‰  NOW 40 WPM  ‰ 
RESONANCE BELOW 3R5 MHZ, AS SHOWN IN FIGURE 7.  ASIDE FROM THE 80
METER VALUE, THE FREQUENCIES OF LOWEST MEASURED SWR AGREE REMARKABLY
WELL WITH THE SIMULATED RESULTS IN FIGURE 3.  THE ENDS OF THE S OCFD
CAN BE BENT TOWARD THE GROUND TO REDUCE THE END TO END SPAN OF THE
ANTENNA BY AT LEAST 30 WITHOUT ADVERSELY AFFECTING THE SWR BEHAVIOR,
TAKING CARE AGAIN TO CHANGE EACH END IN THE SAME 11 9 PROPORTION.
NOTE THAT THIS REDUCED SPAN IS ABOUT THE SAME AS A 3 30 MHZ TFD.

CAN BENEFIT FROM A SINGLE ANTENNA THAT PRESENTS A REASONABLY LOW SWR
ACROSS A NUMBER OF HAM BANDS.  FOR EXAMPLE, STATIONS PARTICIPATING
IN HF AUTOMATIC LINK ESTABLISHMENT HF ALE USE A STANDARDIZED ROTOCOL
TO AUTONOMOUSLY QUERY EACH OTHER FOR SIGNAL REPORTS ON AGREED
FREQUENCIES FROM 160 THROUGH 10 METERS TO INCREASE THE CHANCES FOR
SUCCESSFUL COMMUNICATION.  THE TERMINATED FOLDED DIPOLE TFD IS A
POPULAR ANTENNA FOR HF ALE, BUT A COSTLY HIGH POWER RESISTOR IS
REQUIRED AND IT UNDERPERFORMS A CENTER FED DIPOLE.  THE OFF CENTER
FED DIPOLE OCFD SEEMED LIKE A GOOD STARTING POINT FOR EFFORTS TO
DEVELOP A CHEAPER, MORE EFFICIENT LTERNATIVE TO THE TFD.  OCFDS AIM
TO SOLVE A PROBLEM THAT PREVENTS THE USE OF A CENTER FED DIPOLE
ACROSS SEVERAL OCTAVES OF FREQUENCY HIGH IMPEDANCE RESONANCES AT
EVEN MULTIPLES OF THE DESIGN FREQUENCY MAKE IT DIFFICULT TO MATCH TO
A 50 FEED LINE.  AS AN EXAMPLE, AN 80 METER CENTER FED HALF WAVE
DIPOLE HAS HIGH IMPEDANCE RESONANCES ON 40, 20, 15, AND 10 METERS.
OCFDS TYPICALLY FEED THE ANTENNA AT A POINT ONE THIRD FROM THE END
OF THE ANTENNA.  THE OCFD SWR REFERENCE IMPEDANCE IS 200, WHICH CAN
BE EASILY MATCHED TO 50 COAX BY A PROPERLY DESIGNED 4 1 CURRENT
BALUN.  FIGURE 1 SHOWS THE SWR OF A CONVENTIONAL 80 METER OCFD HALF
WAVE ANTENNA.  THIS ANTENNA COVERS SIX HAM BANDS, BUT GIVES

FIGURE 2 DEMONSTRATES THAT THIS DESIGN COVERS SEVEN HAM BANDS BUT
CANT BE EASILY MATCHED ON 17 METERS.  FEED POINT POSITIONING FIRST,
WE NEED TO SELECT A FEED POINT WHOSE POSITION DOESNT CAUSE A
HARMONIC OF THE HALF WAVE RESONANT FREQUENCY TO FALL INSIDE OR TOO
CLOSE TO A HAM BAND.  SECOND, WE MUST MAINTAIN A LOW SWR AT THE
HIGHER FREQUENCIES TO AVOID SIGNIFICANT MISMATCH LOSSES IN THE FEED
LINE.  THIRD, THE SWR AT THE TRANSMITTER SHOULD BE EASILY MATCHED BY
AN AUTOTUNER, WHETHER BUILT IN TO THE RADIO OR AVAILABLE SEPARATELY,
OR BY A LOW LOSS MANUAL L C TUNER.  SEVERAL FEED POINT POSITIONS
DELIVER USEFUL RESULTS, BUT FIGURE 3 INDICATES THAT THE 45 FEED
POINT IS A GOOD SOLUTION FOR ALL THREE GOALS ON EIGHT OF THE MOST
USED HF AMATEUR BANDS.  THE SWR VALUES SHOWN IN TABLE 1 SHOULD BE
EASILY MATCHED BY EMBEDDED AUTOTUNERS OR COMMERCIALLY AVAILABLE
EXTERNAL MATCHING NETWORKS.  MOVING THE FEED POINT SLIGHTLY TO ONE
SIDE OR THE OTHER REBALANCES THE 40 METER AND 12 METER SWR LEVELS,
AS DOES FEEDING THE ANTENNA IN THE VICINITY OF THE 22R5 FEED POINT,
BUT THE 45 FEED POINT MEETS 
‰  END OF 40 WPM TEXT  ‰