Hello and welcome to Xtract 19 of the HX Files.
In this Xtract.
A new 23cms
transceiver for the shack.
I would like to
talk about this project that was made for use as a base transceiver; this
project would be a 60 watt ATV transceiver for 23cms. The first thing to do was
to get a project box that was not just big enough, but structurally strong enough, so with safety hat on a
suitable one was dug out of the stores bunker, as well as a suitable heat sink
for the amps. The heat sink was originally an amp for a mobile phone system
that was in the stores bunker for a couple of years, the inside was stripped
out of its components, some of them for the skip, and some for the stores
department, the heat sink was found to be only a couple of mm shorter than the project
box and it was exactly the same height as it. The project box purchased was a
used piece of scraped test equipment with most of the original parts removed
before sale, after looking at the back of the box and at the heat sink that was
going to be used, it was decided to use part of the original back panel (photo 1 below )as this would help with the fitting of the heat sink.
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After a bit of measuring and marking, a small precision
cutting device was to remove the centre of the panel, (A 100mm angle grinder).
The rest of the panel was lined up with the heat sink and both marked for
drilling some mounting holes. When lining up the panel up with the heat sink
for drilling, care had to be taken that the holes to be drilled would be
between the fins of the heat sink and there would be no need to remove any of
the heat sink. Thanks to a bit of time spent placing the parts and a bit of measuring,
the holes were drilled, they were close, but luckily there was just enough
space to add the washers and nuts. The panel was then removed so that there was
room to place the 2 amps on the heat sink, a couple of paper templates were
made of the mounting holes of the amps to mark out the spots on the heat sink
that were to be drilled but no matter were the templates were positioned the
holes would be over a fin of the heat sink, so as the heat sink was 8mm thick
the holes would be drilled to a depth of 6mm and then be taped. Thanks to
Michael EI 5 GG for the master class in the use of his pillar drill and taps,
and a couple of hours later the job was done. The amps were placed on the heat
sink temporally and were wired up and a few tests carried out making sure they
were giving out their full power, and after 1 hour on transmit the heat sink
was still cool enough and more than likely it would not be transmitting for
that amount of time in one go again. As the heat sink worked so well during the
testing, no fans were to be used in the final design, and with that job done
the back of the unit was refitted to the box. A chassis for mounting all the
various parts that would be used was made from a piece of a scraped metal that
once was the top of and old PC table, this had a couple of benefits as It was
the type that had the perforated top, and the holes could be used for mounting
the various parts, and it would also aid in air circulation. The amp requires a
voltage of 24 volts at 4 amps, but the other parts like the 2 watt driver amp,
the RX/TX boards, relays and various lights, would only need 12 volts to power
them. I was toying with the notion of using 24 and 12 volts from external power
supplies, this would not be a problem as the unit would be a base transceiver,
but to go portable and having to bring a couple of power supplies was not on, so
a 240v AC to 24v DC PSU was fitted into the case (photo 2 below).
As the PSU had two
separate lines out for 24volts, plan A was to use a voltage regulator I had
that would drop the 24 volts to 13 volts and it would be able to handle 6 amps
which was more than I needed, but I had to go with plan B as I could not find
the amp. So plan B was to use a couple of smaller voltage regulators for each
of the TX/RX boards to take the voltage down to the required volts, the
regulators were mounted on a small heat sink that would keep them like the Fonz
(cool) seen on the bottom right of photo 3 below .
The power supply used was one mentioned in a
previous HX file that was purchased at a rally last year, and the fact it also
had a fan installed to help with it’s cooling was not a bad thing, it has a few
taped mounting holes around it’s body so using a couple of bolts of the same
thread and after measuring it, a couple of holes were drilled in the side of
the unit and the PSU was bolted to it.
The PSU was placed on its side (photo 4)
as doing this would leave more room in the box for the other parts. The TX/ RX
boards, preamp, coaxial relay and the other parts were dry fitted in various
locations until I was happy with the layout.
Another benefit of having a
perforated chassis meant I would be able to hide some of the cables, the holes
could be made wider with a reamer and you could install grommets in the holes
if needed so you would be left with smooth edges and not run the risk of any of
the leads chaffing. The front panel was cut from a piece of an old aluminium
sign, the panel would be strong as it is 3mm thick, and the it would be 312mm
wide and a height of 105mm, that’s around 12”x4” in old money. The metal sign
that was to be used for the front panel, was not in great condition as it had a
few marks and scratches on it, so when all the drilling is finished, some
sticky back plastic (well if its good enough for Blue Peter then its good
enough for me) would be used, as it comes in various colours and finishes. But
before all that the first thing to do was to try a couple of designs to see
what want were, after the final design was chosen it was held onto the front panel
with masking tape (photo 5 below
The drill points marked with a punch, and after a
bit of care the holes were drilled first using a 3mm drill bit and then
finished off with the right size drill bits, and with the use of a file and a
reamer the panel was finished, the parts were fitted on the panel and then
removed to be able to apply the plastic covering.
As you can see in photo 6 on the left,the finished front
panel with all the fittings installed. Having the back panel free of any
fittings would mean that the transceiver could be placed close to the shack
wall, and due to the tests carried out earlier, (it not needing any cooling
fan(s), and with the carrying handles it would also mean some type of
protection for the front panel. As I mentioned earlier this project would be a
base unit, but if I did decide to go /P with it I would need a DC to AC
converter to take the 12 volts DC to 240 volts, and as I did not want to bring
a generator. That’s it for this issue of Echo Ireland, and if you would like to
see other pictures of the build you can go to my blog, thehxfiles.blogspot.com.. Below is some more photos of the build.
And finally, that may all your signals be P5. 73’s
Pat.
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| Early layout |
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| Final parts layout |
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| Some tidying up left to do |
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