-

nificant bit set to "1" if a parity error was detected (i.e. if

a value is 128 or more, a parity error is indicated).  If the 

parity check was switched off during demodulation, the values

are un-modifed 8-bit codes.



Important:  If you are intending to save the data using these

options, it is good practice to make it the first thing you do

after demodulating is complete, to guard against loss of data.

But it is particularly important that you do not use the

telemetry decode option (see section 4.2.1) before trying to

save, because the extra memory that this decoding uses will

leave insufficient space for the save operation.  If you do get

into the unfortunate position of wishing to save your buffer-

full of data after you have used the telemetry decode facility,

the only way it can be done is to press the break key and

restart SUDD with the RUN command (see next section), which will

clear the memory needed for the save process.



4.4 Restarting after a break



Pressing the break key at any time will stop the program (except

during demodulation, see section 4.1.3).  If this happens, or if

any other condition has caused a return to BASIC,  SUDD may be

restarted simply by the BASIC command RUN.  If the BASIC loading

program has somehow been lost, the command RANDOMIZE USR 23792

can be used instead.



Any data which was in the buffer before the break will still be

intact and may be processed in the usual way.  Note however, that

settings of some options, in particular the selection of satell-

ite, UC-9 or UO-11, will have returned to their defau 1 values,

so check carefully that the correct options are set before

proceeding.



5. MAKING A BACK-UP COPY OF SUDD or TRANSFERRING TO MICRODRIVE

    OR OPUS DISC



The SUDD program is copyright.  You are, however, permitted to

make a single back-up copy for your own personal use, or to

transfer the program to microdrive or Opus disc.  This is done

automatically by a "hidden" option on the main menu, accessed by

pressing SYMBOL SHIFT and "S" together.



This will bring up a short menu with two options:  tape or micro-

drive (also used for Opus disc, but first see the next sections).

In either case, three files will be created, called SUDD, SUDDC1

and SUDDC2.  For a microdrive save, which is to drive no. 1,

these files must not already exist on the cartridge inserted.



To run the saved program, simply used LOAD "SUDD" or, from micro-

drive, LOAD *"m";1;"SUDD", which will automatically load the

other two files and run.  Note that the title screen is not



		-8-



saved.



5.1 Transferring to Opus disc



Before saving SUDD on an Opus disc system, a small modification

must be made in the BASIC loading program.  First load SUDD from

tape in the normal way, and when the main menu is displayed

press the break key to gain access to the BASIC program.  Line

210 must then be edited to remove the words "REM for Opus", so

that the line now reads

		210 RANDOMIZE USR 64481

Then use the RUN command to re-start SUDD and follow the pro-

cedure for transferring to microdrive as described above.



6. USING A PRINTER



The printing options in SUDD will drive any printer which

operates normally for the LPRINT command.  As noted in section

4.2.2, the option to copy the screen image to the printer only

works if the COPY command is also obeyed normally by the 

printer.



A ZX printer or Alphacom 32 (or equivalent) is particularly

suitable, and will be driven by SUDD without any modification.

Most other printers, with a suitable interface, will also work

satisfactorily, and 80-column printers will provide a neat

print-out of news bulletins, etc.



If additional commands are required to initialize the printer

and its interface, these may be added to the BASIC driving

program as additional lines with line numbers in the range 10 to

80.  For example, if using the ZX Interface 1 to drive a printer

via the RS232 port at 9600 baud, the two lines

		10 FORMAT "t";9600

		20 OPEN #3;"t"

would set this up.  Another line which should be added with these

is to set the byte at 63689 to a value of 1, e.g.:

		30 POKE 63689,1

This signals to SUDD that an 80-column printer is being used,

which will cause the format of the telemetry printing to be

changed slightly to make use of the longer line length.



Having modified the BASIC as appropriate, the customized version

of SUDD should be saved as described in section 5.



One problem which may be encountered is with printer interfaces

which require a small machine code routine to be loaded into the

Spectrum RAM to operate the interface.  Almost all the available

48K RAM is filled by the SUDD program and its data buffer.

However, some interfaces of this type provide an alternative

version of the code which can load into the printer buffer at

23296, and this should operate OK - the commands to load and

execute this code can be added to the SUDD BASIC program as

lines 10 - 80, as described above.



7. USING THE SUDD MACHINE CODE



The following discussion is for the benefit of the more advanced

user who may wish to make use of parts of the SUDD code in their

own programs.  The SUDD code is in two sections: the first, of



		-9-



length 24594 bytes starting at 23792, has been compiled from a

BASIC source.  The section section, of length 1847 starting at

63689, includes the main machine code routines, two of which may

be useful in your own programs.  These are the demodulating

routine, which you could use to input data directly into a

buffer in your own program, and the 64 character per line

printing routine, which can be used in any program to print text

on the screen at this density.



These machine code routines are part of the file "SUDDC1" on the

SUDD tape (this is the fourth file on the tape).  This could be

loaded in your program by, for example,

		CLEAR 63688 : LOAD "SUDDC1" CODE 63689,1847

although a lower RAMTOP will be needed in the CLEAR statement to

make room for a buffer if the demodulator routine is to be used

(see below).



7.1 The demodulator routine



Before calling this routine, a data buffer to receive the demod-

ulated text must be set up.  The size of this will depend on how

much space has been left in the RAM by your program.  You must

tell the SUDD code where this buffer is by POKEing the starting

and ending addresses into certain locations.  These are all

2-byte values stored in the normal Z80 convention of low byte

first:

	63730-1	STBUF - address of start of buffer

	63732-3 END   - address of end of buffer

	63734-5 CEND  - address of last byte in buffer which was

		filled; intiall this should be set to (STBUF-1)





Don't forget that RAMTOP should be set to some value below the

start of the buffer using the CLEAR command.  In addition to

these 2-bytes values, there are two single byte values which mmust

be set:

	63724	BIRD  - set =0 for UO-9, or =4 for UO-11

	63729	PARCH - parity check switch =0 for Off, =1 for On



The entry point for the demodulating routine is 63736, which can

conveniently be called by a statement such as

		LET A = USR 63736

Using this statement, after the end of demodulation the variable

A, which will contain the contents of the bc register, will =0

if termination was because the buffer became full, or =1 if the 

break key had been pressed.



Other values that may be obtained after demodulation are stored

as 2-byte values:

	63734-5	CEND   - address of last byte in buffer which was

		         filled (i.e. no. bytes received = STBUF-CEND+1)

	63727-8 PARER  - no. of parity errors

	63725-6 FRAMER - no. of framing errors



7.2 64 Character per line screen printing



Use of this routine is straightforward.  The code for each

character to be printed must be POKEd into the byte at 65272,

and then the routine at 65273 called.  For example, to print a

string stored in the variable A$:



		-10-



		10 FOR I=1 TO LEN A$

		20 POKE 65272, CODE A$ (I)

		30 RANDOMIZE USR 65273

		40 NEXT I



The characters will appear on the screen two at a time, i.e.

only every other call to the routine will add something to the

display.  Only printable codes are accepted: codes below 32 are

ignored (except code 13, ENTER, which is treated as NEWLINE),

codes above 128 are replaced by 128.  If you want to change

printing colours, etc., this can be down with the usual commands

PAPER and INK.  Print position on the screen can be set by

preceding the call to the routine by a normal PRINT command, for

example PRINT AT 10,0; to make the next character appear at the

start of line 10.



PRINTing at 32 characters per line (as normal) can be mixed with

that at 64 line (even mixed on the same line) by using the

normal PRINT statement.  However the UDG character "U" (i.e.

GRAPHIS-U) should be avoided as this is used by the routine.



8. SAMPLE DATA RECORDINGS



On the second side of the SUDD tape you will find two sample

recordings of UoSAT data, the first from UO-9, the second from

Uo-11.  You may like to use these to acquaint yourself with the

facilities of SUDD.  Each sample contains examples of both a text

bulletin and telemetry data.



9. FURTHER INFORMATION ON UoSAT



If you require further information about the UoSAT spacecraft,

there are two principal sources of information in the UK: AMSAT-

UK and the University of Surrey.



The address of AMSAT-UK is given below.  It is a purely voluntary

organisation and a stamped addressed envelope should accompany

any enquiry:

		AMSAT-UK

		R.J.C. Broadbent, G3AAJ,

		94 Herongate Road,

		Wanstead Park,

		London E12 5EQ.

Membership of AMSAT-UK is recommended to anyone interested in

the amateur satellite scene.  The bi-monthly journal Oscar News

is a major source of information on all current and future

satellites, including the UoSATs.



The University of Surrey issues up-to-date information in the

news bulletins which you will now be receiving fom the UoSATs

(mainly UO-11 at weekends). In addition, the university issues

printed data sheets, the "UoSAT Spacecraft Data Booklet" being a

complete digest of information on UO-9 and UO-11.  A telephone

recorded message service gives basic orbital data on both

satellites, the number is Guildford (0483) 61707 for information

on Uo-9, and 61202 for UO-11.



		-11-







 













