Tape Measure, Di-Pole Antenna
EVENT:
ARRL 10-Meter Contest, Saturday, December 14, 2002.
MY LOCATION:
Springfield, Missouri, elevation above sea level 1382 feet.
ANTENNA:
Tape Measure Di-Pole.
ESTIMATED HEIGHT ABOVE THE EARTH:
17 feet at the feed-point.
RIG / TUNER:
Icom 746, at 100 watts, MFJ-969, Drake Filter.
I was able to fully load this di-pole to 100 watts transceiver output (my maximum output).
TOTAL CONTACTS / TIME:
33 contacts, from 4:10 UTC to 8:30 UTC.
Total operating time was 4 hours and 20 minutes.
Average of one contact every 8 minutes.
DX CONTACTS:
The most distant contacts made were: Kyrgyzstan, Netherlands, and British Columbia.
- va7dp, British Columbia
- pa0ijm, Netherlands
- dl2ard, Germany
- tm5c, France
- ex2z, Kyrgyzstan!
- va7xx, British Columbia
- ve6fi, Alberta
- ve5dx, Saskatchewan
Kyrgyzstan lies on the west border of China. For me this was a pretty exciting contact. I've worked other stations in that area of the world, although with my A-99 commercial grade antenna, not a tape measure. It is neat being able to work nearly 1/2 way around the world with a couple $8 tape measures, and had I wanted to (although this would've constituted "cheating" in my mind) I could've used just one tape measure and cut two 104 inch pieces.
The image at the middle-left shows several of my antennas. You can see the A-99 vertical on the left. The bottom of the A-99 is 25 feet above the earth and the antenna itself is approximately 17 feet tall. You can see the tops of the two easels I used as di-poles to the right of the A-99. You can just barely make out the tape measure di-pole along the top edge of the roof.
LOWER 48 CONTACTS:
| | w1air, CT |
| w1sj, VT |
| n7lox, WA |
| k7zz, OR |
| n7bes, WA |
| w7ovb, WA |
| | k1ur, MA |
| w6yx, CA |
| w6cus, CA |
| nv7v, MT |
| ki6cg, CA |
| aa1jd, MA |
| | ke7no, MT |
| n1hra, RI |
| n7tt, WA |
| af1t, NH |
| n7uvh, ID |
| w6kc, CA |
| | ke6zsn, CA |
| w7zr, AZ |
| wa7nd, OR |
| w0ra, AZ |
| n1ea, MA |
| k6idx, CA |
| | n7pp, WA |
DISCUSSION:
This antenna was arranged as an "inverted vee". The photos show the di-pole extending along the ridge of the roof, which runs along a East-West axis, however, I changed my mind. I rotated it 90 degrees from that shown in the images so it would have it's maximum gain to the East-West instead of North-South. The feed point remained at 17 feet height.
Each tape measure was extended outward 104 inches. This is the point at which I attached the wires leading from the Altoid's box (see below). I placed a plastic "dog bone" insulator inside the hose clamp, placed the exposed end of the wire on the bottom of the tape measure, and hand-tightened the clamp.
This antenna worked very well, which is not very surprizing. In fact, it worked so well, I am again considering climbing into my attic and installing a number of back-up di-poles along the rafters. Heck, if I can stalk to a station a stone's throw away from China, it's a good back-up antenna!
Sometime during the few hours I was operating this di-pole the wind picked up. When I went on the roof to switch to the folding chair di-pole I noted the leg (originally) pointing south, had blown upward and bent into a rounded-L. So, I ended up with an antenna configured very close to an "L" on it's side versus an inverted di-pole. I am uncertain when this happened. Before or after Kyrgyzstan is my question!
There are well-known plans for directional antennas used in Transmitter Hunts, which use pieces of tape meaures for the elements. They work quite well!
For anyone in ARES, RACES, or other emergency radio deployment situations, I would suggest you consider placing at least two metal tape measures in your "go bag". You never know when measuring something is handy and you can't have too many back-up antennas!