Sunday, May 24, 2015

Stormy Weather

I have always been one to be concerned about lightning damage to my solid state gear. In the old days of tube gear, other than a direct lightning strike, I never thought about it too much. Oh, if a thunderstorm was coming, I would disconnect the antennas, often leaving the connector lying behind the radios or sometimes on the window sill before I had the leads dropped down through the wall.

Even then I knew about inducing of high voltages in long wire antennas by nearby lightning activity. It was brought home to me one night during a storm when I kept hearing a frequent “ Snap! Snap! Snap “ sound. It actually woke me out of a deep sleep. It took a few minutes to figure out what it was. The antenna lead I had disconnected from the radio and left lying on the window sill was arcing over to the aluminum window frame which was grounded! The arcs were well over an inch long. It scared me a bit and I got up, opened the window and tossed the lead outside!

The next morning, I got to thinking about what had happened. The antenna I had at that time was about seventy feet long and suspended between two wooden masts that were twenty feet high. After reading a bit and talking with some of the older hams at the local radio club, I figured out that nearby lightning activity was inducing currents into the antenna, just as passing radio waves did. The “ signals” from the lightning were just a whole lot stronger, and certainly well over the several microvolts the radio signals might have brought.

The tube receivers were physically pretty stout in those days. Voltage spikes don't scare 12SK7's or 6BZ6's much. After seeing the arcs, I did get concerned about the small Litz wire that the antenna coupling coils were wound with and thus began my protective attitude toward the radios. I still did not disconnect the antennas every day, only when I suspected a storm was coming. And I still used the radios during stormy weather if the cell with its attendant wild lightning was not directly overhead.

When I got my first really long antennas up, that changed a bit. At one point I had a long horizontal “T” up that was supported by a salvaged utility pole and that spanned our entire back yard and two neighboring lots, running along the rear of the neighbors garden and home and all the way to a street that connected to the road in front of our house. There was probably almost 300 feet of wire up. Now that thing really did collect the voltage! In fact it was not just during thunderstorms, but I heard the arcing behind the receiver once during a blowing dust storm. Static electricity was building up on the wire and finally arcing over.

There was no damage to the radio, but the fact that there was arcing inside the house led my parents ( I was 13 at the time) to tell me to “ do something about that”. The answer was a big knife switch outside the house that would allow easy grounding of the wire during scary or threatening times. In fact, it became a habit to ground the thing any time not in use. A shorter longwire or simple dipoles or verticals were used during rough weather. Of course, when lightning was in the immediate area, all activity ceased.

When I began working at my first radio station job, I learned more about lightning protection. The four broadcast towers at my first radio station frequently arced over during storms, with the transmitter tripping off momentarily, then automatically resetting after the arc stopped. There were two large metal balls near the base of the tower only about an inch apart just for the purpose of sending the current from a near or direct strike to ground. One was connected to the ground system, the other to the tower and they were spaced just far enough apart for the RF not to arc across them during normal operation. During storms it was common to see and hear arcs across the spark balls. There were also static drain chokes across the inputs of the antenna tuning units at the base of the towers ( if you ever wondered what was in those little “dog houses” at the bases of broadcast towers, that's it...they contain matching networks-usually T-networks—to match the impedance of the towers to the impedance of the transmission line and in some cases to provide part of the phase shift for the directional system)

All of this gave me ideas on how to protect my gear at home. Some amateur handbooks also called for putting neon bulbs across antenna inputs of receivers. They would normally be open, but if the voltage on the antenna ever got higher than the break over or firing voltage of the neon bulbs, they would ignite and conduct the charge to ground. There were also RF chokes to put across the receiver inputs or 100 megohm resisters to drain the static charges.

The best overall protection, however was to disconnect the antennas and thus not use the radio at time of highest danger.

With the advent of solid state receivers, the problem became more acute. The junctions in the early transistors and connections in the newer forms of transistors and other chips just won't handle the higher voltages that can appear on antennas at times. The newer rigs have some protection built in, usually in the form of high resistances across the input, chokes and diodes...but despite all that, these rigs are more vulnerable than the old tube gear. I lost the front end of my venerable old FT-101 during a storm during which I was operating a contest. I had watched the weather, had the radar on a local weather channel up on the tv and watching and figured that the core of the storm was far enough away. However, an errant lightning strike in my neighborhood took out the front end of the FT-101 even though my antenna was not hit.

That incident got me a little paranoid about using gear even to listen when the weather got questionable.

Which brings me to this past weekend. It was time for a cluster of small contests...including the UN ( Kazakh) contest and the Baltic States contest and I really wanted to get in there and see what there was to see. I am sure the newer gear is more protected than the older solid state stuff, but I was still nervous. I told myself that when the static crashes got strong on the lower bands or became audible on the higher bands, I could just shut down. That lasted about thirty minutes, because it began to look like it would be dicey the entire weekend.

Then came the answer. I wouldn't use the new gear. I would unlimber some of my old favorites that I knew would be “safe” ( or at least “safer”). Thus brought the old Drake 2 B into play along with my venerable old Hammurland HQ-170. The Drake doesn't use narrow filters in two IF's like the newer Icom, but it does have a very good Q multiplier that operates in the 50 kHz IF. The Hammurland also is triple conversion with a 60 kHz IF. While they don't have the digital readout, why is that really necessary when DX-ing the ham bands as long as you have crystal calibrators to tell you where the band edges are.

Did it hurt using the older gear? Well there is the continuous hiss and ringing sound when using the Q-multiplier on the Drake and the hollow “ wind blowing across the end of a pipe” sound of the Hammurland in the narrow selectivity mode...but the results were good. The DX was probably just as good, or nearly as good, while the operating convenience was not as good. After a few minutes the feel of using the Drake came right back...and it was particularly comfortable using a receiver that has been in the shack almost fifty years. The Hammurland has been with me since 1976 and the trick of swapping sides of zero beat with the BFO to get rid of pesky QRM came back quickly.

Did I miss anything? Perhaps. But I do know I what I did NOT miss using those old friends. There was still the long strings of JA's the first evening on 15 meters and the first morning on 40. There was still a long list of UN-prefixed stations on 40, 20, and 15 ( the band was just not cooperative on 10...or was it the receivers? I could not tell...maybe some of you could tell me in the “comments”.) There were several stations from South Korea in the log ( DS and HL). There were 4X and 4Z stations from Israel. There was SV5/DL3DRN from the Dodecanese. And there was

3B9, VP8, SV2, YB8, several ZL and VK stations, several UA's and R's from various locations, UX's and UR's, TA, S5's, and later in the weekend during non contest hours OJ0 ( Market reef) TF3,5Z0L, T88,A45 and JW9. Not too shabby for fifty-plus year old radios. And the solid state, new, high tech stuff got to live to fight another day and I did not have to miss logging the goodies because of nearby storms.

Now none of this is to say that I took chances or advocate taking chances with bad weather. At the first sign of really nearby lightning or the sound of thunder less than a few seconds behind flashes seen in he window, the plug was pulled and the feedline thrown out the window. I want to make sure I get to live to tune another day!!

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