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AM stereo turned off at 2BL

The ABC AM station 2BL/702 switched off broadcasting in stereo a couple of months ago. The situation is dire. Virtually nobody broadcasts in AM-stereo any more.

Spectrum is so scarce. Not maximising what we can do with what is available is such a travesty. Given all the work SILICON CHIP and EA contributed to the format, I was hoping you might have a few ideas about raising profile and getting some publicity.

Mike Ryan,
via email.

Comment: since 2BL is mainly talkback, they probably figured that no-one would miss AM stereo.

Another solution for SPAM email

Since I am plagued with between 40 and 50 spam emails a day, I was interested to read 'What You Should Do About Spam' in the September 2002 edition. However, you did not mention the solution that I and other heavy SPAM recipients have adopted in order to live with this problem. We have installed a front-end or pre-processor program to our mail readers.

In my case, I use Mailwasher from which I bought for $US20. It has proved to be money well spent.

Mailwasher downloads ONLY the headers of all email waiting for me on my ISP. I then check a Blacklist box for any obvious spam. Email I want to receive I add to a Friends list. Emails I am unsure about I can click on the header and the body of the message will start to download to the screen.

With practice one can judge within seconds if it is a real message or another 'I have $US32 million trapped in a Nigerian Bank and I will give you 35% if you help me to get it' type email. Clicking the Blacklist box stops the download.

One can add wild cards to the Blacklist List to trap obvious spam variations like and There is also a Filter capability.

After vetting, one 'Processes' the emails. Blacklisted emails are bounced and deleted. Genuine emails are down-loaded. In this way future emails are preprocessed with my Blacklist and Friends Lists. Friends do not appear in the listing while the Blacklisted ones appear for my reconfirmation.

I do not see that one can stop email spam the way one can totally block junk faxes. Spam email is worldwide and I regret I cannot see any of your proposed solutions being effective. Preprocessing email is just part of my routine to read my email. It is a price one has to pay for living in an Internet world. Spam does not get me angry or frustrated. I never see it beyond the headers.

Peter Crowcroft,
DIY Electronics, (HK) Ltd,
Hong Kong.

Long-term EA reader changes over

After EA changed their format, I pulled out when my subscription ran out and emailed them to say they wouldn't last. While talking to a friend with similar views recently, I did a check and found that my words had come true!

We are both around the 50-mark and dedicated technicians of the old school - both deriving an income from this trade incidentally!

Whilst I had continually heard of SILICON CHIP magazine, I had never bought a copy, and so I find it amazing that you guys have taken over the complete history and are continuing on with the very type of publication that has been going for Donkey's Years that satisfies people like us!

I have immediately taken out a subscription but only for one year, 'cos I don't trust anybody any more! I have every hope that your publication will satisfy us - of course, I'll soon let you know if it doesn't!

Thanks, guys. People like us will thank you for your efforts and I hope will support you with input, etc. I certainly hope to supply some input when I have had a chance to enjoy your product.

Rick Boston,
R B Electronics,
Warooka, SA.

Comment: thanks for your qualified endorsement. We have long been frustrated by how long it has taken EA's dissatisfied readers to realise that there was an alternative - us.

SILICON CHIP has now been running for over 15 years and yet there are many people out there who have never bothered to even pick up a copy. If you know someone who would appreciate SILICON CHIP, please put a copy under their noses!

Support for fuel cell project

Just a follow-on from Jacob Westerhoff's email to the editor in the September 2002 issue. I wish to add my support to his suggestion for SILICON CHIP to come up with a prototype fuel cell project.

Australia is not taking this technology seriously and therefore falling behind in providing the next generation of scientist and engineers a look into a small part of our future using this cleaner source of power generation. The USA and Europe are putting millions of dollars into fuel cell technology and research, to bring about change to our present internal combustion engine.

There are experimenters' type fuel cell kits in the USA and UK but the exchange rate makes them very expensive. Therefore I agree with Jacob that SILICON CHIP should do a follow-up article by providing links to where an experimenter can purchase the parts needed at reasonable cost and start up a technology and experimenters' page.

Chris Lock,
via email.

Likes change to nanofarads

Well done on changing from .0047μF to 4.7nF, etc. It is certainly easier to use, especially when you have to write or type the values out. By the way, will you be moving to get rid of the decimal point. For example will you be changing from 4.7nF to 4n7?

I was always led to believe that decimal points can be a problem when printed and then copied a few times. Sometimes the decimal points can get lost in the printing process, making values hard to read or at worst, be incorrectly read as a different value. I came across this problem many times when I used photocopies of photocopies of circuits with small print.

I guess though in such a clearly drafted magazine as SC that should not be a problem.

Once again a great issue and I particularly found the article on the Barlow Wadley receiver extremely interesting. I have a Yaesu FRG7 which works on a similar system and performs very well. I pity the poor repair person having to follow the circuit of the Barlow Wadley; it is drawn in a non-conventional style to say the least!

Leon Williams,
via email.

Comment: at this stage we do not plan to eliminate decimal points from component value labelling on circuits and other diagrams. While many people like that approach, it entails yet another hurdle for the beginner to overcome.

Environmentalists are ranting

After Ross Tester's farcical article in March 2002 on solar power, I was very close to writing a letter taking him to task over his preposterous statements. Apathy prevailed, although I was pleased to see a number of readers did respond.

Upon reading your October 2002 editorial referring to the "doom and gloom" greenies, SILICON CHIP's attitude toward any environmental cause can be summarised along the lines of "As long as it doesn't affect our comfortable lives or cost a couple of cents more, all well and good, otherwise it isn't worth the trouble or cost". It is a position that I am saddened and surprised by, given the scientific mindset that you and your colleagues would most likely share.

As you wrote, the likening of the economy to an amplifier is not new. In fact, it can be extended to encompass the effects of human technology as a whole. Take for example our production of food. From foraging and hunting, the burdening of beasts for tilling farms freed us from manual labour and greatly increased food output. The time that was freed allowed research into other pursuits which (among other things), gave us the industrial revolution.

Today, it takes only a handful of people to fell, sow, irrigate and tend to great swathes of land. The vast majority of the population is fed by the labours of a relative few. An impressive amplification indeed.

Similiarly, however, our industrial inputs and outputs (both useful products and waste) have magnified with time. Keeping in mind the Earth's biosphere is a finite source and a finite sink, the positive feedback of this system will eventually hit a limit. Conventional economic thinking doesn't recognise these limits and assumes consumption can continue unabated. The environmental movement recognises these limits and seeks to place some negative feedback into the system by maintaining the health of the biosphere which ultimately supports us.

You rejoice in the fact that our lives and economy have improved in the last 30, 40 and 50 years. This is only a tiny fraction of the amount of time it has taken for the earth to generate the petrochemicals, coal, timber and other resources on which our whole economy is hinged. Some resources are renewable (eg; fisheries) however we deplete them at rates far in excess of the natural restock rate.

Unless we are careful, it will take only a further fraction of geological time before we have consumed all "banked" resources and are forced to take only what can be sustainably restocked. Our current economically enriched lives will become a curious and fleeting moment in history.

As publishers of a magazine, I believe you have a duty of care in the views that you present and the influence it wields. I would highly recommend that you read "Naked Ape to Superspecies" (ISBN 1865081957) by David Suzuki. It may help you understand why the greenies are "ranting".

Ben Haszard,
via email.

Comment: if you had read all the Publisher's Letters going back 15 years, and further back in "Electronics Australia", you would know that we have deep concerns about the environment. However, we do not resile from our March 2002 article on solar power.

Moving goal posts on the auto ammeter

Thank you for the magazine. It is much appreciated and read from cover to cover when it arrives.

I noticed in the October 2002 Circuit Notebook pages a clamp used in a DC auto tester and wonder if the same principal can be used in the June 2002 ammeter. This would then enable the tester to be much more portable and used in a commercial application. If so, would calibration settings still be the same? Someone always wants to alter the goal posts, don't they?

Bob Hocking,
via email.

Comment: yep, people are always moving the goal posts. In principle, since both circuits used the same Hall Effect pickup, the clamp idea should work with the June 2002 circuit. Wish we'd thought of it.

Amateur radio articles wanted

I would like to support the suggestions made by G. J. Wilson in October's edition of SILICON CHIP, regarding radio-related articles. I realise that radio and scanning related topics are not everyone's cup of tea. This has obviously been proven by the demise of any related magazines as well as the lack of new people taking on these hobbies, but if we all sit back and watch it happen it obviously will.

It is no secret that the Internet has taken the gloss away from Amateur Radio. After all, what young person would want to endure the stress of studying and sitting for an Amateur licence when they can just jump on the web with only the most basic computer skills. And the cost involved now in purchasing a scanner capable of being able to follow the trunking network for a lot of people would be over the top.

But SILICON CHIP could from time to time run related articles. This could spark the interest of people that previously had no knowledge of these hobbies or simply had overlooked them. It could even rejuvenate interest in people that have long ago sent their equipment to retirement into the back of the wardrobe. And nothing can strike up interest like a review on some new piece of equipment.

P. R. Dawson,
VK5NCM, via email.

Comment: have a look at the article on the simple VHF FM/AM radio in next month's issue.

Placement of padder capacitors

I believe that Rodney Champness is largely correct in his response to Stan Hood about placement of padder capacitors (page 85, October 2002 issue). Not only 'Radio & Hobbies' but also 'Radiotron Designer's Handbook' generally put padders at the earthy end of the oscillator coil secondary. They were also sometimes put at the top end of the coil but in such a way that the grid capacitor was connected to the fixed tuning capacitor plates; never as shown in the Tasma circuit.

I suspect that the reason was that it made dual (or more) wave switching simpler because another set of contacts would have been needed for the extra padder(s). I have a vague memory also that the early variable padders were made in such a way that it was convenient to earth the adjustment screw side to avoid capacitive disturbance during alignment.

The 'Colpitts' argument is really a bit of a red herring because that circuit uses the capacitance divider to achieve the phase rotation necessary for oscillation whereas the oscillator coil uses the transformer action of the two windings to achieve that result.

The reason the Tasma circuit is so effective is that the full voltage developed across the oscillator coil secondary is applied (via the grid capacitor) to the grid of the mixer. Any other arrangement must result in a (probably variable) voltage divider effect with the distinct possibility that oscillation will be less reliable at the low-frequency end of the band.

In my early days, it was standard practice to replace the mixer when 2FC could not be received although it was sometimes possible to postpone the inevitable by tuning higher up to get the oscillator working and then inching back to the desired lower frequency. Nobody that I knew then used the Tasma trick as a cure.

Alan March,
via email.

Cable modems vulnerable in thunderstorms

As a cable modem user I am worried about the high incidence of damage to cable modems caused by lightning strikes. I am told that the cable system of Telsta Bigpond has no protection. During a recent mild electrical storm in the Brisbane region, a very high percentage of cable modems were destroyed.

I am hoping that in the near future somebody might publish a device to add into the cable to prevent such incidences from happening.

Derek J. Gratz,
via email.

Comment: there are power boards with surge and phone line protection (eg, DSE Cat M-7868 for $39.80) but these do not protect cable modems. The only foolproof method of protection against lightning strikes is to disconnect your computer and modem from the power and cable socket - otherwise the modem is the meat in the sandwich.

Even if there is no direct hit on the lines, a distant lightning strike may raise the earth potential of the exchange sufficiently high to cause a modem breakdown when it is earthed locally via the mains. Of course, the computer itself is also at risk.

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