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Author Topic: HF Wire Antennas  (Read 7284 times)

HAM2BE

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HF Wire Antennas
« on: June 27, 2001, 12:41:51 PM »

Hey all,
        I have a question or two.  First off, I live in an apartment, on the second floor, with no patio/deck.  My VHF/UHF antennas are in the attic, and work fine for repeaters and simplex.  If conditions are favorable, I can get into the Roanoke, VA. repeater from my apartment in Kernersville, NC.  Thats a pretty good distance.  I am not full quieting, but readable.

I have just aquired a Kenwood TS-930 withh the built in antenna tuner.  I am upgrading very soon and want to go ahead and get an antenna in place so that I can begin using the rig as soon as I am legally able.

I realize I cannot reasonably expect to work 160 meters with limited space, but if possible, I would like to be active on 80-10.  Would I be better off using one dipole, 135' (I think thats right) for all bands, or should I cut individual dipoles for each band?  All this has to fit in the attic...I looked at doing a wire around the building, but it would be noticeable on the front, and all the power, tv and cable comes in on the back of the building in various locations, so thats out.  

If I do the seperate dipoles with one feed line, will the Tuner on the radio properly tune?  That may be a stupid question, but I didnt know.  I am very strapped for cash right now, so an external tuner is out of the question.  Whatever I do will have to be simple, low budget, and somewhat capable of radiating further than the parking lot.

Any and all suggestions are welcome, but please dont waste bandwidth suggesting I move.  Thats kinda hard when you are in the middle of a nasty divorce, and she got all the money.....

One other question.  Station Grounding..how?  the cold water pipes are PVC, and it would be a 20' run out the window to a grounding rod.  I am sure that the ground line would resonate on some portion of the HF bands, so does anyone have any ideas?  I want to operate safe...

Thx & 73
Tim, KG4MQD
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KL7IPV

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HF Wire Antennas
« Reply #1 on: June 27, 2001, 11:47:32 PM »

My suggestion is, since you have a tuner; go to a shortened dipole with traps and place it in the attic. There are a couple of them available commercially and seem to work well.  As far as getting a station ground, use the ground at the outlet. Be sure it is solid to the ground for the electrical to your building and check it for low resstance from the electrical ground back to the outlet you'll be using. That isn't the best place to go but it seems it is about your only real choice. It will give you a solid ground reference and some protection too. Hopefully it won't be a correct length for any frequencies you'll be operating on. Be sure the radio is clean or every one in your building will know when you are on the air. I am sure you'll get lots more on this item. Good luck
73,
Frank
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VK4JAM

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HF Wire Antennas
« Reply #2 on: June 29, 2001, 09:34:45 PM »

Hi Tim,
I use a multi-dipole in my attic with reasonable results. It is bacically 3 dipoles (10, 15 and 80 metres) connected into a balun which then runs back to the radio on RG58 cable. When I fists built the antenna (many years ago) I spent the time adjusting the lengith of each dipole to achieve a good VSWR - the antenna was mounted hig and in the open then.  However when I installed it in the attic - it was just cram it in as best I could. It still seems to work OK via the ATU - and even performs well on 20m.  A similar antenna will probable work OK for you, depending on how good the ATU is.  I use a Kenwood TS520 and the an AT-200 ATU.
Good luck & 73's
Andrew
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W6DXO

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HF Wire Antennas
« Reply #3 on: July 05, 2001, 02:55:16 PM »

Hi Tim..

I use a mulit element inverted V antenna with one element (dipole) for 40 and 15M, one for 20M, and one for 10M.  The antenna is now mounted at 30' up on my roof.

BEFORE I was able to get the antenna installed I simply had it up on the second floor of my house strung between the tops of some bedroom doors(!)

The antenna has performed beyond all my expectations.  I have over 60 countries worked QRP,
 (FT 817 and Z-11 tuner) and finished my WAC in only about 30 days.

Your rig's tuner will take care of everything.  I'll bet it will even allow you to work 17M by tuning the 20M element.  You'll be really surprised how well the wire antennas will do.

Good luck.

harry edwards
W6DXO
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N6AJR

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HF Wire Antennas
« Reply #4 on: July 12, 2001, 11:29:57 PM »

I have used both the full sized 135 foot dipole and the multiple dipoles connectd to one feed line and have had great luck with both.  The multiple dipoles seem easier to tune and you can cut them to your fav freq's and use with out the tuner.. but the tuner will allow you to tune them just about any where... as for ground, also make up a set of ground radials but call them a counterpoise.  

Make on for each band a 1/4 wave length long, so you need one wire around 66', one around 33', one around 16 1/2 ', ( the 40 meter will work ok for 15 meter) and one around 8 1/2 ' .  you can make these out of some multi wire rotor cable ( my favorite, flat, easy to cut to length and hides well) or other wire and run it around the room , or under the rugs and furniture as an "artificial ground " for your station. You hook the one end of all of them connected together to the ground on your radio or tuner, and be sure to tape the other end because it can develope some awesome voltages.  A counterpoise moves all the "extra " rf a quarter wave away from the radio, keeps the rig from bitting you and helps cut down on rfi/tvi, and even helps the antenna work better...

Nothing new here, just letting you in on what I've learned from others over the years... good luck have fun. Any antenna ids better than no antenna at all!!!

tom
N6AJR
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NB6Z

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HF Wire Antennas
« Reply #5 on: July 16, 2001, 11:22:12 AM »

If you can get 135 feet of wire spread out in your attic, then go for it. It is the quickest and easiest to make and maintain... If you can't get 135 feet, go with 66 feet and forgo 80 meters. Or, use as much wire as you can and let the tuner try to put energy into it on the lowest band.
Use high grade TV twin lead instead of coax for this antenna! Build (or buy) a 1:1 voltage balun to put on the output of the tuner (dipoles and twin lead are balanced devices). (If you go with a random length of wire, you may have better luck tuning with a 4:1 balun.) Keep the lead and antenna away from metal as possible.
Any thing you do that is an "indoor" installation is going to be a major compromise. A tunable dipole will work as well (or as poorly) as any other type you might come up with. The digital hams are using indoor wires and getting great results on modes like psk31 and hellscheiber.
With a dipole you may not need a ground at all. RF in the shack is a real possiblity with indoor antennas. You may want to use QRP or other RFI techniques I have seen described on this web site.

GL. Griff
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KF4ZGZ

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HF Wire Antennas
« Reply #6 on: July 23, 2001, 06:35:26 AM »

If you have the room for the 135 ft. feed it with ladderline and a tuner and use it. If not ,try an 88 ft. dipole. You'll get 80m-10m with ladderline ( and maybe even coax- I never tried it )and a tuner. Go with 44 ft. on each side- keep it even on each side to reduce the possibility of rf. This gives about the same pattern as the 135 ft. dipole except it doesn't have as much gain.                                                 73 and good luck de Matt, KF4ZGZ
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Matt
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