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Antenna set up for home use

 
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Antenna set up for home use
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terri
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Joined: 17 Dec 2004
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Post Antenna set up for home use Reply with quote
I'm a radio novice who purchased P d'oh! CI Max simply for home and yard use... so please go easy on me with the radio tech lingo

I've conquered a few problems with an external sound card, external power source and adjusting the EQ. Thanks so much for the previous advice with these items.

One last issue... the antenna. The only way I can get rid of a background "buzz" in the radio reception is to hold the antenna in my hand. This is the case with the wire antenna provided with the PCI Max and a coax cable I also tried. I don't really want to be a human antenna.. it doesn't pay well

What do you recommend for my antenna set up.. both on the transmitter and the receiver (the main living room receiver is about 20 feet away). What kind of antenna (on each)? Recommendations on antenna placement? What does my body do for the antenna that takes away the buzzing sound?

I greatly appreciate your guidance!
Sat May 07, 2005 1:41 am View user's profile Send private message
Dogen
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Location: Northwest USA

Post Re: Antenna set up for home use Reply with quote
terri wrote:

What do you recommend for my antenna set up.. both on the transmitter and the receiver (the main living room receiver is about 20 feet away). What kind of antenna (on each)? Recommendations on antenna placement?


If your receiver is 20 feet away, the simple wire that comes with the PCI-Max should do just fine for home broadcasting. You may, however, need to improve upon the antenna you have on your receiver. If it is a home stereo receiver, they usually come with a simple wire dipole antenna. If this is the case with your system, make sure the antenna isn't buried on the floor crumpled up. Pin it up to the wall so that it is fully stretched out either horizontally or vertically.

If you are still getting static, increase the power using the PCI-Max driver. If that doesn't work, you may be overmodulating and the static is, in fact, distortion. Try lowering the volume level of your audio input until you get a clean sound.

If you wish to improve upon the wire antenna that comes with the PCI-Max, making a dipole is the simplest solution, especially for home use. The PCI-Max uses an F connector, so the easiest thing to do is go to Radio Shack or your local Audio/Visual electronics store and pick up a 20-25 foot spool of RG-6 TV coax with the F connectors already installed. (RG-6 is 75ohm coax. The dipole feedpoint impedance is also near 75ohms so they are a good match and don’t present too much of a mismatch for the 50ohm antenna connector on the card) Since this is for indoor use, don't scrimp on the cheap cable. Buy the coax with the most shielding you can get. At a hardware store, purchase a 6 foot length of the thickest copper wire you can find and a square wooden dowel 5 to 5 1/2 feet long.

A dipole is just two pieces of wire that, when connected to the feedline, form a half-wave radiator for the frequency you are broadcasting on.

Step 1. Go to http://www.kwarc.org/ant-calc.html Use the calculator to find out the length the dipole will need to be on your chosen frequency (or divide 468 by your frequency for the total length in feet).

Step 2. Cut your copper wire into two pieces of equal length based on the length determined by the equation above. Each section should be 1/2 of the total length of the antenna (1/4 wave length per side).

Step 3. Tape each wire to the dowel with electrical tape, leaving approximately 2 inches between the wires in the middle. If the wire is insulated, expose about 1 1/2 inches of bare wire on each leg where they meet in the middle.

Step 4. Take your coax and cut off one F connector. With a razor, carefully cut off about 3 inches of the rubber insulation from the end of the coax exposing the woven copper shielding. Be careful when cutting that you don't nick the shielding. Using a knife tip, carefully nudge the woven shielding apart to form a small hole. Bend the coax over and wiggle the dielectric underneath out through the hole.

Step 5. Carefully cut away about 1 1/2 inches of the dielectric, leaving the center conductor (copper wire) exposed. Be careful not to nick the center conductor when doing this.

Step 6. Take the woven shielding and twist it into a firm snake - kind of like a stranded wire. Using a soldering iron, tin the braid (i.e., heat up the braided wire and allow some solder to melt into it).

Step 7. Connect the coax center conductor to one leg of the dipole by twisting the wires together firmly. Do the same with the tinned shield to the other leg.

Step 8. Solder the coax center conductor and shield to each leg of the dipole.

Step 9. Cover the entire antenna with electrical tape, paying special attention to where the coax and dipole meet in the center. If the wires stick off the end of the dowel a little, it's okay, just tape the wire up so no bare wire is exposed.

Step 10. Make a choke balun. Make several loops of coax about 4-6 inches in diameter close to the feedpoint of the dipole. You want the coax loops to be touching each other in parallel. You don't want them to be crossing over one another. You want to end up with a coil that you can tape together. Use about 4-6 loops. This will help keep the outer braid of the coax from radiating RF energy.

Step 11. Place the antenna in a convenient spot as far away from your PC as possible. Hang it in a corner vertically or near the ceiling horizontally.

Step 12. Connect the other end of the coax to your PCI-Max and you should have a dandy little antenna for broadcasting around your house/yard/neighborhood.

Without an SWR meter, it will be impossible to tell if your dipole is, or is not, truly resonant on your frequency but it should be close enough for your purposes (and far better than the wire you are currently using). If you purchase an SWR meter that covers the FM broadcast band, you will be able to adjust the length of the dipole to be near perfect on your frequency.


Last edited by Dogen on Sun May 08, 2005 8:57 am; edited 2 times in total
Sat May 07, 2005 9:03 am View user's profile Send private message
pcs
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Wow, cool post! Thanks!

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Sat May 07, 2005 10:27 am View user's profile Send private message Visit poster's website
terri
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Joined: 17 Dec 2004
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Post Reply with quote
Yes, thanks alot!! I'll get to work and let you know how I make out.
Sat May 07, 2005 12:48 pm View user's profile Send private message
mambo57
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Post coper wire gage Reply with quote
Dogen,

I may have over done it. The thickest coper wire at home depot is gage 6, it's way to thick to twist to make the connection to the coax. So I'm wondering if there is an alternative way to make the connections or should I get a thinner wire?

Also are there any issues using an insulated coper wire verses a bare coper wire? I'm asking since the instructions say to cover everything with electrical tape. Wouldn't having it be insulated to begin with make it easier?

Thanks for the instructions, they are easy to follow. My tech days are long behind me (20+years) and having clear steps to follow is great!

John
Sat Jul 02, 2005 4:37 pm View user's profile Send private message
Dogen
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Joined: 01 Mar 2005
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Location: Northwest USA

Post Re: coper wire gage Reply with quote
mambo57 wrote:

I may have over done it. The thickest coper wire at home depot is gage 6, it's way to thick to twist to make the connection to the coax. So I'm wondering if there is an alternative way to make the connections or should I get a thinner wire?


Try using small metal hose clamps to make the connection. If you have a large 200+ watt soldering gun, you might also be able to solder the connections once they are secured by the hose clamps. A small torch would also do the trick.

The reason I said to use the thickest wire you could find is that, as a general rule, large diameter radiating elements, are more broadband (lower Q), so you gain some frequency flexibility. If you used 1 inch copper pipe, you might have 2-3 megahertz of good SWR coverage while if you used 16 gauge wire, you might only have a few khz worth of low SWR. Larger diameter radiators also tend to shorten the overall length of the dipole a bit. There is a website out there somewhere that has a chart to help gauge the shortening effect, but I cannot seem to locate it. It won't matter as far as your signal strength so if you want to use a higher gauge wire to make things easier, by all means do so.

Quote:
Also are there any issues using an insulated coper wire verses a bare coper wire? I'm asking since the instructions say to cover everything with electrical tape. Wouldn't having it be insulated to begin with make it easier?


There will be no noticeable difference between insulated vs. uninsulated wire. And, yes, if you use insulated wire, you only need to tape up the feedpoint and wire ends (especially important when you are broadcasting with higher wattage since the voltage on the ends is enough to cause burns - not a problem with PCIMax w/o the amplifier.) I just happen to like the look of a completely taped up antenna in this configuration.

Good luck!

Dogen
Sat Jul 02, 2005 7:43 pm View user's profile Send private message
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