Pennant/Flag antennas.
If you are on a small lot, have a noise problem. or both, a Flag or Pennant antenna may be your better choice for a receive antenna. Most man made noise comes to us against ground. A ground independent antenna can eliminate or reduce noise by disconnecting the ground side connection.
- Pennant and flag 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.
- The loss of signal due to ground dependence is due to an
effect called the Pseudo- Brewster angle, and explained in the ARRL Antenna Handbook.
- Flag and Pennant antennas operate with low signal levels. A 20-25 db gain preamplifier, made for low bands is necessary. The preamplifier is usually located physically in the radio room. 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 antennas. Use a light weight insulated support rod, such as fiberglass, from the antena mast to the transformer for physical support of the transformer and coax cable.
- Reception direction. If you are standing under the termination resistor, reception is from the direction of the transformer.
- One of the problems with poor reception, and poor front to back is
coupling to the transmit antenna. Transmit element detuning is necessary. A relay may have to be installed at the transmit antenna feed point to disconnect the coax, or to disable other element tuning components while receiving.
- Increased decoupling of the coax cable is often done by
adding turns to ferrite cores, beyond the transformer, where the coax first meets ground. Or a choke made from random winding several turns of coax in a 6-8 inch diameter coil, (plastic ties or taped together), and placed where the coax first meets the ground.
- A deep null on the back of the antenna is useful for interference control.
- Typical terminations are 905-915 ohms point terminated Pennant, and 940-950 ohms Flag.
Beverage antenna notes
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