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I am really new to ham radio and have a couple of questions. I bought
a used Yaesu FT-980 and now am trying to set up an antenna for it. Option 1: AT-100 Pro / 4:1 balun / randome long wire. I am experimenting with this in my office at the moment. I cut a copper wire (about 3/16 inch strand) and attached it to the antenna line of balun. I ran another short wire to the ground of the wall receptacle. Connected balun to AT-100 Pro with 25 foot coax, then connected the antenna tuner to FT-980. I powered up the transceiver and tried a few differant frequencies. The AT-100 Pro made some grinding noise and was able to bring the SWR down to around 2, the power meter went to about 100. The antenna was drapped across some cubicles (dilbert office). After a short while the antenna wire got a bit hot to touch, and tingled a bit when I touched it. Is this normal? Should I use a longer wire? Option 2: I am thinking of getting an MP-1 vertical antenna instead of random wire. Can I use the antenna tuner with this? Will it heat up? How do I ground it? Do the counterpose wires spread out act as a ground? Sorry for all the questions, I am a total beginner. Thanks for your help, Glenn PAMREMOVE |
#2
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Glenn wrote:
I am really new to ham radio and have a couple of questions.ffice). After a short while the antenna wire got a bit hot to touch, and tingled a bit when I touched it. Is this normal? Yes - it's not a good idea to touch an antenna when it's transmitting - especially 100 watts. Option 2: I am thinking of getting an MP-1 vertical antenna instead of random wire. Can I use the antenna tuner with this? Yes - although you may not need it: the MP1 has an adjustable coil that should do the matching for you, rendering the tuner superflous. Will it heat up? Shouldn't if it's tuned up right. How do I ground it? Do the counterpose wires spread out act as a ground? Yes. Hi, Glenn - I hope the experts will have something to say, but someone ought to mention that you shouldn't expose your officemates to 100W of rf energy. Can you get that random wire outside? Those cubicle dividers have metal tops & skeletons, no? Those are no doubt coupling to the antenna wire if it's draped over them. This just generally messes up the situation. Another reason to get that wire outside. The wire heating up is no doubt due to this coupling with office furnishings. The voltage varies along the wire, and at places it can be thousands of volts. A metal object in contact with such a spot could arc with the antenna wire. An antenna wire should be as high as possible and *in the clear* (not touching any buildings, tree limbs, lamp posts, etc). That's why an insulator is put at the end of an antenna wire, with a rope going the rest of the way to the antenna support (tree, etc.) The MP1 has been used and it works. Being a shortened vertical, it tends to radiate mostly upwards on the lower bands. This can be good (40M in the daytime to talk within a few hundred miles) or bad (40M at night when you might want to do dx may not be so great). Can you put the MP1 outside, even temporarily? The counterpoise wires constitute the rf "ground" in that case. They should be cut to 1/4 wave on the lowest band you want to operate on and fanned out around the base of the antenna. Please don't hesitate to ask more questions. Hope this helps. Antenna boys - please chime in! 73 - Lee H, NB7F |
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