80-Bus News


January–March 1982, Volume 1, Issue 1

Page 40 of 55

by the ever increasing number of half wave dipole aerials which are appearing on the roof tops. It surprises me that Busby hasn’t done himself a severe damage by getting his undercarriage entangled in the ever growing forest of ‘big twigs’ which are sprouting and pointing skywards. Now the reason for the increasing number of large aerials is because the local breakers are taking it upon themselves to overcome interference from other local stations. The regulations restict the user to an inefficient aerial system, a base loaded 1-5 metre dipole. Now a halfwave dipole (which is some 5 and a bit metres long) is essentially the ‘fundamental radiator’ of radio signals and is very efficient. By buying a half wave aerial, you obviously ‘get out’ (radiate or transmit) better, meaning that the person you are in contact with will receive you better as your signal is now stronger that the others and thus overcoming the others by taking advantage of the capture ratio effect. However, this simply aggravates the problem as your strong signals will blot out the signals from the more legal breakers around (with 1.5 metre base loaded aerials), who in turn will be persuaded to go and equip themselves with larger aerials likewise. And so we the problem gets worse not better.

The same thing happens when ‘boots’ or ‘burners’ are used (linear power amplifiers), the local CB emporia are chock full of linears ranging from 10 to 500 watts. Up to about 50 watts a linear is relatively cheap, certainly not much more than the cost of a couple of tanks full of petrol (which will be burnt by a mobile breaker cruising round the country side trying to get good ‘copies’ (contacts) over the following few weeks anyway). So someone puts 25 watt boots on his big twig, and surprise surprise, for a few weeks he can get out over the top of the rest. The average conversation goes as follows:

“On the side. On the side. Who’s the breaker bending my needle.”
“You got Bulltwit, good buddy. What’s yer handle?”
“Ya got Brain Damage here. Say, thats some signal you’re putting on me. What’s yer twenty?”
“Willesden. What’s yours?”
“You’re coming across wall to wall in Finchley, good buddy. What’s your rig and you pushing ‘wellies’ or somethin’?”
“Roger-dee. The rigs a Harrier and I’m poking 50 watts up a Procom GP27 half wave.”
“That so, Bulltwit, Yeah, I’m thinkin’ of getting some ‘wellies’, got any ideas?”
  ...... and so on

I’m not saying that that is a typical conversation, but it does follow sufficiently well established lines for us to call these types ‘Three What Breakers’; that is the ‘Three Whats’, Whats your handle?, Whats your twenty? and Whats your rig? … end of conversation. So not only do all the locals start running large aerials, but the power goes up progressively as well. This would seem to be a never ending spiral, limited only by the necessary funds for the equipment and the (unlikely) intervention of the Radio Regulatory Division of the Home Office.

To digress for a moment, what I’m about to write is perfectly true. A breaker round our way who was already running 200 watts decided to increase this already over adequate power further by fitting a ‘Bremi 500’, about the biggest 500 watt linear around. It worked, so he thought why not drive the Bremi 500 from his existing 200 watt linear which if it worked, would, according to his simple mind give him something like 10KW output. Well he didn’t expect the arrangement to be very efficient, but thought he might get a couple of kilowatts if he was lucky. What he did get was a lovely explosion and following fire which needed the attention of the local fire brigade. It completely gutted his living room.

So the first requirement would be an efficient aerial system and bags of power to punch the data over and above the rest.

Now what about the locals who are not likely to tolerate data transmission anyway. This can be overcome by the mode of transmission employed. Now it would be quite feasible to transmit the Nascom tape signal. The audio bandwidth required would be 2.4KHz which is approaching the limits of the capability of the CB system, but provided the deviation were kept to sensible levels the modulation index would not be exceeded thus ensuring adjacent channel interference would be kept within the prescribed limits. The data rate had better be kept to 300 BAUD for greater data integrity, but at short range this should be acceptable (excepting that it might be

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