Delta, Pennant, Flag receiving antennas
A Flag antenna may be your better choice for a receive antenna if you are on a small lot, have a noise problem, or both. Many man made noises come to us against ground. A ground independent antenna may eliminate or reduce noise by disconnecting the ground side connection.
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Delta, Pennant, Flag antenna transformer
- 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.
- 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.
Questions? Call, or email k1fz@MyFairPoint.net