who hid a radio under the stairs?

Here’s some more Iran sense. I especially like the bit where the Content is Free comments pit tries to explain to the Iranian all about Mohammed Mossadegh and all. that. jazz. Of course, he’s essentially reiterating the former head of the IRGC’s line.

I’ve said before that the practicalities of this depend largely on what kit is available inside Iran. If there are a lot of Thurayas/other satellite terminals about, it might be possible to buy airtime and send the vouchers, or better, just the numbers off the vouchers. How many minutes could you fit in one encrypted e-mail? Quite a lot. But they are expensive, trying to buy one openly there would be the height of stupidity, and some of the biggest users are the military and the oil’n’gas sector.

He refers to this Japanese comsat project, which is indeed cool (in fact, pretty much everything JAXA does is quite cool) and is designed to use the classic footy’n’porn 45cm satellite dish antenna. The technology – phased-array beamforming antennas and on-satellite packet switching! – is impressive. However, as comments here pointed out way back in June, the problem with this is that dishes are quite visible and ‘totherside has already got used to the idea of harassing and intimidating satellite TV users. You don’t need to do electronic warfare to detect dishes – you just need your thugs to go around looking for dishes and stomping people.

Clearly, a key element in designing something like this will be minimising the antenna requirement. (Actually, the antenna is the key element in designing any radio whatsoever.) Again, the land-mobile satellite systems offer a good model – for things like the Globalstar/Iridium/Thuraya handsets, which do voice and messaging and up to 144Kbps of IP, the form factor is rather like a clunky early 90s GSM device, and the Inmarsat BGAN broadband terminals use a rectangular folding antenna, about the same size and rough design as a netbook. (The smallest available is the Thrane & Thrane Explorer 110, which breaks down in two parts, measures 20 by 10 cm, does burst speeds of 384kbps and Tx power of 10dBw.)

Similarly, I’m dubious of the idea of having a specific satellite – they are predictable, after all. Again, it would probably be better to hide in the “legitimate” traffic and the existing satellite constellation. So, it looks like the solution would be a low cost radio board that drives whatever antenna you feel you can hide, using one of the land mobile satellite services or possibly the radio hams’ AMSAT. It must do at least 10dBw and not require any fixed installation. (The AMSAT people have a linkbudget calculator here; clearly, that Thrane & Thrane device must be doing something clever.)

The Inmarsat stuff works in the L-band, around 1550MHz (check out the coffee mug antenna while you’re there), which is handy as the other band they use is too high for the Universal Software Radio Peripheral, the open-source radio kit. Which currently costs about $700 – and it’s illegal to sell them to Iranians if you’re in the US, which the manufacturer is. Not that buying one would be the smartest move either, but there you go.

So, it needs to be cheaper than the USRP, it needs to be feasible to make it from parts available in – say – Iran. On the up side, it doesn’t need to be as smart as the USRP because it’s specialised to task, rather than a general purpose device that has to be capable of a lot of different radio profiles.

  1. Surely you could stash a satellite dish under a radio-transparent cover? Inside an attic under tiles, for instance? Used to be the favourite trick to avoid paying a TV licence (or so I hear).

    The existing sat-phone systems are in trouble, friends of mine who do fieldwork in remote Australia have been told “I could sell you this, but it’s an expensive paperweight”. Unless someone has something new up and running over the last year or so, I wouldn’t count those chickens.

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