Delta, Pennant, Flag antenna notes


KB5

    • 900 ohm low capacitance primary antenna connection. Isolation: Less than 6pf (3-4pf typical) inter-winding capacitance for minimum common mode transfer, and best ground independence.


    • Available in SO-239, BNC, or F type fittings for matching 50 or 75 ohm coax.


    • Flag, Pennant, and Delta antennas, in order to receive low angles, need to be decoupled from ground to achieve ground independence.


    • Ground independence requires common mode signal decoupling of the coax cable shield. This is done by minimizing the matching transformer primary to secondary capacitance. A BN-73-202 binocular core, with low capacatance windings, can provide the needed isolation.


    • As per Earl, K6SE (sk). The Delta receiving antenna has been the favorite of many DX-peditions, requiring only one non-metallic support at the top apex. The lower corners are typically fastened with ropes to tent pins that can be easily relocated to change antenna direction. eham K6SE delta-FO0AAA antenna info


    • Flag, Pennant, Delta antennas operate with low signal levels. A 15-20 db gain preamplifier, usually located in the radio room, is necessary. The preamplifier in your transceiver is not adequate in gain, although it may help in conjunction with the external one.


    • Use insulators where the transformer and termination resistor connect, to take mechanical strain away from components.


    • For rotatable flag, pennant, delta antennas. Use a light weight support rod, such as fiberglass, from the antenna mast to the transformer for physical support of the transformer and coax cable.


    • Reception direction. If you are standing by the termination resistor, reception is from the direction of the transformer.


    • Any problem with poor reception, and/or poor front to back is most likely coupling to the transmit antenna. Transmit antenna detuning may be necessary. A relay may need to be installed at the transmit antenna feed point to disconnect the coax, or to disable/change other element tuning components while receiving.


    • A deep null on the back of the antenna is useful for interference control.


    • Typical terminations resistors are, 903 ohms for point terminated Pennant antennas, 945 ohms for Flag antennas, and 948 ohms for Delta antennas.


    • Avoid using heat shrink wrap over termination resistors. Protective coverings are not necessary.






    • Increased common mode decoupling of the coax cable was often accomplished by addng a coil of many coax turns, beyond the matching transformer, where the coax first met earth ground. As time passed the number of turns were reduced by adding ferrite cores.



    • Now a popular choke is constructed by winding 6-8 turns of small diameter coax in a 6 inch diameter coil and held together with plastic ties. One mix 31 ferrite 'clamp on' core Amidon 2x31-1081P2, or equivalent is installed over the windings.





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    Questions? Call, or email  k1fz@MyFairPoint.net

    73

    Bruce-K1FZ
    Clark Electronics
    65 Patterson Hill Road
    Belfast, ME 04915-7300
    (207) 338-0474

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