QRO precautions ??
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With the possible eminent presentation of a VERY QRO amplifier to the
Elecraft family, there is certain to be a number of us, with only QRP experience, jumping in and "playing" with gobs of RF energy for the very first time. Let's hear it from those with experience, some do's, don'ts and caveats that go along with running the legal limit. I hate learning stuff the hard way... Thanks, Bill K3UJ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Bill, K3UJ wrote:
With the possible eminent presentation of a VERY QRO amplifier to the Elecraft family, there is certain to be a number of us, with only QRP experience, jumping in and "playing" with gobs of RF energy for the very first time. Let's hear it from those with experience, some do's, don'ts and caveats that go along with running the legal limit. I hate learning stuff the hard way... ----------------------------------------- I'd start with the observation that any part of the antenna circuit of a QRO rig should be treated with the same respect you'd give the inside of your household mains circuit breaker box. The RF from a QRO amplifier won't likely kill you like touching the terminals behind the safety cover of a circuit-breaker box will, but if you get onto high voltage RF you may wish you were dead. The pain of serious RF burns is deep and long-lasting. Permanent nerve damage is not unusual. Once I was working with a guy installing a large, self-supporting antenna on a ship when he got a burn on his hand from induced RF from a nearby broadcast station. We were using a container crane to position the antenna for bolting to the ship. I was on the ship and he was "riding the crane" with the antenna. When he reached across to position to base so I could drop the bolts in place, I saw the glow of an RF arc between the brass antenna base and the ship. He let out a howl that would have done the Wolf-man proud. I later figured out that the 200-foot high container crane, grounded at its base on it's metal tracks to ensure workers are absolutely safe from electrical shock, formed a giant loop antenna with the ship sitting in salt water. We were only a few hundred meters from the broadcast towers. It made a black mark about two inches long on his palm in a fraction of a second. He was in such severe pain for several weeks that is was very difficult to use that hand at all. Remember, that was just the induced RF from a nearby antenna. No direct connection at all. Several hundred watts from a Ham rig can be at least as destructive if you touch it. Also, I've seen arcs 6 inches and longer erupt from high-impedance points of a kilowatt transmitter antenna system across a dirty insulator. They not only pose a serious injury hazard, they can and will start fires. Temporary or indoor antennas are no place for QRO power levels. Like all high voltages the voltages resulting from high RF power levels need not be dangerous or harmful if treated with respect. Good insulators, decent distance between people and the antenna, and good safety procedures when working around the equipment make a kilowatt no more dangerous than QRP. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Able2fly
Hello,
I recently reactivated a Swan linear and an older Hallicrafter HT33A, When I exceeded about 500 watts on 40 or 80, the GFI breaker in the upstairs bathroom would trip and the electric bed also upstairs would start running. (A real No-No if the XYL was in it). I had a lot of bothersome RF in the shack from a 135' OCF antenna that didn't cause any problems at 100 watts. I also had a little TVI in the TV upstairs. Using an old linear, you miss QSK. However I solved all of these problems. On the GFI breaker, I replaced it; the new ones are RF resistant. I used an AC line filter I had in the shack and that fixed the electric bed problem. On the RF, I used all standard fixes: short grounds, better ground on the coax shield before coming into the shack. All helped but but it took a dozen or so turns of RG8X on a 2 gallon chlorix bottle where the coax came into the house to get rig of it completely. I installed two LPF filters in the coax from each linear to its tuner and that took care of the TVI. For QSK, I reactivated a QSK1500 external switching unit on the Swan and Omni-VI that gave me back QSK at anything less than 1500 watts. On the newer linears, some of them have QSK built in, so if you want QSK, buy a linear with it build in. I'm assuming the Elecraft linear has it. It goes without saying that you need heavy duty coax switches, RG8 or at least RG8X coax and even LMR-400 on long runs. You need high power antenna tuners, lightning arresters, heavy duty grounds and adequate power to the shack. I have a separate 220 v circuit going to the shack. Operating, you don't need a linear most of the time, especially on CW. Sometimes it's helpful on SSB particularity on 20, 40 and 80. Frankly, If I had to buy a new 3K linear (dollars), I'm not sure it would be worth it. You have to see what kind of operating you do. Of course, from Elecraft's point of view, if there are linears to be sold, a good, relatively inexpensive kit has a lot of potential. At 01:31 PM 5/26/2005, you wrote: >With the possible eminent presentation of a VERY QRO amplifier to the >Elecraft family, there is certain to be a number of us, with only QRP >experience, >jumping in and "playing" with gobs of RF energy for the very first time. >Let's >hear it from those with experience, some do's, don'ts and caveats that go >along with running the legal limit. I hate learning stuff the hard way... > >Thanks, > >Bill K3UJ >_______________________________________________ >Elecraft mailing list >Post to: [hidden email] >You must be a subscriber to post to the list. >Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > >Help: http://mailman.qth.net/subscribers.htm >Elecraft web page: http://www.elecraft.com 73, Chas, W1CG _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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