Adding an Artillery Command Post to a Military Vehicle Collection – Part 9 – Clansman Installation Designs – August 2013

The end of a Busy Month by Richard Taylor – 2E0TUH

It’s now the end of August and looking back I am surprised how much I have achieved.  I did pass the Intermediate exam and am now 2E0TUH – thanks to Bob, Chris and Sheila from Plymouth Radio Club for their patience.  This means that I can use all the sets at their maximum power, although whether this will make a difference is moot.

On the truck I am working towards a plan.  I have looked carefully at the construction of the pod, and worked out how it goes together.  It is basically a double walled aluminium box, which was predictable, but all of the fittings are supported by a spreader plate riveted to the wall, with rivet nuts in the plate spaced to take the fitting.  This makes it less adaptable than for instance a Land Rover which has Dexion Racking and can take almost anything.  Having said that, there is nothing to stop me copying the spreader plate idea and using it to fit additional pieces.

IMG_2993The plan I am working to is fairly similar to the Clansman fitting seen in most land Rovers.  I have one 321 set and two 353’s mounted across the front radio table. At the moment I have it set up as 353, 321, 353 – the reason being that there are plates on the right and left of the front wall for the TUAM/ARFAT combination.

 

These link through to the two antenna bases on the front outside of the pod.  I only have one of the 353 sets linked up properly (the RHS one) as the plates on the LHS have been used to mount a filter unit and I need to work out how I can remove this without spoiling the feed to the distribution box. The 321 is connected to the power, but at present I run the antenna from the large co-axial out of the back door of the pod to the junction fitting which is raised to the top of the mast at the rear. I can then run the two arms of the dipole from the junction out to the ground in an inverted V.

Operating in a Sealed Environment

My aim is to be able to run the complete set up with the door closed.  Mainly because winter is approaching and as I found out last January, Caradon in the snow can be a bitter experience.  In order to do this I have decided that I will run cable around the inside of the pod to connectors that allow me to connect the inside to the outside. I already have some BNC connectors in a panel which sits under a canvas flap in the LHS.

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Fitting New BNC\C Type Coaxial Feed Throughs

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My first task has been to fit a BNC/C type connector in to this panel.  I have chosen this combination because most of the external antenna coaxial is fitted with C type plugs and most of the radio output is fitted with BNC. (Apart from the TURF that is).  As I am trying to use as much original cabling as possible, this seemed the answer.

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Using these two connectors I will have the choice of feeding either HF or VHF out on the LHS to a mast set up outside.  The HF can be set up in any way and the VHF can use the pineapple (Elevated Wide Band Antenna) or the ground mounted monopole.  Both do not need the TUAM/ARFAT to operate so a direct cable out will suffice.

Having an exit that way will also help with the HF antenna in that it will enable me to use the length of the truck to take up some of the antenna length and that will give me a smaller overall footprint, which is something that can matter at shows.   I will also fit up the same at the rear of the truck, so that the rear mast can be used with the door shut, although I am not sure yet whether I will enable VHF this way.

I already have the map board, and by chance picked up a military map of the Dartmoor training area from eBay.  Whilst we do not feature on it, it is sufficiently local to make it interesting and as it is the real deal should look the part.  I am now looking for a thin clear cover to go over it to allow me to scribble signs and things without spoiling it.  I have also picked up two field telephones (surprisingly cheaper than one!) and will fit one to its place next to the board.  There is pre-existing cabling going from there to two connectors outside on the rear which accept Don 10.

Planning the Final Mounting for the the HF Sets

I will probably mount the PRC320 towards the rear right of the pod, with an additional TURF which will be connected to the HF whip.  My problem is that unless I do it this way I cannot get the run from the TURF to the whip short enough.  It would either be that or have the TURF a long way from the set.  I am not sure of this at present, as not only do I need to mount the 320, I would also need the DCCU mounted as well.

I still have to fit in the rugged laptop and its data handler and possible a DMU to make it look the part. I would like to be able to carry out rebroadcast as well as having some facility to charge the portable batteries.  I think that there is space, I just need to get some of the remaining racking out.

Meanwhile Back on the Moors and fault finding the 321…

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That apart, I have tried to speak to VMARS from Caradon using the VRC321 again.  Once again without success, but at least I found out why.  I thought this time I would approach the matter more scientifically and not only would I be more accurate with the dipole length, but I would take up a GPS to work out the bearing between me and the VMARS controller so that I could align the antenna for best effect.  That went quickly to rats when I realised I did not know how to put another co-ordinate in to the handset and I had not manual with me.  Not only that I did not know how to switch the thing off, so ended up taking the batteries out.  I made a quick guess on the location of Stoke on Trent and banged the pegs in.

Despite my best efforts I could not get it to receive anything.  It seemed to be tuning fine, but all I could get was mush.  I did not think that this would be down to atmospherics as it seemed a glorious morning, so I fiddled with the cabling and it burst into life.  The problem was fairly simple.  Since the last time I had tried the set I had fitted the SURF above it.  Having been told that this stood for Small Useless Radio Fitting (except see here, – ed.) and as I only had one set in use, I by-passed it and connected the 321 straight to the TURF. This seems to have put a strain on the cable and it was not making a good contact. When I held it together the reception was excellent, but transmitting made it fail completely. So, another cable to make.

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That afternoon I took the Yaesu over to a friend and we set about seeing why it was not receiving properly.  Two hours of logical investigation showed that the attenuator switch was sticking on (sorted by switch cleaner) and the reject filter knob had been fitted out of alignment so that it was full on when it showed off.  Now it receives very well and I have heard transmissions very clearly.

 

 

 

Moving on…

September promises to be an expensive month, so I doubt whether there will be any great additions, but I plan to use the cables and fittings I have assembled to make the installation a little less bodged and a little neater.

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