This blog covers amateur radio advice and techniques. I plan to show the reader how to get started in ham radio after they have passed the exams. A lot of the news will be based on homebrew projects. Please leave comments if you would like more details on any of the subjects I talk about.
Monday, 7 January 2013
Maxitronix short wave radio kit
At work this year I was given a Maxitronix short wave radio
from my “secret Santa”. This is an interesting kit designed for anyone over the
age of eight. I have my doubts that such a youngster could construct this
without the help of an adult. The kit has part number MX-901SW and covers the
frequencies from 6 to 8 MHz and 12 to 18 MHz. The kit has been designed so that
no soldering is required. The wires from the various components link together
by trapping them between spring like connectors. Whereas most of the components
are individual items, there is a constructed circuit board that has several
wires to connect up. The two coils are pre wound which is useful but I was a
little disappointed as I rather like winding these. The instruction manual is well
written and the steps are easy to follow. Here are some images of the parts in
The first task is to “screw” the springs into the cardboard
board. This board has the circuit diagram printed on one side which makes it
easy to see where everything goes. The instructions recommend that you use a
pencil placed on the end of the spring to help twist / push the item so that
half is exposed either side of the board. This seems to be easy until you try
it. The springs refuse to position themselves correctly and tend to distort or
unwind. At one point I managed to cut myself on one of these and liberally
covered the underside of the board in my blood. It is for this reason that I
doubt that an eight year old would have fared any better. My solution to this
problem is to first enlarge the holes on the board by inserting the pencil and wiggling
it about to increase the size. The springs will then screw into the holes as
described with little effort. On the side of the board that is not printed, it
is recommended that you write the corresponding number next to the spring. This
makes it easier to get the wiring correct first time. Here are some images of
the underside of the board with the numbers added and the top side of the board
once all the springs have been connected.
The next job is to insert the components in stages as
described in the instructions. It is a simple case of bending the leads with a
pair of pliers, pushing them through the holes in the board and bending over
the legs. By pushing the spring to one side the coils open up and the leg of
the component can be slid in and trapped. Some of the springs take several
leads so best to place the first ones as low as possible to leave room for the
others. It doesn’t take long to fit these but care needs to be taken when
fitting some capacitors and the battery leads that they are wired round the
right way. One of the coils is fitted to a ferrite rod and the other sits next
to it. The wire from these coils is a little long and could easily be trimmed.
If you do this, you must remember to remove some of the insulation before
trapping the leads in the springs. The pre-constructed circuit board is screwed
to the board and its wires easily connected.
The battery and tuning capacitor
are fixed to the plastic chassis that holds the board. I would then recommend
that you double check the wiring to ensure everything is connected correctly
and the right way round. The transistor has short legs so ensure this is fitted
as instructed and all legs securely clamped. Once you are happy with your work,
you need to decide which frequency range you want to listen to and connect to
correct flying leads. Unravel the antenna and connect the battery and earpiece. Here is an image of the completed radio.
I was able to
construct this in about an hour. Because I was running out of time I wasn’t
able to give the radio a full test. I can confirm that the volume was good and when
tuning across the bands I was able to pick up some Morse. In the second part of
this blog post I will connect the radio to my external antenna and see how it
gets on with receiving some beacons around the country.
If you have any questions about this kit or are having
problems with yours, please contact me and I’ll try to help.