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Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that
Silicon Chip Publications Pty Ltd has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”.
Australia’s history of manufacturing
electronic components
Many people may not be aware of
the extent of electronic component
manufacturing that once occurred in
Australia. We made just about everything necessary at the time, such as
valves (vacuum tubes), resistors, transistors, transformers, etc – even solar
cells.
I recently tried to donate some
examples of discrete Australian made
electronic components to Victorian
museums (some pictured), but sadly,
they weren’t interested. Perhaps a collection should be established somewhere, including a museum collection, as a repository of Australia’s former manufacturing past.
Dr David Maddison,
Toorak, Vic.
Comment: We welcome comments
from readers suggesting a museum
that would be interested in such items.
Perhaps the Powerhouse Museum in
Sydney would want them.
Modifying RF signal generators for
better performance
I am writing regarding the El Cheapo
Modules article on the 35MHz-4.4GHz
Signal Generator in the December 2021
issue of Silicon Chip (siliconchip.com.
au/Article/15139).
I have bought several similar modules from sellers in China – some
standalone synthesizer boards and
4
Silicon Chip
other boards with an onboard microcontroller and an LCD screen. Some
use the ADF4351 or the ADF5355
synthesizer chips, while others use
the MAX2870.
I recommend using the standalone
boards as shown in the photograph
below. There is a mountain of information on interfacing these boards to
an Arduino Uno/Arduino LCD shield
or a PIC microcontroller.
Free Arduino sketches are available
to control the frequency output, or a
HEX file in the case of the PIC microcontroller. This approach gives you
a considerable amount of freedom to
tailor the Arduino sketch or HEX file
to your own needs.
I am currently working on the
ADF5355 standalone board depicted
with an Arduino Uno/Arduino LCD
shield. I have greatly improved the
board’s performance by replacing the
LT1763 power supply chips with the
ADM7150 series (5V/3.3V), which
have dramatically lower noise (1μV
RMS compared to 20μV RMS).
The 5V rail is the one where noise
really matters. Cleaning up the 3.3V
rails had much less influence on the
quality of the RF output.
I am planning to use the improved
board to extend the range of my
RSA3030-TG when examining some
of the higher frequencies, around
4-6GHz.
It is noteworthy that Analog Devices’
very expensive ADF5355 development
board also uses the ultra-low-noise
ADM7150 voltage regulators. The
result is a very low noise synthesizer
– as good as the ADF5355 can deliver.
I would avoid using the ADF5355
Board with GLCD that you can buy
online. Sadly, these boards are just
junk. The outputs look like they have
been modulated with another frequency source – they are extremely
noisy. The ADF5355 ‘black’ boards are
better in noise performance, but you
Australia's electronics magazine
can only realize their full potential by
modifying the power supply.
I am planning to make a control board using just an ATmega328
chip. I will use shielded containers
for both the ADF5355 board and the
ADM7150 power board (5V and two
3.3V outputs), with a very precise
(GPS-
disciplined) frequency standard and perhaps some wideband RF
amplifier modules to make a low-noise
frequency synthesizer that covers the
54MHz to 14GHz region.
This should not be too expensive to
build – probably less than $300.
I have a home workshop complete
with a lathe, vertical milling machine,
metrological instruments and an
assortment of metal cutting tools. I will
be using these to make RF enclosures
for the ADM7150 power board and
the ADF535X frequency synthesizer.
Making quality RF enclosures out
of aluminium stock is not hard, just
time-consuming. However, in retirement, time is what I have in great
abundance.
Samuel Evans,
Hackham West, SA.
R80 Aviation Receiver kit changes
I enjoyed the article on the R80
Aviation Receiver (November 2021;
siliconchip.com.au/Article/15101) so
much that I ordered one through AliExpress. On arrival, I was surprised to
find the receiver, although very similar
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to that in the article, is now at version seven, not six as
described in the magazine.
The circuit has undergone a major revision with the
NE5204 and NE602 front-end replaced with TA2003 AM/
FM receiver chips and other chip changes making a simpler circuit diagram. The PIC controller has also been
moved to the PLL board.
The modifications to the squelch are no longer necessary as the TA2003 chip implements this. The receiver
also includes mono coverage of the FM Broadcast band
for those times you get tired of the endless aircraft movement calls.
All in all, a good kit and easy to put together for someone with moderate skills and knowledge of circuits. The
instructions, supplied on request, are in Chinese, and
you have to work out from the circuit diagram where the
ICs go, as they are different both in type and layout to the
article featured in Silicon Chip.
Nigel Dudley, Denmark, WA.
Comment: see also the letter in the Ask Silicon Chip section of the January issue and Andrew Woodfield’s response
to it. He has provided a translated instruction manual
which we’ve made available from our website.
TV sound levels are all over the place
Thank you for printing my letter titled “Historical articles enjoyed” in the July 2021 issue. I got a great kick out
of finding that you have printed one of my letters in your
very popular magazine.
But reason I am writing in this time is that I’m finding
the sound levels are all over the place in the general television programming. I have a reasonable sound system
that has been built up over the years in my loungeroom.
While we have the level quite low and at a normal listening level, when ads or a news break comes on, the sudden
increase in loudness is quite disturbing.
I know that every television station uses compression to
make the sound level sound ‘the same’ and give it ‘more
punch’, but despite that, the sudden increase in level can
be quite bothersome! It might not be as noticeable on a lot
of televisions, even with a sound bar installed to increase
sound quality.
Changing from channel to channel often brings up
problems with mismatched levels, and one has to readjust the volume then too. Many of the HD channels are
down in level and need adjustment as they are lower in
level than other programming. I think this is to do with
the amount of channels that are transmitted on the one
frequency.
Stephen Gorin, Bracknell, Tas.
Comment: We have noticed the same thing and it is infuriating. There is a simple solution but it would require all
broadcasters and streaming services to adhere to the standard, which would probably be hard to achieve.
Every stream/broadcast/video should have a dB offset
encoded within it; just a simple number, so it should not
be hard to do. This is the dB offset (positive or negative)
needed to be applied to the volume level in a reference
system (representing a decent sound system) to get the
dialog in that program to a certain reference level.
That way, they can still get more dynamic range by
making the dialog quieter, so they can have louder
music or effects or whatever, but then that number will
siliconchip.com.au
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Australia's electronics magazine
February 2022 7
increase. You would then be able to enable a feature in
your TV to automatically apply an offset to the volume
level based off that number. So the dialog in all programs would be at the same level, regardless of how it
is recorded or processed.
This might need to be combined with some sort of compression technique to limit the maximum volume level
(perhaps via a second coefficient).
But we believe this would be much better than the current situation with each program having an arbitrarily
different loudness level.
Another amusing old magazine
I have never replaced any components in it, and it still
gives a perfect picture (from analog signals, of course)
with a slight frame buzz, no doubt due to some of the
electrolytics drying out. It is a hybrid valve/transistor set.
Some time ago, I made a Heath Robinson modification
so that I could receive the US Armed Forces TV, which
was broadcast in NTSC.
I only needed to adjust the vertical hold for the different number of lines and switch in the ceramic capacitor
to change the sound carrier frequency. The simple modification worked perfectly!
Christopher Ross, Tuebingen, Germany.
What a surprise to open the November issue and see
the image I sent in of the portable radio from 1936 (page
8). I recently came across a 1937 issue with the cover
shown adjacent.
With COVID-19 travel restrictions now lifting and caravans coming out again for the summer break, please do
not leave the wife in the caravan cooking bacon and eggs
while motoring to the next comfort stop!
Graham Street, Auckland, New Zealand.
Ultra-LD Mk.4 alternative transistor
Vintage TV is still going strong
My subscription copies of Silicon Chip (it’s a great
magazine) seem to be arriving regularly in Germany now,
albeit around the middle of the month.
I was very interested in your Vintage section on the
Sony TV. I thought it might be interesting to mention the
TV I bought in 1970 (shown in the photo at the end of
this item).
8
Silicon Chip
Your response to the letter from I.P.V. of Karrinyup, WA
(Ask SILICON CHIP, August 2021, pages 109-110) suggesting the IMX8-7-F as a replacement for the now unobtainable HN3C51F got me searching for a closer match.
I found the HN4C51J, which appears to be identical to
the HN3C51F except that the two transistor bases are tied
together (hence it comes in a five-pin package rather than
six), and the pinout is different.
To accommodate the new pinout, the PCB will require
slight modification. First, cut the PCB track between pins
5 and 6 of where the HN3C51F was originally located.
Next, install a jumper between pins 6 and 2 in the original configuration. The HN4C51J may now be installed
with pin 4 of the HN4C51J placed where pin 1 of the
HN3C51F was to go.
Cutting the track between the original pins 5 and 6
should be straightforward. The jumper between the original pins 6 and 2 might be more challenging. The easiest
solution might be to fit the HN4C51J first, then install a
‘bodge wire’ from pin 3 of the HN4C51J directly to the
pad of the nearby 68W emitter resistor.
Mark Fort, Brassall, Qld.
Comments: that should work. We agree that it will be
easier to solder a wire after fitting the part. If doing this,
make sure to cut the track thoroughly. If we revisit the
design, we will adjust it to use this transistor. Having said
that, we think substituting the IMX8-7-F will not affect
performance, and it is a direct replacement with no PCB
modifications required.
More on Digital TV standards
This email was prompted by Bryce Cherry’s letter, published in the November 2021 issue (page 6), regarding
Australia's electronics magazine
siliconchip.com.au
DVB-T2 digital TV and MPEG-4 for Ultra HD TV and
better spectrum utilisation (ie, more TV channels in the
same bandwidth).
I wrote to the Household Assistance Scheme administrators and requested MPEG-4 capability be compulsory, but also to not pay any antenna installer who used
an antenna designed to receive any channel in the range
0-5A, pointing out that there will be no broadcasts on
those channels and the antenna will produce less reliable reception due to noise. Now you cannot buy a new
band 1/3 antenna.
I also have made submissions to Standards Australia
to make MPEG-4 compulsory, not optional.
Examining the specifications for current TVs, it is difficult to see if they support both DVB-T2 and HEVC, which
are needed for broadcasters to transmit Ultra High Definition TV, in competition with the video-on-demand companies. UHD from the internet requires HEVC, but DVBT2 is only needed for over-the-air broadcasts.
If DVB-T2 is used for broadcasting, all receivers must
be capable of receiving it or, a DVB-T2 set-top box will be
required. They are used in some overseas countries. This
is how we converted from analog to digital TV.
Initially, HDTV used MPEG-2, but it was too data-
hungry, so MPEG-4 had to be used. If Australian Standard AS 4933 in 2010 had made MPEG-4 compulsory, in
2015, all programs could then have switched to MPEG4, allowing most programs to go high definition. SD programs on TV are still using MPEG-2. We need an update
to AS 4933 and AS 4599.1:2015 to include UHD and other
new developments.
In 2014, TV channels were restacked to allocate a block
of consecutive channels to each transmitter site. Except
for Darwin, all capital cities have their main transmitters
in VHF’s channels 6-8, 10-12 (Block A). All other sites
use one of these blocks: B (28-33), C (34-39), D (40-45),
and E (46-51).
Notice there is a spare channel in each channel block.
The only exceptions are Alice Springs, Melbourne and
Adelaide. These are for Community TV, which the Government is trying to push online, so they are only giving
12-months extensions to their licences. The other community stations went bankrupt under these conditions.
Some remote towns have VHF and UHF, but the transmitters are in different locations. Why are Australian
antenna manufacturers selling VHF/UHF antennas except
for caravans?
Alan Hughes, Hamersley, WA.
Praise for Voice Modulator
I just completed building Warwick Talbot’s “voice modulator” circuit from page 91 of the August 2019 issue of
Silicon Chip (siliconchip.com.au/Article/11777), and it
didn’t work. The carrier was audible at the output and
the input signal was distorted.
I noticed on the circuit diagram that the diodes are
arranged in a bridge rectifier configuration. I then read
that the diodes are meant to be wired in a circular layout,
ie, anode to cathode to anode etc.
I subsequently changed both the germanium and silicon
diode orientation, and wow, what an amazing instrument!
My circuit uses a cheap (about $15) square/sine/triangle
generator board containing an ICL8038 IC, and I added
siliconchip.com.au
Australia's electronics magazine
February 2022 9
Warwick’s circuit on Veroboard. I want
to build another on one PCB to minimise the mess of wires!
Was the error drawn by Warwick or
the Silicon Chip graphics department,
either thinking “bridge rectifier”?
Ian Horacek,
Essendon, Vic.
Comment: Sorry about the drafting
error which was introduced when we
redrew the circuit. It was mentioned
in the Notes & Errata section of the
October 2019 issue and also on page
two of our 2019 Errata Sheet.
October issue enjoyed
You have excelled again with your
October 2021 issue. Congratulations
to all involved. The article on Gravitational Waves is a beauty and the
2/3-way Active Crossover looks like
it will be useful.
I have already ordered the cute SMD
Test Tweezers kit from your shop.
David Humrich,
Perth, WA.
Comment: you weren’t the only reader
who ordered that kit! We expected
it to be popular but were still overwhelmed. We only caught up with
demand in early November. The USB
V
Cable Tester project, which debuted in
November, has also been extremely
popular, again beating our expectations. While we were better prepared
for that, it still took us a few weeks
to catch up.
Documenting old switchboards
Last year, I got to visit a location I
had visited several times in the 1980s
when I was a kid. Last year it was wet,
so I only packed my DSLR camera.
However, a few days ago, another
opportunity to visit arose, low wind
and dry weather, airspace classification checked etc. The people who let
me in were amazed that I could see
the site from the air. While there, I
was asked if I wanted to see anything
else, so being me, I said “the main
switchboard”.
What a beauty it was, 1960s vintage,
looking far more impressive than the
main switchboards for a large major
metropolitan supermarket. Needless
to say, I took photos of it (and of the
drawings that were with it).
It has multiple boxes, each with a
lever switch on the side and a small
door on the front that took cartridge
style fuses (a bit like a giant version
of a 3AG or M205 fuse). Each area of
the then-new buildings had two threephase cables going to two small cabinets with circuit breakers (one for
off-peak night store heating and hot
water, the other general power and
lighting).
That main switchboard also fed five
existing buildings as well as outdoor
lighting, swimming pool stuff and the
caretaker’s house.
The site had its own transformer
outside as well. I didn’t touch anything as I knew that parts of it (quite
possibly all of it) are still live.
It’s definitely more interesting to
look at than the switchboards at work,
which are a mix of 1993 and 2018 vintage beige cabinets with boring rows
of circuit breakers.
Even the main distribution boards
look boring. I have access to the plant
room, being the in-store maintenance
assistant.
I suggest, if it is safe to do so, take
photos of the older gear. It makes great
visual references for drawings and
other arts and also helps to record our
built/industrial heritage.
Darcy Waters,
SC
Wellington, New Zealand.
intage Radio Collection
March 1988 – December 2019
Updated with over 30 years of content
Includes every Vintage Radio article published in Silicon Chip from March 1988 to December 2019.
In total it contains 404 (not an error) articles to read, or nearly 150 more articles than before.
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