[R-390] Skyhighgain Coaxial Cable Consumer Safety Alert

[James Miller]

This is early.  April 1 is still a few days away.

Norman Ryan wrote:
> 
> 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
> _______________________________________________
> R-390 mailing list
> R-390@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/r-390