Using the DMYCO V8 Finder, [Corrosive] demonstrates how to set up the
device to pick up terrestrial amateur streams. Satellite reception
typically involves the use of a low-noise block downconverter, which
downconverts the high frequency satellite signal into a lower
intermediate frequency. Operating at the 1.2GHz amateur band, this isn’t
necessary, so the device is configured to use an LNB frequency of
10000, and the channel frequency entered as a multiple of ten higher. In
this case, [Corrosive] is tuning in an amateur channel on 1254 MHz,
which is entered as 11254 MHz to account for the absent LNB.
[Corrosive] points out that, when using an F-connector to BNC adapter
with this setup, it’s important to choose one that does not short the
center pin to the shield, as this will damage the unit. This is due to
it being designed to power LNBs through the F-connector for satellite
By simply reconfiguring a satellite finder with a basic scanner
antenna, it’s possible to create a useful amateur television receiver.
If you’re wondering how to transmit, [Corrosive] has that covered, too. Video after the break.
There was a time — not long ago — when radio and even wired
communications depended solely upon Morse code with OOK (on off keying).
Modulating RF signals led to practical commercial radio stations and
even modern cell phones. Although there are many ways to modulate an RF
carrier with voice AM or amplitude modulation is the oldest method. A recent video
from [W2AEW] shows how this works and also how AM can be made more
efficient by stripping the carrier and one sideband using SSB or single
sideband modulation. You can see the video, below.
As is typical of a [W2AEW] video, there’s more than just theory. An
Icom transmitter provides signals in the 40 meter band to demonstrate
the real world case. There’s discussion about how to measure peak
envelope power (PEP) and comparison to average power and other
measurements, as well.
Although the examples use a ham radio band, the concepts will apply
to any radio frequency from DC to light. If you want to do similar
measurements, you’d need a scope, a peak-reading watt meter, and a dummy
load along with the transmitter.
We enjoyed that he uses a scope probe as a pointer, but we can’t really explain why. If you are ambitious, you can build your own SSB transceiver. Another common way to modulate RF is FM and we’ve talked about it before, too.
Who doesn’t like to look up at the night sky? But if you are
into radio, there’s a whole different way to look using radio
telescopes. [John Makous] spoke at the GNU Radio Conference about how
he’s worked to make a radio telescope that is practical for even younger students to build and operate.
The only real high tech part of this build is the low noise amplifier
(LNA) and the project is in reach of a typical teacher who might not be
an expert on electronics. It uses things like paint thinner cans and
lumber. [John] also built some blocks in GNU Radio that made it easy for
other teachers to process the data from a telescope. As he put it,
“This is the kind of nerdy stuff I like to do.” We can relate.
The telescope is made to pick up the 21 cm band to detect neutral
hydrogen from the Milky Way. It can map the hydrogen in the galaxy and
also measure the rotational speed of the galaxy using Doppler shift. Not
bad for an upcycled paint thinner can. These are cheap enough, you can
even build a fleet of them.
This would be a great project for anyone interested in radio
telescopes or space. However, it is particularly set up for classroom
use. Students can flex their skills in math, engineering, programming,
and — of course — astronomy and physics.
The general public thinks there is one thing called a radio.
Sure, they know there are radios that pick up different channels, but
other than that, one radio is pretty much like the other. But if you are
involved in electronics, you probably know there are lots of ways a
radio can work internally. A crystal set is very different from an FM
stereo, and that’s different still from a communications receiver. We’d
say there are several common architectures for receivers and one of the
most common is the superheterodyne. But what does that mean exactly?
[Technology Connection] has a casual explanation video that discusses how a superhet works and why it is important. You can see the video, below.
Engineering has always been about building on abstractions. This is
especially true now when you can get an IC or module that does most of
what you want it to do. But even without those, you would hardly start
an electronics project by mining copper wire, refining it, and drawing
your own wire. You probably don’t make many of your own resistors and
capacitors, neither do you start your design at the fundamental
electronic equations. But there’s one abstraction we often forget about:
architecture. If you are designing a receiver, you probably don’t try
to solve the problem of radio reception; instead you pick an
architecture that is proven and design to that.
There are other examples. Do you really work out a binary counter
every time? Or how to make an op-amp amplify? You start with those
building blocks. Of course, true innovation means you have to stop doing
that and actually think of new and different (and possibly better) ways
to do the same task. But most of the time you aren’t trying to
innovate, you are trying to get the job done.
The video is pretty straightforward and doesn’t assume you have much
radio background. However, it does manage to do some real demonstrations
and it is worth a watch. There are many other receiver architectures,
of course. Regenerative,
superregenerative, homodyne (direct conversion), Hilbert, and Weaver
are all types of receivers and there are doubtless more. The funny part
is that many of the ideas we still use today came from one man: Edwin Armstrong.
How hard is it to build a ground station to communicate with
people via a satellite? Probably not as hard as you think. [Modern Ham]
has a new video that
shows just how easy it can be. It turns out that a cheap Chinese radio
is all you need on the radio side. You do, however, benefit from having a
bit of an antenna.
It isn’t unusual for people interested in technology to also be
interested in space. So it isn’t surprising that many ham radio
operators have tied space into the hobby. Some do radio astronomy,
others bounce signals off the moon or meteors. Still others have
launched satellites, though perhaps that’s not totally accurate since as
far as we know all ham radio satellites have hitched rides on
commercial rockets rather than being launched by hams themselves. Still,
designing and operating a ham radio station in space is no small feat,
but it has been done many times with each generation of satellite
becoming more and more sophisticated.
While it is true you’ll get better results with a directional
antenna, it is possible to make some contacts with a fairly modest one.
Back in the 1970s and 1980s, tracking when the satellite was overhead
was a major task, but the modern ham just needs a cell phone app.
If you have images of hams sitting at their radios having long-winded
discussions, you haven’t seen a typical satellite pass. You don’t have
much time, so the contacts are fast and to the point. In fact, this
video dispels a lot of ham stereotypes. A young guy shows how you can do
something exciting with ham radio for very little investment and it
doesn’t matter if you have deed restrictions because all the gear would
fit in your garage when you aren’t using it.
The downside is that [Modern Ham’s] demo didn’t show him making any
solid contacts although he was clearly hearing the satellite and people
were hearing him. He admits it wasn’t his best pass. The second video
below shows a much more typical pass with the same kind of setup. If you
want to see what results you can get with a more modest antenna, check out this video.
In addition to satellites built by hams, some have started life doing a different task and been taken over by hams later. If you don’t have a ham license (and, by the way, they are easier to get than ever), you can still listen in to some very interesting space communications.