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Test Master origin revealed
I was just browsing the March 2021
issue and I found an item that made
me very excited. On page 18, in the article on Urban Electronic Archaeology
(siliconchip.com.au/Article/14773),
there was an ‘apparatus’ called a “Test
Master”. I made this thing! I was a
third-year apprentice/trainee tech
with Telecom in 1984. This was one
of the big projects we all had to complete as part of our apprenticeship.
We had to cut and fold the mild
steel base and lid, drill all the holes
and populate the PCBs. The lid and
base were anodised off-site.
Every hole had to be precisely located, or we would have to start over. No
one dared muck it up. The wiring had
to be accurately laced as lacing cables
would be, for many of us, our bread
and butter when we qualified. It had
to be perfect.
I still have mine in my garage, slightly the worse for wear though, and I still
occasionally use it.
I cannot say for how many years
this was part of apprentices’ training,
but even when I was building it, I felt
pride that I built it just about from
scratch. At the time, there was some
discussion about whether we should
have made the PCBs from scratch (they
were premade).
Ahh, great memories!
Tony O’Halloran
Former tech, Telecom/Telstra,
Healesville, Vic.
More details on the Test Master
In the March 2021 issue, you had a
great article on hoarding by Dr David
Maddison. One piece of equipment
he found was a “Test Master”, and
he was wondering about the origin of
the device.
Any Telstra technician who did
their apprenticeship at the Tooronga
training facility will immediately recognise it. It was built as a training ex4
Silicon Chip
ercise by many apprentice electronic
technicians.
It taught metalwork, soldering, basic electronic theory, circuit reading
and much more during the construction. Including, yes, cable lacing; considered an important and useful skill
back in those days.
I made my “Test Master” in the early-to-mid-80s, and it sat on my hobby
desk, actually being used for many
years. It’s currently packed away in
a box after a move a couple of years
ago, but was still occasionally used up
until then. I hope this information is
useful, though no doubt plenty of other ex Telstra techs will write in with
similar stories.
Peter Tremewen,
Drouin, Vic.
Very high-quality AM reception
with DAB+ radio
I am writing again with what will
probably be the last update of my alternative AM/FM/DAB+ radio code,
described in the Mailbag section of
the October 2020 issue (January-March
2019; siliconchip.com.au/Series/330).
I received a lot of feedback and suggestions from my friend Ingo Evers
and have added a fair number of new
features to the earlier version, and resolved many of its problems.
It was helpful working on a project
like this with a friend, because we have
each found and fixed small problems
with the way we constructed our radios. And by seeing the same unexpected behaviours on two independent radios, we have noticed and corrected
some software problems.
I’m motivated to share this update
because we made a surprising discovery. A few weeks back, Ingo was
lamenting that AM quality on this radio was not up to the standard of his
other receivers despite great DAB and
FM performance. I agreed that I felt my
radio’s AM was the same.
Australia’s electronics magazine
But then I remembered from earlier
in the lock-down when I was studying
the radio chip’s programming guide,
there was an AM setting for changing
the audio bandwidth.
I went back to the data, found that
setting, and saw that the radio chip
defaults to an AM audio bandwidth
of 3.5kHz, which is barely equivalent
to an analog telephone.
You can easily change this setting
in multiples of 100Hz. A quick experiment showed that the Silicon Chip
DAB+ radio is more than capable of
astonishing AM fidelity, and I was
surprised in a good way.
Now we can say even more than
earlier that the radio is capable of providing a superb sound quality through
a decent hifi setup, and we are even
happier than we were with how the
project has turned out.
The latest version of my revised
software lets you configure the AM audio bandwidth on a station-by-station
basis, from the radio’s minimum of
1.5kHz (which sounds rather muffled)
up to its maximum of 10kHz (which
sounds almost the same as a welltuned FM station). You can change the
audio bandwidth in near real-time, so
the improvement is very noticeable as
you wind it up.
I had always assumed that the audio
bandwidth of Australian AM broadcasts was just 4.5kHz (half of the 9kHz
nominal channel spacing), and that
this was the reason for the muffled
sound we have all become accustomed
to over the years. Clearly, that is not the
case, and Australian AM broadcasts
are transmitted with at least 10kHz of
audio bandwidth.
When I searched for information
about how much audio bandwidth
Australian AM broadcasters are permitted to utilise, I could not find the
answer. It would be interesting if you
can find out.
I had also assumed you’d hear a
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Silicon Chip
I never cease to be amazed at the geographical diversity of Silicon Chip correspondents and contributors. The
March 2021 issue is a good example.
The Circuit Notebook section contained contributions
from Sofia, Bulgaria; Paraná, Argentina; Oran, Algeria;
and Capetown, South Africa. There was also a letter in
Mailbag from Singapore.
A quick look at recent issues showed contributions
from Dunedin and Hukerenui, New Zealand; Cambodia;
Vindhyanagar, India; Tehran, Iran; and Hetauda, Nepal.
Designs from Sofia and Tehran are prolific, and perhaps warrant a short biographical story on each of these
clever circuit designers.
To me, this indicates the worldwide appeal of Silicon
Chip content.
Peter Johnston,
Merimbula, NSW.
Average speed tracker needed
Prices are subjected to change without notice.
6
9kHz squeal if the receiver’s AM audio was not severely
band-limited. I guess that unlike traditional analog receivers, digital radios don’t have that problem. It would
be great to explore that more.
This (maybe) final version of the alternative software
implements almost all of the features of the original Silicon Chip software, and several more. One of the many
changes in this version is a new infrared remote control
configuration file, to make it easier to use any remote
control device without modifying the BASIC program.
There are also now optional favourite buttons on the
main screen; the in-built speaker is supported properly,
there’s a mute function, it is much easier to customise the
colour scheme and so on.
As the code size grew, Ingo complained to me that it
would no longer fit into his Micromite. I discovered that
the Linux “CRUNCH” script that I’d been using actually
generates smaller crunched code than the built-in MMEdit
crunch function. The difference is rather significant; the
MMEdit crunched code is maybe 15% larger than the Linux crunching script’s output.
But MMEdit will happily load the Linux-crunched output onto the Micromite, so just load the pre-crunched version into MMEdit and download to the Micromite as you
previously would have done with the uncrunched code.
Cheers, and thanks again for publishing this design. I
think I’ll screw down the lid of my radio now and move
onto the next project!
Stefan Keller-Tuberg,
Fadden, ACT.
Comment: we appreciate all the effort you’ve put into this.
Legislation determines that an AM radio broadcast can
be nominally flat to 7kHz, and while it can extend past
9kHz, it must be attenuated beyond 9kHz. Therefore, a
receiver bandwidth greater than 9kHz may improve the
resulting frequency response.
The supplied software is freely available for download
at siliconchip.com.au/Shop/6/4940
As usual, I’ll start by saying that Silicon Chip is a great
magazine. I used to be a subscriber, but I like going into
newsagents and browsing. Some Australian magazines
have been lost lately (for example, Australian Model
Australia’s electronics magazine
siliconchip.com.au
WHAT IF WE COULD STOP DISEASES
BEFORE THEY COULDN’T BE STOPPED?
The key to beating more illnesses is earlier detection, and ADI’s
precision sensing technology is powering new, ultra-fast disease
testing, bringing us one step closer to a healthier future for all.
Analog Devices. Where what if becomes what is.
See What If: analog.com/WhatIf
Engineering Magazine), and I think
one of the reasons was the low sales
volume. Once it dropped out of the
public eye, the closure was inevitable. I don’t want that to happen to
Silicon Chip.
You recently asked for feedback.
Yes, I don’t read the whole magazine,
but I read most articles. I don’t build
many projects any longer, but I look
forward to what is on offer as I like
the idea of building things.
I am in Bathurst, and recently our
cash-strapped local government has
changed the time/speed/distance cameras to monitor all traffic – it used to
be just trucks – and at the same time
has lowered the allowed error to +3%.
There is one of those machines just
east of Bathurst, in a 100km/h area
for about 26km. The road is virtually straight with no blind spots, some
overtaking lanes, and generally very
safe. Not a ‘blackspot’, so seemingly, this is just a cash-raising exercise.
My idea is to have an Arduino or
Raspberry Pi take GPS data and convert that to an average speed. A large
button could start the process, and
a second press could clear the data,
ready to begin again.
I am not advocating speeding or
unsafe driving, but it is quite easy to
stray slightly over the limit, and the
penalties are severe. A loss of license
would be catastrophic to my ability to
work – yes, at 69, I am still working
and plan to for a few years yet.
Ed Pinder,
Bathurst, NSW.
Comment: You’ll be pleased to know
that we are working on an updated
version of the GPS Car/Boat Computer (originally from April 2016), and
have added this to our list of features.
It should appear in the magazine later
this year. Thanks for the idea!
Compact compass for
Car/Boat Computer
I have used the Micromite LCD
BackPack for many purposes over the
years. Recently, we bought an old Cray
boat with a Sumlog, which was not
reliable. I have replaced it with Greg
Hoyes’ version of the BackPack-based
Boat Computer, which works well.
This version has the best compass; it
works like a gyro repeater and is easy
for navigation.
I have upgraded the code to give a
speed readout in knots to one decimal
place, and it is very reliable.
8
Silicon Chip
I am currently working on upgrading
it to use the BackPack V3. The bigger
display looks more in scale with other
instruments, and is easier to read. But
I came unstuck with the compass card,
as the code is customised to the 2.8in
screen. I am having some difficulty
modifying this code to work with the
3.5in screen, as it is not documented
and uses lots of constants.
Ross Munn,
Paynesville, Vic.
Comment: we agree that this compass
card style is useful, so we have added
support for it to our new GPS Car/Boat
computer, which also uses the 3.5in
screen and will be described within
the next few months.
Advantages of DIY electronics
The request to comment in your
Editorial Viewpoint, January 2021, is
much appreciated. I am a long-time
reader of your magazine, and for over
60 years I have built my own electrical
equipment and continue to use many
past projects from Silicon Chip and
other magazines that no longer exist.
I live off-grid in a remote location,
and have built my own power supplies, mainly from salvaged materials
at a fraction of the cost of the commercial alternatives.
I have a bias towards building my
own gear which I can repair myself,
as I have to drive around two hours
to where I can purchase replacements
for anything that fails.
I believe that some of my projects
work much better than the commercial alternatives. For example, I get
almost twice the usable power from
my solar panels, so don't need anywhere near as many.
When I went to tech school in the
early sixties, there was a hoard of us
kids who made our own crystal sets
etc, and tried to repair valve radios.
We just went through every copy of
Radio, TV & Hobbies.
L. Ralph Barraclough,
Licola, Vic.
Details about VNG radio shutdown
Thank you for replying to my query
about projects requiring the insecure
and buggy Windows OS; I did not know
about Bootcamp for Mac, so I might
try it (but I see that Windows 10 is
still required). I have tried WINE with
some success on simpler programs, but
things like SPICE need libraries (DLLs)
that are only provided with Windows.
Australia’s electronics magazine
The article on time sources was most
interesting, especially VNG, as hearing its "beeps" is what introduced me
to shortwave listening, thence Amateur radio. Did you know that when
the Western Sydney site was going
to be shut down by the short-sighted
government, the then NSW Division
of the Wireless Institute of Australia
considered running it from its Dural
site VK2WI?
Unfortunately (or perhaps, fortunately), the idea was discarded, as the
power bill would have been prohibitive (not to mention wiping out the
callbacks!).
As for the "talking clock", there
used to be a human one, consisting
of a woman sitting in front of two
clocks with a telephone by her side.
I have long since lost the link to the
photograph.
Dave Horsfall VK2KFU,
North Gosford, NSW.
Information on Philips BX205 radio
Charles Kosina's article on the
Philips BX205 B-01 radio in the February 2021 issue (siliconchip.com.au/
Article/14756) was both interesting
and excellent. It started with some
head-scratching regarding the unmarked dial. I can possibly enlighten him.
It was originally intended for use in
the tropics, which meant Indonesia or
Malaysia in the 1940s and 1950s. Apparently, new radio stations popped
up, disappeared or changed frequency at random intervals. Regulation was
not a strict affair.
All radios destined for the tropics
were fitted with a 'standard' dial layout, having a zigzagged centre line,
sometimes embellished with frequency or wavelength indications. Other
manufacturers, mostly Dutch, also
copied this layout.
Bakelite versions were known as
"Radio Roti" and were mostly transformerless. Yes, exciting times!
Ben Heij,
Caloundra, Qld.
Building a DC-DC battery charger
Being a semi-retired electronics engineer, I have tried to build my own
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the commercial DC-DC chargers are
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nomads’ on a limited income.
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I built mine using a Geekcreit 400W
DC-DC boost converter module I bought
from Banggood for $15 (siliconchip.
com.au/link/ab77).
I found that if I set the output to
14.5V, it would charge the half-discharged camper battery bank (two
100Ah AGM deep cycle batteries) with
the voltage at the Anderson plug on the
4WD showing 12.5V. But it runs fairly
hot at 15A, so it would require a cooling fan if mounted in an enclosure.
I was reasonably happy with the performance of this cheap solution. Still,
I noticed that without the vehicle running, the voltage would drop below the
minimum required for the module at
this load, and the output voltage would
drop. Even when the vehicle was restarted, the output voltage would not
recover until the Anderson connection
was broken and reinserted.
Most commercial DC-DC chargers
have an MPPT solar input as well,
so if that could be incorporated, I’m
sure it would be a very popular project. I know MPPT can be complicated, so perhaps just an input from a
solar charge controller would suffice.
An LCD status screen would also be a
nice addition.
The option of selecting either
lead-acid or lithium-ion type storage batteries of different chemistries
would also be great. Onboard Bluetooth or WiFi could be used to monitor
the charger remotely using a suitable
app on a smartphone.
I hope your technical team will give
some serious thought to a project such
as this. With the explosion of caravan
and camper sales due to COVID-19,
and the popularity of off-road self-sufficient camping, there is a real need
for a reasonably priced DC-DC charger to keep these expensive batteries
in peak condition.
Bruce Hinton,
Cleveland, Qld.
High voltage and current tracking
supply wanted
Here’s a challenge for you. How
about taking the 45V 8A Linear PSU
(October-December 2019; siliconchip.
com.au/Series/339) and turning it into
a bi-polar or tracking supply?
One obvious use of a bench supply
would be to test a power amplifier.
±45V DC at 4A or so should cover a
lot of the power amplifier applications
out there. I’d imagine that a bi-polar
supply is well within your capabil10
Silicon Chip
Australia’s electronics magazine
ities. The trick would be a sensible
modification to the original project. If
that could be done, then serious kudos to you.
Iain McGuffog,
Indooroopilly Centre, Qld.
Easier way to transfer files
to and from Raspberry Pi
I am writing about your article “A
Virtual Electronics Workbench” from
the February 2021 issue (siliconchip.
com.au/Series/357). After installing
RealVNC on a laptop and enabling
VNC server on the Raspberry Pi, Tim
Blythman then describes how to install and use WinSCP to transfer files
between the RPi and laptop. But there’s
an easier way; VNC viewer and VNC
server can both perform file transfers.
To transfer files from the laptop to
the RPi, move your mouse to the top
middle of the VNC viewer window on
the laptop, and a drop-down menu will
automatically appear. Click the centre
icon, which has a left and right arrow.
This is for file transfers. In the pop-up
box, click “Send files ...”, navigate to
the file you want to transfer to the RPi
and double click it. It will appear on
the RPi desktop.
Transferring files from RPi to the
laptop is similar. Move your mouse
to the RPi taskbar and right-click the
VNC server icon. Select “File Transfer ...” from the pop-up box. Click
“Send files ...”, navigate to the file
you want to transfer to the laptop and
double-click it. It will appear on the
laptop’s desktop.
Peter Ihnat,
Wollongong, NSW.
Comment: thanks for this very helpful
information.
Various comments
on the March issue
It was interesting to see the article on Fetron valve substitutes by Dr
Hugo Holden in the March 2021 issue. Late last year, I mentioned the
Fetrons to my ex-Telecom mate. To
my surprise, he told me that Telecom
used them and that he had experience
with them.
Also, Fetrons were not the only
FET-based valve substitute. Earlier
this year, I found an advertisement in
a magazine for another brand of FETbased valve substitutes, but I cannot
remember the magazine or issue. Perhaps another reader will mention it.
I was also happy to see the Battery
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12
Silicon Chip
Balancer project. For anyone who wants a battery system
of some power, this is the solution for balancing the batteries. It is even more desirable for batteries that are charged
from a limited power source. Unfortunately, I suspect that
the SMD parts and their availability will probably deter
some people from it.
It is probably overkill for the small systems that I use.
Also, the processor is not a PIC chip, and that goes against
the project. It is not that I dislike the SAM processors. It
is just that I prefer to use projects which are PIC-based. If
things go wrong, I already have the means to reprogram
it etc. I do not want to invest in tools that I might only
use a few times.
I read Dr Maddison’s article “Hoarding: Urban Electronic Archaeology” with some interest, since his friend
and I are obviously clones. With a deep interest in most
things technical, and the space to store things that might
be useful, it is not hard to gather a large number of items
that are personally desirable, even if others think that
they are rubbish.
I am faced with the same problem that Dr Maddison’s
friend would have faced in his later years: what I should
do with my collection? The beneficiaries of my will don’t
want these items, but at the same time, I do not wish to
dispose of them because they provide me with parts for
my projects etc.
I have asked those who have suggested getting rid of
most of it to please tell me what I will need in the future.
Then, I can dispose of the other things. Of course, prediction is impossible, and the replacement cost of what I
have works against getting rid of anything.
I have been experimenting with Li-ion cells. I have a
large quantity of used but good 18650 cells. To get batteries with the desired voltage and sufficient current capability, I need to connect the cells in parallel and then
connect the parallel assemblies in series.
I am trying to find the limit for the number of cells
in parallel, if there is one. I know that four cells can be
joined, but is that the limit? I have seen websites warn
about connecting cells of different capacities in parallel,
but that makes no sense. I can understand that cells of
different types should not be combined but not ones of
varying capacity.
Cells with different internal resistances will charge and
discharge differently. Still, I would expect that cells with
different capacities would maintain the same voltage, and
hence the same level of charge. However, there might be
other factors involved which are unknown to me.
George Ramsay,
Holland Park, Qld.
Comments: now that Microchip owns Atmel, pretty much
all their chips (including the SAM series used in the Battery Balancer) can be programmed using their software
and the latest PICkit (as mentioned in the article last
month). So the use of that microcontroller should not be
a negative point for the Battery Balancer project.
We agree that if it’s OK to connect two cells of the
same type in parallel, there should be no practical limit to the number that can be combined as such, as long
as their chemistries are identical. It would be a good
idea to use cells of the same age/lifecycle point to prevent one or more from failing prematurely and taking
out the whole pack.
SC
Australia’s electronics magazine
siliconchip.com.au
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