Countermeasures

[Albert H]

It's always a hassle "losing" rigs to the authorities, rig thieves and competing stations. Whenever I put something on, I always used some kind of countermeasures to prevent discovery of the gear, to make it difficult (or even impossible) to remove if it was found, and to make it unpleasant for the person taking it away by means of several nasty tricks including the use of biological agents and even by the installation of tracking devices and "sending the boys 'round" to the culprit's home to get the gear back!

Over the years, I've used all sorts of tricks:

One set-up we had used two phase-coherent transmitters - high power and low power, a mile or so apart, and carefully set up to be an exact number of wavelengths apart. The DTI tried to track this each weekend it was used, and each time they ended up somewhere in the middle of the two sites, scratching their heads as their gear couldn't be wrong... It was a nightmare to set up and difficult electronically, and was really just a "proof of concept" because it wasn't really viable for the long term. It was an interesting experiment, anyway!

I put a stereo link in the vestigial sideband of a TV station. It required a link receiver with some really tight filtering to keep the vision buzzes away, but when Gotts and Co tried to track our link, he kept ending up at Crystal Palace!

Counter-measures, like putting your rig down a Dry Riser and securing it with a jack will stop the casual thieves, but if OFCOM want the gear, they'll get it out. You can make it hard for them, but it's much better to stop them finding it in the first place!

Don't use dipoles. They're too obvious. A J-pole or a Ground Plane Vertical are better - they radiate more in the direction that you want to go and give a reduced field strength into the building below.

One of my ⅝-wave jobs was used on and off for over 10 years without being sussed - most people thought it was a CB aerial. It was on top of the communal aerial mast at the top of one of the highest and best sited blocks in London. It remained a closely guarded secret, but was used by half-a-dozen stations over the years. It gave a great match between 93 and 96 MHz, so I'll leave it to you to work out the stations in the late 80s and early 90s that used it.

We bricked rigs into walls. The cabling went up inside the wall, and the power was often "abstracted" from the back of an existing mains socket, into the wall....

I built PAs into aerial poles, so that the DTI only took away the cheap bit! The exciter had to be in an impressive-sized box, with a light bulb inside to make it warm to the touch, to be convincing. Gotts took away a lot of £8 exciters!

We used "dummy rigs" - a normal rig-sized metal box containing a light bulb and a couple of bricks, with a mains transformer inside to power the concealed gear down the "aerial" coax. We even screwed a cheap heatsink to the outside to make it look more "real" and pop-riveted the box shut to prevent inspection. The final touch was a "link" coax with a TV-type Belling-Lee aerial plug and socket with a short from inner to outer. The "link" coax would go away from the "rig" in the opposite direction to the "transmit" coax, making it look credible. Unplugging it would disconnect the power. Later, more sophisticated versions included a cheap car headlight relay relay holding on the 24V AC that was going off to the real gear. Unplugging the "link" coax would result in the relay switching off with a loud click and the power to the rig going off! Disconnecting the PL259 from the "output" socket whilst the box was still powered would usually result in a reasonable arc flash as it was unplugged - and of course the real rig would go off. Job done - as far as Gotts thought and a five-minute re-installation of a £15 box to get back on!

We used ordinary TV Yagis and Band IV for links. Nobody notices a TV aerial on top of a house or a block. A TV Yagi can have loads of gain and be very directional, allowing very low-power, difficult to locate links. I often used just a 200mW Band IV transmitter into a 30-element TV Yagi to link several miles. TV receiver front-ends have an IF of around 35 MHz, so mixing with a crystal can bring that down to the usual 10.7MHz to feed an ordinary IF strip. These receiver modules were really well made, easy to programme and spectacularly sensitive. They were also incredibly cheap. My typical Band IV receiver would cost about £15 - 20 to build. There's lots of unused space amongst the TV channels!

A horn and a microwave receiver can work well over short range, and is difficult to detect, but the gear is getting scarce these days, so prices are rising, and drifting microwave signals are usually a dead giveaway to let the opposition know that that's the technology you're using. Try other frequencies! Band I is too easy these days - go up to 600MHz and enjoy the wide open spaces....

If you have any other favourite counter-measures, add them to this thread. It doesn't matter if OFCOM read about them - they're going to worry about Shigella infections (one of my favourites, easy to do, and VERY nasty), and they won't know which of the many tricks you've employed!

[Analyser]

An interesting read Albert but fortunately, or unfortunately ofcom have virtually stopped hitting people. As a friend said to me recently "the regulator isn't regulating any more". They have worked out that it's cheaper to send councils a letter making them responsible for allowing pirate installations on their roofs so the council duly look out for aerials and take the stuff down.
In South London there's a team driving round looking for aerials every day so some people are getting hit quicker than they ever used to when ofcom were around. Ask any station who's actually on air in London at the moment, getting a good roof is a nightmare and they only lose rigs to thieves.

[NOYB]

Great stuff Albert - very creative!

In the 80's my first low power station (3w) from a tower block we used an indoor wire dipole stretched across the window diagonally. Almost entirely imperceptible. Despite what you might think it covered our target student halls well, and far beyond. Awful varicap design that drifted, especially when warming up, but fortunately in those days receiving apparatus was quite forgiving - PLL was still too cutting edge then!

I've often thought (but never tried), what about a fibreglass tube with your choice of (real) omni antenna up the middle, with a dummy rusty old TV yagi at the top? Maybe some hollow co-ax taped up the side of it as well for added effect!

Antenna in a tree is always a good one - Our favourite tree was in a churchyard on a hill!

[pirateaddict]

Interesting stuff again Albert.. I'm just soaking it up at the moment. Reading things like this does make the old grey matter go in to overdrive.. Lovin it cheers Albert..

[NOYB]

The phased transmitter thing is interesting. Makes me wonder how Ofcom would cope with a pirate DAB SFN when/if that starts happening. As long as the TX's were not too widely spaced and had plenty of overlap I can imagine it would be difficult to triangulate - no possibility of finding a null (more accurate), so would have to rely on coarse signal peaking, and using visual clues. Just saying!

[McDonalds]

having dipole or rig in loft might help and in a row of houses so be harder to tell which one its from but I think they will get you if they want it.

[Albert H]

having dipole or rig in loft might help and in a row of houses so be harder to tell which one its from but I think they will get you if they want it.

An indoor aerial loses 90% of your power - a waste of a good rig!

The answer is to use something that doesn't look like a Band II aerial - that's why the ⅝-wave and ⅞-wave were so good. They had a great radiation pattern (little went straight up and almost nothing went straight down), they had useful gain, and they could look like a CB aerial!

One experimental Band I link aerial I used was made of the finest single-strand wire I could find, suspended between two chimneys on a house with fishing line. It was invisible from just a few feet away, but worked well enough.

I've known people to use flagpoles and any other vertical, elevated structure that you can imagine. I sometimes used to assemble an "improvised J-pole" at the top of scaffolding, with just a quarter-wave stub and the coax. It used jubilee clamps for connections, and nylon scaffolding clamps to hold it together. I used one of these for three months up a block in South London while it was being refurbished. It worked flawlessly and was not discovered. Unfortunately, I lost the coax and the clamps when they finished the job and took down the scaffolding!

[Santiago]

Albert, how I've missed your wise old tales


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[Maximus]

Haha! That's brilliant Albert. Thanks for the refresh as I kinda remember your humble tales from the old forum.
Btw did you have anything to do with a station in Brighton around 89' ish?


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[Albert H]

I probably did.

[Maximus]

Does the name Eugene Jarvis ring any bells?


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