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and Duplex Radio...
Rain and Snow Clouds Contain More Than Rain and Snow
The Phenomenon and the Cure!!
By Kevin Custer W3KKC
Fiberglass antennas in general suffer from Corona Discharge and Precipitation Static. These phenomena exist when a charged cloud is near, and an aurora is formed around the antenna creating receiver desensitization. Also, when it rains, water droplets discharge to the radome creating noise. It is also possible that dust can be charged and blown against an antenna and will cause static similar to precipitation static. As the static is built up on the antenna, receiver desensitization occurs. Many times the limiter current meter can be observed during these phenomena and you note the current go up. On my 145.270 KQ3M repeater, I use a Sinclair SRL-229 fiberglass Superstationmaster-like antenna. The receiver limiter metering point on my MICOR receiver reads usually around a couple of uA when receiving no signal on a typical day.... then the clouds come! I have seen the limiter stage go into hard limiting (40 uA.) with a storm cloud comes near. Obviously a user would have to be stronger than the noise for the squelch to open, and then the user will most certainly be very noisy even though he may normally be DFQ (dead full quieting) into the repeater. You can hear the instant the static has dissipated, when a user is into the repeater the receiver will quiet and then the sequence starts all over again gradually building up and then like a switch, bam, DFQ. The association to the instant when the repeater quiets up is when lightning has struck and has dissipated the excess static near the site. The lightning doesn't have to hit the site; it could have discharged miles away. The building up of static (to another strike) sounds like electrical interference from a running engine that slowly builds rotational speed (RPM). The noise usually sounds like a tone rising in frequency until lightning dissipates it, then it starts all over. This problem happens with or without the transmitter being on, but is sometimes worse with the transmitter on.
Before a rain, Corona can build up on a fiberglass causing static, but once the rain starts and the antenna gets wet, the effect of Precipitation Static can occur. The corona charge drains off of the antenna and the desense from the charges of each individual water drop of precipitation dominates. At that point, the effect of precipitation static on an exposed dipole antenna can be greater than on the fiberglass antenna. A number of side by side tests with both types of antennas have shown this crossover effect to be true.
These corona and precipitation problems can be solved by using a static dissipation device, like a "Static Buster." These devices continually bleed off the static charge. After 2 years of suffering with the repeater not working in rainy or snowy weather, I bought one of these devices, from a Dayton Hamvention vender called "Static Buster", and installed it on the 2-7 machine..... problem solved. Interestingly enough, Sinclair was also at Dayton that year and I confronted them with my problem, and they said "we have never heard of this." That's funny because this exact same antenna is used on four other 2M repeaters in the area and they all suffer greatly from corona discharge. Most of the owners had called Sinclair about their problem to no avail. This problem is most severe when your antenna is the highest on a structure or tower (i.e. top mounted). Fiberglass antennas seem to suffer more than the exposed dipole arrays, perhaps because the dipole arrays are DC grounded.
Although not marketed as a lightning deterrent, it is interesting to note that after this device has been installed, lightning will likely NOT strike this antenna because of the lack of ability of the antenna to build a counter charge where discharge from a cloud would be attracted.
As I explained, I obtained a few Static Buster devices from Mike Norton KE4NS in the early nineties. Mike started the company "Static Buster" and had sold them at shows and hamfests. They have proven to do their job across the country and around the world. I've teamed up with Mike and host the only outlet for the device here at Masters Communications.
Click Here to see a picture of the Static Buster (** note -- color can be black or white)
Click Here for more detailed information on Corona Discharge, P-Static from the Inventor
Click Here for Ordering Information
Click here for Detailed Mounting Instructions
Copyright July 19 1998 Kevin K. Custer W3KKC. All Rights Reserved.
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