Hello and welcome to the HX Files 028, and to 2014.
As there was no newsletter before Christmas, I hope you had a happy Christmas and have a happy and prosperous new year.
What to do next.
Over Christmas, I was looking at some of the bits and bobs, (well its better than looking at Bobs bits) in the projects pending department (the sheds). The items that were bought over the last few rallies, and indeed some stuff that was given to me for parts, needed to be sorted out. Space was becoming a problem and finding the part or parts needed with nothing falling on me, and getting out alive was getting harder. Those of you with space can decide on whether to dismantle the donor item as some of the parts needed are often safer to store in their original housing rather than taken apart. With the parts removed a trip was made to the recycling center with the unwanted and unusable items, and with the hope I did NOT see anything I could use.
Protection
The HX stores normally wait until a good coat of protection (dust) has appeared on a particular item that has been in the shed for a while, and that it will no longer be used for what the manufacture intended it to be, and then the parts removed. It was on this particular rummage that the monitor featured was unearthed; it is an old security monitor measuring around 15 inches cubed. This cube was bought at a rally years ago, and was used for a while and then retired. With the parts bin in mind, it was noticed that the housing of the monitor was made from panels that were screwed and riveted to a frame, the plan was to remove them and add the sheets to the metal pile.
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| View inside of the monitor |
On removing the back of the monitor I saw that there was some space in it, see photo 1 on the left, and then an idea came to mind, (and no it did not hurt much) it was decided to see if firstly it still worked, it did, (it would not have been my first project that had to be modified or scrapped when the main part had gone faulty during storage) so it was left on overnight with a DVD playing some film to see if the picture and sound stayed working, all was good the next day and so I started on the project.
Parts and fitting
There was not enough space in the one area to accommodate the TX/RX in a single unit, so a separate transmitter and receiver boards would be used instead in the monitor, see photo 2 below left.
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| The ATV units installed in the monitor |
The individual TX/RX boards were enclosed in separate metal boxes (used from other projects) some patch leads, switches and a relay were added to the mix, also a small amp was fitted to the transmitter, the metal box would act as a heat sink. I wanted to keep everything inside the cube, fitting the parts to the inside of the cube involved the drilling of its case, but I did not want screw or bolt heads sticking out of the unit as they could snag and mark other equipment around it. The metal on the case was thick enough to allow the use of some tapered screws for a flush fitting, with all the screws, nuts and bolts in stock I had none of the flush fitting type in stock, so a trip to the local hardware store was on the cards and the items needed purchased. After some moving around to see what would fit best in the space available some marking out was done and then the drilling carried out. The drilling was a bit awkward, as the case of the monitor was not only bolted to the chassis but it was also pop riveted and it would have been difficult to take everything apart without damaging other parts of the unit, the monitor was turned upside down for some of the drilling to keep the waste from dropping onto the other parts and some sticky tape to mop up the waste. The back panel was easy to remove by removing a few screws, it is a sturdy piece of metal and I would be mounting an “N” type socket into it. Power for the ATV equipment would be from either a 12v power supply or car battery, the monitor would be powered by mains if at home or an invertor if it is being used portable.
A word of caution
I would have to take care, as in use at home it would mean there would be mains power in use and it could be fatal if any adjustments were to be made whilst the unit was in use. Fitting of the parts was not too bad having done a dry fit first, but once you start adding the various cables and leads you would start running out of space all to quickly. The first plan was to place as many of the controls on the back, but the thoughts of hands reaching around the back of the unit that would be ran off 240v made me decide to have a remote switching box, (see photo 3 below),
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| The control box |
that would lay on top of the unit and then a removable cable used to connect the unit to the switching box.
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| View of the control box before the wiring is fitted |
Photo 4 on the left shows the control box without the wiring, the bar in the center holds a fuse holder and a connection strip, it should be noted that this bar is shown up side down just for the picture, the decision to use two microphone sockets instead of a six pin one was taken due to the fact that the dc cable was nearly as thick as the audio/video leads and I wanted to give myself a bit of room to work with. Using the 2 pin dc connector was not without some trouble, as those old experimenters out there (author included) may remember the old 2 pin Yaesu dc leads, and the fact that there were 3 types that had different distances between the pins and the grief to get ones to pair up to make a spare dc lead. RF output of the unit is just under 10 watts and it will certainly be more than enough for what is needed.
With the fittings on the back panel,see photo 5 on the left, the leads were longer than they needed to be, as they would have to be long enough to allow the back panel to be removed and to be out of the way to carry out any adjustments.
In use
I have used the unit several times and having great fun with it. But nearly dropping it on more than one occasion out portable, a couple of sturdy handles will be fitted to it in the near future when I get ones sturdy enough.
That is it for this issue,
I hope to see you at the Society’s AGM in Galway.
May your signals be P 5.
73 Pat.
