Original article from: Wayne Sarosi 
 Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo.
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SUBJECT: Wire antennas - Part 4
 Both of the following antennas are using 12 guage wire.
 Wire Dipoles: Use the formula 468/fMHz to cut the dipole.
 String it up in the area you have planned. Attach your coax and a balun.
 Check the SWR.  If it is within your spec's it's ready to use.
 If not,do the following:
 o Check the SWR from the bottow of the band to the top.
   Don't step on anyone having a QSO!
   Use the least amount of power to do this.
   I'll use 40m as an example:
              7.0       1.7:1
              7.05      1.8:1
              7.1       2.1:1
              7.15      2.2:1
              7.2       2.5:1
              7.25      3.0:1
              7.3       3.5:1
 This indicates that the antenna is too long and the resonate frequency of 
he
antenna is below the band.  This could happen because of the following:
 o A thicker diameter wire was used.
 o You mis-measured.
 o Something near the antenna is resonating with it.
 o Too low to the ground.
 Solution: trim off about six inches either side and try again.
 o Case two:  SWR Readings;
              7.0       4.0:1
              7.05      3.5:1
              7.1       3.3:1
              7.15      3.0:1
              7.2       2.4:1
              7.25      2.0:1
              7.3       1.8:1
 This indicates the antenna is too short.
 "But I keep cutting off wire and it's -still- too short." (Raised eyebrows.)
 All is not lost here.
 Solution:  add telescoping elements to the ends.
 Aluminum tubing,3/8-in & 1/4-in dia.,secured with a screw should do the
trick.  3/8-in dia. = 1-ft,1/4-in dia. = 11-in in length.
                  __________________ wire attaches here
     =============__________________
 Now you can adjust the ends of the dipole until the SWR reaches the desired
level at the desired frequency. This problem can happen when the guage of 
ire
used is smaller than the recommended size.
 Remember: Thicker => shorter;  Thinner => longer.
 Here's some Dipole measurements for HF:
    BAND      LENGTH-FT           DESIGN FREQUENCY
    10m       16' 5 1/2"          28.45 MHz
    12m       18' 9"              24.94 MHz
    15m       21' 11 1/4"         21.335 MHz
    17m       25' 10"             18.11 MHz
    20m       33' 0"              14.2 MHz
    30m       46' 3"              10.12 MHz
    40m       65' 5"              7.15 MHz
    75m       123' 2"             3.8 MHz
    80m       130' 0"             3.6 MHz
    160m high 240' 0"             1.95 MHz
    160m low  252' 10"            1.85 MHz
Have fun!
-WS
--- GoldED 2.42.G1219
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