Tuesday, 2 August 2016

Clansman Manpacks for Amateur Use - Part 5a

Bear with me (grrrr!) - we're almost done!

So, so far we've talked about which of the Clansman series manpack radios are suitable for amateur use, what you'd need to get one powered, and how to actually listen and talk on it if you have one (I offer no guarentee that theres anyone listening!), so all thats left is to discuss the basics of antennas for them.

Now, as these are the man portable radios, the antennas i'll mention are also man portable. The general operational doctrine in the field was usually that, with the exception of inter-section comms, the manpack would be talking to either a vehicle mounted system, or either a fixed or field commcen (communications center) which could be a couple of 12m masts and tents, an RN ship, or something a little bigger like DHFS Forrest Moor with its huge HF log periodics. The onus often, especially for HF, being on the more capable station taking the brunt of the link.

I'll start with the PRC350, and move on 'up the chain' as it were

PRC-350 Antennas

The PRC-350 has a bayonet fitting antenna socket for what are termed 'battle whips'. There are two common types, with corresponding differences in performance. The first is a 'rubber duck' type flexible 60cm helical antenna. This has an advantage of being pretty much indestructable, but of course not a great range! More useful is the 1.2m sectional whip. More rigid, but with a sprung ball and socket mounting, this comprises four tubular sections attached with an elastic cord.

0.6m flexible battle whip

1.2m sectional whip

Both of these are ok if your actually carrying your PRC-350 on your back or hip. Often available for very little money, but probably of very limited use, is the 'trailing wire' antenna. This is a 1.2m long length of braided antenna wire and a bayonet connector. Its tactical use can be appreciated, but for amateur purposes its little more than a curiosity.

Trailing wire antenna

So those are your usual antenna options for the PRC-350. Doesnt give you much leeway for your 2W does it? But, you may have noticed your radio has a dinky mini-BNC socket on it. We'll see why shortly,

PRC-351 and -352

The higher powered PRC-351, with its thobbing 4W, also has the same bayonet fitting antenna connector as the -350, and so can use any of the above antennas. But, it also has a BNC connector. This BNC is to allow you to use it with the big brother antenna, the GSA (Ground Spike Antenna)

The GSA is a kit, available in Long or Short Rod versions, comprising a base matching unit, several antenna rods, coax lead, carry bag, and the namesake ground spike.The general idea is to fit to the base matching unit the desired number of push together antenna rods (number per frequency range is conveniently printed on the side of the base), attach this to the spike, ram the spike into the ground, and run the coax off to the radios BNC connector. In the tactical environment, this meant the antenna could be out in the open where it was effective, whilst the radio and the squaddie hid away in cover. Incidentally, if you have a short rod kit, just use double the numbers on the data plate.

The GSA antenna is essential if you have a PRC-352, as this cannot be used with the battle whips.

Have you discovered the odd 40cm coax lead that came with the kit? Yep, thats the adaptor for the mini-BNC on the PRC-350!

The GSA is not too bad an antenna, but its still rather low down. VHF likes height, so another kit is available, the EKGSA (Elevation Kit, Ground Spike Antenna). Supplied, hopefully, in its own carrying satchel, this kit comprises all you need to mount the GSA on top of the 5.4m mast (of which more later), or to hang it from a tree or other suitable support. The key to it is the set of measured coax cables and the mast mounting inductor unit. These between them provide an artificial ground for the GSA.

 There is also a 'long wire' antenna system available, but this never seems to turn up intact, rather the antenna wire spools show up but not the terminating resistors or feed inductors. Other antennas you will see are the 'pineapple' which is similar to the GSA but of a wideband design. This is not by any form of clever matching system, but rather by a terminating resistor! Not great for your measly few watts. Another you might see for sale is the 'ground mounted monopole', commonly known as the washing line, for reasons that should be apparent to anyone whos ever used a rotary clothes airer! Again, probably not of any great use, but if you have the money, by all means get one.

To use the EKGSA at height, if you dont have a nice tall tree with spreading boughs, you'll need a mast. The EKGSA (and many other antennas for the HF side of things) are designed to be used with the 5.4m Fibreglass mast kit.

5.4m Mast Kit
It is true that these can be erected, as the manual states 'by a single well trained soldier' but its far easier with two or more people! Six interlocking thick wall fibreglass tubes and two sets of three guy strings, plus five ground anchor pegs. There should also be a odd looking short tube with a wire attached, why, we shall see when we talk HF antennas.

Im going to put HF antennas in their own post, as theres more options there than with the VHF kit.

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