LP Doctor’s input stage

Paint me shocked or have you people learned nothing in your years in the magazines? Look at your RIAA preamplifier in your LP Doctor (January & February 2001). Is anything wrong with it? The variable impedance of the RIAA filter will be reflected into the input, the cartridge! Result equals distortion!

The only cure that I know of is to interpose an amplifier between the filter and the input socket. For a test, try a source follower in that place and listen to the improvement! David Tillbrook wrote of this with his Series 5000 preamplifier (ETI, July 1981). This was a seminal article in the annals of hifi.

Bob Phelps,
(via email),

Comment: the input impedance of the LP Doctor is 50kΩ shunted by 100pF (plus input cable capacitance) which is close to ideal for the majority of magnetic cartridges. The RIAA feedback network does NOT reflect back to the non-inverting input stage. The result is low distortion, as measured.

Tips for dubbing onto CDs Let me compliment you on the LP Resurrection article in the January 2001 issue. It provides comprehensive coverage on what is an extremely complex topic if you really get into it. I have a couple of points which might assist readers when using the various pieces of software. When using Adaptec CD Creator, it is essential to use the "Disk at Once" option. This allows CDs to be played on those players which have any type of anti-shock memory system; ie, in a car or a portable. Using the other options will enable disks to be played on the majority of home decks but not on those with memory as mentioned above. When the other options are used, these players just sit there after the first track and wait for you to press the track advance button to proceed through the disk. Not using this option can also cause a "glitch" when changing tracks if the CD is played back on standard CD players. It could be the closing of the disk or the fact that the laser turns off between tracks that causes this (I believe it is due to the latter). The other point that your readers should be aware of is that when using SoundForge 4.5, the minimum graphics card memory is 8Mb. Less than this causes the audio to stutter when playing the wave file at some magnifications. SoundForge also requires a reasonably fast PC, say a Pentium II 333, with 128Mb RAM to really fly properly. This kind of system is a bit "old hat" now but still adequate for most applications. If you have the hard drive space available I’ve found it preferable to record the whole side of the LP at once and then split it up after level matching, EQ, etc. This enables you to find the loudest point on both sides of the LP and gain match each side appropriately so as not to go over the magic 0dB level. Doing this keeps both LP sides level in relationship to each other throughout all the tracks rather than one track at a time. Brad Sheargold, (via email).

C too difficult for PIC programming

The PIC Programmer & TestBed in the January 2001 issue is an excellent idea, providing the hardware options required for simple program testing. However, using the MPLAB all-inclusive software (free) might prove a bit too much for beginners, who have no experience with assembly language or the ‘C’ language.

Assembly coding is always a bit tedious and it is usually better to use a "user-friendly language" compiler. My introduction to the PIC world was through the BASIC Stamp modules, which provided user-friendly programming and were very simple to use. Unfortunately, these units are relatively expensive and so I use the PIC16F84 for small projects.

My programming board is a kit obtained from Jaycar (Cat KD-6062), which connects to a PC parallel port. I use the PicBasic Compiler, which has an enhanced version of the BASIC Stamp1’s programming language. This software is from MicroEngineering Labs and came from Microzed Computers.

The creation/editing of programs is done using any text editor, using filenames with the .bas extension. Simplest is the DOS Edit screen, which can be called from within Windows by using Start/Run Edit.

The actual encoding of the PIC is achieved using the "P16PRO Light" software, a free download for home users, at www.allofmaine.com/picprogrammer/#p16prolight. This is a DOS program but it is easy to use inside Windows, opened from the desktop using a shortcut icon.

The compiler, P16PROL, and all associated files are held in one directory and the compiler is called using the Windows Start/Run facility (Start/Run: "C:\progra~1\pbc\pbc filename"). This will produce .hex and .asm files from the original .bas file.

The only real downside to using the PBasic Compiler is the lack of Debug support, as is available in the Stamp1, but this is not a problem with simple programs. I usually sort out any problems by setting up temporary software traps outputting to I/O ports (eg, operating LEDs).

The PBasic Compiler also allows sections of Assembly language to be inserted inside the program. It supports the Basic "Peek/Poke" commands and read/write of external serial EEPROMs. Although it was necessary to pay for the compiler ($A132), it has proved to be a good choice.

Ken McCarroll,
(via email).

Biorecognition accuracy and security

Your article on biorecognition in the January 2001 issue was interesting but very light on technical information. Whilst it lists 10 different biometrics, it only describes (fairly briefly) two of them.

One critical area that the article failed to address is the accuracy and reliability of the different techniques. Biometric authentication can fail in at least three different ways: false negatives (incorrectly denying access), false positives (incorrectly allowing access) and the probability of two people having the same biometric signature (especially in the case of identical twins). Providing an acceptably low error rate is a major impediment to the wider deployment of this technology.

The claim that the device is secure against penetration because it can’t allow access if it is ripped off the wall also fails to address electronic penetration. As a networked device, it (and the master database) also needs to be secured against unauthorised access from other devices on the network. The provision of modem access just expands the opportunities for an unauthorised person to gain access.

Finally, a quick comment on your wireless LAN article in the same issue. Whilst wireless LANs have many benefits, security is (in general) not one of them. Radio waves do not recognise corporate boundaries and by default most wireless LANs will allow any suitably equipped PC to join the network. Do you really want someone across the road reading (or even changing) the files on your network?

Peter Jeremy,
(via email).

Comment: although not mentioned in our article, the wireless LAN described uses frequency hopping technology and, for even greater security, also allows you to encrypt transmissions.

Informed enthusiasts have always done their own wiring

I’ve been reading the opinions concerning the electrical licensing debate with great interest and entirely agree with what you have said on the matter.

Brian J Spencer’s letter in the January 2001 issue appears to suggest that an increase in electrocutions and fires will result if the present regulations are scrapped.

I fail to see any reason for this, simply because ‘non-qualified’ people have been doing their own wiring since electricity became available for domestic use, and they will continue to do so.

It’s the same with other services like phone and water. Go into the house of most electrically/electronically minded people and there’s a good chance that the phone and mains wiring has been modified and not by ‘qualified’ personnel either.

The reality is that most of these jobs are of good workmanship and pose no threat to safety. Of course, you do get some really dumb mistakes, particularly with light fittings because of the loop connection, but in these situations the would-be electrician gives up and does in fact call an electrician to sort out the mess.

I have read more overseas electronic magazines and DIY books than I can remember and it is normal for the homeowner to legally do their own wiring in most places. It would be interesting to see statistics from the UK and NZ (as they have 240VAC too) to see how the rate of electrocutions and fires compares to Australia.

I somehow think there will be minimal difference because the facts are that people will continue to do their own wiring if they feel knowledgeable enough to do so, whether it’s legal or not.

Most people do have a fear of touching any wiring and rightly so, if they don’t understand it; for these people, having someone qualified to do the job will not change.

John Hunter,
(via email).

The New Zealand electrical wiring experience

I was interested in your editorial in the November 2000 issue in that anyone should be able to do their own house wiring, quoting the NZ experience. Over here they realised that in allowing one to do various electrical jobs around your house they still required you to get the work checked by an Electrical Inspector before connecting to the 240VAC supply and before a Certificate of Compliance is issued.

We are also allowed to do limited plumbing work but not drain laying or connecting to the sewer, etc. Also there is some talk of allowing suitable applicants who are not in the relevant trades to obtain a limited wiring certificate or something similar to enable people who meet the relevant criteria to do electrical work legally.

W. Davis,
Auckland, New Zealand.

The WIA in the 21st Century

For some time I have been concerned that the Wireless Institute of Australia (WIA) as it is currently structured does not, and cannot, work in the best interests of radio amateurs. To promote discussion and initiate change I have prepared a paper showing why the WIA’s current organisation is not suitable for dealing with the issues facing Amateur Radio in the 21st Century and stating how it should be changed.

I have held an amateur radio licence since 1966 and have been involved with the WIA at State council level in two states and as a national director.

Since the WIA’s peak in membership of over 8000 in 1982 there has been a steady decline to about 4500 members. This decline has occurred while there has been recruitment of new members. The WIA organisation seems unwilling to face the problem.

Blame is attributed to external factors such as a declining interest in Amateur Radio. The facts are that more radio amateurs have left the WIA since 1982 than are currently members!

Motions to change the WIA at Federal Council have been defeated. The last was not even allowed to be discussed. If the elected officials of our organisation are unable or unwilling to make the necessary changes then the members themselves must make their views known.

The organisation has become negative and defensive with no real goals and objectives. People who have a vision of bettering amateur radio find themselves frustrated. The WIA office is still in Melbourne yet we deal with the ACA based in Canberra. One of the smallest allocations in the WIA budget is for ACA liaison. A strong national approach is required if Amateur Radio is to continue far into the future.

Martin Luther, VK5GN,
Willaston, SA.

The detailed paper is available via email from luther@mail.mdt.net.au or at http://www.alphalink.com.au/~parkerp/wianat.htm

In defence of Vintage Radio I have had an interest in vintage radios for some time now and find restoring the great old radios a rewarding pastime. If it wasn’t for people like myself who take the time to restore these radios how would our younger generation understand where modern technology has come from? This is all a part of our history and we all seem to want to learn about our past. If you don’t believe me, then why do we have museums, antique collectors, restorations and people tracing their ancestry, etc? If vintage radio is old hat, then why do some of the younger generation come to me for advice and assistance in repairing various items? I’ve got my favourite old hat and I wouldn’t get rid of it for quids! Leo, it wasn’t that long ago you were telling us not to throw those old black and white TVs away as in 20 years or so the young people won’t know anything about them. I agree with your views on this. K. Lang, Esperance, WA.

Vintage Radio is important

Your correspondent Alfred Fischer seems to have missed the point regarding the value of the Vintage Radio pages in SILICON CHIP. To condemn Vintage Radio to the rubbish bin because it is past its "use by date" is to condemn history. Nobody would suggest that we revert to valve technology for current electronic applications but to ignore this important period of our electronic history is to ignore the efforts of the pioneers in theory, design and manufacturing on which much of our modern electronics is based.

If we were to use this philosophy for every field of engineering endeavour that is superseded by new technology, we would have no interest in old cars, aircraft, buildings, etc and an important part of their history would also be lost.

The "revival of corpses" that Mr Fischer refers to is in fact the preservation of important examples of Australia’s and the world’s electronic history.

It should be remembered that from the early 1920s to 1975 Australia had a vibrant radio, and later TV, manufacturing industry with over 50 companies at its peak employing many thousands of people. From the earliest days Australia’s isolation ensured that a significant number of developments in the field of radio were "home grown".

With over 900 members, many of them SILICON CHIP readers, the HRSA is active in promoting the preservation and restoration of these important examples of our electronic heritage. The valuable information contained in the Vintage Radio pages of SILICON CHIP and other magazines encourages newcomers to the hobby and helps to awaken an awareness in others that we should preserve, rather than scrap, as many examples of radios of the period as possible.

I would like to extend an invitation to Mr Fischer to attend one of our regular meetings and see for himself that there is more to Vintage Radio than he may think.

Warwick Woods, President,
Historical Radio Society of Australia Inc.

Rodney Champness has his say

Alfred Fischer’s email in the January 2001 "Mailbag" is provocative. Certainly he is entitled to his view and by expressing it, he may invoke others to really think about their interests in all sorts of things. However, I’d like to put a few points in favour of Vintage Radio and other historical interests shared by hundreds of millions of people throughout the world.

Should we pull down all the magnificent castles and cathedrals in Europe? Should we use the rubble from the great pyramids of Egypt to make a new highway along the Nile valley? While we’re about it, how about using all of the vintage and veteran cars as land fill or perhaps melt them down to make tower cases for computers? Isn’t this what Alfred Fischer would have us do with our history and heritage?

Certainly, I write the Vintage Radio column but I do have other interests in the electronic field. I work with computers, programmable logic controllers, ICs and transistors, MF, HF, VHF and UHF equipment, satellite receivers and (would you believe it?) valves. I am a great believer in appropriate technology and although valves are used in very few things these days, they are still used.

However, solid state is more appropriate in 99% of applications these days. I have just been asked to design and build an electronic timer for feeding liquid fertiliser into an irrigation watering system. It never occurred to me to use valves, as three ICs and a few transistors will do it all.

I don’t agree that vintage radio is about the revival of corpses. It is about the evolution, social activity and history of radio in its various forms over the last century. It is about getting to know how valve radios (and transistorised ones too) worked, generally having fun doing it and being proud of what has been achieved.

Just think how our ancestors designed things – have a look at the old engineering text books; it is incredible to see how things were done when, comparatively, resources were so limited.

The point is we can learn much from our history whether it be vintage radio, vintage cars or what have you. By looking at history we can adapt some of the old ideas and by using new components we can achieve the best of both worlds.

Rodney Champness, VK3UG,
Mooroopna, Vic.

Computer parts should be saved

You suggested in your magazine not so very long ago that older computers that are no longer being used should not simply be dumped, if at all possible, as they can provide a useful source of spare parts. How right you were.

Recently, I was in the middle of a session on a fairly new computer when I got that dreaded message that says, in effect: "Somebody had done a naughty thing and this computer will shut down" The cause of this catastrophe turned out to be a defunct CPU fan and hence an overheated CPU. The computer was only a little over 12 months old (just out of warranty). The computer down-time plus replacement costs of a rather expensive part was averted thanks to your advice.

I had saved some parts from an older computer, including the power supply fan. The CPU fan was a 50mm type compared with the power supply fan which is an 80mm type so obviously I could not simply replace one with the other. To solve this problem, I made up an adaptor from fairly thin aluminium to mount the 80mm fan on the CPU heatsink. The computer has been running happily ever since.

H. Nacinovich,
Gulgong, NSW.