[R-390] Skyhighgain Coaxial Cable Consumer Safety Alert

[Norman Ryan]

Fellow Mavens,

Please read and heed the following Consumer Safety Alert:

The recent popularity of a new antenna cable called Skyhighgain Coax has
created a safety problem for users and a nightmare for firefighters. 
SHGC was developed theoretically by Tricenters Experimental
Laboratories, Inc., as a signal-boosting element for use in radio and
television transmission lines.  Scientists at TELI discovered that when
a bias voltage is applied to the special material used to make SHGC, the
effect was incredible.  Instead of simply reducing signal loss, the
signal strength increased! 

Amplification of RF signals in the new coaxial transmission cable was
actually greater than 3 db (decibels) per meter per meter.  (Please read
that again.) 

In laymen's terms, that means that for every 10 centimeters a signal
travels through the cable the signal strength doubles!  Put 1 Watt of RF
energy into one end of a one meter length of SHGC and you get 2 Watts at
the other end (assuming you supply the bias voltage, of course).  At two
meters you get 4 Watts.  At three meters the signal strength increases
to eight Watts.  Doubling the power every meter the total effective
power of the signal exceeds 1,000 Watts by the time it has traveled only
10 meters up the line.

Now imagine what would happen if you had a 100-meter SHGC cable.  (The
actual figures are shown below.)

In conventional transmission lines there is always some loss of signal
depending upon frequency and the electric characterists of the cable. 
But with SHGC, instead of a loss, you get a gain in signal strength. 
This is the stuff every radio engineer has dreamed of.

But here's the problem:  The unwary (and mathematically challenged)
average user seems to think that if a short section of SHGC inserted in 
his transmission line is good, then a longer one is better.  If one were
to, say, substitute SHGC for the complete run from the radio shack to
the top of a tower, the signal would have more energy than the cable (or
the antenna) could withstand. 

Designed to be used in short sections between standard coax and the
antenna, SHGC is not currently available, pending the resolution of
certain limiting manufacturing capabilities.  Some reports have
surfaced, however, that a few samples of the hot-pink colored coax have
somehow slipped past reality checkpoints and made their way into the
Amateur community.  Without official spec sheets and installation guides
SHGC poses a significant hazard to the uneducated.

The following table dramatically illustrates the danger of using too
much Skyhighgain Coax in any transmission line:

Length of Coax / Power Output

     1 meters - 2 Watts 
     2 meters - 4 Watts 
     3 meters - 8 Watts 
     4 meters - 16 Watts 
     5 meters - 32 Watts 
     6 meters - 64 Watts 
     7 meters - 128 Watts 
     8 meters - 256 Watts 
     9 meters - 512 Watts 
     10 meters - 1,024 Watts 
     11 meters - 2,048 Watts 
     12 meters - 4,096 Watts 
     13 meters - 8,192 Watts 
     14 meters - 16,384 Watts 
     15 meters - 32,768 Watts 
     16 meters - 65,536 Watts 
     17 meters - 131,072 Watts 
     18 meters - 262,144 Watts 
     19 meters - 524,288 Watts 
     20 meters - 1,048,576 Watts 
     21 meters - 2,097,152 Watts 
     22 meters - 4,194,304 Watts 
     23 meters - 8,388,608 Watts 
     24 meters - 16,777,216 Watts 
     25 meters - 33,554,432 Watts 

As you can see, by the time you reach only 20 meters, the signal power
has exceeded a million Watts!  Assuming your facility's commercial power
mains could handle the load, the signal would exceed 30 million Watts at
only 25 meters from the transmitter.

Of course, most power main breakers would trip long before the million
Watt level, but once the signal starts up the transmisison line the peak
envelope power (PEP) climbs so fast that there is a possibility that the
circuit breakers would either fuse or the electric current would simply
jump the breaker's open switch gap and power would continue to increase
until the primary main lines evaporated in what could only be described
as a bolt of artificial lightning, showering every surrounding structure
with hot plasma and sparks.

73...
Norman