Saturday, 17 September 2016

Modern Transceiver Internal Frame Design for Rucksack, Radio, DPM, IRR

With the accelerated release of Clansman radio surplus by the MoD, which nowadays seems to consist much more of mixed stillages of random items rather than stillages piled up with actual radios, or seemingly whole pallets of NOS 4Ah batteries, the once quite rare 'Rucksack, Radio Carrier, DPM, IRR' seems to be more freely available.

These are the ideal way to carry your PRC-320 or PRC351/352 (or PRC-350), if you have a requirement for comfort over distance. If your need is to display the radio then your better off with a GS carrier frame, but I wouldnt advise using that much further than the shows tea waggon!

I now have three of these Bergens. (for those who dont know, Bergen, a town in Norway associated with British Army arctic warfare training, gave its name to an early form of rucksack, and hence since has become a colloquial term in the forces for any rucksack. Not to be confused with a 'Norwegian', or 'Norgi', which is a fleece jumper, and in itself should not be confused with a 'Norgy' - a large insulated food carrier, usually containing either 'Range Stew', ie everything left over from breakfast, 'Coftea' a mix of coffee and tea, 'Screech' - fruit and nitric acid flavour cold drink, or frequently all three!). One of these has my PRC-320 in it of course.

As much as I love the Clansman CNR Manpacks, they do have, lets face it, a number of drawbacks for typical amateur use. First among these is of course the weight, but a very close second is frequency agility, and coming in at third place is transmit power.

Lets compare a PRC-320 to, say, an FT-857. The Yaesu is clearly far more advanced, and much more pleasant to use for general tuning about, working split, etc etc. It is smaller and lighter. But it suffers a major drawback for activities such as SOTA - its fragile! Now, how great would it be to take a radio like the 857 or its ilk, an ATU, and a modern battery system, and protect them in a nice convenient padded backpack?

This is what I intend to do with one of my Bergens. This leads straight away to a problem - the Bergen is intended to carry the radio strapped in. Modern radios would just not fit this way. A frame is needed in order to mount the radio and other equipment.

Above is my sketch of what is needed. The height measurement is based on the strap for the PRC-320 - this is how high it goes before the reinforcing for the buckle. I intend making this using square aluminium rod salvaged from equipment racking. It might be an open frame, it depends on how strong it turns out. The idea is that inside the frame, the fixings could be adjusted to suite whichever equipment is to be fitted.

One thing I may do though, is reinforce the top right of the frame and fit a genuine Clansman PRC-320 antenna rod socket. This will instantly open the system up to use the Clansman 2.4m antenna and wire antennas.

I suspect that at least the bottom of the frame will require a solid plate, to prevent the soft Bergen from pushing in on the equipment.

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