Computers, Radio and more

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  • What was wrong with BASIC?

    The BASIC programming language was introduced in 1964 at Dartmouth College by John Kemeny and Thomas Kurtz. It was one of the first time sharing systems, where students could sit behind a teletype and begin typing their programs and start running them immediately. In those days it was far more common that you had to type your program on punched cards, hand it over to the computer centre and get your printout back after a few hours.

    BASIC was easy to learn and it was useful to university students who were not computer specialists. It supported many mathematical functions and early on, it supported matrix operations, a feature that got lost when BASIC was later ported to microcomputers. And what else got lost too?

    No Structured Programming

    The earliest versions of Dartmouth BASIC did not support structured programming, other than the FOR..NEXT loop. BASIC used line numbers for two different purposes:

    • To support editing of programs. Terminals were teletypes that printed everything you typed on paper. There was no computer screen , where you could move the cursor around and start editing code anywhere in your program. The internal editor kept the program ordered by line number. If you want to insert a line into a program, you simply enter a line with an intermediate line number (therefore you started your program using line numbers that incremented by 10, so there were intermediate numbers). By entering a line with an existing number, you replace that line. When you enter the line number by itself, you delete that line.
    • As labels for GOTO and GOSUB.

    At least in FORTRAN, you had labels only at lines to which you wanted to jump. In BASIC, every line could be jumped to. This may be somewhat easier to learn, but it made programs harder to maintain.

    The first version of FORTRAN had no subroutines at all, but all versions after that, had named subroutines, with local variables and named parameters. Nothing of that in early BASIC. In BASIC you had GOSUB to a line number. With Assembly language you could at least give your subroutines meaningful names. This was not the case with early versions of BASIC (including early versions for microcomputers). That made BASIC feel like an even lower level language than Assembly language in that respect. If you renumbered your program to get the line numbers less haphazard, your subroutines would change line numbers.

    The very earliest BASIC could only specify line numbers in an IF statement, for example:IF A<B THEN 30 ELSE 50

    All versions of Microsoft BASIC I know, did allow you to execute one or more statements conditionally, so you did not need line numbers and implied GOTO statements for all IF statements, for example IF A<B THEN PRINT "TOO LOW": C=C+1

    Not all versions of Microsoft BASIC had ELSE though. And ANSI Minimal BASIC only supported the variant with line numbers, as did TI BASIC.

    Too Much Variation

    Microsoft was the main developer of BASIC implementations for microcomputers. But Sinclair, Acorn and TI had their own implementations of BASIC. There was very little that the BASIC versions had in common. Some only supported variable names of a single letter (Sinclair, other than numeric scalar variables), others allowed arbitrary length names. Most had string variables that allowed strings of variable length, but some versions of BASIC had all strings in a string array the same length (Sinclair).

    Even within Microsoft itself, there was a wild difference between the commands and functions supported. For example, some BASIC versions supported user-defined functions, but only with numeric values and a single numeric parameter. Others supported both string and numeric functions with an arbitrary number of parameters of any type. Some BASIC versions did not have user defined functions at all. In some versions of Microsoft BASIC you had long variable names, all characters significant, but in other versions, only the first two characters of a variable name counted. So the variables DEBT and DECLARED would be the same. And if you dared to use a variable name MORTGAGE, the parser would mix up and tokenise the letters OR into a single byte (the OR operator). This happened only in some versions of Microsoft BASIC (for example MSX BASIC), but not in others (for example GW-BASIC on MS-DOS). On some computer systems, the disk BASIC was not even compatible with the cassette BASIC on the same machine.

    Acorn introduced BBC BASIC in 1981. It had structured loops like REPEAT..UNTIL, it had named procedures and named multi-line functions, while it was still largely compatible with the then current versions of Microsoft BASIC. Later versions of BBC BASIC added a full block-structured IF-THEN-ELSE-ENDIF, a proper WHILE loop and more. Procedures and functions did had parameters and local variables.

    Unfortunately, BBC BASIC completely ignored the ANSI standard for full BASIC. Microsoft did not. When they introduced Quick Basic and later QBASIC, they had named subroutines (with local variables and parameters) and the usual block-structured constructs, but they were completely different from those of BBC BASIC.

    You really can’t call two versions of BASIC the same language if the basic constructs for named subroutines or procedures are so different. You might as well call Ada and Pascal the same language.

    Specialised Syntax

    In BASIC, each command tends to have its own unique syntax. For example, the PRINT statement uses commas and semicolons between parameters to determine how the output will be formatted. A numeric parameter starting with # specifies a file to print to. Many BASIC versions have a USING parameter to allow formatted output. We have funny specialised syntaxes in Microsoft BASIC for OPEN (admittedly quite readable), like : OPEN "name" FOR INPUT AS #1

    And we have funny little syntaxes for line drawing, like LINE (100,100)-(200,150)

    User-defined subroutines always have to be called with CALL, like CALL MYSUB(10,20)

    They are not allowed to look like normal BASIC commands and they can certainly not have the same wild syntax variations as built-in commands.

    Pascal commits the same sin to a lesser degree. Pascal is very rigid in not allowing procedures with a variable number of parameters or parameters of different types. But the built-in procedures read and write can have a variable number of parameters and parameters of many different types. Add to this the weird formatting syntax like write(a:12:7); to specify that the number A must be printed with 12 characters and 7 digits after the decimal point. But other than the colon formatting syntax, calls to read and write look like ordinary procedure calls.

    C on the other hand,has no specialised syntax for printf or fopen. These are just ordinary functions. the printf function does have a variable number of arguments and it is somewhat of a challenge to implement such a function, but it can be done. Details of the I/O library are not baked into the syntax of the language itself.

    And the Good Things?

    Of course, BASIC did have some good things too:

    • Most versions of BASIC supported variable length strings and quite a few functions to manipulate strings. Standard Pascal lacked a variable length string type and the language went out of its way to make you suffer. You ended up counting out spaces to make all messages the same length, for example if they had to be passed as parameters. Turbo Pascal did have a usable string type, but with extensions like this, there is no standardisation among implementations.
    • Data embedded in the program. READ, DATA and RESTORE may look clumsy compared to initialised C arrays, but standard Pascal did not have a way to embed data in the program itself. You had to read it from file or you had to type endless lines of assignment statements to initialise the elements of an array.
    • Low memory usage. This was key in early microcomputers. A simple Microsoft BASIC fit into 8 kilobytes of ROM and programs were stored in RAM in such a way that every keyword occupied one byte. There was no separate storage of source code and parsed byte code. The LIST command showed you the program as you had typed it, with all byte tokens converted back to full keywords and all binary representations of line numbers printed in decimal.Interpretation was usually rather slow, but it got done with very little memory.
    • Floating point support and a full set of mathematical functions. Apart from integer BASIC versions of some very stripped down versions, you had full trigonometric and logarithmic functions.

  • Cross-border AM radio: the big thing that’s gone missing

    Back in the early 1980s, The Netherlands had four national radio stations and three of these were on mediumwave. They could be heard far outside our national borders. On the other hand, two Dutch language stations from Belgium could be heard throughout The Netherlands, as well as two French language stations from that country. That was not all you could hear though: there were a bunch of German stations and some English stations to be heard as well. BBC World Service was booming in on 648 kHz. During some years, we had some good pirate stations too.

    Much radio listening still happened on mediumwave, as not all radios had the FM band back then and one of the national radio stations in The Netherlands was on mediumwave only. Starting in 1985, we got an additional national station (Hilversum 5) and it was on mediumwave only, but it took the frequency of Hilversum 1, which became FM-only.

    If your radio had longwave too, you got a bunch of foreign stations: from France, Luxembourg, the UK, Germany and some other countries. After sunset, the mediumwave band came to life and if you took the trouble, you could hear radio stations from all over Europe. These were some of the main national programmes of those countries, hence it was quality stuff. BBC Radio 1 played the latest British pop songs, weeks or sometimes months before they were allowed to enter our country. Radio Moscow once had a Dutch language service on mediumwave, one of the few international broadcasters to have one, along with South Africa (that and an even more objectionable regime and that was on the 16 meter band on shortwave). But at night the mediumwave band was indeed used as another shortwave band, on both sides of the Iron Curtain.

    If you had a good radio and you were skilled with the rotating ferrite bar antenna, you could often pick up two different stations on the same channel. Hearing stations outside Europe was a challenge though, as there were many more European stations occupying those frequencies. Today it’s relatively easy to pick up North Africa for example.

    And of course many, many countries had a presence on shortwave. Back in the day, the 49 meter band was chock full of stations, whatever time of the day you listened. Most European countries were all there, all the time. Higher shortwave bands, like 25m, 19m and 16m gave you the more distant stations. Shortwave was not listened to by everybody though. But everybody got exposed to mediumwave during day-to-day listening. And everybody occasionally heard foreign stations, if only unintentionally.

    We are less exposed to radio stations from other European countries than we were a few decades ago. Since 2003, the FM band in The Netherlands was reorganised and it became very overpopulated, reducing the opportunities to hear foreign stations on that band. DAB has a far shorter reach across the border than FM used to have. We have internet radio now, but some countries (in particular the UK) reduce their internet radio streams to within their own country. With true broadcast radio, there’s nothing between you and the station you want to hear, that can be controlled by governments. You can add jamming stations, but you can’t take radio propagation away. Compare that to the many links that exist between an internet radio station and you.

    Exposure to radio stations from other European countries was a good thing, even if you were not intentionally listening to them. It created an awareness of a being part of a larger Europe. In most places in The Netherlands we have access to over 50 stations on DAB+, but many of these are non-stop computer generated playlist stations without a soul. BBC World Service is actually available on DAB+ in The Netherlands, which is a good thing. But this will only last as long as somebody pays to have it there. And we should have German and French voices as well, plus something from Belgium. Some of those more-of-the-same popular music stations can really be missed and be exchanged for existing foreign radio stations. I know,this is not how commercial radio works. But why should everything work according to the rules of commercial radio?

    The UK is the last country with a significant presence on mediumwave in our part of Europe and it will likely stop by the end of this year. Nobody will bring mediumwave back. But maybe the EU should facilitate airing public radio broadcasts outside national borders, to replace what mediumwave used to do for us naturally. There’s spare capacity on some DAB+ multiplexes, like that of our national public broadcaster NPO. It carries 10 programmes, 2 of which will likely be axed by the end of this year. You can easily have 12 programmes with good audio. Why not get some Belgian, French or German stations there?

  • Why the Dutch keyboard layout never caught on.

    The Netherlands is one of the few countries in Europe that uses the US-QWERTY keyboard layout for computers. Before there were personal computers, we had typewriters and nearly all typewriters sold in The Netherlands had two dead keys: one dead key contained the acute and grave accents and the other contained the diaeresis and circumflex accents. When you press a dead key on a typewriter, the accent is printed, but the carriage does not advance. The next letter you type gets printed under the accent you just typed. The positions of many symbols on the keyboard were not standardised: different brands of typewriters could have the question mark in a different location. The letters always followed the QWERTY layout. Some did have a special key for the letter ij, on others you had to type the letters I and J separately.

    Typewriters in the UK and the USA typically didn’t have dead keys. If you really, really want to type an accented letter, you could type the apostrophe, then backspace and then the letter. The same could we done with the double quote to get something that resembled a letter with an umlaut or diaeresis. In The Netherlands we used to type a comma, then backspace and then the letter C to get a C-cedilla (ç). Typewriters in Germany had dedicated keys for Ä, Ö, Ü and ß. Typewriters in Sweden had Ä, Ö and Å, in Norway and Denmark they had Æ, Ø and Å. Most of them had dead keys for accented letter too.

    France and Belgium had the weird AZERTY layout. French typewriters typically had a single dead key for circumflex and diaeresis, the few letters with acute and grave had their own keys, as did c-cedilla, but all only in lowercase.

    When personal computers were introduced, nearly all European countries standardised on a keyboard layout that was similar to the layout of the local typewriters, except for The Netherlands, that used the US layout, without any support for accented letters. In Dutch, accented letters are infrequent, but they are still important. The IBM-PC allowed you to type arbitrary symbols by holding down the Alt-key and then typing the numeric code of the character on the numeric keypad. For example the letter ë could be had by typing Alt-1-3-7. Oddly enough, this still works in modern Windows, even though it no longer uses that character encoding at all. Yes, the old CP-437 codes are translated to whatever Unicode character is applicable.

    National keyboard layouts other than US-QWERTY, all have one additional key left of the leftmost letter on the lower row. On QWERTY, this means left of the Z key, but on QWERTZ, it’s left of the Y and on AZERTY, it’s left of the W. In most national layouts, this key has the less-than and greater-than symbols..As there is an extra key in that position, the left shift key is much smaller than on the US keyboard. Some US keyboards (ISO layout) have this additional key too, while it is redundant for US-QWERTY. Many typists prefer the true ANSI layout with the wider shift key and the horizontal Enter key, over the ISO layout with the narrow shift key and the vertical Enter key.

    National keyboard layouts other then US-QWERTY, also use the right Alt key (marked as Alt-Gr) to access additional symbols. The ASCII characters @, [, ], { and } often require the Alt-Gr key. Most national keyboard layouts use the keys right of the letters for national letters (like Ä, Æ or Ñ) and/or dead keys, making fewer keys available for symbols. Only the UK keyboard layout does not have national letters or dead keys and is very similar to US-QWERTY. It swaps the @ and double-quote, it puts the £ instead of the # above the 3 and it puts the # on the key normally used by the \ symbol, which moves to the additional key left of the Z.

    Programmers prefer the straight US-QWERTY layout over any national keyboard layout, because of the easy access to square brackets and curly braces, which are used frequently in C and similar programming languages.

    Interestingly enough, the Netherlands does have a national keyboard layout. See https://en.wikipedia.org/wiki/List_of_QWERTY_keyboard_language_variants under Dutch. This keyboard has dead keys, like the old typewriters and shuffles the symbols around quite a bit. the square brackets end up on the key left of the Z. These proper Dutch keyboards are very rare. They may have been used by government institutions and Dutch publishers, but as 99% of the users has US-QWERTY at home, they are used to it and want to use it for work too.

    The reason why the Dutch layout never caught on may be a combination of programmer preference and cost awareness. US keyboards are made in larger series, therefore they tend to be somewhat cheaper. Schools may have selected US-QWERTY because it is more practical for programming.

    In Belgium, even in the Dutch speaking part, AZERTY is still the norm. Some programmers do use QWERTY keyboards, but that’s always a special order.

    At least since the 1990s, Windows lets you configure the US-QWERTY keyboard as US International with dead keys. This changes the following:

    • the apostrophe and double quote key becomes a dead key for acute accent and diaeresis. The same goes for the Caret (circumflex on shift 6) and the grave and tilde key.
    • The right Alt key gives access to many additional symbols and accented letters. Unfortunately for Dutch users, the letters ë and ï are not accessible this way, they require the dead double quote key instead.

    The US International layout with dead keys, is considered the Dutch keyboard layout, but this is not the same as the real Dutch keyboard layout. The big disadvantage is that you need to type an additional space whenever you type an apostrophe or double quote (or caret, left quote or tilde). This is super annoying for programmers, but it can also get in your way when typing just text..

    Linux distributions come with another option: US International with AltGr dead keys. It differs from US international with dead keys in the following way:

    • The dead keys only become dead when you type them with AltGr (the right Alt key). When you type the apostrophe key normally, you just get the apostrophe. It only becomes the dead acute accent key when typed with AltGr.
    • The set of symbols accessible with AltGr (without dead keys) is changed somewhat. the imported Dutch accented letters ë and ï are now in.

    But there are other layouts based on US-QWERTY as well, see for example: https://altgr-weur.eu/

    In Linux you can also configure a Compose key. You can use the right Control key, the right “Windows” key or the Menu key for that purpose. The disadvantage is that it requires three keystrokes to get a composed character. For example you type Compose, followed by /, followed by o to get ø. The advantage is you get access to many more symbols than with just dead keys or Alt-Gr combinations and that these symbols are mostly logical and easy to remember combinations of ASCII characters.

    Finally, Linux allows you to type any arbitrary Unicode character by typing first Ctrl-Shift-u, then the hex code of the desired character and finally Enter. For example Ctrl-shift-u, then the letter e b, then Enter gives you ë.

  • Open source radio receiver projects

    Today’s single-chip radio tuner chips make it possible for hobbyists to construct decent quality broadcast receivers. One chip that has been around for 15 years or so is the Skyworks (formerly known as Silicon Labs) Si4735. This chip contains a full LW/MW/SW/FM radio tuner from antenna to audio. It requires a microcontroller to control it, for example the 8-bit AVR processor used by Arduino. There are many hobbyist and open-source designs based on this chip. The Si4735 is an SDR radio internally, it does all filtering and demodulation on its internal DSP. There is a custom firmware blob for it that can demodulate SSB. However, this firmware blob is not open source. The AVR sends the Si475 its commands to tune to a specified frequency and set its other operating parameters, The AVR controls the display and the user controls of the radio. There are many ready-made Chines radios designed around this chip (or the Si4732) and an Arduino/AVR. This chip gives nearly continuous LW/MW/SW coverage up to 30 MHz.It is also the main part (or the final IF filter/demodulator) of nearly all world band radios currently on the market.

    Another single-chip radio tuner is the TEF-6686, designed by NXP. This chip contains a very capable FM tuner, along with LW, MW and SW. SW coverage is limited to 27 MHz (not 30) and there is no way to do SSB. As microcontrollers are now predominantly 32-bit, the TEF-6686 radios (and some newer Si473x designs too) uses an ESP32 microcontroller. One such open-source design was provided by PE6PVB https://www.pe5pvb.nl. This design has found its way to numerous ready-made Chinese radios too.

    There is also the Skyworks Si4684, a complete FM/DAB+ radio on a chip. PE5PVB designed a very capable DAB+ radio around it, using this chip, an ESP32 and a colour display. As the ESP32 does slide show decoding and display, the software uses nearly all the flash of the ESP32, so the FM side of the chip cannot be accessed using the current software. Unfortunately, there are no ready-made Chinese versions of this radio yet. DAB+ is not a thing in China and many markets these Chinese radios get exported to.,

    As interesting as these projects are, they leave the nitty-gritty radio stuff to a closed-source DSP and the open-source part is only about user control and sometimes RDS decoding or decoding of other digital data that comes with the radio signal. The Pico Rx project is different though. See https://github.com/dawsonjon/PicoRX There a Raspberry Pi Pico does all the hard work of an SDR in software. It uses minimalistic front-end circuitry (a set of analogue multiplexers to act as an IQ mixer and some frontend filters) and uses the on-board circuitry of the Pico itself for the rest, including A/D converters and the I/Q oscillator signal generation. This circuit gives you a capable all-mode HF receiver (0-30 MHz), optionally with a spectrum display. All the DSP stuff is done on the Pico, which is a fairly powerful dual-core 32-bit microcontroller in its own right. The radio can run on batteries and draws little current.

  • Should DAB be on portable shortwave radios?

    At least since the 1970s, portable world band radios have covered the FM broadcast band (and of course mediumwave). People would purchase a radio to listen to shortwave broadcasts when on holiday, but they could also use it as a normal radio while at home. Back in those days there was no internet and international phone calls were prohibitively expensive. Shortwave was often the only viable way to receive information from your home country.when you travelled abroad. Some countries even ran a service to alert specific persons about an urgent situation at home, like an unexpected death. Radio Netherlands was such a station and my father and I were very keen never to skip this broadcast for a single day.

    The market for shortwave receivers has decreased and shortwave listening has shifted from the broadcast bands to the amateur bands. There are far fewer stations broadcasting on shortwave and the ones that remain are mostly either religious propaganda or China Radio International. In the western world. any interesting broadcast could be listened to more conveniently via the internet.

    But as any avid shortwave listener knows, you do not listen to shortwave broadcasts just to get the information, but for the thrill of receiving a signal from a great distance, especially if that signal was not supposed to reach you at all. For example if a religious broadcaster beams from Australia to India, but the signal takes the next hop and reaches Europe too.

    If you live in an apartment with no real possibility to have an outdoor antenna, portable radios are the way to go. Even a nearby park in your home town gives you better reception than when you are at home.

    None of the world band radios currently on the market has DAB+, but I think it should be included for the following reasons:

    • If it was a good idea back then to have FM, why shouldn’t we have DAB+ on today’s world band radios? It’s the main broadcast band in many European countries.
    • Some EU countries (but not The Netherlands) have laws that require all broadcast receivers to support digital radio. Apparently this is not widely enforced for shortwave radios, but why can’t we just have DAB+ on some of these radios anyway?
    • Nearly all DAB+ radios also receive FM, but it is almost always implemented very poorly in terms of usability. One of my Sony DAB+ radios has excellent FM reception, but it mutes for over a second when you tune, even if just one 50 kHz step. This makes it impossible to explore the band by manual tuning. Some other radios refuse to stop on a station that’s too week, but they could hear the station if you do manage to get on that frequency eventually. The least thing we need is a DAB+ radio where the FM band can be manually tuned the same way as on traditional radios. And how much more DX-friendly could we make the DAB-side of things? In terms of manual tuning and useful information to identify a multiplex?
    • When I’m actually travelling, I would want to pack one radio and have coverage of both local DAB+and the other bands such as mediumwave, shortwave and FM. Plus SSB on the amateur bands.

    There are reasons why DAB+ isn’t included on world band radios:

    • DAB+ is only a thing in Europe (and not even in all EU countries) and a few select other countries like Australia. It’s not used in China, where all manufacturers are and not in the USA, where China’s biggest export market is.
    • Radios made by Tecsun (the largest manufacturer), have a numeric-only display. A DAB+ radio needs to be able to display station names. Tecsun radios don’t have RDS on FM either, even if they contain a tuner chip that demodulates the RDS bitstream..
    • Some radios do have 14-segment displays for station names (like the Sangean ATS-909x), even some DAB+ radios do, but for serious DAB+ support you are practically required to have a matrix display. Matrix displays require a more complex CPU to control them and they cannot stay on while the radio is off. Many portable world band radios display the time when they are off, which is very practical when you use your travel radio as an alarm clock. The CPU needs very little power to maintain a 7-segment display.

    There is a whole cottage industry in China that produces longwave, mediumwave, shortwave, FM receivers based on the Si4732 or TEF6686 tuner chips, combined with a colour matrix display and an ESP-32 microcontroller. Some of these have numeric keypads, some of them have airband coverage and some combine the Si4732 (that can do SSB) and the TEF6686 (that has better overall AM and FM reception) in one radio. Some of these designs are open-source. There is a separate open-source design based on the Si4684 that receives DAB+ (even though the chip can do FM, this is not enabled). There are SDRs based on the Raspberry Pi Pico, that can receive 0-30 MHz in all modes with little more than a Raspberry Pi Pico, some analogue multiplexers and frontend filtering.

    The chips exists, the designs exists, so why shouldn’t some hobbyist throw an Si4732 and an SI4684 in one box to create some half decent world band radio with DAB+? Or turn the Raspberry Pico Rx into a capable receiver for 0-30 MHz and pair it with the Si4684 for DAB+ and FM?