Great wire antenna site :
http://www.qsl.net/va3iul/Antenna/Wi..._ham_radio.htm
Great wire antenna site :
http://www.qsl.net/va3iul/Antenna/Wi..._ham_radio.htm
أبدا ستعمل تعطيك ما يصل
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I hate to criticize another ham's skywire, but the one time I tried an OCF antenna
(2nd story bedroom closet), there was tons of RF in the shack, owing to feedline radiation.
With a center fed dipole, the feeder currents are balanced, and all your radiation will be
from the antenna proper where it can do more good.
OCF? In a closet? what were you working, 1296?Originally Posted by W9JEF
Actually, it was 80 meters. Originally had a half-wave folded dipole
made entirely of 300 ohm line, slung between opposite corners of the yard.
With an eye toward multiband operation (and feedpoint closer to the shack),
I replaced it with a 120 foot Windom, fed with a pair of B&W air-wound balun coils.
Alas, my signal reports on 80 meters were reduced by about 10 db.
On the bright side, the RF induced in the house wiring
compensated for the key-down dimming of the lights. :)
My first antenna after a 26 year absence in ham radio was a 260' long OCF fed with 300 Ohm twinlead. It was up about 90' in the air, using some huge fir trees, and the antenna ran N/S, in the clear. The feed point did sag a little, and was was at about 35/65 % lengths, as this was convenient, more than from a calculation.
Station (RF) ground was top rail of a chain link fence with each section "bonded" with sheet metal screws and wire jumpers... this fence had a total length of about 200', and was just outside the shack window.
This simple antenna was pretty damn good, tuned well, and I had no problems at all with an older MFJ VersaTuner II running a Ten Tec Omni D barefoot.
No RF in the shack at all, on any band, except when I screwed up and didn't tune the antenna correctly. My crappy PC speakers would sing like mad, and the upstairs stereo system would pick it up too.
When tuned correctly, almost all the RF went to the antenna, so no RF in the shack. Simple.
Last edited by WØTKX; 01-19-2014 at 12:42 AM.
"Where would we be without the agitators of the world to attach the electrodes
of knowledge to the nipples of ignorance?" ~ Professor "Dick" Soloman
Tying the 4 feeder wires of my 80 meter turnstile together
configures it as a top-loaded cage "umbrella" vertical.
The shack is ground floor; antenna fed against many on-ground radials.
The powerline service entrance is in the same room;
the neutral is tied to the station ground, and each hot phase
bypassed with .01 @ 2500 volt mica.
When your feedline is radiating, unless there's a good RF ground reference,
you have the classic case of "the tail wagging the dog"--RF in the shack.
Last edited by W9JEF; 01-19-2014 at 12:40 PM.
Ah yes, the ghost of Big Daddy Roth still haunts us. (;->) An above post reminded me of the time I couldn't use an earthing rod for lightning protection so I ripped one of several old and unused cable TV lines off the building and used it as a ground wire connecting it to a neighbor's chain link fence directly below the antenna mast. Considering how long it was it made a good ground passing the light bulb test with flying colors. Light bulb test? A 150W bulb connected between the AC mains hot and outer braid of the coax lit up to full brilliance. Anyway, good luck and I say that most sincerely, you'll be happy when you banish that nasty looking rat from the shack... and send him back to Rat Shack where he belongs.
"The universe is under no obligation to make sense to you."
Neil deGrasse Tyson
73 de Warren KB2VXA
Station powered by atomic energy, operator powered by natural gas.
Once, I ran a lead from the radials for an indoor/porch antenna to the screw that mounts the plastic plate on the 120 vac house outlets. This was circa 1996 and I had a 486-DX2 computer running Windows 95 with 16 megs of RAM. One day while working on a Sweep Tube amplifier, my computer locked up and died. Because it was still under warranty, I had it serviced for free; the hard drive had crashed.
Weeks later, under similar circumstances, again the computer died and the hard drive had to be replaced. At that time, I had just started forming conclusions as to why the hard drives died in the same way under the same conditions but, I wasn't for-sure.
On the third occurrence, while still under warranty, the Technician said, "I cannot figure out why you keep blowing up these hard drives."
The 110 vac 3 wire plug uses 1/2 of the 220 vac service with the neutral and the ground tied together; effectively, my return path from the antenna was connected to the whole of the building wiring.
There was not a fourth RF caused hard drive failure.
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Last edited by koØm; 01-20-2014 at 07:18 PM.
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